Enumeration of Microbes

Binary fission

A form of asexual reproduction in single-celled organisms by which one cell divides into two cells of the same size

CFU

Colony forming unit

CFU/ml

colony forming unit per ml

CFU/g

colony forming unit per gram

Decline phase

final phase of bacterial growth cycle, also known as death phase because it's when the bacteria die

Dilution factor

reciprocal/inverse of the dilution

Dilution series

making a series of dilutions of a sample, pulling from the previous tube each time a new dilution is made. also known as serial dilution

Direct count

methods that can determine bacterial concentration without the need for advanced equipment/techniques.

Exponential growth

growth whose rate becomes ever more rapid in proportion to the growing total number or size.

Generation time

the time interval required for the cells (or population) to divide

Growth rate

the rate at which the bacterial population is increasing

Hemocytometer

an instrument for visual counting of the number of cells in a blood sample or other fluid under a microscope.

Indirect count

Microorganisms in a sample are diluted or concentrated and grown on a suitable

medium; the development of growing microorganisms (for example, colony formation on

agar plates) is then used to estimate the numbers of microorganisms in the original sample

Lag phase

the first phase, when bacteria adapt themselves to growth conditions. It is the period where the individual bacteria are maturing and not yet able to divide

Log phase

the second phase, is a period characterized by cell doubling

OD

optical density, as measured by a spectrophotometer, helps determine the concentration of a sample.

Plate count method

method of plating serial dilutions to discover initial concentration of sample

Spectrophotometer

A machine that takes optical density readings to determine the concentration of a sample.

Spread plate method

Stationary phase

The third phase, when growth rate and death rate are equal

TFTC

Too Few To Count, when the number of colonies on a plate is less than 30

TNTC

Too Numerous To Count, when the number of colonies on a plate is greater than 300

Serial dilution

making a series of dilutions of a sample, pulling from the previous tube each time a new dilution is made.

Petrifilm

a method for determining concentration, each red dot represents 1 colony.

Countable range

30-300 CFU/plate

innoculation

The introduction of a microorganism into a culture medium

pure culture

a culture that contains only one strain of bacteria