Micro Exam 2

Enriched media

(blood agar) • Supportive media supplemented with special nutrients.

Supportive media

(tryptic soy broth and agar) • Sustain growth of many microorganisms.

Psychrophiles

0 oC to 20oC

Psychrotrophs

0 oC to 35oC food spoilage

What are the phases of growth curve? Generation time?

1. Lag Phase • Cell synthesizing new components. • Replenish spent materials (that is, ribosomes and ATP). • To adapt to new medium or other conditions. • Eventually, cells replicate their DNA, increase in mass, and divide. 2. Exponential Phase • Rate of growth and division is constant and maximal. • Population is most uniform in terms of chemical and physical properties during this phase.• During exponential phase, cells grow as quickly as they can for the conditions available. • Final net growth increases with the initial amount of the limiting nutrient present. • Growth rate increases with nutrient concentration, but it saturates. 3. Stationary Phase • In a closed system, growth eventually ceases. • Total number of viable cells remains constant. • Balance between cell division and cell death. • Population may cease to divide but remain metabolically active. • Reasons for stationary phase: • Nutrient limitation • Limited oxygen availability • Toxic waste accumulation • Critical population density reached. 4. Death Phase • Number of viable cells declines exponentially, with cells dying at a constant rate. • Nutrient deprivation and the buildup of toxic wastes cause irreparable harm to the cells. 5. Long-Term Stationary Phase • Bacterial population continually evolves. • Process marked by successive waves of genetically distinct variants. • Natural selection occurs within a single culture. Generation (doubling) time (g): Time required for the population to double in size. • Varies depending on species of microorganism & environment

phases of microbial growth curve in proper sequence with the earliest phase first

1. Lag phase 2. Exponential phase 3. Stationary phase 4. Death phase 5. Long-term stationary phase

Mesophiles

20oC to 45oC

Fungi pH preference

4.0-6.0

Thermophiles

45 C to 85 C

Hyperthermophiles

85C to 100C

Biocide-

All Antimicrobial agents that control microorganisms. • Physical, chemical or biological oil spills

Visible light

At high intensities generates singlet oxygen 1 2 ( O ), a powerful oxidizing agent. • Carotenoid pigments protect many light-exposed microorganisms from photooxidation.

Which reproductive strategy is most common in bacteria? Endospore formation Multiple fission Budding Binary fission

Binary fission

Energy source

Chemoorganotrophs - obtain energy from the breakdown of organic molecules by fermentation or respiration. • Chemolithotrophs - oxidize inorganic ions to obtain energy to fix CO2. • Photoautotrophs - use photosynthetic pigments to fix CO2. • Photoheterotrophs - derive energy from photosynthesis, but their carbon comes from growth on organic molecules.

Complex medium

Contains some ingredients of nonspecific chemical composition. breakdown of yeast, beef, soy, and proteins

New appraoaches to culturing microbes.

Culturomics • Use miniature cultures and incubate in many different conditions to find the best one. Bring natural environment into the lab , (seawater). • Diffusion chamber that slows nutrients to diffuse but retains the microbes. • Dilution can contain a single cell. Co-culturing • Growth on animals or tissues in lab.

Selective toxicity

Death or inhibition of pathogen with minimal damage to host

Therapeutic dose

Drug level required for treatment of an infection

Defined/synthetic medium

Each ingredient can be defined with a chemical formula E.COLI

Neutrophiles

Grow best between pH 5.5-8. (Most bacteria and protists)

Acidophiles

Growth best between pH 0 and 5.5. fungi 4-6 arachaea

Alkaliphiles (alkalophiles)

Growth best between pH 8 and 11.5. • distributed among all three domains of life.

Carbon source

Heterotrophs - obtain carbon from organic compounds (meat and plant extracts are added to supply this nutrient) • Autotrophs - derive their carbon from fixing CO2.

Hypertonic solution

Higher solute concentration outside the cell than inside the cell.

