#Microbiotiful - A toilet brush

Is there a microorganism that means to science what Muhammad Ali meant to sports? If so, the answer must be Escherichia coli. A true legend, E. coli (as it is famously abbreviated) is probably the best-known bacterium of all time. For millennia it was just one of many bacterial species that line the intestine of human beings and numerous animals before it rose to fame in the 20th century to become a heavyweight champion of fundamental research, molecular techniques, and water quality monitoring. But beware: E. coli can knock you out. Certain pathogenic strains (e.g. O157:H7) cause dangerous gastrointestinal disease.

Along with a few very similar genera, Enterobacter belongs to the “coliform” group of bacteria, named after its superstar, E. coli. Like most coliforms, Enterobacter species inhabit the intestines of humans and animals, so it’s hardly surprising to find them on a toilet brush. They 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.

Dozens of fungal genera feature in the human intestine, with Cladosporium among the most common. However, these molds are abundant throughout nature (except in the polar regions), and at least some level of Cladosporium is encountered in just about every household as whenever you open the window the spores get blown in—so they can find their way onto a toilet brush without any digestive assistance. Their presence is not necessarily a problem because Cladosporium species are rarely pathogenic to humans. They are, however, significant allergens, and can affect people who suffer from asthma or respiratory diseases where they occur in great numbers.

Many bacteria in nature have capabilities that animals and plants don’t. Take Sphingomonas, ovoid to cylindrical shaped microbes of the soil that produce pigmented colonies of yellow or off-white color. In 2008, a Canadian schoolboy won a prize for demonstrating that enriched soil bacteria can degrade 17 percent of carrier bag plastic within six weeks, with Sphingomonas having the biggest appetite for the polyethylene. But there’s no need to worry that they’ll decompose your toilet brush.

Bacteria make up most of our natural gut microbiota, but there are other microbes as well. A significant proportion are methane-producing archaea, notorious for their role in flatulence, which look like bacteria under the microscope but are, oddly, not at all related to them (in fact, in the evolutionary tree archaea are closer to us humans than to bacteria). And then there are fungi that our intestines accommodate, for example the Geotrichum yeasts. They are also found in soil, water, sewage, on plants and elsewhere. While they cause us grief by spoiling citrus fruit, cucumber and tomato crops, we make use of them commercially to inoculate the outside of cheeses such as Camembert, Saint-Nectaire and Reblochon, giving them a velvety white coat.