‘Facultative anaerobe’ is the long name that describes how some microbes produce 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), but some microbes, prefer to live in non-oxygenated environments, called ‘anaerobes’. Just because they don’t like oxygen, however, 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 – a facultative anaerobe.
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, 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.