PNAS: Plasmids can spread between different bacterial 'communities'

DNA molecules called plasmids, some of which protect bacteria from antibiotics, can spread rapidly through bacterial "colonies" treated with antibiotics, a new study sho.

Plasmids are present in bacterial cells and sometimes slow the bacteria's reproduction -- but they carry genes that prevent antibiotics from working (called antimicrobial resistanc.

The new laboratory study, by the University of Exeter, found that plasmids that benefit one or more species are not only spread through those species, but also to other species in the communi.

Bacterial communities exist both in the environment and in the "microbiome" of individual organisms, including huma.

"Typically, antimicrobial resistance isn't related to the bacteria themselves -- it's encoded in the plasmids they carry and can be passed on," said Arthur Newbery, lead author of the stu.

Plasmids can hop between bacteria, and while most do not cause antimicrobial resistance, those plasmids confer immediate resistance in new hos.

"When antibiotics are available, these plasmids become beneficial, which is one reason why resistance emerges in hospitals and spreads rapid.

As one or more bacterial species benefit from carrying the plasmid, the plasmid reaches a "higher density" in the population -- making it more likely to spread to other speci.

This, in turn, makes the plasmid more likely to be passed on to a pathogenic (disease-causing) species in the community -- even if the species has not been exposed to antibioti.

Dr Dirk Sanders, also from ESI, said: "Our results suggest that exposure of microbial communities - including human microbial communities - to antibiotics may facilitate the spread of other plasmid-encoded genes, including antimicrobial resistance gen.

The study used a network approach—a very effective way to examine complex situations ranging from bacterial communities to epidemi.

The team is already expanding the study to test with more plasmids and more complex bacterial communities (including tests of how plasmids spread in wastewate.

"There is a high potential for plasmid-induced antimicrobial resistance to spread in the environmental setting," explained .

The paper, published in the Proceedings of the National Academy of Sciences, is titled: "Two-part interacting short-term fitness effects shape the network structure of reciprocal and antagonistic communiti.

Fitness effects of plasmids shape the structure of bacteria–plasmid interaction networks