Intro to Bacteria 8/15/25

Vocabulary flashcards covering key concepts from growth, genetics, virulence factors, transmission, culture, and antibiotic resistance topics in the lecture notes.

Binary fission

Asexual bacterial reproduction where a cell divides into two genetically identical daughter cells, with complete genome replication and envelope synthesis.

Generation time

The doubling time; the time required for a bacterial population to double in number; varies by species.

Chromosome

The main circular, haploid bacterial DNA molecule that carries essential genes.

Plasmid

Extrachromosomal, double‑stranded circular DNA that replicates independently of the chromosome and often carries accessory genes.

Plasmid (definition in context)

Extra pieces of DNA outside the chromosome that can carry traits like antibiotic resistance.

Transmissible plasmids

Plasmids capable of transferring between bacteria via conjugation, spreading traits such as resistance.

Non-transmissible plasmids

Plasmids that cannot transfer by conjugation and may remain within the original cell.

Conjugation

DNA transfer between bacteria through direct cell contact, mediated by a sex pilus; often involves transfer of a plasmid.

F plasmid

Fertility plasmid that carries genes for the sex pilus and conjugation machinery.

Sex pilus

A pili used to connect donor and recipient cells during conjugation to transfer DNA.

Transduction

DNA transfer between bacteria mediated by bacteriophages (phages); can move virulence or resistance genes.

Virulent phage

A lytic bacteriophage that immediately kills the bacterial host and can spread bacterial DNA.

Temperate phage

A phage that can integrate into the bacterial genome and later transfer DNA via transduction.

Transformation

Uptake of naked DNA from the environment by competent bacteria, followed by recombination and integration.

Homologous recombination

DNA exchange requiring long stretches of sequence identity between similar sequences.

Non‑homologous recombination

DNA exchange not requiring extensive sequence identity; can insert DNA at non‑homologous sites.

Horizontal gene transfer

Movement of genetic material between organisms other than parent-offspring (transformation, transduction, conjugation).

Mutation

Heritable change in DNA sequence that can alter phenotype; arises during replication or due to damage.

Frameshift mutation

Insertion or deletion that shifts the reading frame, drastically altering downstream amino acids.

Silent mutation

Nucleotide change that does not alter the encoded amino acid.

Missense mutation

Nucleotide change that substitutes a different amino acid in the protein.

Nonsense mutation

Nucleotide change that creates a premature stop codon, truncating the protein.

DNA polymerase

Enzyme that copies DNA by adding nucleotides in the 5′→3′ direction.

DNA primase

Enzyme that synthesizes RNA primers to start DNA synthesis.

DNA helicase

Enzyme that unwinds the DNA double helix to create a replication fork.

DNA ligase

Enzyme that seals nicks between Okazaki fragments on the lagging strand.

Topoisomerase/Gyrase

Enzymes that relieve DNA supercoiling during replication; targets of fluoroquinolones.

Bidirectional replication

DNA replication proceeds in two directions from the origin around the circular chromosome.

Circular chromosome

Single, circular, haploid bacterial chromosome; lacks introns and splicing.

Haploid

Single set of genetic information; bacteria typically have one chromosome.

70S ribosome

Bacterial ribosome composed of 30S and 50S subunits (70S total), a common antibiotic target.

30S subunit

Small ribosomal subunit; target of aminoglycosides and tetracyclines.

50S subunit

Large ribosomal subunit; target of macrolides and chloramphenicol.

Biofilm

Surface-attached microbial communities embedded in a matrix; protect bacteria from immune clearance and antibiotics.

Capsule

Polysaccharide exterior to the cell wall; anti‑phagocytic; capsule antigens can be vaccine targets.

Coagulase

Staphylococcus aureus enzyme converting fibrinogen to fibrin, shielding bacteria from immune detection.

IgA protease

Enzyme that cleaves IgA at mucosal surfaces, aiding colonization of mucosal tissues.

Protein A

Staphylococcus aureus protein that binds the Fc region of IgG to inhibit opsonization.

Endotoxin

Lipid A component of Gram-negative LPS; released on cell death and triggers inflammation.

Exotoxin

Protein toxins secreted by bacteria; can be AB, cytolytic, proteolytic, or superantigenic.

AB toxin

Toxin with A (active) and B (binding) subunits; diverse activities (e.g., cholera toxin).

Superantigen

Toxins that non‑specifically activate T cells by bridging MHC II and TCR, causing a cytokine storm.

Lecithinase (alpha toxin)

Phospholipase C that hydrolyzes phospholipids in membranes, causing cell lysis (e.g., C. perfringens alpha toxin).

Hylauronidase

Spreading factor that degrades hyaluronic acid to promote tissue invasion.

Collagenase

Enzyme that degrades collagen to aid tissue penetration and dissemination.

Streptokinase

Enzyme that activates plasminogen to plasmin, dissolving clots to enable spread.

Endospores

Dormant, highly resistant forms produced by some Gram‑positive bacteria (Bacillus, Clostridium).

Spore staining

Schaeffer‑Fulton method using malachite green (with heat) and safranin to visualize endospores.

Portals of entry

Sites where pathogens enter the host (e.g., respiratory, GI, genitourinary, skin, parenteral, conjunctiva, placenta).

Obligate aerobe

Bacteria that require oxygen for growth (e.g., Mycobacterium tuberculosis).

Microaerophilic

Bacteria that grow best at reduced oxygen levels (e.g., Campylobacter).