Microbial Growth and Environmental Factors

Binary Fission

Primary bacterial reproduction method involving cell division.

Cytokinesis

Division of cytoplasm during cell division.

FtsZ Protein

Protein that directs cytokinesis in bacteria.

Z Ring Assembly

Formation of divisome for cell division.

Generation Time

Time required for bacterial population to double.

E. coli Generation Time

Approximately 20 minutes for population doubling.

S. aureus Generation Time

Approximately 30 minutes for population doubling.

B. subtilis Generation Time

Approximately 120 minutes for population doubling.

M. tuberculosis Generation Time

Approximately 15-20 hours for population doubling.

Population Size Calculation

Predicts cell number using Nn = N0 * 2^n.

Lag Phase

Initial phase with no population change after inoculation.

Log Phase

Exponential growth phase with active cell division.

Stationary Phase

Phase where cell replication equals cell death.

Death Phase

Phase with more cell death than replication.

Closed Culture

Culture system with limited resources and nutrients.

Open System Cultures

Culture system with infinite resources and nutrient replenishment.

Chemostat

Device maintaining continuous culture with constant nutrient supply.

Culture Density

Number of cells per unit volume in a culture.

Exponential Growth

Growth pattern where population increases rapidly.

Sporulation

Process of endospore formation under stress conditions.

Persisters

Surviving cells with slow metabolism during adverse conditions.

Virulence Factors

Molecules that enhance pathogenicity of microorganisms.

Microscopic cell count

Cells counted manually under a microscope.

Fluorescent staining

Staining method to distinguish live and dead cells.

Coulter count

Measures cell density via electrical resistance.

Viable cell count

Counts only living cells on solid media.

Optical Density

Measures turbidity using a spectrophotometer.

Direct microscopic cell count

Cells counted in calibrated slide chamber.

Petroff-Hausser chamber

Calibrated slide for direct cell counting.

Colony Forming Units (CFU)

Count of viable cells per volume.

Serial dilution

Dilution method to achieve countable CFU range.

TFTC

Too Few To Count; <30 CFU/ml.

TNTC

Too Numerous To Count; >300 CFU/ml.

Membrane filtration technique

Filters known volume for microbial counting.

Most Probable Number (MPN)

Statistical method for low cell counts.

Log dilution

Dilution method using logarithmic scale.

Extracellular polymeric substances (EPS)

Matrix secreted by biofilm organisms.

Quorum sensing

Cell communication based on population density.

Budding

Asymmetric division method in some microbes.

Fragmentation

Asexual reproduction via breaking into parts.

Biofilm

Microbial community in protective matrix.

Secondary colonizers

Microbes that join established biofilms.

Autoinducer

Molecule triggering cellular responses in quorum sensing.

Biofilm

Community of microorganisms adhering to surfaces.

Quorum Sensing

Cell communication regulating biofilm formation.

Autoinducer

Molecules triggering cellular responses in quorum sensing.

N-acylated Homoserine Lactones

Signaling molecules in Gram-negative bacteria.

Short Peptides

Signaling molecules in Gram-positive bacteria.

Normal Biota

Beneficial microorganisms residing in the body.

Antibiotic Resistance

Biofilms protect microbes from antibiotic effects.

EPS

Extracellular polymeric substances aiding biofilm structure.

Oxygen Level

Concentration of O2 affecting microbial growth.

Optimal Oxygen Concentration

Ideal O2 level for microbial growth.

Minimum Permissive Oxygen Concentration

Lowest O2 level allowing microbial growth.

Maximum Permissive Oxygen Concentration

Highest O2 level allowing microbial growth.

Obligate Aerobes

Require oxygen for survival and growth.

Facultative Anaerobes

Can grow with or without oxygen.

Aerotolerant Anaerobes

Tolerate oxygen but do not use it.

Microaerophiles

Require low oxygen levels for growth.

Fluid Thioglycolate Medium (FTM)

Medium used to determine oxygen tolerance.

Optimal Growth pH

Most favorable pH for microbial growth.

Acidophiles

Microbes thriving in acidic environments.

Mesophiles

Microbes growing best at moderate temperatures.

Halophiles

Microbes requiring high salt concentrations.

Barophiles

Microbes thriving under high atmospheric pressure.

Photoautotrophs

Organisms using light for energy and carbon.

Selective Media

Promotes growth of specific organisms while inhibiting others.