Microbial Growth, Cell Division & Endosymbiotic Hypothesis

Vocabulary flashcards summarizing key terms and definitions related to microbial growth, bacterial cell division mechanisms, cytoskeletal proteins, and the endosymbiotic origin of eukaryotic organelles.

Growth (microbial)

Increase in the number of microbial cells.

Binary Fission

Cell division in which one cell enlarges to twice its minimum size and splits into two daughter cells.

Generation Time

Time required for a microbial population to double in number.

Septum

Cross-wall that forms between daughter cells during binary fission.

Bacterial Cell Cycle

Sequence of events from a cell’s formation to the next division, involving DNA replication/partitioning and cytokinesis.

Origin of Replication (oriC)

Specific site where bacterial chromosome replication begins.

Terminus

Site opposite the origin where chromosome replication ends.

Replisome

Protein complex that carries out DNA synthesis during chromosome replication.

Cytokinesis (Septation)

Physical splitting of the cytoplasm and formation of a cross-wall between daughter cells.

Divisome

Protein apparatus, built around Fts proteins, that orchestrates bacterial cell division.

FtsZ

Tubulin homolog forming the contractile Z ring at the cell center.

ZipA

Anchor protein that connects the FtsZ ring to the cytoplasmic membrane.

FtsA

Actin-like protein that links FtsZ to the membrane and recruits other divisome proteins.

FtsK

Divisome protein involved in chromosome segregation and resolution of chromosome dimers.

Min Proteins (MinC, MinD, MinE)

Proteins that oscillate to prevent FtsZ ring assembly at cell poles, confining it to mid-cell.

Z Ring

Contractile ring made of FtsZ polymers that marks the future division plane.

MreB

Actin homolog that forms helical bands, dictates rod shape, aids chromosome segregation, and directs peptidoglycan synthesis.

Crescentin

Intermediate-filament-like protein in vibrioid bacteria that localizes to the curved side, producing cell curvature.

Autolysins

Enzymes that cleave existing peptidoglycan to allow insertion of new cell-wall material.

Peptidoglycan Synthesis (during division)

Insertion of new cell-wall material at openings created by autolysins, typically starting near the FtsZ ring.

Plasmid Segregation

Active separation of plasmid copies to opposite cell poles, mediated by Par proteins.

ParM

Actin-like filament that polymerizes to push plasmids to opposite poles.

ParR / ParC

Plasmid proteins that bind plasmid origins and anchor ParM filaments.

Endosymbiotic Hypothesis

Theory that mitochondria, hydrogenosomes, and chloroplasts evolved from bacteria engulfed by ancestral eukaryotes.

Mitochondrion

Double-membrane organelle, site of TCA cycle and oxidative phosphorylation; reproduces by binary fission.

Cristae

Folded inner mitochondrial membrane hosting electron transport and ATP synthase complexes.

Matrix (Mitochondrial)

Innermost compartment containing bacterial-sized ribosomes, circular DNA, and TCA enzymes.

Hydrogenosome

Double-membrane organelle in anaerobic protists that generates ATP via fermentation, producing H₂, CO₂, and acetate.

Chloroplast

Photosynthetic plastid with double membrane, derived from cyanobacterial endosymbiosis.

Parental Cell

The original bacterial cell preparing for division by enlarging wall, membrane, and volume.

Autonomous Replication

Ability of plasmids to replicate independently of the bacterial chromosome.

Peptidoglycan

Mesh-like polymer forming the bacterial cell wall, synthesized during growth and division.

Tubulin

Eukaryotic cytoskeletal protein homologous to bacterial FtsZ.

Actin

Eukaryotic cytoskeletal protein homologous to bacterial MreB.

Vibrioid Morphology

Comma-shaped cell form resulting from combined action of MreB (elongation) and crescentin (curvature).