Microbial Growth and Binary Fission

Vocabulary flashcards covering microbial growth mechanisms, binary fission, mathematical calculations, batch culture phases, continuous cultures, biofilms, and quorum sensing based on the lecture transcript.

Binary fission

The primary mechanism of cell replication in bacteria, in which a cell grows in size, replicates its chromosome, separates the chromosome copies to opposite poles, and divides into two daughter cells.

PAR-A and PAR-B proteins

Proteins in most bacteria that help pull replicated chromosome copies to opposite poles of the cell prior to cytokinesis.

FitZ filaments

Filaments that assemble into a ring around the center of a bacterial cell to constrict it during cytokinesis.

Growth rate

The time required for bacteria to complete binary fission, representing how fast a cell doubles from one cell to two cells.

Generation time

The time required for a bacterial population to double in size.

Generation time equation

The mathematical formula $g = \frac{t}{n}$, where $g$ is the generation time, $t$ is the growth time, and $n$ is the number of generations.

Exponential growth equation

The mathematical formula $b = B \times 2^n$, where $b$ is the cell count after growth, $B$ is the cell count before growth, and $n$ is the number of generations.

Batch culture

A closed culture system used in a laboratory where no additional nutrients are added and no waste products are removed.

Lag phase

The initial phase of growth in a batch culture where cells adjust to new conditions and synthesize necessary proteins without undergoing binary fission.

Log phase

The growth phase where exponential cell division occurs, used to calculate generation time and measure growth using exponential growth equations.

Stationary phase

The growth phase in a closed culture where total cell count remains steady because cell division rate equals cell death rate, and secondary metabolites are produced.

Death phase

Also called the decline phase, the growth phase in which the rate of cell death exceeds the rate of cell division due to nutrient depletion and waste accumulation.

Secondary metabolites

Molecules produced during stationary phase that are not required for basic growth, but assist in survival and competition, such as antimicrobials and toxins.

Continuous culture

An industrial bacterial culture system where nutrients are continuously added and waste products are continuously removed to maintain a constant growth phase.

Chemostat

A continuous culture vessel (referred to as chirostats) that controls environmental factors like oxygen, pH, and temperature while continually adding nutrients and removing waste.

Biofilms

Complex, dynamic microbial communities adhering to surfaces and to each other, often consisting of hundreds of species embedded in a protective matrix.

EPS

Extracellular polymetric substances; a gel composed mostly of polysaccharides that maintains biofilm integrity and protects cells from chemicals and antibiotics.

Planktonic cells

Free-floating microbial cells that initiate biofilm formation by attaching to a surface.

Quorum sensing

A cellular communication mechanism where bacteria use autoinducer molecules to coordinate gene expression based on cell density.

Autoinducer

A signaling molecule secreted during quorum sensing that diffuses away at low cell density, but at high density re-enters cells to turn on expression of key genes.