bi374 lab exam

Ammonification

proteins broken into ammonia

Nitrification

ammonia oxidized to nitrate

Denitrification

nitrate reduced to N2

Nitrogen fixation

N2 converted to ammonia

Nitrogenase

fixes atmospheric nitrogen gas

Durham tube

traps nitrogen gas produced

P. aeruginosa

positive control, full denitrification

E. coli

negative control, stops at nitrite

Nitrate reductase

nitrate to nitrite enzyme

NA

free media

Sulfur oxidation

S compounds to sulfate

Starkey broth

uses elemental sulfur source

Thiosulfate broth

uses sodium thiosulfate source

Bromocresol purple

turns yellow when acidic

Sulfuric acid

lowers pH, causes yellowing

Acidithiobacillus

acid

Sulfate reduction

anaerobic, produces H2S

Desulfovibrio

primary sulfate reducing bacteria

Dissimilatory reduction

sulfate as electron acceptor

Wastewater sludge

inoculum source for lab

Floral succession

bacterial species change over time

Leuconostoc

early sauerkraut fermenter, heterolactic

Lactobacillus

late sauerkraut fermenter, acid

Homolactic

produces only lactic acid

Pasteurization

kills pathogens before fermenting

Yogurt starter

Lactobacillus and Streptococcus cultures

Alcoholic fermentation

sugar to ethanol, CO2

Specific gravity

measures sugar via hydrometer

Saccharomyces cerevisiae

wine fermentation yeast

MacConkey agar

selects Gram

Antibiotic

Producing Bacteria

Actinomycetes

mycelium

Antibiosis

microbial competition via antibiotics

AIA

selective media for Actinomycetes

Air

drying

Zone of inhibition

clear ring, antibiotic works

Serial dilution

reduces bacterial concentration stepwise

Streptomyces

major antibiotic

Indicator organisms

test antibiotic spectrum

Broad spectrum

kills Gram

3

way streak

Mesophile

grows 10

Thermophile

grows 40

Thymine dimer

UV

Photoreactivation

light

Penicillin G

targets Gram

Streptomycin

targets 30S ribosome broadly

Novobiocin

inhibits DNA gyrase enzyme

Vancomycin

targets Gram

Proton motive force

disrupted by pH extremes

Cardinal temperatures

min, optimum, max growth

Viable count range

30–300 colonies only

CFU/mL formula

colonies × dilution × volume

Crystal violet

primary purple stain

Decolorizer

removes dye, gram

Gram stain result

positive purple, negative pink

Sulfur reduction

anaerobic, makes H2S

Reduction sites

sewage, sediment, rumen

Sulfur oxidation

needs oxygen, water

Oxidation effect

lowers pH

Desulfovibrio

key sulfur reducer

Floral succession order

coliforms, Leuconostoc, Lactobacillus

PCA media

grows all bacteria

MacConkey media

gram

ST and LB

S. thermophilus, L. bulgaricus

Hydrometer measures

specific gravity, sugar

Actinomycete life cycle

fungus

Substrate mycelium

grows into medium

Aerial hyphae

multigenomic, grows upward

Sporulation

forms single

Drying soil

isolates spore

Mesophiles range

10°C to 45°C

Thymine dimer

UV DNA damage

Photoreactivation

light repairs dimer

Excision repair

cuts, resynthesizes DNA

Spread plating

isolates single colonies