Microbiology Exam 2

nomenclature when discussing different bacteria

formal names of phyla, classes, orders, and genera are capitalized •for example, the phylum "cyanobacteria" informal names and adjectival forms are lowercase •for example, talking about a group of "cyanobacteria" or "cyanobacterial" cell traits genus and species names are italicized •for example, "streptococcus pygense" or "bacillus anthracis" •informal names would include "streptococci" or "streptococcal" *most of our attention will be focused on the genus and species levels*

bacteroides

obligate anaerobes •anything more than a trace of oxygen will kill them •don't have enzymes to combat reactive oxygen species (ROS) very important to human gut health •they ferment a wide range of sugar derivatives from plant material, compounds that are indigestible and potentially toxic to humans •their fermentation products are up to 15% of our caloric intake can cause damage if they migrate to other parts of the body

chlamydias

obligate intracellular pahtogens •lack a true cell wall pure parasites unique life cycle that consists of two stages common human pathogens, cause: •chlamydia •eye trachoma •pelvic inflammatory disease

syphilis can cross placenta and infect fetus

Called congenital syphilis Very dangerous to newborns Pregnant women are routinely screened for syphilis Causes notched teeth, perforated palates, and other birth defects Chronic disease that leads to lifelong complications

Many bacterial species have a positive impact on humans

•help shape the environment and ecosystems •forms commensal bacteria within our bodies

other species have a negative impact on humans

•pathogens cause disease and destruction •can excrete toxins and other harmful compounds

three different types of plague disease

1) Bubonic plague - bacteria moves to lymph nodes and causes inflammation; greatly enlarged lymph nodes called buboes 2) Septicemic plague - bacteria moves into bloodstream; high levels of endotoxin can induce shock and cell death 3) Pneumonic plague - bacteria eventually enters lungs and causes a severe pneumonia Extremely lethal, kills people in 24-48 hours Only form of plague that is transmitted between humans

unique intracellular replication cycle of chlamydia

1) Non-replicating elementary bodies are endocytosed by eukaryotic cells 2) Elementary bodies begin to enlarge into reticulate bodies 3) Reticulate bodies replicate and fill up vacuole (aka inclusion) 4) Reticulate bodies divide into new elementary bodies that are then released

five steps of pathogenesis

1) Pathogen entry - enter through a break in the host's barriers (aka a portal of entry); each pathogen has its own preferred route •Ex. - fecal-oral route, respiratory route, sexual transmission 2) Tissue attachment and colonization - in order to begin growing and dividing inside the body, must first anchor to host tissue layer •If not, can be flushed away from the body 3) Host damage - must cause some sort of disease or damage to be called a pathogen •Damage caused is not malicious, just a byproduct of the pathogen trying to reproduce and grow •Host's immune response can also contribute to increased damage 4) Immune avoidance - must remain undetected or inaccessible to the host's immune system •Pathogens have all developed unique ways of accomplishing this •Can be "defensive" (hiding) or "offensive" (attack) 5) Pathogen exit - after growth and reproduction, needs a way to transmit to a new host and continue living •Usually through the same portal of entry route (fecal-oral, respiratory, etc.)

prevalence of sexually transmitted bacteria

340 million new sexually transmitted infections each year Most common sexually transmitted bacterial infections: Syphilis Steady increase in US incidence (5,973 cases in 2000 vs. 30,644 cases in 2017) Gonorrhea Estimated 1.14 million new cases per year in US (half occurring in people ages 15-24) Chlamydia Estimated 2.86 million new cases per year in US Most common bacterial STI

arthropod-borne infections are a serious public health threat

Account for more than 17% of all infectious diseases, and >700,000 deaths annually around the world

microbial adhesins promote attachment to body surfaces

Adhesin - any microbial factor that promotes attachment Some of the most common types are pili and fimbriae Some bacteria used multiple strategies •Ex. - pili and non-pilus adhesins

adhesins at tip of pilus anchor the bacterial cell

Adhesin tip proteins bind to carbohydrates on host cell membranes •Acts like a stick pin or Velcro to hold bacteria in tight association Different bacterial species use different types of pili •Differ based on their flexibility and function •Some can even act like grappling hooks (attach and thenpull bacterial cell closer by disassembling pilin shaft)

Salmonella's trojan-horse like approach to pathogenesis

After replicating safely inside phagosome of M cell, can exit through bottom intestinal wall Endocytosed by macrophages (immune system cells) Some Salmonella strains can then survive in phagosomes of macrophages and be transported around the body •Express unique virulence antigen (Vi Ag) that encapsulates and protects them

streptococcus pneumoniae is the main cause of bacterial pneumonia

Aka "pneumococcal pneumonia" Majority of humans have S. pneumoniae in their noses and throats Humans are the only natural reservoir of S. pneumoniae 90 different serotypes Disease only in immunocompromised Uses slippery capsule to avoid phagocytosis and removal by mucociliary escalator Causes fluid accumulation and lung damage just like other bacterial respiratory pathogens

