Protozoans and pathogens make for an infectious mix

Single-celled organisms in the environment are protecting pathogenic bacteria and priming them for human infection, an international team of researchers has discovered.

Microorganisms such as protozoa and bacteria have been conducting an “arms race” for billions of years. Now scientists investigating how the environment affects bacterial interactions with human hosts have discovered that for pathogenic bacteria, such as Vibrio cholerae, these interactions may have made them not only stronger but much more infectious.

The results provide a new understanding about the mechanisms of infection and disease transmission.

The new observation that strains of V. cholerae can be expelled into the environment after being ingested by protozoa, and that these bacteria are then primed for colonisation and infection in humans, could help explain why cholera is so persistent in aquatic environments. Parcels known as expelled food vacuoles (EFVs), which are encased in a membrane, protect the bacteria in the protozoan gut and after they are ejected into the environment.