The Bacteria that Live in Your Coffee Maker

This article was originally posted on RealClearScience.

Wherever you live, bacteria live. Wherever you can’t live, bacteria live. From hydrothermal vents to acid mines, microbes have the planet covered. They also have your Nespresso machine covered. Recently, Spanish researchers decided to inventory the microbial community that dwells inside George Clooney’s favorite coffee maker.

The team analyzed several Nespresso machines that had been operated for at least one year. They sampled the drip tray and subjected the microbes to high-throughput DNA sequencing. They found a wide diversity of bacteria, with Enterococcus and Pseudomonas appearing most frequently. The latter genus is particularly notable because certain species are known to degrade caffeine. Enterococcus and many of the other bacteria present probably cannot degrade caffeine, but simply tolerate an environment that many other species find unpleasant.

The authors then decided to observe the microbial colonization of a brand new Krups coffee maker over a two-month period. Their results are depicted below:

The figure shows an unstable and rapidly shifting community. A particular group of bacteria dominates for a few days and is then gradually replaced by another group. By the end of the two-month period, however, Enterococcus and Pseudomonas showed up. Combined with the results from the Nespresso machines, this suggests that these two genera are particularly suited to life inside a coffee maker.

This sort of “ecological succession” is not unusual. Indeed, scientists have observed elsewhere that “generalist” bacteria are often the first colonizers but are eventually replaced by more “specialist” bacteria. Something similar could be happening here.

From a more practical standpoint, the authors may have begun to uncover the sort of microbes that could be useful in wastewater treatment. Caffeine has been detected off the coast of the Pacific Northwest, and its impact on the environment is unknown. Perhaps one day, wastewater treatment facilities could employ a community of microbes to decaffeinate our pee.

Source: Cristina Vilanova, Alba Iglesias & Manuel Porcar. “The coffee-machine bacteriome: biodiversity and colonisation of the wasted coffee tray leach.” Scientific Reports 5, Article number: 17163. Published online: 23-November-2015. doi: 10.1038/srep17163