Bacteria were one of the first life forms ever to appear on earth and are found in practically every single environment across the globe. They can be found in the deepest and darkest depths of the sea, suspended in ancient and secret ice caverns, and thriving in the most extreme climates imaginable. Deinococcus radiodurans was first discovered from experiments using radiation treatment on canned food, with this organism thriving in radiation.

Other interesting microorganisms that can survive extreme climates are those that can produce endospores! One of the most well-known examples of this is the genus Bacillus! During the Apollo 16 space mission, the endospores of Bacillus subtilis were researched to determine the survivability of these spores in both space vacuum and solar UV irradiation. Due to the wide variability of environments that bacteria can be found in, there is an equally wide variability of relationships that it can play with the natural world. Bacteria can be parasitic, symbiotic, and mutualistic, and many even have commensalism relationships with their environment.

Bacteria come in all different shapes, colors, and sizes, which we call morphology types. These differences can be observed at eye level and also at a microscopic level! The most common way to determine bacterial morphology at the cellular level is by doing a Gram stain. This can give insight into the shell shape, multicellularity, and cell wall typing of the bacteria. To determine the morphology type at the visual level, you’ll need to look for the following characteristics: culture condition, colony shape, colony elevation, colony edge, colony size, colony surface type, colony opacity, colony color, and any other defining characteristics.

Let us look at the image below.

The appropriate colony morphology would be the following: Tryptic Soy Agar (TSA) @ 30 °C, circular, raised, smooth, small, glistening, opaque, and yellow colony type. This organism is Rhodococcus fasciens. Having detailed colony morphologies can give better insight into microbial samples prior to identification. This is because variation in colony morphology may be indicative of variation in phenotyping, which is typical for organism adaptation in various environments. These adaptations may result in increased virulence or antimicrobial resistance.

Becoming familiar with the organisms you work with can not only help you better understand the IDs you receive from Biolog Lab Services – but will also have you prepared for anything new that may come your way!


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Describing bacterial colony morphology (