Bio 2215 - Intro to Microbio - Exam 1
HIV/AIDS
- AIDS is caused by HIV - Can be transmitted by blood transfusions, sex, contaminated needles, mother to fetus, etc. - No effective vaccine or cure - There are several antivirual drugs that can prolong life
About how many species of bacteria are harmful?
- About 100 are involved in causing serious disease - Most microorganisms are beneficial
Storage granules of bacteria
- Accumulation of polymers synthesized from excess nutrients - Example of a storage molecule: glycogen found in eukaryotic cells to store excess glucose
Typical viral life cycle
- Adsorption - Penetration - Biosynthesis - Assembly - Release
Domain Bacteria
- All are prokaryotic (they have no membrane bound nucleus or organelles) - Rigid cell walls - Divide by binary fission - Motile bacteria have flagella - Common shapes: cocci, bacilli, spiral
Spirilla
- All bacteria that have a spiral shape - Spirilla are helical, look like a corkscrew, and are rigid - Spirochetes are also helical bur more flexible, have whip-like external flagella
In lab, viruses are grown in:
- Animals - Bird embryos (eggs) - Cell lines & tissue cultures
Growth and survival of microbes depends on
- Availability of nutrients and energy sources - Ambient temperature of locality - Presence or absence of certain gases - Osmotic pressure of solutions - pH - Presence or absence of light or radiation - Presence or absence of other organisms in the environment
Stationary phase
- Average cell population remains constant - Nutrients are depleted and production of toxic materials that decrease cell growth increase
What 3 domains are bacteria placed in?
- Bacteria - Archaea - Eukarya
What does the diverse microbial world include?
- Bacteria - Fungi - Protozoa - Algae - Viruses
What benefits do we get from microorganisms?
- Bacteria and fungi decay organic matter - Bacteria and fungi make most antibiotics - Some bacteria contribute in the production of vitamins K and vitamin B - Bacteria are used to make ethanol, pesticides, dietary amino acids - Bacteria degrade oils, clean natural and artificial oil spills - More than 50% of photosynthesis is performed by microorganisms, producing a major part of oxygen in the atmosphere
microaerophiles
- Bacteria that require a small amount of oxygen - e.g. treponema pallidum and Actinomyces israelii
Obligate aerobes
- Bacteria that require oxygen and produce enzymes to detoxify oxygen byproducts - Can live in presence of oxygen
Obligate anaerobes
- Bacteria that will die if exposed to oxygen because they do not produce enzymes that can detoxify the toxic oxygen byproducts - e.g. Clostridium tetani and C. botulinum
Types of light microscopes
- Bright field - Dark field - Phase contrast - Fluorscent
How can you obtain pure cultures?
- By streak plate or pour plate methods - Easiest and most practical for a pure culture is the streak plate method
Nucleic acids (virus)
- Can be RNA or DNA (never both) - Small genomes
Isolate bacteria in a pure culture
- Can be done in a liquid or solid but for a pure culture, the most practical method is use of a solid medium - Agar, an extract obtained from marine algae, is used to solidify bacterial growth media in the lab - Agar solidifies at 45 C and remains solid at room temp
Direct cell count
- Can be performed using microscopic count or cell counting instruments to determine the total number of cells - Disadvantage: does not distinguish between living and dead cells
Small pox
- Caused by Variola virus - Estimated to have killed 500 million people before its eradication - Last case reported in 1977 - Was around for ~3000 years total
Choler
- Caused by Vibrio cholerae, a comma shaped Gram negative bacteria - Transmitted orally from contaminated food or water - Causes severe diarrhea - could lose up to 4 gallons of fluid per day - If not treated the sudden loss of fluid can cause shock, collaapse, and death - Fluid and electrolytes essential to treatment
Bubonic plague
- Caused by Yersinia pestis - vector for the plague is a rat flea - Transmission to humans can be by a rat flea bite, handling dead or infected rats, or airborne - Yersinia pestis grows in lymph nodes causing swelling and necrosis of the nodes in the groin and arm pits - Can get into the lungs and cause pneumonic plague which is fatal
Genital herpes
- Caused by a dsDNA enveloped virus - Transmitted by sexual, oral, anal contact or from mother to fetus - One of the most common STIs - about 45 million infected people in the US and half a million new cases every year - No vaccine or cure - Can be transmitted even when symptoms are not present
Tuberculosis
- Caused by an acid fast organism called Mycobacterium tuberculosis - cell wall contains wax-like material therefore it resists drying - Transmitted by close contact or inhalation of droplet nuclei - Difficult to treat - Multi drug resistance M. tuberculosis is now common - A vaccine is available but not used in the USA - called BCG - Kills up to 2 million/year and about 1/3 of the world's population is infected by it
Leprosy (Hansen's Disease)
- Caused by mycobacterium leprae - 2-20 year incubation period - Can lose fingers, toes, nose, eyelids - An obligate intracellular parasite - cannot be grown in artificial media - Can be controlled if treated early - Not easily transmitted
Log phase
- Cells grow exponentially and have increased metabolic activity - Doubling takes place at each generation - Synthesis of secondary metabolites - At this state, bacteria are most sensitive to antibiotics
Basic dyes
- Chromophore is attached to the positively charge ions - Examples of basic dyes: crystal violet, safranin, and methylene blue
How did Leeuwenhoek classify bacteria?
