What is a facultative anaerobe? How bacteria ‘breathes’ (or not)

This is the long name that describes how a microbe produces energy to live. If a microbe is an ‘aerobe’ it means it uses oxygen to live. You, in fact, are an aerobic organism (an aerobe). Some microbes, however, prefer to live in non-oxygenated environments, called ‘anaerobes’, but just because they don’t like oxygen, doesn’t make them bad. Many anaerobes can be beneficial.

A facultative anaerobe such as Gardnerella vaginalis is different to an anaerobe and an aerobe, because it can switch between both methods, both needing and not needing oxygen to make energy depending where it finds itself. If G. vaginalis is amongst oxygen, it will use it to make energy (ATP), and if it finds itself in an oxygen-deprived environment, it can switch to fermentation or anaerobic respiration, or ‘breathing under water’ for the likes of us.

Some other types of facultative anaerobes are Staphylococcus spp. (toxic shock syndrome), Streptococcus spp., Escherichia coli (E. Coli), and Listeria spp., all of which you have probably heard of before. ‘Staph’ is that skin infection that kids get most often, ‘Strep’ you will know of as the throat infection, and E.coli and listeria will both give you diarrhoea given half a chance.