colony

Examples of colony in the following topics:

• Viable Cell Counting

  • The colony becomes visible to the naked eye and the number of colonies on a plate can be counted.
  • Fewer than 30 colonies makes the interpretation statistically unsound and greater than 300 colonies often results in overlapping colonies and imprecision in the count.
  • At the end of the incubation period the colonies are counted by eye, a procedure that takes a few moments and does not require a microscope as the colonies are typically a few millimeters across.
  • The total number of colonies is referred to as the Total Viable Count (TVC).
  • Again the colonies would be counted and the viable cell count calculated.

• Direct Counting

  • If the cells are distributed on the plate properly, it can generally be assumed that each cell will give rise to a single colony.
  • The colonies can then be counted and, based on the known volume of the culture that was spread on the plate, the cell concentration can be calculated.
  • Bacterial colony counts made from plating dilutions of bacteria are useful to estimate the strength of bacterial infections; for example, a urinary tract bacterial infection.
  • Otherwise, instead of obtaining single colonies that can be counted, a so-called "lawn" of thousands of colonies will form, all lying atop each other.
  • Additionally, plating is the slowest method because most microorganisms need at least 12 hours to form visible colonies.

• Measurements of Microbial Mass

  • The measurement of an exponential bacterial growth curve in a batch culture was traditionally a part of the training of all microbiologists; the basic means requires bacterial enumeration (cell counting) by direct and individual (microscopic, flow cytometry), direct and bulk (biomass), indirect and individual (colony counting), or indirect and bulk (most probable number, turbidity , nutrient uptake) methods.
  • If the cells are efficiently distributed on the plate, it can be generally assumed that each cell will give rise to a single colony.
  • The colonies can then be counted, and based on the known volume of culture that was spread on the plate the cell concentration can be calculated.
  • As is with counting chambers, cultures usually need to be heavily diluted prior to plating; otherwise, instead of obtaining single colonies that can be counted, a so-called "lawn" will form, resulting in thousands of colonies lying over each other.
  • Additionally, plating is the slowest method of all: most microorganisms need at least 12 hours to form visible colonies.

• Cyanobacteria

  • Cyanobacteria include unicellular and colonial species.
  • Colonies may form filaments , sheets, or even hollow balls.
  • Some filamentous colonies show the ability to differentiate into several different cell types, including:
  • Many cyanobacteria form motile filaments called hormogonia, that travel from the main biomass to bud and form new colonies elsewhere.
  • To break away from the parent colony, a hormogonium often must tear a weaker filament cell, called a necridium.

• Recombinant DNA Technology

  • Modern bacterial cloning vectors (e.g. pUC19) use the blue-white screening system to distinguish colonies (clones) of transgenic cells from those that contain the parental vector.
  • In these vectors, foreign DNA is inserted into a sequence that encodes an essential part of beta-galactosidase, an enzyme whose activity results in formation of a blue-colored colony on the culture medium that is used for this work.
  • Insertion of the foreign DNA into the beta-galactosidase coding sequence disables the function of the enzyme, so that colonies containing recombinant plasmids remain colorless (white).
  • If the ligation was successful, the bacterial colony will be white; if not, the colony will be blue.

• Citric Acid and Other Organic Compounds

  • The black dots covering the colonies are Aspergillus spores.

• Biofilms

  • The development of a biofilm may allow for an aggregate cell colony (or colonies) to be antibiotic-resistant.
  • Dispersal of cells from the biofilm colony is an essential stage of the biofilm life cycle.
  • Recent evidence has shown that one fatty acid messenger, cis-2-decenoic acid, is capable of inducing dispersion and inhibiting growth of biofilm colonies.

• Aseptic Technique, Dilution, Streaking, and Spread Plates

  • Microbiologists rely on aseptic technique, dilution, colony streaking and spread plates for day-to-day experiments.
  • Samples can then be taken from the resulting colonies and a microbiological culture can be grown on a new plate so that the organism can be identified, studied, or tested.The streaking is done using a sterile tool, such as a cotton swab or commonly an inoculation loop.
  • Successful streaks lead to individual colonies of microbes.

• Glycocalyx

  • Streptococcus pneumoniae attaches itself to either lung cells, prokaryotes, or other bacteria which can fuse their glycocalyxes to envelop the colony).
  • It may permit bacterial colonies to survive chemical sterilization with chlorine, iodine, and other chemicals, leaving autoclaving or flushing with boiling water as the only certain methods of decontamination.

• Diagnosing Microbial Diseases

  • Upon incubation, colonies will arise and single cells will have been isolated from the biomass.
  • The use of plates for microbial culture aid in identification of microbes based on size, shape, colony formation and nutrient requirement.