Microbial Growth and Control

Flashcards covering microbial growth mechanisms, quantification methods, and environmental requirements such as oxygen, pH, and temperature based on the provided lecture slides.

Binary fission

The process in bacteria where the cell elongates, DNA is replicated, a division septum forms in the center, and two daughter cells of similar size separate.

Salmonella typhimurium

A species of bacteria shown in electron micrographs undergoing binary fission.

FtsZ proteins

Proteins that assemble to form a Z ring anchored to the plasma membrane to facilitate cell division.

Z ring

A structure that pinches the cell envelope to separate the cytoplasm of the new cells during division.

Growth curve

A graph representing a bacterial culture by plotting the logarithm of the number of live cells as a function of time.

Lag phase

The initial phase of the bacterial growth curve where cells are preparing for growth but not yet dividing.

Log phase

The phase of the growth curve where cells divide at a constant rate and population growth is exponential.

Stationary phase

The phase of the growth curve where the rate of cell division and cell death are roughly equal, resulting in a plateau.

Death phase

The final phase of the growth curve where the number of dying cells exceeds the number of new cells.

Semilogarithmic scale

A plotting method where the y-axis values are logarithmic, causing the growth rate during the log phase to appear linear.

Petroff-Hausser chamber

A special slide with an etched grid of known areas designed for counting bacterial cells in a measured volume of a sample.

Serial dilution

A method involving the dilution of a fixed volume of cells mixed with a solution using the previous dilution as an inoculum, resulting in exponential dilution.

Fragmentation

A replication method used by filamentous cyanobacteria where the organism breaks into pieces that grow into new individuals.

Budding

A type of division seen in Gemmata obscuriglobus where a daughter cell grows from a larger mother cell.

Gemmata obscuriglobus

A bacterium noted for its budding reproduction and having a nucleoid (N) and a forming nuclear envelope (NE).

Biofilm

A complex community of microorganisms that goes through specific stages in its formation and life cycle.

Rumen

The first compartment of a cow’s stomach that serves as an oxygen-free incubator for methanogens and obligate anaerobic bacteria.

Thioglycolate tubes

A medium used to determine the oxygen requirements of bacteria based on their distribution of growth within the tube.

Obligate aerobes

Organisms that require a supply of oxygen for growth and typically cluster at the top of a thioglycolate tube.

Obligate anaerobes

Organisms that are killed by oxygen and grow at the bottom of thioglycolate tubes, away from oxygen.

Facultative anaerobes

Organisms that can grow with or without oxygen but generally show better growth where oxygen is present.

Aerotolerant anaerobes

Organisms that do not use oxygen for growth but are not harmed by its presence.

Microaerophiles

Bacteria that require oxygen for growth but at lower concentrations than are present in the atmosphere.

Anaerobic jar

A specialized container used to hold Petri plates and maintain an oxygen-free environment for cultures.

Catalase test

A diagnostic test that identifies the presence of an enzyme by looking for the release of bubbles when hydrogen peroxide is added.

Neutrophiles

Prokaryotes that grow best at a near-neutral pH.

Acidophiles

Prokaryotes that have optimal growth at pH values near $3$.

Alkaliphiles

Prokaryotes that have optimal growth at pH values above $9$.

Denaturation

The rapid breakdown of proteins that occurs when temperatures rise past the optimum for a microorganism's growth.

Optimum temperature

The specific temperature at which a microorganism exhibits its maximum growth rate.