Chapter 7: Microbial Nutrition, Ecology, and Growth

Vocabulary-style flashcards covering major topics from the lecture notes: ecological associations, biofilms, transport mechanisms, nutritional needs, growth factors, oxygen and environmental requirements, and growth dynamics.

Mutualism

Obligatory, dependent symbiotic relationship; both members benefit.

Commensalism

Symbiotic relationship where the commensal benefits and the host is not harmed.

Parasitism

Symbiotic relationship where the parasite benefits and the host is harmed.

Syntrophy

Cooperative interaction where members share nutrients.

Antagonism

Non-symbiotic interaction where one organism inhibits or destroys another.

Symbiotic

Two organisms live together in a close partnership; relationships may be obligatory.

Nonsymbiotic

Organisms that are free-living; relationships are not required for survival.

Biofilm

Community of microorganisms attached to a surface, embedded in an extracellular matrix and forming layered structures.

Quorum sensing

Cell-to-cell communication that coordinates group behaviors in biofilms and communities.

Endocytosis

Process of taking substances into a cell via vesicles; requires energy.

Phagocytosis

Endocytosis of solid particles or cells.

Pinocytosis

Endocytosis of liquids; ingestion of fluids.

Diffusion

Movement of molecules down a concentration gradient; passive (no energy).

Osmosis

Diffusion of water across a semipermeable membrane.

Facilitated diffusion

Passive transport aided by carrier proteins; moves down gradient.

Active transport

Energy-dependent transport across a membrane, often against a gradient.

Carrier-mediated active transport

Active transport using membrane permeases to move specific solutes with energy.

Group translocation

Active transport where the transported molecule is chemically modified during transport.

Exocytosis

Release of contents from a vesicle to the exterior of the cell.

Saprobes

Free-living microorganisms that feed on organic detritus from dead organisms.

Parasite

An organism that feeds on a host; benefits at the host's expense.

Pathogen

A parasite that causes disease.

Heterotroph

Obtains carbon from organic compounds produced by other living organisms.

Autotroph

Uses inorganic carbon (e.g., CO2) as its carbon source.

Chemoorganotroph

Gains energy from organic chemical compounds.

Chemolithotroph

Gains energy from inorganic chemical compounds.

Phototroph

Gains energy from light via photosynthesis.

Growth factors

Organic compounds that organisms cannot synthesize and must obtain from the environment (e.g., essential amino acids, vitamins).

Capnophile

Grows best at higher CO2 tensions than normally present.

Psychrophile

Optimum growth temperature below 15°C; can grow at 0°C.

Mesophile

Optimum growth temperature between 20°C and 40°C (many human pathogens).

Thermophile

Optimum growth temperature above 45°C.

Barophile

Requires high pressure to grow; ruptures under normal atmospheric pressure.

Halophile

Requires high salt concentration for growth.

Osmotolerant

Tolerates high solute concentrations but does not require them.

Neutrophile

Grows best at near-neutral pH (around pH 6–8).

Acidophile

Grows in acidic environments (low pH).

Alkalinophile

Grows in alkaline environments (high pH).

Microaerophile

Requires only a small amount of oxygen.

Aerobe

Uses oxygen and detoxifies it; overall category of organisms that require oxygen.

Obligate aerobe

Cannot grow without oxygen.

Facultative anaerobe

Uses oxygen but can grow without it.

Anaerobe

Does not utilize oxygen.

Obligate anaerobe

Lacks enzymes to detoxify oxygen; cannot survive in oxygen.

Aerotolerant anaerobe

Does not utilize oxygen but can survive in its presence.

Growth factors

Organic compounds organisms must obtain from their environment because they cannot synthesize them.

Niche

Totality of adaptations an organism has for its habitat.

Oxygen by-products/toxins

Reactive oxygen species formed during metabolism; cells use enzymes like SOD and catalase to neutralize them.

Oxygen requirement categories

Different classes (aerobe, obligate aerobe, facultative anaerobe, microaerophile, anaerobe, obligate anaerobe, aerotolerant) describing how microbes deal with oxygen.

Capnophile (revisited)

Grows best with higher CO2; often used to describe certain pathogens like N. gonorrhoeae in clinical settings.

Niche adaptation

How environmental factors select for specific enzyme activities and metabolic capabilities.

Generation time

Time required for a microbial population to double (complete fission cycle).

CFU (Colony Forming Unit)

A unit used to estimate viable cell or microbial colony counts from a sample.

Viable plate count

Method of estimating number of viable cells by counting colonies formed on agar.

Growth curve phases

Lag phase (adjustment), Exponential (log) phase (rapid growth), Stationary phase (growth rate equals death rate), Death phase (deaths exceed growth).