strains of S. aureus express many different toxins

All serve distinct functions and result in specific disease symptoms Disseminated throughout body and can cause systemic issues •Many act as superantigens to induce overactive immune responses that damage the body

attachment of E. coli uses pili and secretion systems

All strains use specialized pili (type IV pili) that act as grappling hooks to tether bacterial cell to host cell, then pull them together •E. coli are also acid resistant which helps them survive stomach acid EHEC and some other strains then use a type III secretion system (like a syringe) to inject virulence factors into cell •Virulence factors instruct host cell to rearrange its cytoskeleton to form membrane pedestals •Lift the bacteria up and away from host cell so that the bacteria can avoid being engulfed (endocytosed)

attaching and effacing lesions generated in host

As a response, the host cells will call for help from the immune system Inflammation is induced and results in the elimination of intestinal cell layers (microvilli) Holes that form in intestine are called attaching and effacing lesions because they are caused by the attachment of E. coli •Allows red blood cells and white blood cells to enter intestine and contribute to bloody diarrhea

>2,000 types of S. enterica

Based on O and H antigens on bacterial cell surface •O antigen = type of LPS •H antigen = type of flagellar protein Each are given unique names •Ex. - Salmonella Heidelberg, Salmonella Dublin All cause different types of "salmonellosis"

antibiotic resistance in S. aureus

Basically all (99.9%) S. aureus isolates are resistant to penicillin Majority (60%) are also resistant to methicillin now •Methicillin-resistant S. aureus (MRSA) Penicllin-binding protein is key virulence factor of MRSA •Normal protein involved in cell wall synthesis that has been mutated •Can bind to class of antibiotics and inactivate them MRSA is very dangerous infection because it is hard to treat •Hospital acquired and community acquired •Epidemic rates in the US •Methicillin not even used anymore

clostridium neurotoxins

Botulinum toxin secreted by Clostridium botulinum Tetanus toxin secreted by Clostridium tetani Similar structures: Heavy chain domain used for binding to neuron receptors and entering the cells via pore formation Light chain is the actual toxic enzyme that is released into the cytoplasm Protease function allows the toxin to disrupts cellular exocytosis of neurotransmitters Neuron can no longer communicate with cells around it

clostridium botulinum and clostridium tetani

Botulism caused by C. botulinum Transmitted via contaminated food Especially anaerobic canned goods Affects the peripheral nervous system Results in paralysis Infant botulism leads to "floppy head syndrome" in infants Via ingestion of spores in soil Tetanus caused by C. tetani Introduced to body via trauma Necrotic tissue is anaerobic Affects the central nervous system Results in constant muscle contraction and spasms (Ex. - painful lockjaw)

streptococcus species also characterized by their ability to lyse red blood cells

Can be tested on blood agar plates Alpha hemolysis - red blood cells are partially lysed by bacterial production of hydrogen peroxide •Produces a greenish halo on blood agar Beta hemolysis - red blood cells are completely lysed by bacterial production of a hemolysin enzyme •Produce clear halos on blood agar •Include many dangerous pathogens Gamma hemolysis - red blood cells are not lysed by the bacteria Include many commensal species

staphylococcus species characterized by their ability to lyse red blood cells

Can be tested on blood agar plates Alpha hemolysis - red blood cells are partially lysed by bacterial production of hydrogen peroxide •Produces a greenish halo on blood agar Beta hemolysis - red blood cells are completely lysed by bacterial production of a hemolysin enzyme •Produce clear halos on blood agar •Include many dangerous pathogens Gamma hemolysis - red blood cells are not lysed by the bacteria •Include many commensal species

different strains of S. pyogenes express different virulence factors

Capsule - thick layer around bacteria to help prevent phagocytosis M protein - pilus-like protein that inactivates component of the immune system Streptolysins - enzymes that lyse red blood cells (hemolysins) Streptokinase and hyaluronidase - enzymes that degrade connective tissue to help the bacteria spread more rapidly Streptococcal pyogenic exotoxins (SPEs) - induce a damaging overreaction by the host immune system

bacterial exotoxins have a variety of effects

Categorized into classes based on cell targets Also includes superantigens (excessive activation of the immune response)

E. coli includes six separate pathogenic strains

Classified based on O and H antigens on bacterial cell surface •O antigen = type of LPS •H antigen = type of flagellar protein 1) Enteroinvasive E. coli (EIEC) 2) Enterohemorrhagic E. coli (EHEC) 3) Enterotoxigenic E. coli (ETEC) 4) Enteropathogenic E. coli (EPEC) 5) Enteroaggregative E. coli (EAEC) 6) Diffusely adherent E. coli (DAEC)

