Microbial Growth, Genetics, and Modern Applications

Vocabulary practice flashcards covering microbial growth, genetics, and modern molecular applications from Chapters 9, 11, and 12.

Generation Time

The amount of time required for a bacterial population to double in number; also known as doubling time.

Binary Fission

A process of bacterial reproduction in which one cell divides into two identical daughter cells.

Bacterial Population Growth Formula

The formula $N_n = N_0 \times 2^n$, where $N_n$ is the final number of cells, $N_0$ is the initial number of cells, and $n$ is the number of generations.

Lag Phase

A phase of bacterial growth with little or no cell division during which cells adapt to their environment and synthesize enzymes and cellular components.

Log (Exponential) Phase

A bacterial growth phase characterized by rapid cell division, a constant doubling rate, and the highest metabolic activity.

Stationary Phase

A bacterial growth phase where nutrient limitation causes the growth rate to equal the death rate, stabilizing population size.

Death Phase

A bacterial growth phase in which cells die faster than they divide, resulting in a population decrease.

Petroff-Hausser Counting Chamber

A microscopic device used for direct total cell counts that measures both living and dead cells.

Plate Counts

A viable cell count method where serial dilutions are plated on agar, living cells form colonies, and results are expressed as colony-forming units (CFU).

Most Probable Number (MPN)

A viable cell count method using multiple tubes of growth medium to estimate bacterial concentration statistically.

Spectrophotometer

An instrument used as an indirect method to estimate bacterial population density by measuring turbidity (cloudiness).

Biofilm

A community of microorganisms attached to surfaces and embedded in a protective extracellular matrix.

Quorum Sensing

Bacterial communication using chemical signals called autoinducers that alter population-wide gene expression when a concentration threshold is reached.

Autoinducers

Chemical signals used in quorum sensing that allow bacteria to monitor population density and coordinate group behaviors.

Obligate Aerobe

An organism that strictly requires oxygen for growth.

Obligate Anaerobe

An organism for which oxygen is toxic and cannot grow in its presence.

Facultative Anaerobe

An organism that uses oxygen if present but can also grow in the absence of oxygen.

Aerotolerant Anaerobe

An organism that does not use oxygen for growth but can tolerate its presence.

Microaerophile

An organism that requires low concentrations of oxygen for growth.

Acidophile

An organism that grows best in acidic environments.

Neutrophile

An organism that grows best near pH 7, comprising most bacteria.

Alkaliphile

An organism that grows best in basic (alkaline) environments.

Psychrophile

A cold-loving organism that thrives in cold temperatures.

Psychrotroph

An organism that grows in cold temperatures but prefers warmer conditions.

Mesophile

An organism that thrives in moderate temperatures, encompassing most human pathogens.

Thermophile

An organism that thrives in high temperatures.

Hyperthermophile

An organism that thrives at extremely high temperatures.

All-Purpose Media

Culture media that supports the growth of many microbes, such as nutrient agar.

Enriched Media

Culture media containing additional nutrients specifically required for fastidious organisms.

Selective Media

Culture media designed to inhibit unwanted organisms while permitting target organisms to grow.

Differential Media

Culture media designed to show visible differences between different organisms.

Defined Media

Culture media in which the exact chemical composition is known.

Enrichment Media

Culture media that enhances the growth of a desired organism while suppressing competitors.

Genome

The complete heritable material that stores genetic information passed to future generations and contains genes coding for proteins and regulatory functions.

Central Dogma of Molecular Biology

The framework describing the flow of genetic information: $\text{DNA} \rightarrow \text{RNA} \rightarrow \text{Protein}$.

Genotype

The full genetic makeup of an organism.

Phenotype

The observable characteristics of an organism, which can be influenced by environmental effect on gene expression.

Point Mutation

A mutation involving a change in a single nucleotide, which may alter one amino acid.

Frameshift Mutation

A mutation caused by the addition or deletion of nucleotides that changes the reading frame, usually resulting in major protein damage.

Silent Mutation

A mutation in which a codon changes but codes for the same amino acid, causing no change in phenotype.

Missense Mutation

A mutation that causes a different amino acid to be produced, potentially leading to a poorly functioning protein.

Nonsense Mutation

A mutation that creates a stop codon, producing a shortened, truncated protein.

Photoreactivation (Light Repair)

A DNA repair mechanism that utilizes photolyase enzymes to repair UV-induced thymine dimers.

Nucleotide Excision Repair (Dark Repair)

A DNA repair mechanism in which damaged DNA is removed, DNA polymerase fills the gap, and DNA ligase seals the strand.

Mutagen

Any physical or chemical agent that increases the likelihood of genetic mutations.

Ames Test

An assay using mutant bacteria to measure how often chemicals cause mutations to revert to normal, assessing whether a substance is mutagenic and potentially carcinogenic.

Transformation

A form of horizontal gene transfer in which a bacterium takes up naked DNA directly from its environment.

Transduction

A mechanism of horizontal gene transfer where DNA is transferred from one bacterium to another by a bacteriophage.

Conjugation

A horizontal gene transfer process where DNA is transferred through direct cell-to-cell contact using a sex pilus.

Transposons

DNA segments known as jumping genes that move to different locations within the genome using the enzyme transposase.

Inducible Operon

An operon that is normally OFF and is turned ON when its substrate is present, such as the lac operon.

Repressible Operon

An operon that is normally ON and is turned OFF when its end product is abundant, such as the trp operon.

Electroporation

A laboratory method that uses electric pulses to create temporary pores in cell membranes, allowing exogenous DNA to enter.

Gel Electrophoresis

A procedure that separates DNA fragments by size and charge as they migrate toward the positive electrode.

Restriction Fragment Length Polymorphism (RFLP)

An analysis technique where DNA is cut with restriction enzymes to create unique fragment patterns used for genetic fingerprinting and outbreak tracking.

Polymerase Chain Reaction (PCR)

A technique used to amplify DNA using a template, primers, Taq polymerase, and nucleotides through denaturation, annealing, and extension steps.

Microarray Analysis

A technique that compares gene expression patterns between samples by binding DNA or cDNA to complementary sequences on a chip marked by fluorescent dyes.