Sporeformers and Antibiotics Lecture Review

Vocabulary-style flashcards covering sporeformer enrichment, biology, sporulation cycles, antibiotic mechanisms, Streptomyces properties, and gene transfer processes.

Direct Isolation

A methodology for growing bacteria by plating a sample directly onto a selective and differential agar medium to identify specific organisms.

MacConkey Agar

A selective and differential medium used to isolate Gram-negative bacteria like Salmonella; it contains crystal violet and bile salts to inhibit Gram-positives.

Neutral Red

A pH indicator used in MacConkey agar that appears red at pH $6.8$ and yellow at pH $8$.

Isolation by Enrichment

A method using a liquid broth designed to favor the growth of a specific organism over competing unwanted organisms before plating.

Endospores

Highly resistant structures that survive extreme physical conditions, such as boiling for $5$ minutes, while vegetative cells are killed.

Bacillus

A genus of Gram-positive sporeformers containing approximately $40$ species that are either obligate or facultative aerobes.

Clostridium

A genus of approximately $100$ species of Gram-positive sporeformers, most of which are obligate anaerobes.

Bacillus anthracis

The specific spore-forming bacterium responsible for causing Anthrax.

Clostridioides difficile

Formerly known as Clostridium difficile, this bacterium causes Pseudomembranous enterocolitis.

Sporulation

A bacterial cell differentiation process occurring under threat (like starvation) that serves as a survival and dispersal mechanism rather than reproduction.

Axial Thread Formation

The first stage of sporulation where bacterial nucleoids fuse and replicate without attaching to the membrane.

Spore Septum

Formed during Stage 2 of sporulation via the asymmetric invagination of the cytoplasmic membrane.

Forespore

The structure created in Stage 4 of sporulation when the mother cell membrane engulfs the daughter cell, resulting in an inner and outer membrane.

Cortex

A thick, protective layer of peptidoglycan synthesized between the inner and outer forespore membranes during Stage 6 of sporulation.

Small Acid-Soluble Spore Proteins (SASP)

Proteins synthesized in the spore core that bind to DNA; they make up $8 ext{-}20\%$ of spore proteins and are broken down during outgrowth.

Dipicolinic acid (DPA)

A molecule that chelates Calcium ions ($Ca^{2+}$) to bind DNA and lead to significant dehydration; it constitutes $10 ext{-}15\%$ of the spore dry weight.

Spore Coat

A layer rich in hydrophobic amino acids and cysteine residues (forming disulfide bonds) that accounts for $30 ext{-}60\%$ of the spore's dry weight.

Exosporium

An additional final outer layer added to the spores of some species, such as B. anthracis.

Germination

The transition stage where a spore releases cations and DPA, experiences partial water absorption, and breaks down the cortex in the presence of nutrients.

Aerobic Respiration

A high-energy metabolism process using Glycolysis, the TCA cycle, and an ETS with oxygen as the terminal electron acceptor, yielding a net total of $38\,ATP$.

Butanediol Fermentation

A metabolic pathway where pyruvate is converted to acetoin and then reduced to $2,3 ext{-}butanediol$.

NADH oxidase

An enzyme used by Bacillus subtilis to transfer excess electrons directly from NADH to Oxygen to solve the electron balance problem during fermentation.

Voges-Proskauer (VP) Test

A laboratory test that detects the intermediate acetoin to identify the butanediol fermentation pathway.

Catalase

An enzyme that protects cells from oxygen damage by breaking down hydrogen peroxide ($H_2O_2$) into water and oxygen.

Spectrophotometry

A technique using a spectrophotometer to measure turbidity (OD or AU) at a specific wavelength, typically $600\,nm$, to quantify cell mass.

Selective Toxicity

The key property of antibiotics to selectively kill or inhibit bacteria without harming the eukaryotic host cells.

Bactoprenol

A carrier lipid in the cytoplasmic membrane that flips the synthesized NAG-NAM-peptide unit from the cytoplasm to the external side.

Fosfomycin

An antibiotic that inhibits the first step of peptidoglycan synthesis: the formation of NAM-peptide in the cytoplasm.

Bacitracin

An antibiotic that binds to bactoprenol, blocking the externalization of the peptidoglycan precursor unit.

Beta-lactam Antibiotics

A class of antibiotics including penicillins and cephalosporins that inhibit the final cross-linking step of peptidoglycan synthesis.

Penicillin Binding Proteins (PBPs)

The transpeptidase enzymes involved in cell wall cross-linking that are irreversibly inactivated by binding to Beta-lactam antibiotics.

Quinolones

Antibiotics such as Ciprofloxacin and Norfloxacin that target and inhibit DNA Synthesis by affecting Gyrase.

Isoniazid

A drug specific to Mycobacterium that inactivates the fatty acid synthesis enzyme required for making mycolic acid.

Aminoglycosides

Antibiotics like Streptomycin and Neomycin that target the $30S$ subunit, causing mRNA to be read incorrectly.

Chloramphenicol

A protein synthesis inhibitor that targets the $50S$ subunit and specifically blocks peptide bond formation.

Actinomycetes

Gram-positive bacteria with high GC content ($63 ext{-}78\%$) that form branching hyphae and reproduce via asexual spores.

Streptomyces

A soil bacterium genus that produces geosmins (earthy smell) and is the source of over $500$ distinct clinical antibiotics.

Conidia

Uninucleate spores produced by Streptomyces at the ends of multinucleate aerial filaments called sporophores.

Secondary Metabolites

Molecules, such as antibiotics produced by Streptomyces, that are not essential for the basic growth or reproduction of the organism.

Kary B. Mullis

The inventor of the Polymerase Chain Reaction (PCR) technique for amplifying DNA sequences.

16S rRNA gene

A primary genetic target for bacterial identification, measuring approximately $1,540$ base pairs and containing $9$ hypervariable regions.

Beta-lactamase

An enzyme produced by resistant bacteria that destroys beta-lactam drugs as a form of antibiotic modification.

Efflux Pumps

Protein systems used by bacteria to resistance antibiotics by actively transporting the drug out of the cell.

Minimum Inhibitory Concentration (MIC)

A quantitative measure of the lowest concentration of an antibiotic that visibly prevents bacterial growth.

Minimum Bactericidal Concentration (MBC)

The lowest concentration of an antibiotic required to physically kill the bacterium.

Transformation

A type of gene transfer involving the uptake of free DNA from the surrounding environment.

Conjugation

The direct, physical cell-to-cell transfer of DNA, typically plasmid-mediated via a sex pilus.

oriR6K

The origin of replication on the pRL27 plasmid which requires the Pi protein (encoded by the pir gene) to function.

Suicide Plasmid

A plasmid like pRL27 that can replicate in a specific donor strain (where pir is present) but cannot replicate in a recipient lacking the necessary replication protein.

aph

The Kanamycin resistance gene on the pRL27 plasmid which encodes aminoglycoside phosphotransferase.

Tn5

A transposable element that utilizes a conservative "cut and paste" mechanism for transposition.

Prodigiosin

A red pigment synthesized by the pig gene cluster in wild-type Serratia marcescens.

Indole Test

A biochemical test for the enzyme tryptophanase that uses Kovac's reagent to detect the breakdown of tryptophan.

OF-Glucose Test

A metabolic test determining if a bacterium is oxidative or fermentative by observing acid production (yellow color) in oxic and anoxic conditions.