Select all that apply Which two of the following activities occur during lag phase? Adaptation to accumulation of acids Initiation of DNA replication Synthesis of enzyme co-factors Release of toxins

Initiation of DNA replication Synthesis of enzyme co-factors

Salt-out (fungi & photosynthetic protists)

Keep salt ions outside of cell. • Synthesize compatible solutes (sucrose and polyols) that do not interfere with growth.

Toxic dose

Level at which drug becomes poisonous to host

Hypotonic solution

Lower solute concentration outside the cell than inside the cell. Most microbes live in hypotonic environment.

Protein structure stabilized by a variety of means

More H bonds. • More proline, less flexible peptides. • Chaperones aid in folding.

Ultraviolet (UV) radiation

Most lethal wavelength is 260 nm because it is absorbed by DNA. • DNA damage can be repaired by several repair mechanisms.

Which of the following has contributed the LEAST to antimicrobials currently in use? Multiple choice question. Plant natural products Chemical modification of antibiotics Soil bacteria and fungi Synthetic compounds

Plant natural products

Which process is critical to binary fission? Filamentation Flagellum synthesis Redistribution of ribosomes Replication of genome

Replication of the genome

Which process is critical to binary fission? Replication of genome Filamentation Flagellum synthesis Redistribution of ribosomes

Replication of the genome

Halophiles:

Require NaCl at a concentration above about 0.2 M.

Extreme halophiles

Require salt concentrations between 3 M and 6.2 M.

Terminology of microbial control.

Sterilization—process by which all living cells, spores, and acellular entities are destroyed or removed from an object. • Sterilant is the chemical agent. Disinfection—killing, inhibition, or removal of disease-causing microorganisms. • Disinfectants—agents, usually chemical, used for disinfection, usually used on inanimate objects. • Does not always sterilize as spores or a few organisms can remain. Sanitization—reduction of microbial population to levels deemed safe by public health standards. Antisepsis—destruction of microbes on living tissue. • Antiseptics—chemical agents applied to tissue to kill or inhibit growth of pathogen.

Ionizing radiation

X-rays and gamma rays • Cause mutations that indirectly result in death. • Disrupts chemical structure of many molecules. • Breaks H-bonds and destroys ring structures. • Bacterial endospores and Deinococcus radiodurans are extremely resistant to ionizing radiation.

streak plate

a technique for isolating pure cultures by spreading organisms on an agar plate soil from lab

Barotolerant—

adversely affected by increased pressure, but not as severely as nontolerant organisms.

Selective media—

allow the growth of particular microorganisms, while inhibiting the growth of others. nutrient agar

Which two groups of organisms reproduce primarily by binary fission? Multiple select question. archaea algae protozoa eukarya bacteria fungi

archaea bacteria

Many new antimicrobial agents have been produced by which two soil inhabitants? Bacteria Worms Fungi Protists Archaea

bacteria fungi

Broth cultures that are grown without the addition of fresh media are called ________ cultures.

batch

Broth cultures that are inoculated and allowed to grow without the addition of fresh media are called ______. axenic cultures continuous cultures pure cultures batch cultures

batch cultures

Reproductive strategies of bacteria v/s archaea.

binary fission - usually both bacteria can reproduce by forming a bud (bud formation) ex. Listeria monocytogenes bacteria go through multiple fission-progeny cells help w/in parent cells til theyre mature uninucliod spores- dispersal spores (fungi) ex. Dermocarpa

pour plate

diluted, hamburger from lab

Differential media—

distinguish among different groups of microbes and even permit tentative identification of microbes based on their biological characteristics. • Blood agar—distinguish between hemolytic versus nonhemolytic bacteria mcconkey broth

Some bacteria can produce multinucleoid filaments that Blank______. divide to form uninucleoid spores constrict the progeny cells in binary fission promote multiple fission are reproductive stalks that form buds

divide to form uninucleoid spores

Facultative anaerobe

do not require O2 but grow better in its presence

What is the term for the part of the microbial growth curve when cells are growing and dividing at the maximal rate for the current conditions? stationary phase lag phase death phase exponential phase

exponential phase

Which phase of the microbial growth curve is immediately before stationary phase? Exponential phase Lag phase Death phase Mobile phase

exponential phase

Chemotherapy

generic term that describes application of chemicals to kill microorganisms. cidal- kill

As a general rule, a better antimicrobial agent has a ________ (greater/smaller) therapeutic index

greater

Aerotolerant anaerobes

grow with or without O2.