S. aureus uses coagulase to hide from immune system

Coagulase - enzyme produced by S. aureus that coats the bacterium in fibrous materials (fibrin) Results in the formation of a microcolony that cannot be accessed by immune cells or antibiotics Build-up of dead bacteria and immune cells over time results in the generation of pus •This abscess must be physically drained to end infection

streptococcus pyogenes is very pathogenic

Common inhabitant of human skin and nostrils Pathogenic when it moves into skin or body Diseases it causes include: •Cellulitis, erysipelas, and necrotizing fasciitis (skin diseases) •Pharyngitis (respiratory tract disease) •Toxic shock syndrome and scarlet fever (systemic diseases) •Rheumatic fever and kidney damage (secondary complications)

staphylococcus aureus is very pathogenic

Common inhabitant of human skin and nostrils Pathogenic when it moves into skin or body Diseases it causes include: •Folliculitis, boils, impetigo, and ecthyma (skin diseases) •Toxic shock syndrome (systemic response) •Pneumonia (fluid in lungs) •Mastitis (inflammation of mammary gland) •Osteomyelitis (bone infection)

whooping cough making a comeback

Current vaccine (DTaP, diphtheria-tetanus-pertussis) is composed of only the purified pertussis toxin and FHA •Very effective, but does wane in adulthood Due to anti-vaccination movement, incidence of whooping cough has been steadily increasing for the past decade Before vaccination: 10,000-20,000 whooping cough deaths per year in the US

eight-legged arthropods (arachnids)

Different species prefer to interact with host in different ways Examples: Mites - attach and burrow under skin Ticks - attach to skin and suck blood to get the nutrients they need(ectoparasites)

The EHEC and EIEc strains of E. coli

EIEC - only invasive strain of E. coli •Causes inflammation and bloody diarrhea •No animal reservoir EHEC - very dangerous pathogen •O157:H7 is most common type •Most likely cause of E. coli outbreaks •Acute diarrhea with high chanceof dehydration •Animal reservoir (gut of cattle) •Can lead to systemic complications

unique three subunit exotoxin of anthrax

Encoded on a plasmid (transferable DNA) Like the AB exotoxins, but with two A components 1) Protective antigen (PA) - core subunit (the B component) that helps the toxin enter the host cell by binding to host membrane and forming a pore 2) Edema factor (EF) - activated upon entry into host cytoplasm; induces secretion of electrolytes and water from host cells into lungs (pneumonia) 3) Lethal factor (LF) - protease that cleaves host cell components of critical regulatory pathways; prevents host cells from producing chemokines and attracting immune cells for help

the plague is still present today

Endemic in 17 western states in the US Wild rodents in Colorado (Case History 10.3) Man was bitten by Y. pestis-containing fleas near his home Developed pneumonic plague but was successfully treated with antibiotics Prairie dogs in New Mexico (Case History 21.1) Rancher had trapped, killed, and skinned two prairie dogs Open wound on hand allowed bacteria to move from rodent to human host Had signs of septicemic plague but was successfully treated with antibiotics

intracellular bacteria escape killing by phagolysosome

Endocytosed like normal into the phagosome Then avoid death by: •Preventing fusion with the lysosome •Escaping into the cytoplasm •Adapting to harsh conditions

"enteric" means they cause GI illness and diarrhea

Enteric - relating to or occurring in the intestines Different bacteria prefer to colonizedifferent regions of the intestines •Due to environment and metabolism preferences Majority of bacterial intestinal infections are caused by Gram-negative bacteria •"Food poisoning"

gonorrhea disease ("the clap")

Epidemic in the US Women are a major reservoir 80% are asymptomatic (but still contagious) Can disseminate around body and cause arthritis, endocarditis, and meningitis Can lead to pelvic inflammatory disease (PID) Also causes eye infections in newborns Very dangerous, can lead to blindness Prophylactic drops given to all newborns No lasting immunity; reinfection is common Antibiotic resistance is common and growing

unique virulence factors used for attachment

Filamentous hemagglutinin (FHA) and tracheal colonization factor •Adhesins expressed on the surface of B. pertussis that allow for attachment to cilia on epithelial cells Strong association with epithelial cells prevents bacteria from getting swept away Binding directly to cilia also impedes the mucociliary escalator

examples of non-pius adhesins

Fimbriae and pili often initiate the interaction between bacterial cells and host cells Then non-pilus adhesins form a stronger attachment Non-pilus adhesins are other proteins on the surface of the bacterial cell that bind to specific ligands on host surface •Examples include: •M and F proteins of Streptococcus •Intimin of pathogenic E. coli •Opa proteins of Neisseria

two main phyla of gram-positive bacteria

Firmicutes and Actinobacteria Main distinction based on GC content of genome (the amount of G-C base pairs compared to A-T base pairs) •Firmicutes: low GC content (45-60%) •Actinobacteria: high GC content (60-70%) •*Differences in GC content often used to detect evolutionary divergence

mechanisms to secrete virulence proteins

General secretion pathway - used by all bacteria to transfer virulence proteins (as well as many other proteins) from cytoplasm to the extracellular environment Some bacteria have severalmore specific secretion systems for transporting specific toxins or for injectingdirectly into a host cell Most of them are repurposed versions of other bacterial structures and pathways •Ex. - pili, flagella, conjugation

