Microbiology Lab Review: Bacterial Enrichments, Growth Characteristics, and Biochemical Tests

Vocabulary flashcards covering bacterial enrichments, oxygen requirements, cellular morphology, and biochemical identification tests from the microbiology lab lecture.

Purple sulfur bacteria

Bacteria that grow phototrophically in the absence of oxygen when provided with a light source.

Streptomyces

A genus within the Actinomyces group comprising species that produce the majority of antibiotics.

Obligate aerobe

An organism, such as Micrococcus, that strictly requires the presence of oxygen to grow.

Facultative anaerobe

An organism, such as Staph, that can grow in either the presence or absence of oxygen.

Azotobacter

Bacteria enriched for their specific ability to fix nitrogen pulled directly from the environment and air.

Ashby's glucose media

A specialized broth lacking nitrogen (such as ammonia or amino acids) used to enrich for nitrogen-fixing bacteria.

Oxidase test

An identification test targeting cytochrome c or related enzymes that yields a bright pink color.

Durham tubes

Tiny glass tubes placed inside fermentation broths to trap gas byproducts, causing them to float.

Shake tubes

Tubes prepared with melted agar to eliminate oxygen, used to distinguish aerobic versus anaerobic growth based on where organisms grow along the oxygen gradient.

Motility test

A procedure where solidified agar is stabbed with bacteria to determine whether cells migrate through the medium using flagella or remain in one spot.

Bromocresol purple plates

Media containing a pH indicator used to identify acid production from glycerol when bacteria are grown aerobically or anaerobically.

TSY media

A rich, non-selective media used on agar slants primarily for the convenient long-term storage of isolated bacteria.

Micrococcus morphology

Slightly larger coccus cells that arrange and grow as pairs or tetrads forming matte/buttery domes

Staphylococcus morphology

Cocci that tend to be smaller than Micrococcus and grow in random, irregular clusters.

Catalase test

A test that checks for an enzyme capable of breaking down toxic oxygen species such as hydrogen peroxide.

What do staph produce when grown aerobically on glycerol?

Acid

Acintomycetes structure and history?

Grow in filamentous structure and were thought to be afungus

What is a pure culture?

A pure culture in the context of microbiology is a culture that has grown from a single cell, so it is a genetically clonal population.