MCB 2610 - Microbial Growth, Nutrition, and Control Vocabulary Flashcards

Comprehensive vocabulary flashcards covering microbial reproduction, growth curves, physical/chemical requirements, culture media, biofilms, staining techniques, biosafety levels, and methods of microbial control.

Binary Fission

The process where a bacterial chromosome replicates and attaches each copy to distinct membrane sites, the cell elongates without dissolving a nuclear membrane or forming a mitotic spindle, pinches centrally, and forms a septum to divide into two mature daughter cells.

Generation Time (Doubling Time)

The time required for one bacterial cell to divide into two cells, thereby doubling the total population size.

Lag Phase

A transition state in a closed growth system where dormant cells switch metabolic machinery to active growth, resulting in equal cell division and cell death rates ($n = 0$).

Log (Exponential) Phase

The phase of active binary fission where cells double every generation period at a constant logarithmic rate; cells are metabolically most active and most sensitive to antimicrobial drugs during this phase.

Bacterial Growth Curve

A graphic representation of bacterial population size in a closed system over time, displaying lag, log, stationary, and death phases.

Stationary Phase

The growth phase where nutrient depletion and waste accumulation cause the rate of new cell production to balance and equal the rate of cell death.

Death Phase

The growth phase where excessive waste buildup and extreme nutrient exhaustion cause cell death to outpace cell division exponentially.

Biofilm

An organized, multi-species microbial community living attached to a surface and embedded in a self-produced matrix of extracellular polymeric substances (EPS).

Quorum Sensing

A chemical cell-to-cell signaling system using autoinducer molecules that enables microbes to sense population density and activate coordinated population-wide behaviors.

Bdellovibrio bacteriovorus

A small, flagellated, obligate predatory Gram-negative bacterium that invades, consumes, and lyses other Gram-negative bacteria (such as E. coli) from the inside out.

Endospore

A dormant, non-vegetative, highly resistant structure produced inside certain bacterial cells through sporulation to protect the genome from extreme heat, desiccation, radiation, and chemicals.

Schaeffer-Fulton Method

An endospore staining procedure using malachite green with heat as the primary stain, a water wash decolorizer, and safranin counterstain to visualize green endospores within pink/red vegetative cells.

Capsule

An outer gel envelope or glycocalyx composed of polysaccharides surrounding the bacterial cell wall that prevents phagocytosis by host immune cells.

Negative Staining Technique

A staining procedure using India ink or nigrosin to stain the background dark, leaving uncharged structures like capsules visible as clear halos around stained cell bodies.

Prototrophs

Wild-type organisms capable of synthesizing all required cellular components from basic organic carbon sources and inorganic nutrients.

Auxotrophs

Mutant organisms that have lost the ability to synthesize one or more essential organic growth factors and must acquire them from the environment.

Psychrophiles

Cold-loving microorganisms that grow at temperatures between $-20^\text{C}$ and $10^\text{C}$.

Psychrotrophs (Psychrotolerants)

Microorganisms that grow between $0^\text{C}$ and $30^\text{C}$, primarily responsible for food spoilage in refrigerated environments.

Mesophiles

Moderate-temperature microorganisms growing between $10^\text{C}$ and $50^\text{C}$, including normal human microbiota and human pathogens ($37^\text{C}$).

Thermophiles

Heat-loving microorganisms that grow at elevated temperatures between $40^\text{C}$ and $75^\text{C}$.

Extreme Thermophiles (Hyperthermophiles)

Microorganisms adapted to extreme heat environments that grow between $65^\text{C}$ and $120^\text{C}+$.

Plasmolysis

The shrinkage of a bacterial cell's plasma membrane away from its cell wall caused by osmotic water loss in hypertonic environments.

Obligate Aerobes

Organisms that require oxygen ($\text{O}_2$) for respiration, grow only where high concentrations of diffused oxygen exist, and possess catalase and superoxide dismutase (SOD).

Facultative Anaerobes

Organisms that perform aerobic respiration in the presence of $\text{O}_2$, but switch to fermentation or anaerobic respiration when $\text{O}_2$ is absent.

Obligate Anaerobes

Organisms unable to use oxygen that are killed by toxic oxygen forms due to a lack of neutralizing enzymes.

