The plural of bacterium is
1 In most formal writing, bacterium is the singular form of the noun, and bacteria the plural form. 2  This is in accord with the word's Latin etymology. 3  However, in ordinary speech, some speakers use bacteria as a singular, with plural either bacteria or bacterias. 4  This is usually considered incorrect.lastics are energy-rich substances, which is why many of them burn so readily. Any organism that could unlock and use that energy would do well in the Anthropocene. Terrestrial bacteria and fungi which can manage this trick are already familiar to experts in the field.