- Cocci (round) - Bacilli (rods) - Spirilla (spiral)
Other bacterial shapes
- Coccobacillus: short round rod - Vibrio: gently curved rods, comma shaped - Pleomorphic: bacteria that vary in shape
Acid fast bacteria
- Contain peptidoglycan and mycolic acid in their cell walls - Mycolic acid increases resistance to chemical agents and prevents dehydration - Acid-fast bacteria are slow growers because their cell walls slow down the entry of nutrients and because they require large amounts of energy to synthesize the lipids that make up the cell wall - Examples: mycobacteria and nocardia
Cell counting instruments
- Count cells in suspension - Cells to be counted pass in single file and an electronic detector counts the number of cells - Can use Coulter counter which detect changes in electrical resistance - Can use flow cytometer which measures the count using a laser light
Gram staining
- Developed by Hans Christian Gram in 1884 - The most common staining procedure used in microbiology and clinical labs - Divides bacteria in Gram positive and Gram negative
Acid fast staining
- Differential staining procedure developed by Paul Ehrlich in 1882 - Requires concentrated carbol fuchsin (primary stain) wich application of heat to the slide by keeping it over the flame and allowing the stain to penetrate the waxy layer - To decolorize the primary stain, the slide is washed with 5% HCl and 95% ethyl alcohol - Acid-fast bacteria will retain the primary color whereas non-acid fast will stain blue from the methylene blue counterstain - Used to stain myobacterium tuberculosis, M. leprae, and Nocardia
Diagnosis of viral diseases
- Difficult to diagnose and treat - Range of symptoms makes it difficult to be accurate - Methods of diagnosis: immunofluorescence, direct examination w/ electron microscopes, PCR, and serologic tests
Unstained bacteria
- Difficult to see using a bright field microscope because of poor contrast - Bacteria is almost transparent - Advantages: study the morphology and mobility
Treatment of viral diseases
- Difficult to treat - Few antiviral drugs available but can have toxic side effects - Antibiotics have no effect
Osmosis
- Diffusion of water across a membrane - Water flow in/out of the cell to equalize solute concentrations - Inflow of water exerts osmotic pressure which may cause it to burst/lyse (hypotonic - solution has a lower solute concentration than the cell so water flows in) - If water flows out, cell can shrivel (hypertonic - solution has a higher concentration of solute than cell so water flows out)
Robert Koch
- Discovered Mycobacterium tuberuclosis and Vibrio cholerae - Isolated Bacillus anthracis - Established that anthrax could be transmitted from animal to animal - Developed the idea of pure cultures - Demonstrated Koch's postulates - 4 rules used to determine the etiologic agent of a disese
Alexander Fleming
- Discovered penicillin, the first antibiotic, from a bacterial plate that was contaminated with a fungus called Penicillum notatum
Ross and Grassi (1898)
- Discovered the vector for malaria (female Anopheles mosquito) - The causative agent for malaria is genus Plasmodium
Louis Pasteur
- Disproved spontaneous generation by boiling nutrient broth in swan-necked flasks that allowed air to circulated but not microorganisms - this proved that microbes could not be generated spontaneously - Demonstrated that microorganisms are killed by heat - Introduced pasteurization process - Discovered the role of yeast in fermentation - Developed immunization procedures and produced vaccines for anthrax and rabies - Developed the process of attenuated vaccines - Established the role of endospores in causing diseases - Considered the father of modern microbiology
Algae
- Diverse photosynthetic aquatic organisms - Can be singled celled or multi cellular - Perform about 90% of all photosynthesis - Have rigid cell walls
Faculatative anaerobes
- Don't require oxygen for metabolism - Can live in the presence of oxygen because they produce catalase and superoxide desmutase - Metabolism occurs by aerobic respiration or anaerobically by fermentation - e.g. Staphylococci and enteric Gram negatives
Bacterial staining
- Dyes are made of salts that carry either positive or negative ions - Dyes are divided into basic or acidic - Under normal conditions, bacterial cells are slightly negatively charged so positive ions (chromophores) that are colored in basic dye is attracted to the negative bacterial cell wall - Negative ions that are colored on the acidic dyes will be repelled
Stained bacteria
- Easy to see using a bright field microscope - Provide a good contrast between a bright feel and the stained bacteria - Disadvantages: kills the bacteria, morphology may be distorted, and mobility is lost
Some emerging or re-emerging diseases
