bi374 final exam

Food spoilage

unwanted food change humans

Highly perishable foods

meat fish dairy eggs

Water activity

measures water available microbes

Pickling

acid added prevents growth

Fermentative preservation

natural acid microbial action

Canning

heat kills all microbes

Psychrotolerant microbes

grow despite refrigeration temps

Stable foods

low water activity level

Freezing preservation

used at negative twenty

Salting and drying

lowers water activity level

Primary treatment

removes solids physically screens

Secondary treatment

biological organic matter removal

Anoxic treatment

makes methane and CO2

Aerobic treatment

trickling filter activated sludge

Tertiary treatment

removes phosphate nitrate chemically

BOD

measures oxygen demand water

Potable water

safe drinkable clean water

Sedimentation

settling via flocculation step

Coliforms

indicator bacteria fecal contamination

MPN and MF

coliform detection test methods

Molecular cloning

isolating DNA into vector

Ideal cloning host

fast growing nonpathogenic stable

Restriction enzymes

cut DNA at sites

Ligase

glues DNA fragments together

PCR

amplifies DNA in lab

Site-directed mutagenesis

creates specific gene mutations

Insulin production

two chains joined chemically

Transgenic organisms

foreign DNA inserted genome

Agrobacterium tumefaciens

transfers DNA into plants

Ice-minus bacteria

prevents frost damage plants

Fermentation

anaerobic breakdown organic compound

Homofermentative

produces mostly lactic acid

Heterofermentative

makes lactate ethanol CO2

Propionate fermentation

made by Clostridium propionicum

Succinate-propionate pathway

gives Swiss cheese bubbles

Butyric acid fermentation

produces butyrate acetate hydrogen

Mixed acid fermentation

enteric bacteria multiple products

Ferredoxin

low redox electron carrier

Hydrogen production

regenerates NAD plus balance

Acetogens vs methanogens

acetate versus methane producers

Signal transduction

detect transmit then respond

Two-component system

sensor kinase response regulator

Chemotaxis

movement toward or away

CheA

sensor kinase detects signal

CheY

response regulator controls flagella

Positive chemotaxis

movement toward attractants nutrients

Negative chemotaxis

movement away from toxins

Quorum sensing

bacteria communicate via chemicals

Autoinducers

signal molecules bacteria release

AHL

acylated homoserine lactone signal

Biofilm

bacteria community stuck surface

Stage one

initial attachment to surface

Stage two

irreversible attachment then colony

Mature biofilm

forms protective matrix layer

Dispersion

cells leave mature biofilm

Biofilm protection

resists antibiotics and disinfectants

Dental plaque

biofilm on tooth surface

Streptococcus mutans

key dental plaque bacteria

Biofilm benefit

better nutrient retention sharing

Biofilm benefit two

cooperative metabolism among cells

Mechanosensitive channels

release solutes prevent bursting

Heat shock response

proteins unfold and aggregate

Heat-shock proteins

refold or remove proteins

Thymine dimers

UV damages DNA structure

Photoreactivation

light repairs thymine dimers

Nucleotide excision repair

dark repair cuts damage

SOS response

last resort survival mechanism

RecA

key protein triggers SOS

Superoxide dismutase

converts superoxide to peroxide

Catalase

breaks peroxide into water

Opportunistic microbes

harmless until conditions change

Skin microbiota

mostly gram positive resident

Propionibacterium acnes

causes skin acne irritation

Helicobacter pylori

colonizes acidic stomach wall

Exotoxin

protein released while growing

Endotoxin

cell bound released upon lysis

Botulinum toxin

causes flaccid muscle paralysis

Tetanus toxin

causes spastic muscle rigidity

Adhesins

help bacteria attach tissue

Siderophores

help bacteria acquire iron

Endemic disease

constantly present low incidence

Epidemic

sudden rise in cases

Pandemic

epidemic across many countries

Sporadic

isolated separated case occurrences

Outbreak

sudden cluster of cases

Carrier

infected without obvious symptoms

Zoonosis

animal disease infects humans

Foodborne intoxication

preformed toxin causes illness

Foodborne infection

live microbes multiply host

Fomites

objects that transmit pathogens