Microbio Exam 2

How do most bacteria and archaea reproduce?

Binary fission: one parent cell divides into two equal daughter cells.

What are the two major phases of the bacterial cell cycle?

1. DNA replication and partitioning. 2. Cytokinesis, which separates daughter cells.

What are the roles of the replisome and FtsZ?

Replisome: replicates DNA. FtsZ: forms the Z ring that helps divide the cell.

What are the four phases of a bacterial growth curve?

Lag phase, exponential (log) phase, stationary phase, and death phase.

What happens during stationary phase?

Cell growth balances cell death, so the number of viable cells stays constant.

What are the five oxygen requirements of microbes?

Obligate aerobes, facultative anaerobes, aerotolerant anaerobes, obligate anaerobes, and microaerophiles.

What is a biofilm?

A community of microbes attached to a surface and surrounded by a protective slime-like matrix (EPS).

What is quorum sensing?

Bacterial communication using chemical signals to coordinate behavior based on population density.

What happens during each step of binary fission?

The cell grows, elongates, copies its DNA, separates the chromosomes, and divides into two daughter cells.

What are ori and ter during chromosome replication?

ori is the origin where DNA replication begins. ter is the terminus where replication ends.

What is the divisome, and what does it do?

A group of proteins that assembles around the Z ring and helps complete bacterial cell division.

How do bactoprenol, MurJ, and PBPs contribute to peptidoglycan synthesis?

Bactoprenol carries NAM-NAG units. MurJ flips them across the membrane. PBPs help form peptide crosslinks.

What causes cells to enter stationary phase? What is RpoS's role?

Starvation, toxic waste, low oxygen, or high cell density. RpoS helps regulate the stress response through RNA polymerase.

What are VBNC cells and programmed cell death?

VBNC cells are alive but cannot grow on normal culture media. Programmed cell death involves cells dying and providing nutrients to survivors.

What is the difference between psychrophiles, psychrotrophs, mesophiles, thermophiles, and hyperthermophiles?

Psychrophiles: optimum ≤15°C. Psychrotrophs: 20–30°C. Mesophiles: 20–45°C. Thermophiles: 55–65°C. Hyperthermophiles: 85–113°C.

What are the differences between halophiles, extreme halophiles, osmophiles, and halotolerant organisms?

Halophiles require salt above 0.2 M. Extreme halophiles require over 2 M NaCl. Osmophiles prefer high sugar. Halotolerant microbes tolerate varying salt levels.

How do UV radiation and ionizing radiation damage microorganisms?

UV causes thymine dimers in DNA. X-rays and gamma rays damage cellular molecules and produce oxygen free radicals.

chemostat

controls growth using a limited nutrient supplied at a fixed rate

Turbidostat

adjusts flow to maintain a set cell density

What is sterilization?

The destruction or removal of all microbial life, including endospores and viruses.

What is disinfection?

Killing, inhibiting, or removing disease-causing microbes on nonliving objects.

What is antisepsis?

Using antimicrobial chemicals on living tissue to kill or inhibit disease-causing microbes.

What is the difference between a bactericide and a bacteriostatic agent?

Bactericide kills bacteria. Bacteriostatic agents stop or slow bacterial growth.

What is the difference between an antibiotic and a chemotherapeutic agent?

Chemotherapeutic agents treat infections through selective toxicity. Most are antibiotics.

What is a D value (decimal reduction time)?

The time needed to reduce a microbial population by 90%, or one log (10-fold) at a specific temperature.

What is a Z value?

The temperature increase needed to reduce the D value by 90% (tenfold).

What is pasteurization?

Heating below boiling temperature to reduce harmful microbes in products like milk, wine, and beer.

What are depth filters?

Thick layers of fibers that trap microorganisms throughout the filter. Sometimes use diatomaceous earth.

What are membrane filters, and what pore sizes are important?

Thin filters with specific pores. 0.2 µm removes bacteria; 0.02 µm is used to remove viruses.

What is a HEPA filter, and where is it used?

High-efficiency particulate air filter used in laminar flow hoods and biological safety cabinets.

What is the difference between UV and ionizing radiation?

UV damages DNA and penetrates poorly. Ionizing radiation damages cellular molecules and produces free radicals.

What are phenolics? Give an example.

Chemical disinfectants derived from phenol. They can be harsh and irritating. Lysol contains phenolics.

What are alcohols used for, and what can they not kill?

70–80% ethanol or isopropanol kills bacteria and fungi but does not kill bacterial spores.

