Lab quiz 4

• Obligate Aerobe
• Obligate Anaerobe
• Facultative Anaerobes
• Microaerophiles
• Aerotolerant Anaerobes

requres oxygen for growth

cannot tolerate oxygen

they lack catalase and superoxide dismutase

Brewer's anaerobic jar

can grow in the presence of oxygen or absence via fermentation

require decreased oxygen (5-10% vs 20%) and increased carbon dioxide conditions.

Candle jar

indifferent to the presense of oxygen

do not require oxygen

Fluid thioglycollate medium

Resazurin dye - indicates the presence of oxygen 

Dye turns pink in the presence of oxygen

Middle and bottom of tube should remain color of agar

Gaspak - contains hydrogen and palladium which removes oxygen by forming water.

Indicator strip of methylene blue

Becomes colorless in the absence of oxygen

• E. coli - facultative - not motile
• C. rubrum - anaerobic
• M. luteus - microaerophil
• B. subtilis - aerobic

Cytochrome c oxidase

an enzyme of the bacterial electron transport chain

Gram negative organisms such as:

Enterobacteriaceae - all oxidase negative

Pseaudomonas, Alcaligenes, Neisseria - oxidase positive

• Staphylococcus - oxidase negative
• Micrococcus - oxidase positive

p-phenylenediamine dihydrochloride - substitutes for oxygen as an artificial electron acceptor

is colorless in its reduced state

in presence of cytochrome oxidase and oxygen, it is oxidized and appears purple

stab thioglycollate tube with needle all the way to the bottom. loosen caps

use a swab to pick up bacteria and put ampoule on it. wait for color change

negative result - no color or gray

positive result - purple

• a. faecalis - positive
• S. aureaus - negative

hydrogen peroxide h202 and superoxide

degrages hydrogen peroxide to water and free oxygen

• hemolytic streptococci - catalase negative
• hemolytic staphylococci - catalase positive

adding h202 to a bacterial sample on a slide

• positive reaction = bubbles
• negative reaction = no bubbles

• K. pneumoniae - positive
• S. salivarius - negative

the carbs (sugars) they are capable of fermenting

glucose - monosaccharide

• lactose, sucrose
• disacharides - must be cleaved into two monosaccharides before used as energy

phenol red - color reagent that is used as a pH indicator

• red - neutral pH
• yellow - acidic pH
• pink - alkaline pH

the organism does not ferment the carbohydrate but rather uses the protein nutrients in the broth resulting in alkaline byproducts

Durham tube - a small inverted tube used for trapping gas (CO2) that may be produced during fermentation

the broth will turn YELLOW and the durham tube may or may not contain gas

• Mannitol
• Sucrose
• Lactose
• Glucose

transfer pinpoint amount of bacteria to broth. loosen caps

• B. cereus
• E. aerogenes
• E. coli
• S. aureus

• m - negative
• s - AG
• l - A
• g - AG

• m - AG
• s - AG
• l - AG
• g - AG

• m - AG
• s - AG
• l - AG
• g - AG

• m - AG
• s - negative
• l - AG
• g - AG

Helicobacter pylori uses to neutralize stomach acids by splitting urea into carbon dioxide and ammonia so it can invade mucosal cells of the stomach and establish disease

Gram-negative rods of the genera Proteus and Morganella

break down the urea from the urea slant releasing ammonia which reacts with the pH indicator phenol red causing the slant to become alkaline resulting in bright pink color change

• negative result - yellow - no urea
• positive - bright pink

use urea slant - fishtail bacteria on top

• P. vulgaris - positive
• E. coli - negative

• gram -
• rod

• gram +
• rod

• gram + 
• cocci
• tetrad

• gram +
• rod
• chains or single

• gram -
• rod
• motile

• gram + 
• cocci
• grape like clusters

• gram - 
• rod

• garm + 
• cocci

• +
• rod

• gram - 
• rod

• gram - 
• rod

AB+

O-

• A
• B
• AB
• O