LSM3232 Prompts

Sec system transports what?

Unfolded proteins across or into the membrane

What does SecA do?

ATPase motor that pushes proteins through SecYEG

What happens to proteins without signal sequence?

They remain in the cytoplasm

What does Type VI secretion system do?

Contact-dependent killing of competitors

Two functions of bacterial capsule?

Immune evasion and shielding antigens

What is the S-layer?

Outer protein coat providing mechanical and stress protection

What directs cell division?

FtsZ ring at mid-cell

What prevents FtsZ ring at poles?

Min system

What prevents division over chromosome?

Nucleoid occlusion

Four flagella arrangements?

Monotrichous

Types of bacterial motility?

Brownian/sliding

Why does glucose inhibit lac operon?

Low cAMP so CAP inactive

Why is oxygen toxic to obligate anaerobes?

They lack SOD and catalase

Enzyme converting superoxide to hydrogen peroxide?

Superoxide dismutase

Example of acidophile and alkaliphile?

Lactobacilli and Vibrio cholerae

What do siderophores do?

Chelate iron for microbial use

Who produces pyoverdine and pyochelin?

Pseudomonas aeruginosa

What is VBNC?

Viable but non-culturable cells

Why VBNC microbes need neighbours?

They lack siderophores to acquire iron

Three methods to measure microbial growth?

Spectrophotometer

Most fresh foods Aw?

0.99

Why low-Aw food spoils in high RH?

Absorbs moisture → Aw increases → microbes grow

Why high-Aw food kept in low RH?

Prevents water loss and quality damage

Aw below which spoilage bacteria do not grow?

Below 0.91

Aw where molds grow?

Around 0.8

Intrinsic vs extrinsic factors?

Intrinsic = food properties

extrinsic = storage environment

Two intrinsic factors?

pH and water activity

Two extrinsic factors?

Temperature and relative humidity

What do protective cultures do?

Increase acidity and inhibit pathogens

What group does E. coli belong to?

Coliforms

Bread mold genus?

Rhizopus

Yeast used for beer and bread?

Saccharomyces

Difference between infection and intoxication?

Infection = organism multiplies

intoxication = toxin ingestion

Staph aureus intoxication incubation?

1–6 hours with nausea/vomiting

What causes fried rice syndrome?

Bacillus cereus

What causes cholera?

Vibrio cholerae

Foods transmitting Vibrio parahaemolyticus?

Raw/undercooked seafood

Why can’t viruses multiply in food?

Need specific host cells

Norovirus symptoms?

Vomiting and diarrhea

Hepatitis A incubation?

15–50 days with fever and jaundice

What does HACCP stand for?

Hazard Analysis Critical Control Point

Two selective media for coliforms?

MacConkey and EMB agar

HTST pasteurization?

71°C for 15 seconds

UHT conditions?

141°C for 2 seconds

Why UHT milk shelf-stable?

Commercially sterile including spores

Example of bacteriostatic method?

Refrigeration

Example of bactericidal method?

Sterilization at 121°C

Example of chemical preservative?

Benzoic acid

What % of environmental microbes are culturable?

≤1%

Why 16S rRNA used?

Conserved yet variable

Example of hyperthermophile?

Pyrococcus furiosus

US drinking water standard for coliforms?

0 per 100 mL

Main fungal cell wall component?

Chitin

Disease caused by Histoplasma capsulatum?

Histoplasmosis

Rose gardener’s disease organism?

Sporothrix schenckii

Fungus causing tinea versicolor?

Malassezia furfur

How diagnose Candida albicans?

Germ tube test

Yeast with large capsule in bird droppings?

Cryptococcus neoformans

Fungus causing PCP?

Pneumocystis jirovecii

Largest viruses producing pocks?

Poxviruses

Antigenic drift vs shift?

Drift = minor mutations

shift = reassortment

Why influenza keeps returning?

HA/NA changes via drift and shift

HIV’s target receptor and enzyme?

CD4 and reverse transcriptase

Two symptoms of AIDS?

Opportunistic infections and weight loss

Two tests for HIV?

ELISA and Western blot