Chapters 6 and 7: Microbial Growth and Control - Vocabulary Flashcards

Vocabulary flashcards covering key terms from Chapter 6 (Microbial Growth) and Chapter 7 (Control of Microbial Growth), including growth, media types, microbial classifications, preservation methods, and disinfection/sterilization concepts.

bacteriostatic

Inhibits the replication rate of bacteria; bacteria remain viable but reproduce slowly.

bactericidal

Kills bacteria; cells die rather than just inhibiting growth.

psychrophiles

Cold-loving bacteria; thrive at low temperatures.

mesophiles

Moderate-temperature-loving bacteria; prefer moderate temps; overlap with psychrophiles.

thermophiles

Heat-loving bacteria; prefer high temperatures.

extremophiles

Organisms (often including archaea) that thrive in extreme environmental conditions.

extreme thermophiles

Thermophiles that thrive at very high temperatures (often associated with archaea).

acidophiles

Bacteria that prefer acidic environments (low pH).

neutrophiles

Bacteria that prefer near-neutral pH (approximately 6.5–7.5).

alkalophiles

Bacteria that prefer basic/alkaline environments (high pH).

pH range of E. coli

Optimum around pH 6–7 (neutrophile); can survive from pH 4.4 to 9.0.

pH range of Staphylococcus aureus

Optimum around pH 7–7.5; can survive from pH 4.2 to 9.3.

halophiles

Organisms that require or tolerate salt; mild (~16%), moderate (6–15%), extreme (15–30%) salt ranges.

phototrophs

Organisms that use light as an energy source.

photoautotrophs

Energy source: light; carbon source: CO2.

photoheterotrophs

Energy source: light; carbon source: organic compounds.

chemoautotrophs

Energy source: inorganic compounds; carbon from CO2.

chemoheterotrophs

Energy source: organic compounds; carbon from organic compounds.

nitrogen in bacteria

Essential element used in amino acids, nucleotides, coenzymes, etc.

phosphorus in bacteria

Essential for nucleic acids, ATP, and other cellular components.

sulfur in bacteria

Constituent of amino acids (cysteine, methionine) and some vitamins.

trace elements

Mineral cofactors (e.g., iron, chlorine) required in small amounts; assist enzyme function.

aerobic vs anaerobic

Oxygen requirements: aerobes require oxygen; anaerobes do not.

facultative anaerobe

Can grow with or without oxygen; flexible metabolism.

obligate anaerobe

Cannot tolerate oxygen; must grow in its absence.

aerotolerant anaerobe

Fermentation-based metabolism regardless of oxygen presence; not harmed by oxygen.

generalized media

Nutrient-rich media (e.g., nutrient agar) that support growth of a wide variety of bacteria.

selective media

Media that favor growth of particular groups by inhibiting others (e.g., salt selects for certain bacteria).

differential media

Media that differentiate colonies by a visible characteristic (often color).

EMB medium

Eosin Methylene Blue differential medium; darker colors indicate greater lactose fermentation by Gram-negative bacteria.

enrichment culture

Liquid medium designed to preferentially enhance growth of a targeted organism from a mixed culture.

viruses and culture media

Viruses cannot be grown on standard culture media and require living cells.

lyophilization

Freeze-drying; long-term storage of bacteria by removing water while frozen.

cryopreservation

Long-term storage by freezing in liquid nitrogen (~-196°C).

binary fission

Asexual reproduction in bacteria; a single cell divides to form two genetically identical cells.

generation time

Time required for a bacterial population to double.

growth curve phases

Lag: adjustment period; Log: exponential growth; Stationary: growth equals death; Death: death exceeds growth.

closed system

Environment with no addition of nutrients and no removal of waste.

membrane filtration (direct count)

Direct counting method by filtering a sample and counting resulting colonies; 30–300 colonies is statistically significant.

spectrophotometer (indirect count)

Measures light absorbance to estimate cell density; fast but cannot distinguish viable cells.

viability testing

Plating and incubating to determine the number of viable cells present.

sterilization

Killing all microorganisms, including endospores.

disinfection

Killing vegetative cells; does not affect endospores.

antisepsis

Killing vegetative cells on living tissue (human host).

sanitation

Reducing microbial counts to public health standards; not necessarily sterile.

Pseudomonas

Bacterium that can survive in disinfectants; a concern in medical facilities due to resistance.

endospores

Resistant dormant forms of certain bacteria that survive harsh conditions and disposal methods.