treponema pallidum lacks true virulence factors

Genome is very small and does not encode any classic virulence factors (or metabolic pathway genes) Intracellular flagella Flagella located in periplasm Hidden from host defenses ("stealth pathogen") Can also change surface protein composition over time to hide from immune response

general characteristics of bordetella pertussis

Gram-negative coccobacillus Aerobic metabolism Transmitted via aerosols Expresses several virulence factors Causes whooping cough (aka pertussis) •Characterized by deep "whooping" coughs, struggle to breath •Coughs are so violent and rapid that they can cause vomiting and broken ribs

general characteristics of yersinia pestis

Gram-negative coccobacillus Facultative anaerobe Non-motile Reservoir in rodents Transmitted via flea bites Causative agent of the plague

general characteristics of neisseria gonorrhoeae

Gram-negative diplococcus Facultative intracellular pathogen Causes gonorrhea

general characteristics of E. coli

Gram-negative mobile rod Facultative anaerobe Normal member of the gut microbiota Usually harmless, but some strains of E. coli contain virulence factors •Due to previous horizontal gene transfer

general characteristics of salmonella enterica

Gram-negative rod Facultative anaerobe Multiple flagella (highly mobile) Intracellular bacteria Many animal reservoirs •Poultry, cattle, reptiles, cats, hamsters

general characteristics of clostridium

Gram-positive rods Strict anaerobes Sporulation leads to club-shaped cells Spores commonly found in soil and water Several important human pathogens Clostridium difficile Clostridium botulinum Clostridium tetani

general characteristics of streptococcus

Gram-positive, spherical shape, grow in chains •Chain-like growth = "Strepto-" •Spherical = "-coccus" Part of the normal microbiota •Oral and gut commensals Aerotolerant but use fermentation •Produce lactic acid that can decrease pH so low that it damages teeth (tooth decay)

general characteristics of staphylococcus

Gram-positive, spherical shape, grow in clusters •Clustered growth = "Staphylo-" •Spherical = "-coccus" Facultative anaerobes Salt tolerant Part of the normal skin microbiota •Produce fermentation products that inhibit the growth of skin pathogens Also contain dangerous pathogenic species

general characteristics of bacillus anthracis

Gram-positive, spore-forming rods Facultative anaerobes Spores can survive for decades in soil Primarily infects animals (cattle) Select agent and potential bioweapon •Used in the 2001 mail attacks

Vibrio cholerae

Halophilic curved rod with single flagellum Acid-sensitive so requires high dose Non-invasive pathogen •Produces cholera toxin to induce secretion of electrolytes and water from intestinal epithelial cells Severe watery diarrhea Rehydration is key treatment Haiti outbreak in 2010 •Contaminated water following earthquake •665,000 cases and 8,183 deaths

six-legged arthropods (insects)

Some have wings, others do not Different species prefer to interact with host in different ways Many examples: Mosquitoes (one of the most dangerous vectors known) Lice Fleas Botflys Bedbugs (can transmit MRSA)

B. anthracis can infect multiple body locations

Inhalation anthrax (aka pulmonary anthrax) •Aerosolized spores enter lungs via inhalation •Most dangerous and lethal form of anthrax (80-90% fatal) Cutaneous anthrax •Direct contact with infected animals or contaminated animal products (Ex. - animal hides, hair) •Infection enters through wounds in the skin •Causes stereotypical skin lesions •20% fatal Gastrointestinal infection •Ingestion of undercooked meat from contaminated animal •Very rare, but lethal (>50% fatal)

M. tuberculosis has a unique cell envelope

Lipid-heavy cell wall of sugar polymers, mycolic acids, and glycolipids •Mycolic acids are unusual lipids with one very long hydrocarbon chain •Capsule is waxy and very hydrophobic Thick, waxy coating inhibits phagocytosis by immune cells and prevents other hostantimicrobial compounds (and antibiotics) from working Causes colonies to appear gooey

endotoxin is the LPS of gram-negative bacteria

Lipopolysaccharide (LPS) forms the outer leaflet of the Gram-negative outer membrane When released from dying bacteria, the lipid A component of LPS interacts with immune system cells and triggers a cytokine storm •Basically a massive overreaction of the immune system that can be lethal

normal immune defenses of the lower respiratory tract

Location deep inside body •Easy to access via aerosol transmission Thick mucus layer coats cells •Secreted by goblet cells •Tough to access epithelial cells for attachment Mechanical nature of mucociliary escalator removes debris and pathogens •Airway epithelial cells have hair-like projections called cilia •Ciliated cells brush mucus-encapsulated pathogen up and out of airways

unique pathogenesis of tuberculosis in lungs

Low risk in people with normal immune system •M. tuberculosis infects 1 out of every 3 people Infect alveoli and form granulomas (clumps of bacteria surrounded by immune cells) •Access to nutrients and high O2 •Constant inflammation leads to lesions in lung tissue Lesions are eventually healed to form calcified Ghon complexes

