To get around, Pseudomonas aeruginosa bacterium use a number of motility strategies, such as twitching and gliding. In this image, we see a special kind of bacterial motility behavior known as swarming, where a mass of bacteria moves collectively across a surface.  This is an example of singled celled bacterial species acting in a multicellular way. For a group of cells to swarm, the bacterium … Continue reading Colonies 4

It may be hard to believe, but this sea of shiny, donut-shaped colonies are Pseudomonas aeruginosa colonies. These Pseudomonas colonies have a genetic mutation that causes many of the bacteria’s genes to be shut off. The donut-shape of these colonies may indicate a two-step growth phase where the younger cells on the outside edge of the colony grow towards more nutrients while the older cells in … Continue reading Colonies 3

No one likes to be in crowded spaces, so when colonies reach a critical cell density, cells within the colony begin to lyse, dramatically changing the architecture of the colony. The colony on the left is a wild-type colony, while the colony on the right is a genetic mutant that exhibits an autolytic phenotype, that is the bacterium’s own enzymes “eat up” its cells. The … Continue reading Colonies 1 and 2

A single bacterial cell is invisible to the naked eye. As that single cell grows and divides into new cells, however, it forms a visible pile of bacteria. In microbiology, we call this pile of bacteria a colony. A colony’s appearance can indicate a lot about the bacterial cells within, such as how they utilize nutrients, if they carry genetic mutations, and how the bacterial … Continue reading Colonies on a Plate