Bacterial and Archaeal Growth Flashcards

A set of vocabulary flashcards covering the reproductive strategies, cell cycle, growth phases, and environmental influences related to bacteria and archaea.

Binary Fission

The most common form of cell division in bacteria and archaea, involving cell elongation, replication of chromosomes, and the formation of a septum to divide the cell into two daughter cells.

Replisome

The DNA synthesis machinery responsible for replicating the cell's chromosome.

ParAB/parS System

The best-known chromosome partition system, identified in $Caulobacter\,crescentus$, where ParB binds to the parS site and is guided by ParA to the opposite pole.

Cytokinesis

The process of formation of two daughter cells following cell division.

Septation

The formation of a cross wall between two daughter cells during cytokinesis, involving Z-ring assembly and cell wall-synthesizing machinery.

FtsZ

A tubulin-like protein that polymerizes to form the Z-ring, which establishes the division site at midcell and serves as a scaffold for cell envelope synthesis.

Nucleoid Occlusion

A coordination mechanism ensuring the Z-ring forms only after chromosomes have moved away; SlmA often coats the chromosome to prevent Z-ring constriction.

Divisome

A complex of proteins, including FtsA, ZipA, and FtsI, that anchors the Z-ring to the plasma membrane and facilitates peptidoglycan synthesis for the septum.

MreB

A scaffold protein in rod-shaped bacteria that creates filaments along the cytoplasmic face of the plasma membrane to direct the elongasome.

Crescentin

A protein that localizes to one side of a cell to produce an asymmetric cell wall, resulting in a curved or vibroid shape.

Lag Phase

The first phase of the microbial growth curve where cells synthesize new components and adapt to a new medium without an immediate increase in number.

Exponential (Log) Phase

The growth phase where the rate of division is constant and maximal, and the population is most uniform in chemical and physical properties.

Stationary Phase

The phase in a closed system where the total number of viable cells remains constant due to a balance between cell division and cell death.

Long-Term Stationary Phase

The final stage of the growth curve where the population evolves and genetically distinct variants emerge through natural selection.

Generation Time

Also known as doubling time, it is the time required for a microbial population to double in size.

Extremophiles

Organisms that grow under harsh environmental conditions, such as extreme temperature or pH, that would be lethal to most other organisms.

Halophiles

Microorganisms that require $NaCl$ concentrations above approximately $0.2\,M$ for growth.

Water Activity ($a_w$)

A measure of water availability defined as the ratio of a solution's vapor pressure to that of pure water.

Acidophiles

Microbes that exhibit optimal growth between $pH\,0$ and $pH\,5.5$.

Psychrophiles

Microorganisms that grow well at $0\,^{\circ}C$ and have an optimal growth temperature at or below $15\,^{\circ}C$.

Facultative Anaerobes

Organisms that do not require $O_2$ for growth but grow much better in its presence.

Reactive Oxygen Species (ROS)

Toxic reduction products of oxygen, such as superoxide radicals and hydrogen peroxide, which must be neutralized by enzymes like superoxide dismutase (SOD) or catalase.

Defined (Synthetic) Medium

A culture medium in which every ingredient can be specified with a precise chemical formula.

Selective Media

Culture media designed to support the growth of specific microorganisms while inhibiting others, such as using bile salts to inhibit Gram-positive bacteria.

Differential Media

Media that distinguish between different groups of microbes based on biological characteristics, such as MacConkey agar for lactose fermenters.