Bacteria are the plural of bacterium, which are microscopic one-celled organisms. They are found everywhere and can be harmful, as in infections; or they can be beneficial, as in fermentation or decomposition. Five types of bacteria are: Coccus, Bacillus, Spirillum, Rickettsia, and Mycoplasma.
I believe the correct word in the blank would be biological. I don't think anything else will fit in, especially when monomers of biological polymers are truly larger and more complex.
