#Microbiotiful - A plastic duck

Crescent-shaped Caulobacter bacteria live in soil and aqueous environments, and that can include bath tubs in which plastic ducks float. The species C. crescentus has proved a useful model organism for researchers studying cell cycle regulation, asymmetric cell division, and cellular differentiation. That’s because its cells come in two varieties: one has a flagellum to make it swim, the other possesses a protruding tubular stalk that carries adhesive material at its end to make the cell stick to surfaces, including plastics. The first cell type can turn into the second after a while, and only this second cell type is able to divide into two. So C. crescentus can do both: roam around and stick in one place.

The bacterial genus Proteus is named after Proteus, a mythological Greek god of the sea, characterized in Homer's Odyssey as highly changeable in appearance. Why? Proteus cells can vary in length and abilities. Under certain conditions, they alter their appearance and collectively swarm across the agar plate, creating visible patterns that change over time. In nature, Proteus bacteria tend to live in rather ungodly places, including decomposing animal matter, sewage, manure soil, as well as in the intestine and feces of human beings, which is probably how the plastic duck picked them up. Some are opportunistic pathogens, causing urinary tract and other infections in hospitals and nursing homes.

Like quite a few other microorganisms, Agrobacterium species can adhere to things, including plastics. But these bacteria are a little different: in nature, they bind to plant cells and inject them with DNA coding for genes that make the plant grow a tumor. This tumor then returns substances that the bacteria need. The species Agrobacterium tumefaciens causes great economic damage to agriculture (hence the “agro” in its name), afflicting grapevines, stone fruits, nut trees, sugar beets, and other crops. While agrobacteria also adhere to plastic ducks, there is no literature to suggest that the ducks grow a tumor.

What is known about the genus Microbacter is that there is only one species, Microbacter margulisiae. This Gram-negative, anaerobic, non-spore-forming and non-motile bacterium was first isolated about ten years ago from sediments of the river Rio Tinto in Huelva, Spain. Maybe Microbacter are a lot more widespread than the information we could find suggests—or our plastic duck has been on a river cruise in Spain. We just don’t know.