A drug that disrupts a microbial structure or function not found in host cells generally has a Blank______ therapeutic index. Multiple choice question. moderate low high

high

Penicillin is considered to be the first true antibiotic, meaning that it Blank______. has only a bactericidal effect was sold commercially is active against a wide range of bacteria is a natural microbial product

is a natural microbial product

Z value

is the temperature change that decreases the microbial population by 90% (one log cycle).

D value

is time required to drop by 10-fold.

During the growth of a bacterial strain in batch culture, the synthesis of enzymes to consume a new carbon and energy source occurs during ______ phase. lag death exponential long-term stationary stationary

lag

When fresh growth medium is inoculated with a microbial culture there is typically a period of adaptation called the ___ phase

lag

Which is the term for the period of adaptation that typically occurs when fresh growth medium is inoculated with a microbial culture? lag phase exponential phase stationary phase death phase

lag phase

Xerotolerant

microbes that withstand high solute concentrations or the effects of dessication. • Microbes grow in desert regions, household dust, preserved foods

Because it is only effective against Gram-positive bacteria, vancomycin is classified as a(n) _______ spectrum drug.

narrow

Microaerophile

requires 2 to 10% O2

Peizophilic (barophilic)—

requires high pressure for growth. • Change membrane fatty acids to adapt to increasing pressure. • Lipids become more unsaturated and shorter.

Obligate aerobe

requires oxygen

Following binary fission, the progeny cells each have ribosomes because Blank______. ribosomes are abundant and do not require a partitioning mechanism ribosomes are partitioned to each cell pole by spindle fibers ribosomes are rapidly synthesized following cytokinesis ribosomes normally reside near the membrane at the cell poles

ribosomes are abundant and do not require a partitioning mechanism

Following binary fission, the progeny cells each have ribosomes because ______. ribosomes are partitioned to each cell pole by spindle fibers ribosomes normally reside near the membrane at the cell poles ribosomes are abundant and do not require a partitioning mechanism ribosomes are rapidly synthesized following cytokinesis

ribosomes are abundant and do not require a partitioning mechanism

A successful antimicrobial agent has the ability to kill or inhibit microbial pathogens with little or no damage to the host, a property called...

selective toxicity

Culture medium—

solid or liquid mixture of nutrients and other compounds. CONTAIN NUTRIENTS

The first drug to successfully treat tuberculosis was Blank______. Multiple choice question. Salvarsan sulfonamide streptomycin penicillin

streptomycin

Following binary fission, the progeny cells each have a nucleoid because Blank______. the nucleoid normally resides near the membrane at the cell poles the cell links DNA replication and septum synthesis to ensure nucleoid partitioning nucleoid-associated proteins also function to move chromosomes following replication the nucleoid is partitioned to each cell pole by spindle fibers during mitosis

the cell links DNA replication and septum synthesis to ensure nucleoid partitioning

The y-axis on a bacterial growth curve indicates Blank______. time the number of cells the rate of cell growth nutrient concentration

the number of cells

The x-axis on a bacterial growth curve indicates ______.

time

The degree of selective toxicity can be expressed in terms of the ratio of which two of the following? Multiple select question. lethal dose lysogenic dose toxic dose therapeutic dose

toxic dose therapeutic dose

Streptomycin is important historically because it was the first drug to successfully treat Blank______. fungal infections Staphylococcus infections syphilis tuberculosis

tuberculosis

Extremophiles

—Grow under harsh conditions that would kill most other organisms.

Osmotolerant

—microorganisms that can grow over wide ranges of water activity but optimally at higher levels.

Obligate anaerobe

—usually killed in presence of O2

Salt-in (archaeal halophiles)

• Accumulate K and Cl in cytoplasm. • Proteins need these high salt levels.