What are heavy metals used for in microbial control?

They are usually bacteriostatic rather than bactericidal and can also be toxic to humans.

What are quaternary ammonium compounds (quats)?

Chemical agents related to ammonia and detergents. Only cationic forms are effective in microbial control.

What are sterilizing gases? Give two examples.

Gases such as ethylene oxide (EtO) and hydrogen peroxide vapor. They are microbicidal and sporicidal

What is selective toxicity?

The ability of a treatment to harm a pathogen without causing significant harm to the host.

What is the phenol coefficient test?

Compares a disinfectant's effectiveness to phenol. A higher coefficient means a better disinfectant.

What is phage therapy?

Using bacteriophages (viruses that infect bacteria) to treat bacterial infections.

What are bacteriocins?

Protein or peptide toxins produced by bacteria that inhibit similar or closely related bacterial strains.

Who was Paul Ehrlich, and what did he develop?

Early chemotherapy drugs, including trypan red and Salvarsan.

Ernest Duchesne

first discovered penicillin in 1896

Alexander Fleming

He accidentally rediscovered penicillin's antimicrobial activity.

Selman Waksman

Isolated Streptomycin, from the soil bacterium Streptomyces.

What is selective toxicity?

Damaging or killing microbes while causing minimal harm to the host.

What is a therapeutic dose?

The drug level needed to treat a particular infection.

What is the MIC?

Lowest drug concentration that prevents visible microbial growth.

What can affect the size of a disk diffusion zone?

Drug concentration, solubility, and diffusion rate.

How does the Etest work?

A drug-gradient strip creates an inhibition ellipse; its intersection gives the MIC.

Cell Wall Inhibitors

Penicillin and cephalosporins

Protein synthesis inhibitor

Tetracyclines and streptomycin

Metabolic antagonist

Sulfa drugs

Nucleic Synthesis Inhibitor

Quinolones

Why are fungal infections harder to treat than bacterial infections?

Fungi resemble human cells more closely, making selective toxicity difficult

What is zinc pyrithione?

A heavy-metal-based antifungal used in dandruff shampoos.

What does Tamiflu do?

It inhibits neuraminidase and is used to treat influenza

What are the four major anti-HIV drug targets?

NRTIs, NNRTIs, protease inhibitors, and fusion inhibitors.

What concentration must a drug reach to work?

Its concentration must exceed the pathogen's MIC.

What are metabolism, catabolism, and anabolism?

Metabolism: all chemical reactions in a cell. Catabolism: breaks molecules down. Anabolism: builds molecules.

What are oxidation and reduction?

Oxidation: loses electrons or hydrogen. Reduction: gains electrons or hydrogen. Remember: OIL RIG.

What are NAD⁺, NADP⁺, and FAD?

Electron carriers that accept and transfer electrons or hydrogen during metabolic reactions.

How do enzymes speed up reactions, and what can affect them?

They lower activation energy at the active site. Temperature, pH, and other extreme conditions can denature them.

What are the three major ways cells regulate metabolism?

Metabolic channeling, changing enzyme amounts through gene expression, and controlling enzyme activity.

What are the three things that flow through the biosphere?

Energy, carbon, and electrons.

What does the equilibrium constant (Keq) describe?

The relative amounts of products and reactants at equilibrium.

What does a negative ΔG mean?

The reaction releases free energy and is exergonic.

What does a positive ΔG mean?

The reaction requires free energy and is endergonic.

What is ATP hydrolysis?

ATP reacts with water and becomes ADP + Pi, releasing free energy.

What is coenzyme Q (ubiquinone)?

An electron carrier in the electron transport chain.

What is an apoenzyme?

The protein portion of an enzyme without its required cofactor.

What is a cofactor?

A nonprotein component needed for an enzyme to function.

What conditions can denature enzymes?

Extreme temperature, pH, or osmotic pressure.

What is competitive inhibition?

An inhibitor competes with the substrate for the enzyme's active site.

What is noncompetitive inhibition?

An inhibitor reduces enzyme activity without competing for the active site.

What is allosteric regulation?

A regulator binds reversibly to a site separate from the enzyme's active site.

What is feedback inhibition?

A pathway's end product inhibits an enzyme earlier in that pathway.

What is a pacemaker enzyme?

An enzyme controlling the slowest, rate-limiting reaction in a pathway.

What are isoenzymes?

Different forms of an enzyme that can be independently regulated.