- Ebola - Lyme disease - Legionnarie's disease - TB - Hantavirus pulmonary syndrome - Mad cow disease - Severe acute respiratory syndrome - Influenza - West Nile virus - Zika
Endospore stain
- Enhances the endospore - Heat used to facilitate staining
Capsules
- External viscous structures made of a polysaccharide (called glycocalyx) found on the surface of some bacteria - Protect bacteria against loss of water and nutrients - Virulence factors because bacteria that produce capsules avoid phagocytosis - Enhance bacterial attachment
Plasmids of bacteria
- Extra-chromosomal circular DNA molecules which are typically 0.1% - 10% the size of the chromosome - Replicate independently of the chromosomal DNA and code for molecules such as antimicrobial resistance
Sporulation
- Formation of endospores - Starts by stopping growth, duplicating DNA, and splitting the cell unevenly into larger and smaller parts - the larger parts engulf the smaller part of the DNA and produces a fore-spore - The fore-spore is then enclosed by two membranes and become the core of the spore - The core wall and the cortex of the spore are made of peptidoglycan - The proteins from the mother cell form the spore coat - When spore formation is complete, the mother cell disintegrates and releases endospore
Envelope (virus)
- Found in animal viruses - Modified pieces of the host cell membrane - Host cell membranes are replaced by viral proteins
Who was the first to challenge and disprove spontaneous generation? How did he do it?
- Francesco Redi - He did a experiment in which he placed meat in a wax sealed or gauze-covered jars and generated that maggots were not generated spontaneously
enteric viruses
- Generally transmitted via fecal-oral route - Often cause gastroenteritis - Some can cause systemic disease
Fluoresence microscope
- Have a built in UV light - when organisms are stained with dyes like fluorescein or rhodamine that emit light or a longer wave light, they will appear fluorescent when UV light hits them
Gram positive bacteria
- Have a thick layer of peptidoglycan located on the outside of the cell wall that makes up 60-90% of the cell wall, up to 30 layers - No outer phospholipid layer - Peptidolycan is permeable to many substances - Small periplasmic area (periplasmic is where most secreted proteins are found) - Have teichoic acids
Gram negative bacteria
- Have only one layer of peptidoglycan located between two cell membranes - The periplasmic layer (where most secreted proteins are found) is larger than in Gram postiive bacteria - Have lipopolysaccharies (LPS)
Domain Archaea
- Have similar shape to bacteria - Divide by binary dission - Have no peptidoglycan - Some can grow at 121 degrees C - Some can grow in high salt concentration
What did John Tyndall's experiment prove?
- He demonstrated that different life forms required different boiling times to die - some were sterile about 5 minutes boiling and others required hours
HIV
- Human immunodeficiency virus that causes AIDS - RNA virus that belongs to the retrovirus group and lentiviruses (slow viruses) subgroup - Kills T-helper cells that play a primary role in immunity - causes a person to become susceptible to many infections - No vaccine or cure
What are some modern advances of microbiology?
- Identification of microbial diseases in a few hours - Use of specific antibodies to target and kill cancer cells selectively - Possibilities of using immunotherapy to treat disease like cystic fibrosis using gene therapy - Discovery of antibiotics to treat microbial diseases - Discovery of the structure of DNA in 1953 - Discovery pf restriction enzyme that cut DNA in specific places - Introduction of the first recombinated DNA molecule - splicing DNA from a virus into a bacterial chromosome - Development of Polymerase Chain Reaction in 1985 - Sequencing of the human genome
Domain Eukarya
- Include algae, fungi, protozoa, animals, and plants - Have true cells (membrane bound nucleus and organelles) - Most are multicellular - Do not have peptidoglycan
Cocci
- Includes all bacteria that are round in shape and are non-flagellated - May also be more oval, elongated, flattened, or pointed - Diplococci: found in groups of two (e.g. Neisseria gonorrheae, streptococcus pneumoniae) - Streptococci: found in chains (e.g. streptococcus lactis, and S. pyogenes) - Staphlococci: found in clusters (e.g. Staphylococcus aureus)
Flagella stain
- Increases the diameter of flagella and makes it easy to see
Joseph Lister
- Introduced aseptic techniques used in surgery - Applied germ theory to medical procedures - Introduced phenolic disinfectants
Resolution/Resolving power of a microscope
- Its ability to clearly and distinctly show two closely located points as two distinct separate points - Maximum resolving power of bright field microscopes is 0.2µm which is sufficient to see most bacteria clearly
What are two other types of bacteria that lack cell walls?
