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Image of petri dishes for an article about what bacterial colonies are.
Published On: December 15th, 2020

Wondering what a bacterial colony is? By simple association, lots of people know that “colony” refers to a group, and “bacteria” refer to a type of microorganism. When you put those two things together, a bacterial colony should refer to a group of bacteria, right? Yes, but it is more than that.

Bacterial Colony Definition and Overview

A bacterial colony is what you call a group of bacteria derived from the same mother cell. This means that a single mother cell reproduces to make a group of genetically identical cells, and this group of cells form a mass, which is known as a bacterial colony.

In the laboratory setting, this refers to a bacterial mass that you can view on a nutrient agar plate.

When bacterial colonies form on an agar plate, their distinct characteristics (also known as colony morphology) are an indication of what type of bacteria they are. For example, Staphylococcus aureus, a commonly found bacteria on the skin, typically form circular, convex, golden-yellow colonies with clear margins.

Of course, the best practice to identify a colony by viewing it under a microscope, but a good primary indicator is a bacterial colony’s aspects visible by eye on the agar plate. Aspects like size, separation from other colonies, circularity vs. ovality, color, smoothness of the border and other characteristics can help distinguish the desired colonies from undesired.

Why Grow Bacterial Colonies?

The cultivation of bacterial colonies in research is widely used to produce specific proteins or enzymes from the bacteria. For example, bacteria that has been transfected with the right gene can produce these proteins of interest.

Plating the bacteria dilutes the individual cells to the point where when they grow into colonies—each is uniquely from a single cell. Alternately, metabiome studies are popular to find unique new bacterial strains for research purposes and can be isolated from humans, animals and plant environments. In addition, these colonies help in the development of industrial/synthetic enzymes. Bacteria can also be manipulated via genetic engineering to make a wide variety of other substances for food, agriculture, and more. As part of the isolation process, the colony grown from a single bacteria cell is collected through a process known as colony picking.

Colony Picking: What It Is and How It’s Done

Colony picking is the process of selecting and isolating microorganisms on an agar plate to reproduce them. When done manually in a lab, the colony picking protocol is somewhat tedious and looks something like this in a simplified manner:

  • An agar plate is studied to identify a suitably isolated bacterial colony to pick.
  • Once selected, the colony is picked up using a toothpick, pipette tip or inoculation loop and transferred to a colony picking cell culture medium, which could be liquid or agar.
  • Medium is then incubated overnight to encourage further bacterial growth.
  • The resulting colonies are then tested to determine if the end goal has been obtained – either the colony successfully produces a product, or a unique bacteria is found with unique therapeutic or other commercial properties.

The process above can take quite a while to carry out when done without using colony picking automation tools like colony picking robots. This is because identifying what a bacterial colony is and selecting it needs to be done with precision and in an aseptic environment to get the best results.

Automation of the colony picking protocol can reduce errors, reduce the need for human resources, and increase the production of colonies by more than tenfold, making it useful in any lab setting that cultures bacteria in mass amounts.

For more information on bacterial colony picking and colony picking lab equipment, contact Hudson Robotics today.