Aerotolerant Anaerobes

Organisms that cannot use oxygen for growth but tolerate its presence because they possess the SOD enzyme to partially neutralize toxic oxygen forms.

Microaerophiles

Organisms requiring oxygen in reduced concentrations ($2\% - 10\%$) lower than atmospheric levels, producing lethal amounts of toxic oxygen species if exposed to normal atmospheric oxygen.

Singlet Oxygen ($^1\text{O}_2$)

Molecular oxygen boosted to a high-energy reactive state by photochemical reactions or peroxidase enzymes, defended against by carotenoid pigments.

Superoxide Radical ($\text{O}_2^-$)

A toxic oxygen species formed during single-electron reductions of molecular oxygen, neutralized by Superoxide Dismutase (SOD) or Superoxide Reductase enzymes.

Nitrogen Fixation

The enzymatic conversion of atmospheric gaseous nitrogen ($\text{N}_2$) into ammonia ($\text{NH}_3$) by specialized nitrogen-fixing bacteria.

Chemically Defined Medium

A culture medium whose exact chemical composition is known down to the precise molar concentration of every individual molecular component.

Complex Medium

A culture medium composed of nutrient-rich extracts and digests of yeast, meat, or plants whose exact chemical composition varies from batch to batch.

Selective Media

Culture media formulated with inhibitory substances that suppress the growth of unwanted microorganisms while encouraging the growth of desired microbes.

Differential Media

Culture media formulated with indicators (such as pH dyes or red blood cells) to visually distinguish colonies of specific organisms based on biochemical reactions.

Mannitol Salt Agar (MSA)

A selective medium ($7.5\%\text{ NaCl}$) for halotolerant organisms and a differential medium (mannitol and phenol red pH indicator) for mannitol fermenters.

MacConkey Agar

A selective medium (bile salts and crystal violet) that selects for Gram-negative enterics and a differential medium (lactose and neutral red pH indicator) for lactose fermenters.

Sterilization

The complete destruction or removal of all forms of microbial life, including vegetative cells, endospores, and viruses, with the possible exception of prions.

Commercial Sterilization

Limited heat treatment applied to canned food to kill endospores of Clostridium botulinum without degrading food quality.

Disinfection

The destruction or removal of vegetative pathogens on inanimate objects or surfaces using physical or chemical agents.

Antisepsis

The destruction or inhibition of vegetative pathogens on living tissue using non-toxic chemical antimicrobials.

Degerming

The mechanical removal of microbes from a localized area, such as scrubbing skin with an alcohol swab prior to an injection.

Sanitization

Treatment intended to lower microbial counts on eating utensils and glassware to safe public health levels.

Decimal Reduction Time (D-value)

The time required for an antimicrobial treatment to produce a $90\%$ drop ($1\text{ log}$ reduction) in a bacterial population.

Autoclaving

A moist heat sterilization method using steam under pressure at $121^\text{C}$ at $15\,\text{psi}$ for $15 - 20\,\text{minutes}$ to destroy all vegetative cells and endospores.

High-Temperature Short-Time (HTST) Pasteurization

A mild heat treatment applied at $72^\text{C}$ for $15\,\text{seconds}$ to eliminate pathogens and reduce spoilage organisms in heat-sensitive liquids without altering food quality.

Ultra-High-Temperature (UHT) Pasteurization

A heat treatment applied at $140^\text{C}$ for $< 1\,\text{second}$ to produce commercially sterile liquid that can be stored in airtight containers for months without refrigeration.

Hot-Air Sterilization

A dry heat sterilization method performed by heating items in an oven at $170^\text{C}$ for $2\,\text{hours}$.

Disk-Diffusion Method

An assay where chemical-soaked filter paper disks are placed on an inoculated agar plate to determine chemical disinfectant efficacy by measuring the zone of inhibition diameter.

Microbial Control Methods Tree

A summary chart categorizing microbial control into physical agents (heat, radiation), chemical agents (gases, liquids), mechanical agents (filtration), and biological agents (predators, viruses, toxins).

Microbial Susceptibility Spectrum

A hierarchical ranking of microorganisms from most resistant (prions, endospores, Cryptosporidium cysts) to most susceptible (Gram-positive bacteria, enveloped viruses).