- K-forms or L-phase variants - mutant bacteria will defective cell walls introduced by a chemical treatment such as lysozyme
Chronic infections
- Last for long period of time - Hepatitis B & C
Phase contrast microscope
- Light is refracted when it passes through a medium like air, glass, or water - A refractive index of a medium is the number that describes how much light bends when it passes through that medium - Because of differences in the refractive indexes of cell cytoplasm, organelles, and nucleus, you can see internal structures of the cell distinctly - Higher contrast can be obtained by staining the organisms
What membrane molecules are found in Gram negative bacteria?
- Lipopolysaccharides (LPS) are only found on Gram negative bacteria - LPS has anti-phagocytic and anti-cell rupture proteins - 3 parts of LPS: Lipid A, core, and carbohydrate chains - Lipid A is toxic and what causes fever, pain, damage to blood vessels, and endotoxic shock (due to BP decrease)
In what ways can vaccines be prepared?
- Live organisms - Attenuated (live weakened organisms) - Killed organisms - Recombinant products
Flagella
- Long external structures made of proteins that bacteria and other organisms use for movement - Use a propeller-like motion to push bacteria in the direction they want to go - Can rotate more than 100,000 times per minute (equal to 82 miles/hour) - 3 parts of the flagella: filament, the long, whip-like portion made of a protein called flagellin, the hook which is the base where a filament is attached to the cell, and a basal body which anchors a flagellum to the cell membrane
Cell membrane/plasma membrane/cytoplasmic membrane
- Made of phospholipids, proteins, and carbohydrates - Contains carrier proteins (aka channels) which protrude to the outside of the membrane - used to selectively transport materials in and out of the membrane - Some membrane proteins are only found in the outer or inner layer of the membrane - Main goal of the membrane: to regulate transport of nutrients and waste materials - They are also involved in secretions and metabolic activities
Prions
- Made of proteins (misfolded protein) - Do not have DNA or RNA - Infect brain and spinal cord - Symptoms may not - Resistant to destruction by heat, UV light, ionizing radiation, and commonly used sterilization processes
Vaccines
- Many safe & effective vaccines are available to protect against viral diseases - MMR, TDaP, polio, smallpox, hepatits, etc.
True active bacterial motion
- Mediated by flagella - Requires energy by the bacteria to occur - Chemotaxis: The flagella are whip-like, long filamentous appendages which are used for movement by rotating clock wise or counterclockwise, causing the cell to spin in one direction - Chomtaxis is exhibited when bacteria sense nutrients or toxic repellents and move either close to or further from the chemicals
Turbidity
- Method based on the amount of light that is transmitted through a bacterial growth culture - The more turbid the culture, the more bacteria that are in the culture
Viable cell count
- Method used to quantify living cells - Valuable in monitoring bacterial growth and is often used when cell counts are too low for other methods
Protozoa
- Microscopic, single-celled organisms - Protozoans do not have rigid cell walls - Protozoa may be aquatic or terrestrial and depend on other organisms for their survival - Mostly motile - get their energy from organic matter
Diffusion
- Molecules move freely from high to low concentration - Are able to move in or out of a cell membrane without using energy - Water, gasses, and some hydrophobic molecules can diffuse through a cellular membrane
Types of flagella
- Monotrichous: a single flagellum at one end - Lophotrichous: several flagella on one end - Amphitrichous: single flagellum on each side - Peritrichous: flagella all over the bacterial cell
Directed movement across the cellular membrane
- Movement of some molecules requires highly selection proteins (carriers and permeases) which span the cell membrane and move molecules from one side to the other - Most transport proteins are produced in response to need and each carrier is used to transport a specific molecule - Facilitated diffusion, active transport, group translocation
Capsule stain
- No heat applied - Stains the background while capsule remain unstained
Fungi
- Non-photosynthetic - Can be single celled (yeasts) or multicellular (molds, mushrooms) - Get their energy from organic matter - Found everywhere
What does growth of prokaryotes depend on?
