Plants grow in interesting ways. You may have noticed that your houseplants “lean” towards the window, seeking the sunlight. This movement towards light is called phototropism. Tropism is a general term referring to any instance of growth or movement of an organism in response to the environment. Vines display another kind of tropism known as thigmotropism, meaning they respond to touch. In this set of … Continue reading Vines

Colonies 5

The colonies in this image display some of the diversity of pigment production in Pseudomonas aeruginosa. The blue-green colonies contain a pigment called pyocyanin, which is known to be toxic to human cells and helps the bacteria establish a niche during infections. The colonies containing a brown halo produce the brown pigment pyomelanin, which is thought to help the bacteria scavenge for iron, an essential … Continue reading Colonies 5

Colonies 4

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

Colonies 3

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

Colonies 1 and 2

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