#Microbiotiful - A kitchen sponge

Sphingomonas are bacteria that can be found in all sorts of natural and household environments, so it’s only a matter of time before they find their way onto your kitchen sponge. While they rarely cause any health issues in humans, S. paucimobilis and some other species do like to form biofilms, protective films of slime in which other, not-so-friendly bacteria can grow alongside. Techniques that remove the biofilms from your kitchen sponge? Forget it.

Crescent-shaped Caulobacter bacteria are regularly found in soil and aqueous environments, including drinking water reservoirs. So it’s not hard to see why they like kitchen sponges. 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 rod-shaped bacteria of the genus Enterobacter are found on the skin and lining the intestines of humans and animals, as well as literally further downstream in lakes and rivers, sewage and soil. They also contaminate food, which is one way they can find their way onto your kitchen sponge. Enterobacter have a flexible metabolism, being able to switch from oxygen-based respiration to fermentation when there is no oxygen. Recent research has shown that there may be a link between how prevalent a certain Enterobacter cloacae strain is in the intestine, and obesity.

If you’re a gourmet or very health-conscious, you’ve probably heard of Lactobacillus. These rod-shaped lactic acid producers are used as starter cultures in industry for controlled fermentation processes, helping to make yogurt, cheese, pickles, and many other foods. Likewise, they go about their fermentation business in and on your kitchen sponge, so if it starts smelling of cheese or sauerkraut or something in between, you’ll know why. However, lactobacilli don’t infect us. Quite the opposite, these bacteria form a key component of our body’s microbiota where they help to keep pathogens at bay. 

Well over a hundred bacterial genera have been detected on kitchen sponges, a prominent one being Flavobacterium. The cells are 4 to 8 µm in length, so slightly larger than most other bacteria. In a Petri dish flavobacteria form characteristic yellow colonies, hence their name (in Latin “flavus” means yellow or blond). They are found in soil, fresh and salt water, and a variety of other environments, and several species cause disease in freshwater fish. However, flavobacteria rarely cause humans any trouble. Sewage plants use their ability to degrade certain substances for the secondary treatment of wastewater.