- Nutritional, physical, and environmental factors - Bacteria require energy sources, elements, growth factors, and trace elements to grow
Respiratory viruses
- Often inhaled via infected respiratory droplets - Generally remain localized in respiratory tract
Latent infections (animal viral infections)
- Often occur many years after a primary infection subsides - Stay dormant and reactivate later in time - Herpes simplex viruses and shingles
Direct microscopic count
- One of the most rapid methods - Number of bacteria measured in a known volume, using a specialized slide counting chamber and the cells are counted - Limitation: you must have at least 10 million cells per mL to have an accurate estimate
Ribosomes of bacteria
- Organelles used for protein synthesis - Composed of a large and small sub-unit made of riboprotein and ribosomal RNA - Prokaryotic ribosomes have a 30S & a 50S sub-units totaling 70S - Eukaryotic ribosomes have a 40S and a 60S sub-unit totaling 80S
Brownian motion (bacterial mobility)
- Passive, random, nondirectional movement of bacteria - Results from bombardment of molecules in motion in a suspension where the bacteria are found - Not a true movement generated by bacteria and does not require energy to occur
Discoveries/introrductions during the Golden Age of Microbiology (1854-1918)
- Pasteurization process - Immunization protocols/vaccines - Pure culturing techniques - Aseptic surgical techniques - Use of oil immersion - Abbe condenser - Gram staining procedure - Discovery of phagocytosis
What antibiotics use peptidoglycan as a target molecule?
- Pennicillin: interferes with bacterial cell wall synthesis by preventing the cross linking of glycan chain tretrapeptides - more effective against Gram positive bacterial - Lysozyme: breaks the bonds joining NAG and NAM which destroys the structural integrity of the cell wall, this is an enzyme found in body fluids like tears and saliva - Lysozyme is also used in research labs to remove the peptidoglycan layer to produce bacteria without a cell wall - known as protoplast in Gram positive bacteria and spheroplast in Gram negative bacteria
Viroids
- Plant viruses - Obligate intracellular parasites - Can destroy crops by causing pigment loss, marks on leaves and fruits, tumors, and stunted growth - Plants generally do not recover from viral infections - Simpler and smaller - Single piece of RNA without a protein coat - Resistant to proteases, replicate autonomously, and a single viroid is enough to infect a cell
Penetration
- Plants/bacteria: nucleic acid is injected into hte cell - Animal: the nucleic acid or whole virus is taken in by endocytosis - if whole virus take in, the viral envelop is digested by enzymes and releases the nucleic acid - Some viruses carry genes that produce proteins that can penetrate a host cell and seal the hole after they get in
Atomic force microscope
- Possible to see live cells at high resolutions, magnification, and in a 3D shape
Capsids (viruses)
- Protein structures that surround their nucleic acid and protects the nucleic acid from enzymatic or chemical digestion - Made of capsomeres - Can be helical or icosahedral - Each virus has a specific # of caspids
Shingles (herpes zoster)
- Reactivation of the virus in people who had chicken pox - Can occur on face, back, abdomen, arms, legs - Has a vaccine
Hydrogen
- Required for organic and inorganic compounds - Maintain pH of cells, form H bonds in macromolecules, and required for oxidation-reduction reactions of respiration
Who introduced the cell theory and what does it state?
- Robert Hook - States that all cells come from pre-existing cells
Influenza
- Seasonal viral disease causesc by influenza biruses - Kills up to 40,000 people a year in the USA - The 1918 influenza epidemic killec about 20 - 50 million - Often mutate their genetic code so they are difficult to control - Symptoms include fever, chills, headaches, muscle aches - Vaccine is prepared in embryonated eggs - every year, the 3 or 4 killed strains from the most prevalent viruses are used to prepare the vaccine
Release
- Self-assembled viruses released by budding/exocytosis - May or may not kill host cell
Acute infections
- Short duration - Disease symptoms resulting from tissue damage and infection of new cells - Host may develop long-lasting immunity
Pili
- Similar to fimbrae but each bacterium normally only has one of two pili
Gas vesicles of bacteria
- Small compartments made of proteins - Provide buoyancy - Can also be used to position the organisms to an indeal position in the environment
Exceptions to Koch's postulates
- Some microorganisms are obligated intracellular parasites - e.g. some cannot be cultured in artificial media - Some organisms cannot be grown in vitra - Some disease cannot be reproduced in experimental animals - The organisms may not be present in the infected person when symptoms occur
Competitive microbial interactions
- Some organisms synthesize toxic substance to inhibit growth of their competitors
Diseases caused by prions
- Spongiform encephalopathy (mad cow disease): degenerative brain disease and deterioration in neurological function caused by sponge like lesions in the brain - Creutzvelfeldt Jakob disease: infects nervous system and causes it to degenerate; fatal - Scrapie: similar to Creutzvelfeldt Jakob disease but only found in monkeys, sheep, and mice - Kuru: seen in New Guinea natives in those involved in cannibalism practices
Spontaneous generation
- States that organisms can arise from non-living matter - Was observed by many scientists who believed that mice, toads, flies, and maggots could be generated from things like manure
How can viruses be classified?