respiratory infections are extremely dangerous

Lower respiratory tract infections kill 4 million people annually (The Global Impact of Respiratory Diseases, 2017) •Kill more people than HIV, tuberculosis, and malaria combined •Leading cause of death in children under 5 years of age (>800,000 per year) Categorized as acute or chronic depending on the length of disease Bacterial respiratory diseases include pneumonia, bronchitis, whooping cough, and tuberculosis (see Table 20.2 for full list) •Caused by both Gram-positive and Gram-negative bacteria •Streptococcus pneumoniae is the most common cause of bacterial pneumonia

immune evasion by N. gonorrhoeae

Majority of strains are sensitive to complement in the blood Endocytosed by neutrophils in the submucosa Resist phagocytic killing by secreting catalase that breaks down ROS and allows bacteria to replicate in phagosomes RecA protein used to repair DNA damage caused by ROS by transformation of DNA from neighboring gonococci Opa proteins on the surface of N. gonorrhoeae bind to receptors on immune cells and inactivate them

extracellular avoidance mechanisms

Many methods to avoid recognition by immune cells: Thick polysaccharide capsules - coat the bacteria and cover/hide bacterial cell wall components •Biofilms are a great example with their exopolysaccharide (EPS) matrix Alter structure or protein expression Mimic host cell proteins Neutralize immune system components •Bind and inactivate antibodies •Cause death of immune cells

taxonomic hierarchy of microbes

Matches what is used for animals and other living organisms •humans are "homo sapiens" broken down based on sequence homology and trait similarity each class has both pathogenic and non-pathogenic bacterial species

streptococcus pneumoniae also responsible for bacterial meningitis

Meningitis - inflammation of the brain tissue Incredibly dangerous and life-threatening S. pneumoniae number one cause of meningitis in infants, children, and the elderly Uses enzymes to cut through mucus, inactivate host lysozymes, infiltrate the blood vessels, andthen slip through blood-brain barrier using itspolysaccharide capsule and pneumolysins Colonizes the meninges and induces inflammation Destroys brain tissue and forms abscesses

bacteria infections of the GI tract are dangerous

More severe than viral GI tract infections •Bacteria can directly invade and destroy cells lining the GI tract •Produce toxins Elicit strong inflammatory responses that can cause damage •Can quickly cause dehydration Outbreaks often lead to foodrecalls for consumer safety •Salmonella •E. coli

AB toxins use two subunits for delivery to host cell

Most bacterial toxins are composed of two subunits •Called AB toxins •A subunit is the toxic component •B subunit binds to host cell receptors, thus transporting the A subunit to its target Examples include: •Staphylococcus alpha toxin •Cholera and E. coli labile toxins •Shigella and E. coli shiga toxins •Anthrax toxin

tick-borne transmission of borrelia burgdorferi

Most commonly carried by deer ticks Bites of deer tick nymphs are extremely hard to detect Borrelia burgdorferi grows in the digestive tract of the tick Upon biting a host, it takes 2 days for the bacteria to travel to the tick's salivary glands Enters host's bloodstream and travels systemically Prefers skin, nerve tissue, joints, and heart tissue

virulence factors of chlamydia trachomatis

Multiple type III secretion systems are expressed from pathogenicity islands in the C. trachomatis genome Inject multiple types of proteins to promote each step of the life cycle: Proteins to trigger actin rearrangement and promote internalization Proteins to prevent apoptosis of the host cell Inc (inclusion) proteins that redirect host vesicles to inclusion for nutrient acquisition

Sources of microbial diversity

New species emerge and evolve over time due to: •Random mutations •Natural selection •Degenerative evolution Different environments enforce different selective pressures on the microbes that live there

chlamydia trachomatis causes multiple diseases

Nongonococcal urethritis Can cause pelvic inflammatory disease if not treated Pneumonia Arthritis Trachoma (eye infection) Prevented in newborns via prophylactic eye drops

clostridium difficile is an important enteric pathogen

Normal member of the intestinal microbiota Resistant to antibiotics Following treatment for other bacterial diseases, C. difficile can colonize majority of intestine Causes extensive damage to intestinal lining and leads to diarrhea and colitis Two main toxins (Toxins A and B) expressed from a pathogenicity island Interact with host cell cytoskeleton proteins to weaken the tight junctions between cells

pathology includes direct pathogen interaction

Not all pathogenesis is caused by side effects of the immune response Pathogens directly target host cells for many reasons: 1) Alter host cell function 2) Hijack host cell machinery 3) Lyse and release all their nutrients 4) Disrupt the immune response Key example of virulence factors are toxins •Endotoxin - a structural component of the bacterium that can cause damage when released during death of the bacterium •Exotoxins - protein toxins that are secreted from a living bacterium

general characteristics of chlamydia trachomatis

Obligate intracellular pathogen Gram-negative-like Causes chlamydia The most frequent bacterial STI Can "hitchhike" on sperm for transmission

attachment is key first step to surviving environment

Once anchored on host tissue surface, often form biofilms Biofilms establish optimal growth environment, concentrate nutrients, and protect the bacteria from the host's immune response and antimicrobial compounds The attachment process is a key target of vaccines

pathogens must evade the immune response to continue growing and continue the infection

