Methods of Studying Microorganisms

A comprehensive set of vocabulary flashcards covering microbial identification, isolation techniques, culture media, staining methods, and molecular analysis based on clinical bacteriology lecture notes.

Kary Mullis

The inventor of PCR and the reason for a major breakthrough in genotypic microbial identification.

LUCA

The Last Universal Common Ancestor; an ancestral form of organism that appeared billions of years ago that modern microbes still resemble in mechanism and biochemistry.

Ubiquitous

A term meaning microorganisms are found everywhere in nature, including soil, water, and air.

Isolation

A technique used to obtain microbes from their source or separate them from their natural environment.

Inoculation

The process of introducing microorganisms into a culture medium.

Pure culture

A bacterial culture that is no longer mixed with other species of bacteria.

Bacterial colony

A visual manifestation or growth of bacteria in a medium, typically containing millions of individual cells.

Biofilm

A specialized community of different species of bacteria, fungi, and protozoans that form a colony-like community on surfaces.

DME

Direct Microscopic Examination; a process involving staining and examining sterile specimens to provide a presumptive idea of organisms present.

Quadrant streak method

The specific type of streak plate method most commonly used in clinical laboratories for pure culture isolation.

Spread plate method

An isolation method using an L-rod to distribute microorganisms evenly, often used for quantitative colony counts ($\text{CFU/mL}$).

Pour plate method

A method where the sample is added to petri dishes followed by nutrient agar; used to grow anaerobic or fastidious cultures.

Selective medium

A growth medium containing an inhibitory agent, such as bile salt, which allows only certain organisms to grow.

MRC-5

A viral culture cell line consisting of fibroblasts derived from the lung cells of an aborted Caucasian fetus.

HEp-2 Cells

A viral culture cell line derived from HeLa cells, named in tribute to Henrietta Lacks.

Enrichment medium

A medium designed to increase the yield of microbes that are hard to recover or present in low concentrations before transfer to selective media.

Slant medium

A solid medium in a tube inoculated in a zigzag motion to observe color changes indicating the utilization of compounds like citrate.

Butt medium

A solid medium inside a tube, such as SIM, inoculated by stabbing at the center to assess motility and indole production.

TSIA

Triple Sugar Iron Agar; a medium containing lactose, glucose, and sucrose used to detect sugar fermentation and differentiate aerobic versus anaerobic growth.

Standard Incubation Temperature

The temperature typically maintained for microbial growth, specified as 35 \text{ } \bgroup \text{\textpm} \bgroup 2^\text{\textdegree}\text{C}.

Cold aerobic technique

A cultivation method where a microbe is grown at $4^\text{\textdegree}\text{C}$ to enhance its growth.

Reducing agent

Substances like Thioglycolate medium, pyrogallic acid, and NaOH used in anaerobic culture methods.

Candle jar

A container used for anaerobic cultivation where a lit candle consumes oxygen until it goes out, creating an anaerobic environment.

Presumptive result

An educated guess of an isolate's identity based on DME, macroscopic, and microscopic examinations before definitive diagnosis.

Darting motility

A type of motion characteristic of Vibrio and Campylobacter which are peritrichous (covered with flagella).

Hanging Drop Method

A microscopic technique using a concavity slide used to observe bacterial motility.

Positive Staining

A simple staining method, such as Methylene Blue, where the dye is attracted to and stains the cell itself.

Negative Staining

An indirect staining method using India Ink or Nigrosine Dye that stains the background rather than the cell.

Gram staining mordant

Grams iodine; it forms an insoluble complex with crystal violet that is trapped in the thick peptidoglycan layer of Gram-positive bacteria.

Acid Fast Bacilli Staining

A specialized differential staining method used to detect Mycobacterium tuberculosis due to its mycolic acid content.

Ziehl-Neelsen

The "hot method" of acid-fast staining that uses heat as a mordant to allow carbolfuchsin to penetrate the cell wall.

Schaeffer and Fulton

A specific staining method used to identify bacterial spores.

Catalase test

A biochemical test used to separate the genus Staphylococcus (positive) from Streptococcus (negative).

Kirby-Bauer Technique

An antimicrobial susceptibility testing method using antibiotic disks to measure the zone of inhibition (ZOI).

MIC

Minimum Inhibitory Concentration; the lowest concentration of an antibiotic that inhibits visible growth.

PCR Cycle

A repetitive molecular process involving DNA denaturation, annealing, and extraction/extension.

Agarose gel electrophoresis

A molecular analysis technique that separates DNA fragments based on size as they migrate toward a positive pole.

NCBI

National Center for Biotechnology Information; an open-source public database established in 1988 for molecular biology information.