- Structure (enveloped or naked) - Nucleic acids (DNA or RNA) - Shape (helical, icosahedral, complex)
Endospores
- Structures produced by bacteria when nutrients are depleted in their environment or when they sense the occurrence of starvation - Each bacterium produces only one endospore - Examples: genera Clostridia and Bacillus
Growth factors
- Substances that some bacteria require to grow in a culture but cannot synthesize them on their own - A bacteria that requires special growth factors are known as fastidious organisms
What membrane molecules are found in Gram positive bacteria?
- Teichoic acids which give the cell its negative charge - Teichoic acids are used to regulate ionic movement, prevent autolysis, and are involved in the growth of lipoteichoic acids
Temperature and microbial growth
- Temp. one of the most important environmental factors required for microbial growth - Has significant effect on enzymatic and metabolic functions - Microbes cannot control their own temp. and depend on ambient temp. - Each species has a narrow growth temp. range where it can grow
Acidic dyes
- The chromophore is attached to the negatively charged ions - Examples of acidic dyes: sdoium eosinate, negrosin
Generation time
- The time it takes one cell to divide into two cells - Different for different types of bacteria - Varies with different environmental conditions such as temperature, availability of nutrients, pH, etc.
Fimbriae
- Thin hair-like structures found in some Gram negative bacteria - Used to attach to surfaces
Magnification
- Total magnification is obtained by multiplying magnification obtained by objective lens by magnification of the ocular lens - Example: ocular lens has 10x and the objective lens has 10x - the total magnification will be 100 x (10 x 10 = 100)
Differential staining
- Two or more dyes are used to stain bacteria - Examples: Gram staining and acid fast staining
Electron microscopes
- Use electrons, electromagnetic lenses, and fluorescent screen to produce an image - Magnification and resolutions are much higher than those of a light microscope - The source of illumination is an electron beam produced by an electron gun and focused my magnets - Are able to see organisms with a diameter of 0.3nm
Bright field microscope
- Used in most clinical and teaching labs - Uses visible light to form an imagine and produces total magnification up to 1,000x
Colony counts
- Used to count bacteria - A count of viable cells growing on solid culture medium - Based on the assumption that one cell gives rise to one colony
Transmission electron microscope
- Used to observe fine details of organisms - Directs a beam of electrons and as electrons pass through they scatter at the surface resulting in light and dark areas - dark areas are more dense and light areas are less dense - Possible to achieve a total magnification of 100,000x
Dark field microscope
- Used to observe organisms that have diameters of less than 0.2µm - Examples: Treponema pallidum (syphilis), Borrelia burgdorfoi (Lyme disease) - The object will appear bright and the field of view will be dark
Scanning Electron Microscope (SEM)
- Used to observe surface details - During preparation of the specimen, it is coated with a metal (usually gold) - A beam of electrons scans the surface and the electrons are released and reflected into a viewing chamber - Not able to view living organisms - during preparation, procedures like thin sectioning, freeze fracturing, or freeze etching kills the organisms
Pleomorphism
- Variations of size and shape among a species - Due to variations in cell wall structure caused by nutritional or slight hereditary differences - Examples: Corynebacterium diphtheriae and Mycoplasmas
How do tumor causing viruses work?
- Viral DNA integrates into the genome of the host cell - Introduce mutations resulting in uncontrolled cell growth
Biosynthesis
- Viruses replicate inside the host cell - Some viruses carry genes for copying their genome, capsid genes, tail, and head
Cooperative microbial interactions
- Waste produced by some organisms is food for others
Biofilm formation
- When bacteria attach to surfaces, like teeth, and grow in layers with open channels for movement of nutrients and waste materials - May cause diseases that are difficult to treat because the architecture of the biofilm makes it difficult for the immune system and antimicrobials to function
What resolution can a scanning electron microscope have?
0.02nm
What resolution can a transmission electron microscope have?
0.2nm
What resolution is obtained with all light microscopes?
0.2µm
Acidophiles pH range
1 to 5
What magnification can a electron microscope have?
1,000,000 x
Gram staining process
1. Crystal violet: the primary dye which stains all cells purple by binding to peptidoglycan layer of Gram postive bacteria or the outer phospholipid layer of Gram negative bacteria 2. Iodine: a mordant - used to fix crystal violet to the cell by forming a complex and making it bind tightly 3. Acetone/alcohol: dissolves the outer phospholipids of Gram negative bacteria and removes the primary dye (crystal violet) - Gram negative bacteria will become colors at this point; Gram positive still retains the purple primary dye 4. Safranin: the couterstain which will bind to the decolorized Gram negative bacteria turning them pink
What is the maximum magnification of a light microscope?
