Microbes and Man Exam 2 (Shorter Version)

Obligate intracellular parasite

A pathogen (like a virus) that can only replicate inside a living host cell.

Structure of a virus

Nucleic acid (DNA or RNA) enclosed within a protein coat called a capsid.

Lytic vs. Lysogenic cycle

Lytic results in host cell lysis and death; Lysogenic integrates viral DNA into host genome as a prophage without immediate lysis.

Prophage

Viral DNA integrated into the bacterial chromosome during the lysogenic cycle.

Bacteriophage therapy

The therapeutic use of targeted viruses to treat antibiotic-resistant bacterial infections.

Viroid

An infectious sub-viral agent made solely of single-stranded RNA (ssRNA) with no protein coat, primarily infecting plants.

Prion

An infectious protein particle containing no nucleic acid that causes misfolding of healthy brain proteins (PrP^c -> PrP^Sc).

Diseases caused by prions

Transmissible Spongiform Encephalopathies (TSEs) including CJD, Mad Cow Disease (BSE), Scrapie, Chronic Wasting Disease, and Kuru.

Biological vector vs. Mechanical vector

Biological: Parasite develops/multiplies inside vector; Mechanical: Vector passively transfers pathogen on body surfaces.

Helminths

Multicellular parasitic flatworms or roundworms; often transmitted via ingestion of cysts in meat.

Arthropod vector examples

Ticks (Lyme disease), Fleas (Plague), Mosquitoes (Malaria/Zika), Tsetse flies (Sleeping sickness), Copepods (Guinea worm).

Glycolysis net yield

2 ATP, 2 NADH, and 2 Pyruvic acid per glucose molecule under anaerobic conditions.

Fermentation ATP yield

0 ATP beyond glycolysis; regenerates NAD+ to keep glycolysis running.

Aerobic respiration net ATP yield

38 ATP per glucose molecule in prokaryotes.

Binary fission

Microbial cell division where a single parent cell splits into two equal daughter cells.

Phases of bacterial growth curve

1. Lag Phase, 2. Log (Exponential) Phase, 3. Stationary Phase, 4. Decline/Death Phase

Log (Exponential) phase

Phase of growth characterized by rapid cell division and minimal doubling time.

Turbidity measurement limitation

A spectrophotometer measures cloudiness (total biomass) but cannot distinguish between live and dead cells.

Plasmolysis

Shrinkage of the bacterial cytoplasm caused by hypertonic solutions (water rushing out of the cell).

Autoclave operating standard

121 degrees C at 15 lb/sq in pressure for 20 minutes.

Pasteurization vs. Sterilization

Pasteurization uses heat to kill pathogens and lower bacterial count without sterilizing the liquid.

Sulfanilamide mechanism

Competitively inhibits bacterial folic acid synthesis by acting as an analog to PABA.

Mechanism of Penicillins

Inhibit bacterial cell wall synthesis by preventing peptidoglycan cross-linking.

Beta-lactamase

A bacterial enzyme that breaks the beta-lactam ring of penicillin, conferring resistance.

Quinolones (e.g., Ciprofloxacin) target

Inhibit bacterial DNA gyrase, stopping DNA replication.

Direction of DNA synthesis

5' to 3' direction exclusively by DNA polymerase.

Okazaki fragments

Short fragments of DNA synthesized discontinuously on the lagging strand during replication.

Central Dogma of Molecular Biology

DNA -> Transcription -> RNA -> Translation -> Protein

Start codon

AUG (codes for Methionine).

Stop codons

UAA, UAG, and UGA.

Frameshift mutation

Deletion or insertion of nucleotides not in multiples of 3, shifting the reading frame completely downstream.

Transformation

Direct uptake of naked exogenous DNA from the surrounding environment by a bacterial cell.

Transduction

Transfer of bacterial host genes from one bacterium to another via a bacteriophage virus.

Conjugation

Direct transfer of genetic material (plasmids) between bacterial cells via physical contact using a sex pilus.

Restriction Endonucleases

Bacterial enzymes that cut double-stranded DNA at specific recognition sites.

Methanotrophs

Bacteria that consume methane and can metabolize toxins into harmless CO2 and salts during bioremediation.

Pathogen in Typhoid Mary case

Salmonella typhi, transmitted via the fecal-oral route.

Healthy carrier

An individual infected with a pathogen who shows no clinical symptoms but can transmit the disease to others.

Discovery of Penicillin

Discovered by Alexander Fleming in 1928; mass-produced and purified by Howard Florey and Ernst Chain.

Discovery of Streptomycin

Isolated by Selman Waksman from soil Streptomyces; provided the first effective treatment for tuberculosis.