Bacterial and Archaeal Growth - Vocabulary Flashcards

Vocabulary flashcards covering key terms and concepts from the lecture notes on bacterial and archaeal growth.

Binary fission

Asexual bacterial reproduction in which the cell elongates, DNA replicates and moves to opposite poles, and a septum divides the cell into two daughter cells.

Chromosome partitioning

Movement and separation of replicated chromosomes to opposite poles during cell division, often involving Par proteins and parS near oriC.

Septum

The dividing wall that forms between two daughter cells during cytokinesis.

Z-ring

A contractile ring formed by FtsZ at midcell that constricts to drive septum formation during bacterial cytokinesis.

FtsZ

Tubulin-like cytoskeletal protein that polymerizes to form the Z-ring and initiates cytokinesis.

Divisome

Multi-protein complex coordinating peptidoglycan synthesis at midcell during bacterial division (≈30 proteins).

Min system

System that prevents FtsZ assembly at cell poles, promoting midcell Z-ring formation.

Nucleoid occlusion

Mechanism (e.g., SlmA) that prevents Z-ring formation over the chromosome until partitioning is complete.

parS

DNA site near oriC bound by ParB, involved in chromosome partitioning.

ParB

Protein that binds parS and helps with chromosome partitioning.

ParA

ATPase that forms a gradient to move chromosomes during partitioning.

oriC

Origin of replication in bacteria where DNA replication begins.

Crescentin

Cytoskeletal protein in curved bacteria like Vibrio that influences curvature by modulating PG synthesis.

MreB

Actin-like protein directing lateral cell-wall synthesis; part of the elongasome.

Elongasome

Complex responsible for inserting new peptidoglycan along the length of a growing cell.

NAG-NAM-pentapeptide

Building blocks of peptidoglycan synthesized in the cytoplasm.

MurJ flippase

Enzyme that flips lipid-linked peptidoglycan precursors across the cytoplasmic membrane.

Bactoprenol

Lipid carrier that shuttles peptidoglycan subunits across the membrane.

Transpeptidases (PBPs)

Enzymes that form crosslinks in peptidoglycan.

Peptidoglycan synthesis

Process of building and cross-linking the bacterial cell wall.

Cocci

Spherical bacteria; growth often focused at central septum with little elongation.

Bacilli

Rod-shaped bacteria with elongation along the length (elongasome).

VBNC (Viable but Non-Culturable)

State where cells are alive but cannot be cultured by standard methods.

Great plate count anomaly

Discrepancy where microscopic counts exceed viable plate counts due to VBNC and other factors.

Batch culture

Growth in a closed system with no addition of nutrients or removal of wastes.

Lag phase

Adaptation period with no immediate division; ribosome/ATP synthesis and acclimation.

Exponential phase

Period of rapid, balanced growth with doubling time; high cell density.

Stationary phase

Growth rate equals death rate due to nutrient limitation and waste accumulation.

Death phase

Cells die faster than they replicate; viability declines.

Long-term stationary phase

Persisting cells fueled by nutrients from dying cells; waves of replication and death.

Generation time

Time required for a population to double in size.

N_t = N0 × 2^n

Equation describing population size after n generations in binary fission.

Chemostat

Open culture system with constant nutrient input and waste removal; growth rate set by limiting nutrient.

Turbidostat

Open culture that maintains a target turbidity (cell density) by dilution.

Biofilm

Surface-attached microbial communities embedded in exopolysaccharide matrix; protected and often antibiotic-tolerant.

Quorum sensing

Cell-density signaling via small molecules (e.g., AHL) coordinating biofilm formation and behavior.

Exopolysaccharide (EPS)

Polysaccharide-rich matrix produced by biofilms for protection and cohesion.

Pili/Fimbriae

Filamentous structures enabling attachment to surfaces during biofilm initiation.

Attachment

Initial binding of microbes to a surface during biofilm development.

MacConkey agar

Selective/differential medium that supports Gram-negative bacteria and differentiates lactose fermenters.

Blood agar

Enriched/differential medium used to detect hemolysis and support fastidious growth.

Defined (synthetic) medium

Medium with precisely defined chemical composition and concentrations.

Complex medium

Medium containing ingredients with undefined composition (e.g., extracts, digests).

Agar

Solidifying agent used to make semi-solid or solid media; many bacteria cannot metabolize agar itself.

Broth

Liquid nutrient medium without agar.

Streak plating

Technique to obtain a pure culture by spreading a sample in streaks to isolate colonies.

Aseptic technique

Procedures to minimize contamination, including sterilization with flame and sterile tools.

Flow cytometry

Technique using lasers to count and analyze cells in suspension.

Direct counting with counting chambers

Manual cell counting in a defined grid area; can be stained to differentiate viability.

Viable counting (CFU)

Counting colony-forming units by plating; only viable cells form colonies.

Oxygen categories

Groups of microbes by oxygen needs: obligate aerobes, microaerophiles, facultative anaerobes, aerotolerant, obligate anaerobes.

Obligate aerobe

Requires oxygen for growth.

Microaerophile

Grows best at lower-than-atmospheric O2 levels.

Facultative anaerobe

Grows with or without oxygen, often faster with O2.

Aerotolerant anaerobe

Tolerates oxygen but does not use it for growth.

Obligate anaerobe

Inhibited or killed by oxygen.

Osmotic concentration

Environmental osmolarity that affects water balance and growth.

Halophile

Requires high salt concentrations to grow.

Osmotolerant

Grows over a wide range of water activity.

Xerotolerant

Withstands very dry or highly osmotic conditions.

pH neutrophile

Grows best at neutral pH (~7).

Acidophile

Grows best at acidic pH (low pH).

Alkaliphile

Grows best at alkaline pH (high pH).

Psychrophile

Grows best at cold temperatures (0–20°C).

Psychrotolerant

Grows over a wide temperature range including cold (0–35°C).

Mesophile

Grows best at moderate temperatures (roughly 20–45°C).

Thermophile

Grows best at high temperatures (generally 45–85°C).

Hyperthermophile

Grows best at very high temperatures (85–100°C).

Taq polymerase

A thermostable DNA polymerase from Thermus aquaticus used in PCR.

S-layer

Proteinaceous surface layer found in some archaea and bacteria; in archaea linked to cell envelope structure.

SegA/SegB

Archaeal ParA/ParB-like proteins involved in chromosome organization and segregation.

G2-like state

A post-replication pause in some archaea where DNA replication and cytokinesis aren’t synchronized, resembling G2 in mitosis.

Z-ring in archaea

In some archaea, the Z-ring is linked to S-layer synthesis rather than peptidoglycan wall formation.