Option 1: Hide/Avoid •Bacteria can hide from immune system by living inside of host cells (intracellular bacteria) •Requires specialized gene functions and mechanisms •Bacteria can also avoid the immune response while living extracellularly •Form biofilms or other protective measures to keep the immune response away Option 2: Fight back •Secrete toxins and virulence factors to deactivate or disrupt the immune response

virulence factors commonly found in pathogenicity islands

Pathogenicity island - a type of genomic island that encodes several pathogenicity/virulence genes •These are the genes used by the pathogen to accomplish the 5 steps we just discussed Large blocks of DNA acquired via horizontal gene transfer One of the signature features of genomicislands is that their GC content is usually different than the surrounding chromosomal DNA •GC content matches the microbe that donated the island

endocytosis and phagocytosis used by host cells to destroy pathogenic microbes

Pathogens are identified and engulfed (endocytosed) by host cells They are then contained in an intracellular vesicle (phagosome) that can interact with other vesicles (lysosomes) filled with acidic conditions and antimicrobial compounds Thus, the pathogen is lysedand degraded within the hostcell

respiratory tract infections

Pathogens target different regions of the respiratory tract Upper respiratory tract - nasal passages, oral cavity, and pharynx Lower respiratory tract - trachea, bronchi, alveolar ducts, lungs •All surfaces covered in ciliated epithelial cells and mucus

the gram-positive cell wall

Peptidoglycan - multiple layers, very thick Teichoic acids - chains of glycerol or ribitol threaded through the peptidoglycan •Reinforce the peptidoglycan •Help pathogens attach to host cells Surface layer (S-layer) - crystalline layer of thick protein or glycoprotein subunits •Additional protective layer •Permeable to molecules

the gram-negative cell wall

Peptidoglycan - one or two layers, very thin Periplasm - the region between the outer and inner membranes; contains distinct proteins compared to the cytoplasm Outer membrane - additional lipid bilayer that confers defensive abilities and has toxigenic properties •Murein lipoprotein forms bond between outer membrane and the cell wall •Porin proteins permit entry of a variety of nutrients •Outward facing lipids are lipopolysaccharide (LPS)

B. pertussis expresses multiple exotoxins

Pertussis toxin - classic AB-type toxin that enters host cells and disrupts cell signaling pathways •Results in the secretion and accumulation of fluid in the lungs Tracheal cytotoxin - damages ciliated epithelial cells, thus inhibiting the mucociliary escalator •Corresponding accumulation of mucus can support the colonization and growth of other bacteria

mechanisms of borrelia burgdorferi pathogenesis

Poorly understood because of unique lifestyle and unusual genome Genome consists of 1 linear chromosome and 21 linear/circular plasmids Two of the plasmids are mainly used for the expression of virulence factors Expresses many typical virulence factors Adhesion factors for attachment Surface proteins to inactivate the innate immune response in the blood Glycosaminoglycan-binding proteins on the surface of the bacteria bind to and cleave proteoglycans that make up host connective tissues

sexually transmitted bacteria infect the reproductive tract

Reproductive tracts of both genders include organs and glands directed towards producing offspring Warm, moist environment provides an ideal environment for the growth of pathogenic microbes All infections of the reproductive tract are communicable and represent important public health threats

unique stages of syphilis pathogenesis

Primary syphilis - a painless chancre forms 2 to 6 weeks after transmission Infection then goes latent (hidden) for up to 5 years Secondary syphilis - generalized rash, fatigue, and fever Returns to a latent stage for several years Tertiary syphilis - cardiovascular and nervous system-associated symptoms Systemic formation of gummas (soft tumor-like growths composed of dead tissue surrounded by inflammatory cells) Onset of dementia and eventual death

general characteristics of mycobacterium tuberculosis

Rod-shaped, non-spore forming, non-motile bacteria Highly aerobic (requires high levels of O2) Very slow growing (divides every 18-24 hours) Neither Gram-positive or Gram-negative due to unique cell envelope Causes tuberculosis (TB) •One of the deadliest infectious diseases in human history

S. aureus secretes multiple exotoxins

S. aureus remains in abscess and produces exotoxins that cause damage and disease elsewhere •*Damaged tissues are often not actually infected* Exfoliative toxin causes scalded skin syndrome •Protease that specifically cleaves cell adhesion molecules in the skin, opening up space for S. aureus to spread •Results in skin blistering Toxic shock syndrome toxin (TSST) is a superantigen that is disseminated in the blood and induces severe systemic symptoms

s. pyogenes causes "strep throat" and complications

S. pyogenes causes the most dangerous form of pharyngitis Referred to as "strep throat" Secrete SPEs which can travel systemically and cause scarlet fever M protein (used by bacteria to evade immune response) induces an autoimmune response where the host attacks its own heart tissue

pili are assembled from monomeric units

Several types of pili, all assembled the same way Starts with an adhesin protein ("stick pin") at the tip Pilin subunits are then strung together to form the shaft and push the tip protein further out from the bacterial surface

