chapter 4 microbiology

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Microbial Growth

The increase in the number of microorganisms in a population.

Robert Koch

A German physician known for studying disease-causing bacteria and developing methods of cultivating bacteria.

Agar

A gelatinous substance derived from seaweed used to solidify culture media.

Binary Fission

The process by which prokaryotic cells divide, resulting in two daughter cells.

Exponential Growth

A rapid increase in population size where the number of cells doubles with each division.

Generation Time

The time it takes for a microbial population to double in number.

Biofilm

A complex community of microorganisms growing together on surfaces.

Extracellular Polymeric Substances (EPS)

Substances produced by bacterial cells that facilitate attachment and growth in biofilms.

Pure Culture

A population of cells derived from a single cell, allowing the study of one species.

Streak-Plate Method

A technique used to isolate pure cultures by spreading out cells on a solid medium.

Chemostat

A device that maintains continuous growth of microorganisms by replenishing nutrients and removing wastes.

Extremophiles

Microorganisms that thrive in extreme environmental conditions.

Psychrophile

An organism that grows best at temperatures between -5° and 15°C.

Thermophile

An organism that grows best at temperatures between 45° and 70°C.

Acidophiles

Organisms that thrive in acidic environments, typically at pH below 5.5.

Osmosis

The movement of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration.

Halophiles

Organisms that require high salt concentrations for growth.

Catalase

An enzyme produced by almost all aerobic organisms that converts hydrogen peroxide into water and oxygen.

Aerobic Respiration

A metabolic process that requires oxygen to produce energy.

pH

A measure of the acidity or alkalinity of a solution.

Lag Phase

The initial phase in a growth curve where cells do not increase in number as they adapt to their environment.

Log Phase

The phase of rapid cell division in a growth curve.

Stationary Phase

A phase in the growth curve where the number of viable cells remains constant due to limited nutrients.

Death Phase

A phase in the growth curve where the total number of viable cells decreases.

Nutrient Medium

A substance containing nutrients used for culturing microorganisms.

Environmental Factors

Conditions such as temperature, atmosphere, pH, and water availability that influence microbial growth.

Reactive Oxygen Species (ROS)

Harmful by-products of aerobic respiration including superoxide and hydrogen peroxide.

Optimum Growth Temperature

The temperature at which a microorganism grows best.

Staphylococcus

A genus of bacteria that can tolerate high salt concentrations.

Bioremediation

The use of microorganisms to remove or neutralize pollutants from the environment.

Exponential Growth Consequences

The rapid increase of harmful pathogenic bacteria in food items, such as 40,960 cells from just 10 in a few hours.

Bacterial Growth Curve

A graphical representation of the growth of bacterial populations over time, showing phases like lag, log, stationary, and death.

Microbial Interactions

The relationships between different microbial species, which can be cooperative or competitive.

Continuous Culture System

A system that maintains continuous growth of microorganisms by constantly adding nutrients and removing wastes.