1000x
temp range for mesophiles
15 to 45 C - Most human pathogens belong to this group
temp range for thermophiles
45 to 80 C
temp range for psychrophiles
5 to 25 C
Optimum pH for most bacteria
6.5-7.5
temp range for hyperthermophiles
60 to 110 C
Alkalophiles pH range
8.5 to 10
How many bacteria must be in the colony to be visible?
About 1 million
How many cells does a human being have?
About 10 trillion
How many bacteria live in/on the human body?
About 100 trillion
Bacillus
All bacteria that have a rod shape
What type of life forms can viruses infect?
All life forms but only a specific organism or cell type
Microscope
An optical instrument composed of one or more lenses used to observe microorganisms and other objects that cannot be seen with the naked human eye
Anton Van Leeuwenhoek was the first to observe what?
Bacteria
Lag phase
Bacteria adapt to growth environment, increase in size, adjust their metabolism, and repair cell components
Aerotolerant
Bacteria that grow in the absence or presence of oxygen
What is the most resistant life form?
Bacterial endospores - Can remain viable in extreme heat, drying, freezing, radiation, and chemicals - Likely due to its thick protein layer outside the membrane, high concentration of C++ ions, dipicolinic acid, and resistance to dehydration - Can remain dormant for millions of years - the oldest known spores are about 850 million years old
Complex media
Bacterial growth media such as nutrient broth, blood agar, and chocolate agar - contain ingredients that cannot be qualified exactly
What is the ideal number of colonies to count per plate?
Between 30 and 300
How do prokaryotes divide?
Binary fission - one cell divides into two cells, two into four, etc. - Cell growth is exponential, doubling the population with each cell division
HIV primarily infects
CD4 (T-helper) lymphocytes and macrophages
Halophilic bacteria
Can grow in 25% NaCl
Major growth elements (macronutrients) or organisms
Carbon, oxygen, hydrogen, nitrogen, sulfur, phosphorous, potassium, magnesium iron, and calcium - These are essential components for macromolecules
Slow infections
Caused by prions that have long incubation periods (up to 10-20 years) after initial infection
Who was able to purify penicillin in 1940 so it could be produced in large amounts?
Chain and Florey
Where do heterotrophs derive their energy from?
Chemical compounds
Nutrients
Chemical substances required by cells for metabolism, growth, maintenance
Trace elements (micronutrients) for organisms
Cobalt, zinc, copper, molybdenum, and magnese - Required for growth but needed in small amounts
Bacterial growth culture media may be classified as
Complex, chemically defined, selective, or differential
Where do RNA viruses replicate in humans?
Cytoplasm
Death phase
Death of cells occur due to physical stress, lack of ribosomal repair, and protein depletion
Photoheterotrophs
Derive their energy from sunlight and carbon from organic compounds
What viruses cause most tumors or cancers?
Double-stranded DNA viruses
Ferdinand Cohn used John Tyndall's experiment to discover what?
Endospores
Axial flagella (endoflagella)
Flagella located at the ends of a cell and beneath a sheath - Examples: Spirochetes
Where are chromosomes of bacteria found?
Found in the cytoplasm (nucleoid space) typicall as a single chromosome
What does HIV use to bind to C4 receptors?
GP-120
Is reactivation more common in shingles or genital herpes?
Genital herpes
Chemically defined media
Growth media that are composed of precise amounts of pure chemicals
Selective media
Growth media that are used to inhibit growth of unwanted organisms and allow only sough after organisms to grow - Examples: Thayer-Martin agar used for Neisseria gonorrhoeae, MacConkey used to isolated Gram-negative bacteria
Differential media
Growth media that contain substances that bacteria change in a visible way - Blood agar which shows hemolysis as a result of breaking of the red blood cells - MacConkey agar which contains pH indicator to identify bacteria that produce acid - Mannitol salt agar which will show color change
Attachment pili
Help bacteria adhere to surfaces
Streak plate method
Isolated colonies with different shapes, colors, and textures can be observed
Who discovered viruses?
Ivanosky
4 stages of the bacteria growth curve
Lag, log (exponential), stationary, death
Who discovered HIV?
Luc Montagne in 1981
Lytic viral life cycle
Lyse the cell
What is one of the top killers in the world?
Malaria - kills about 1 million people every year
How many antibiotics are on the market today?
More than 200 million
Neutrophiles pH range
Neutral range (around 7)
Can viruses be cultured in artificial growth media?
No
Was Alexander Fleming able to purify penicillin?
No
Do mycoplasma have a cell wall?
No - strength of the membrane is provided by sterols - Lack of a cell wall causes them to appear in many shapes
Are viruses organisms?
No - they are acellular infectious particles
Do archaea have peptidoglycan in their cell walls?
