Bacteria behind acute periodontitis. Aggregatibacter actinomycetemcomitans most often lives peacefully in the mouth until circumstances lead it to become infectious. It forms flower-like colonies, here under a microscope sporting a colorful stain added by a researcher. Aa is gram-negative. Credit: Derren Ready (2012) CIL:38942, CIL. Dataset. https://doi.org/doi:10.7295/W9CIL38942 Creative Commons license
Mythbuster: Ideas that bacterial collaborations within microbiomes are generous and exclusive appear to be quite wrong.