transmission of sexually transmitted bacteria

Sexual contact (most common) Intimate contact between mucous membranes Direct contact transmission Infections can be passed to urogenital tract, rectum, or oral cavities Associated with risky behavior Childbirth Newborn child can be infected by mother's bacteria in uterus or vagina Vertical transmission Mothers are often screened for infections during pregnancy

proteobacteria: a vary diverse group many important human pathogens

Shapes: include cocci, bacilli, spiral-shaped cells, etc. Metabolism: heterotrophs, lithotrophs, phototrophs Common feature among them all: Gram-negative cell envelope Enterobacteriaceae is the most well-known family •Facultative anaerobic rods •Grow in digestive tracts, lakes, and streams •Many are motile (have flagella) •Many form biofilms Escherichia coli (GI illness) Salmonella (GI illness) Yersinia pestis (bubonic plague) Legionella (pneumonia-like illness) Vibrio cholerae (cholera - GI illness) Neisseria (meningitis, gonorrhea) lithotrophs •acidithiobacillus- used in metal leaching • oxidize ("eat") iron and copper, thus solubilizing the metals and extracting them from rock •nitrifiers play a big role in wastewater treat intracellular bacteria •rickettsia- tick-borne pathogens that cause rocky mountain spotted fever rhizobium- live in plant cells and help with nitrogen fixation

EHEC strains express Shiga toxins

Shiga toxins 1 and 2 •Cleave host ribosomal RNA, thus halting protein synthesis and killing the host cell to release nutrients •Can spread systemically throughout body •Kidney and brain cells are most vulnerable •Results in formation of microclots to block damage Identical to those produced in Shigella (another Gram-negative enteric) •Transferred to E. coli using bacteriophage transduction

streptococcus causes many types of disease

Skin disease Streptococcus pyogenes Respiratory disease Streptococcus pneumoniae Streptococcus pyogenes Systemic disease Streptococcus pyogenes Neurological disease Streptococcus pneumoniae

staphylococcus species cause many types of disease

Skin disease •Staphylococcus aureus •Staphylococcus epidermidis Urinary tract disease •Staphylococcus epidermidis •Staphylococcus saprophyticus Gastrointestinal disease •Staphylococcus aureus Joint disease (arthritis) •Staphylococcus aureus

establishment of intracellular infection

Specifically bind to M cells in the intestine Uses type III secretion system to inject multiple toxins Toxins induce changes in host cell cytoskeleton to cause membrane ruffling •Induces engulfment of the bacteria by the host cell Once inside phagosome, injects more toxins into host cell to prevent fusion with lysosome

Helicobacter pylori

Spiral-shaped bacteria with multiple flagella Urease enzyme protects it from stomach acid so it can swim to mucosal layer of stomach Only known cause of infectious gastritis •Results in formation of painful ulcers Risky experiment by Barry Marshall

general characteristics of treponema pallidum

Spirochete Corkscrew-like shape Minimal metabolic activity Motile using intracellular flagella Causative agent of syphilis Recognized disease since 1500s

borrelia burgdorferi causes lyme disease

Spirochete transmitted via tick bites Most common vector-borne illness Endemic areas in US and around the world Considered an emerging infectious disease Bacterial cause only identified in 1982 Has unique genome of one large linear chromosome and 21 plasmids Systemic pathogen

three stages of lyme disease

Stage 1: Local dissemination of the bacteria Results in a "bull's eye" rash Inflammation as immune cells try to infiltrate infection site Stage 2: Bacteria spread from blood to organs Side effects include arthritis, muscle pain, and cardiovascular complications Stage 3: Severe neurological and joint complications Severe arthritis Changes in memory, mood, and sleep

streptococcal pyogenic exotoxins induce a cytokine storm

Streptococcal pyogenic exotoxins (SPEs) are superantigens that nonspecifically activate many components of the immune system Results in a systemic overreaction Induce production of a massive amount of cell signaling molecules ("cytokine storm") Recruit and activate wide array of immune cells and inflammation Leads to shock, cardiovascular collapse, loss of blood pressure, etc. Directly associated with the systemic diseases caused by S. pyogenes Scarlet fever, toxic shock syndrome, and necrotizing fasciitis

high potential for antibiotic resistance

TB is a chronic disease because it is very hard to eliminate all the bacteria •Waxy coating blocks antibiotics Long periods of antibiotic treatment increase the odds of M. tuberculosis developing antibiotic resistance Multidrug resistant tuberculosis (MDR-TB) and extreme drug-resistant tuberculosis (XDR-TB) strains now very common •One of the top public health threats of the future

history of the plague

The Black Death 14th Century Transmission of Yersinia pestis by rat fleas killed 1/3 of Europe's population

divided into groups based on surface glycoproteins

Use antibodies that interact with different surface glycoproteins •Distinct polysaccharides and teichoic acids in each Streptococcus species Referred to as Lancefield groupings because technique developed by Rebecca Lancefield in 1933 Group A streptococci (GAS) are highly important human pathogens •Range from minor illnesses to very serious disease •Beta hemolytic •Includes mostly Streptococcus pyogenes