No - they have polysaccharides and/or protein
Are viruses living or non-living?
Non-living
Formula for growth rate
Nt = N0 x 2N
Where do DNA viruses replicate in humans?
Nucleus
Akkermansia munciniphila, a human intestinal mucin (protein) degrading bacteria is associated with what?
Obesity, diabetes, inflammation
Light microscope
One or more lenses are used for magnification and the source of illumination is visible light
Simple staining
Only one dye is used to stain bacteria
What molecule provides the rigidity of the bacterial cell wall?
Peptidoglycan - Found only in bacteria - Provides a strong support and prevents cell wall from bursting - Peptidoglycan is a complex molecule made of N-acetylglyucosamine (NAG) and N-acetylmuramic acid (NAM) which are joined together by glycan chains - Gylcan chains are held together by 4 amino acid tetra-peptide chain
What disease do mycoplasmas cause?
Pneumonia
Pure culture
Population of bacteria derived from a single bacterium
All bacteria are _____ organisms
Prokaryotic
Immersion oil
Reduces scattering and increases the amount of light passing through the objective lens
Assembly
Repeated viral subunit particles self-assemble inside the host cell
Sodium
Required for cell function and transport
Calcium
Required for cell wall stabilization, cell function, and endospores
Magnesium
Required for chlorophyll, membranes, in ribosome stabilization, and cell energetics
Iron
Required for cytochrome pigments
Oxygen
Required for making organic compounds
Phosphorus
Required for nucleic acids, cellular energy transfer (ATP), phospholipids, and coenzymes
Sulfur
Required for protein structure and enzyme function
Potassium
Required for protein synthesis and membrane function
Nitrogen
Required to make proteins, DNA, RNA, and ATP
Carbon
Required to make proteins, carbohydrates, lipids, nucleic acids, and CO2
Structure of a bacterial cell wall
Semi-rigid, porous, and complex structure used to maintain cell shape, form, and to protect bacterial cells from bursting when water enters through osmosis
Proton motive force
Several enzymes facilitation the production of energy and the formation of proton motive force which is used to drive other transport mechanisms
What affect did the use of disinfectants have?
Significantly decreased fatality rates in surgical practice
Necrotizing fasciitis
Sreptococcus pryogenes causes flesh eating
Where do autotrophs derive their energy from?
Sunlight
In bacteria what is the site where there is energy production?
The cytoplasmic membrane which produces energy through a series of embedded proteins in the electron transport chain
Water
The most important molecule in any cell
pH
The negative log of the hydronium ion concentration in a solution (H+)
Isotonic solution
The solute concentration is equal inside & outside cell. Hence, net movement of water molecules in and out of the cell is the same.
Hypertonic solution
The solute concentration is greater outside the cell, thus water leaves the cell and the cell shrivels.
Hypotonic solution
The solute concentration is less outside the cell. Therefore, water enters the cell and may burst it
Microbiology
The study of both living microorganism and non-living infectious agents like viruses and prions
Koch's postulates
To say a particular organism is the causative agent of a disease, the etiologic agent must be: 1. Present in all infected patients with same symptoms 2. Isolated and grown in a pure culture 3. Injected in an experiment animal and disease reproduced 4. Re-isolated from the experimental animal
What are other methods of determining bacterial numbers?
Total cell mass, turbidity, or total weight
Chemolithoautotrophs
Use inorganic carbon for energy and CO2 as carbon source
Chemoorganoheterotrophs
Use organic compounds for energy and carbon source - Method humans and all other animals use for energy
Photoautotrophs
Use sunlight and CO2 to manufacture their own food
Conjugation pili (sex pili)
Used as DNA transfer tubes from one bacteria to another
Lysogenic life cycle
Viral genome is inserted into the host DNA
Adsorption
Virus binds to specific receptors on host cell
Akkermansia and christensenellacae (bacteria) are associated with what?
Weight gain
Is the cell membrane of a bacteria similar to the cell membrane of an animal?
Yes
Sexually transmitted viruses
can cause lesions on genitalia and/or cause systemic infections
Girolamo Fracastoro was the first to realize that microorganisms are involved in ______
causing diseases
A microscope with at least two lenses is considered a
compound microscope - Has 1 or 2 ocular lenses and several objected lens (e.g. 5x, 10x, 40x, 100x)
Most bacteria live in ____ or ____ solutions
isotonic or hypertonic
Structure of a virus
nucleic acid surrounded by a protein coat called a capsid
Prions are infectious _________
proteins
Robert Hook was the first person to observe ________
the basic units of life, which he called cells
Zoonotic viruses
transmitted from animal to human via animal vector
Viruses are obligate intracellular parasites. What does this mean?
viruses can only replicate within a host cell
