Exam 2 Study Guide Flashcards: Microbiology and Bacterial Genetics

Comprehensive vocabulary flashcards covering microbial growth, environmental adaptations, disinfection methods, DNA replication, gene expression, and genetic variation based on the study guide for Exam 2.

Binary Fission

The most common mechanism for bacterial cell division.

List the four steps of bacterial cell division

1. Elongation of the cell

2. Replication of the chromosome

3. Separation of the chromosomes into the two parts of the cell

4. Formation of septum in the middle (Cytokinesis, or septation)

Origin of replication

The specific site on a chromosome where DNA replication begins.

Cytokinesis

The division of the cell into two via formation of a cross wall (septation) between the two daughter cells.

Penicillin-binding protein (PBP)

A group of proteins that hydrolyze bonds in existing peptidoglycan strands and link together new strands during cell division.

N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)

Major components of peptidoglycan that bind to a membrane protein called bactoprenol.

Autolysins

Enzymes that degrade polypeptide chains where new NAM-NAG units are inserted into the peptidoglycan layer.

Crescentin

A bacterial protein that is a homologue of eukaryotic intermediate filaments.

Budding

Budding off daughter cells; seen in Listeria monocytogenes

Baeocyte formation (multiple fission)

A type of asexual reproduction involving multiple rounds of cell division (multiple fission) seen in Cyanobacteria.

Spore formation

Form multinucleoid filaments that ultimately divide to produce spores with a single nucleus.

Lag Phase

The period in the bacterial growth curve with no net growth although abundant because bacteria are adjusting to new conditions despite abundant nutrients.

Log (Exponential) Phase

The phase where nutrients are abundant and bacteria divide at their highest rate; the best phase to calculate generation time.

Stationary Phase

The growth phase where the number of viable microorganisms is stable because nutrient levels level off and waste products accumulate.

Generation time (GT)

The specific amount of time it takes for a microbial population to double.

Hypertonic

A solution condition where the concentration of solutes is higher outside the cell than inside, causing the cell to shrink.

Hypotonic

A solution condition where the concentration of solutes is lower outside the cell than inside, causing the cell to burst.

Psychrophiles

Organisms that grow between $0^{\circ}C$ and $20^{\circ}C$, typically associated with refrigeration temperatures.

Mesophiles

Microbes that grow between $20^{\circ}C$ and $45^{\circ}C$, which includes most human pathogens.

Hyperthermophiles

Organisms, usually archaeans, that grow between $85^{\circ}C$ and $113^{\circ}C$.

Obligate Aerobes

Organisms that require oxygen for growth and die without its presence.

Facultative Anaerobes

Microbes that grow better with oxygen than without it, but oxygen is not strictly needed for their survival.

Sessile

Microorganisms that grow attached to a surface rather than floating freely as planktonic cells.

Biofilm

A complex of slime-enclosed colonies that stick to each other on a surface, forming a heterogeneous community of microorganisms.

Quorum Sensing

A strategy where bacteria coordinate the expression of certain genes based on their population density.

Sterilization

The removal or destruction of all viable microorganisms in a medium.

Disinfection

Process involving killing, removing, or inhibiting disease-causing organisms in a medium.

Sanitization

The reduction of microbial populations to "safe" levels according to public health standards.

Antisepsis

The prevention of infection of living tissue by microorganisms.

Bacteriostatic

An agent that inhibits the growth of bacteria rather than killing them.

Pasteurization

Treating heat-sensitive beverages like milk and beer at controlled temperatures well below boiling to slow spoilage by reducing the total microbial load.

Ionizing radiation

A physical control method using gamma radiation to penetrate deep into objects to destroy bacterial endospores by creating free radicals.

Ultraviolet (UV) radiation

A physical agent that causes thymine dimers to prevent replication and transcription; most bactericidal at $260\,nm$.

Quaternary ammonium compounds

Amphipathic antimicrobial detergents that have the ability to denature proteins and disrupt microbial membranes.

Genome

The entire set of DNA present in a cell or virus.

Genotype

The specific set of genes an organism possesses.

Phenotype

The collection of observable characteristics of an organism.

Transformation

The ability of organisms to take up naked DNA from the environment and incorporate it into their chromosomes.

Nucleoside

A molecular structure consisting of a pentose sugar attached to a nitrogenous base.

Nucleotide

A molecular structure consisting of a pentose sugar, a nitrogenous base, and a phosphate group bound by phosphodiester bonds.

Purines

Nitrogenous bases with double-ring structures, including Adenine and Guanine.

Pyrimidines

Nitrogenous bases with one-ring structures, including Cytosine, Thymine, and Uracil.

Chargaff’s rule

The principle that the amount of Guanine in DNA equals Cytosine, and the amount of Adenine equals Thymine.

Replisome

The molecular complex that carries out DNA replication.

Okazaki fragments

Short pieces of DNA produced on the lagging strand during discontinuous DNA synthesis.

Catenanes

Interlocking chromosomes that form during the termination stage of DNA replication.

Telomere

Repeat nucleotide sequences at the $3^{\prime}$ end of linear chromosomes that act as a buffer to protect genes from erosion.

DnaB (Helicase)

An enzyme that unwinds double-stranded DNA at the replication fork, separating the old strands.

Gyrase

A specialized type 2 topoisomerase that introduces negative supercoils ahead of the replication fork.

Pribnow Box

A sequence found 10 bases upstream in the promoter that helps initiate transcription specifically in bacteria.

Shine-Dalgarno Sequence

A region in the mRNA's leader sequence that initiates translation.

Polycistronic mRNA

A type of mRNA that carries genetic information for the translation of multiple polypeptides.

Aminoacyl-tRNA synthetase

A group of enzymes responsible for "charging" tRNA molecules with the correct amino acid.

Lac Operon

An inducible operon that undergoes both negative and positive control to regulate enzymes for lactose breakdown.

Attenuation

A control mechanism that results in the premature termination of transcription at the leader sequence.

Riboswitch

A site on the leader sequence of an mRNA that interacts with a metabolite to alter transcription or translation via folding changes.

Histones

Small proteins that DNA wraps around in eukaryotes to form structures called nucleosomes.

Alternative splicing

The process where the same pre-mRNA can be spliced differently to include or exclude certain sequences, resulting in different proteins.

Enhancers

Activator proteins located far away from the gene they activate that increase transcription levels.

RNA interference

A process where miRNA or siRNA inhibits gene expression by binding to mRNA and either degrading it or preventing translation.

Nonsense mutation

A mutation that converts a "sense" codon to one of the three stop codons, leading to premature termination of the polypeptide.

Conjugation

The transfer of genetic material between bacteria through direct cell-to-cell contact involving a sex pilus.

Transposable element

A segment of DNA, often called a "jumping gene," that can repeatedly insert into one or more sites of a genome.