general characteristics of gram-negative enterics

Transmitted via the fecal-oral route Two main methods of causing diarrhea and illness: 1) Invasive bacteria - penetrate the cells lining the intestinal wall and induce a bloody, mucoid diarrhea due to inflammation and the recruitment of immune cells Ex. - Salmonella, enteroinvasive E. coli, Shigella, Campylobacter 2) Enterotoxigenic bacteria - live on surface of intestinal cells and produce enterotoxins that induce secretion of fluids and result in watery diarrhea Ex. - Vibrio cholerae, enterotoxigenic E. coli

distinct subspecies of treponema pallidum

Treponema pallidum pallidum causes syphilis Sexually transmitted multi-stage disease Treponema pallidum pertenue causes yaws Multi-stage disease transmitted via direct skin contact Genomes are 99.6% identical with no major differences in genes Pathogenesis has not been fully explored because cannot be grown in the lab

virulence factors of yersinia pestis

Two horizontally acquired virulence plasmids Uses biofilm formation in flea midgut to increase transmission to new hosts Secretes an extracellular matrix to induce biofilm formation Biofilm blocks flea digestion, making the flea feel constantly starved Flea continuously jumps host to host looking for more blood to feel full Uses a type III secretion system to inject YopB and YopD Yop proteins disrupt host cell actin cytoskeletonto help bacteria avoid phagocytosis Plasminogen activator is a proteasethat can dissolve blood clots in human bloodstream and promote spread

transmission via arthropod vectors

Vector - a carrier of a disease-causing agent Arthropods - invertebrate animals with exoskeletons and jointed appendages Include insects and arachnids Transfer bacterial infections by biting infected host and then healthy host

type III secretion systems function like a syringe

Virulence proteins are injected directly into host cell •Do not have to travel through extracellular environment and find specific host receptor Built in very similar manner to flagella Found in Salmonella, Shigella, and Yersinia pestis

the life cycle of yersinia pestis

Zoonotic disease that is transmitted to humans from animals Sylvatic cycle - transmission in the wild, the natural infectious cycle Urban cycle - transmission in urban settings Fleas bite humans for blood when normal rodent hosts aren't around

spirochetes

cell shape is a long, tight spiral •flexible like a phone cord •unique intracellular flagella •not the same as spirilla cells •spirilla are flat, helical gram-negatives grow soil and water important pathogens: •treponema pallidum (syphilis) •borrelia burgdorferi (lyme disease)

even closely related genetic variants can be profoundly different

example: •Bacillus thuringiensis grows in the soil and is harmless to humans •Bacillus anthracis causes anthrax and is extremely deadly to humans •Share >97% genome sequence similarity

firmicutes: "tough skin"

grow commonly as rods (bacilli) or spheres (cocci) •depending on arrangement of cells after division, more nomenclature can be added •"staph-"= arranged in clusters (grape-like); example: staphylococcus •"strep-"= arranged in chains; example: streptococcus include many common human commensals and pathogens •stapylococcus- commonly found on skin, can cause MRSA •streptococcus- commonly found in mouth and throat, can cause "strep throat" and tooth decay •enterococcus- commonly found in human GI tract, can cause urinary tract infections bacillus genus •rod-shaped microbes •commonly found in soil and food •form endospores and are thus very hard to eradicate •can cause serious disease in humans (anthrax) clostridium genus •obligate anaerobes •commonly found in soil and water •also form endospores •excrete neurotoxins to cause tetanus and botulism lactococcus and lactobacillus genera •"lactic acid" bacteria •ferment milk to make yogurt and cheese listeria genus •uniquely able to move around within human cells using actin tails •can grow at low temperatures (such as on refrigerated foods) •can cause listeriosis (severe GI illness)

cyanobacteria

key to biosphere and ecosystems •perform oxygenic photosynthesis (produce O2) •wide variety of species with diverse shapes and traits •no known pathogens •some form lichens (mutualistic association with fungi)

outcomes of S. enterica infection

most common cause of bacterial enteritis (inflammation of GI tract) •diarrhea with some blood •very similar to other enteric pathogens strains that can spread systemically cause typhoid fever •long lasting stepwise fever •endemic in southeast asia treatment using antibiotics

actinobacteria

the "high-GC Gram-positives" include a wide variety of major pathogens and antibiotic producers streptomyces genus •grow as branching filaments •secrete antibiotics •procedure spores which disperse into air propionibacterium genus •special fermentation pathway that produces propionic acid •can be "good" (swiss cheese) or "bad" (acne) myobacterium genus •exceptionally thick and complex cell envelopes (gives gooey appearance) •can cause very bad human diseases (tuberculosis and leprosy)

two main phyla of gram-negative bacteria

•proteobacteria and bacteroides •proteobacteria demonstrate an incredibly wide range of form and metabolism •bacteroides are obligate anaerobes