Scientists at the John Innes Center (England) have discovered plasmids - small molecules of bacterial DNA - that can influence the survival of microorganisms even in the absence of visible advantages for the hosts. This is reported in an article published in the journal PLOS Biology.

The researchers studied the plasmid gene encoding the RsmQ protein from the soil bacterium Pseudomonas fluorescens. It turned out that RsmQ can influence how the host bacteria perceive the external environment. When RsmQ was present in the plasmid, the cell reacted differently to changes in the external environment, improved its ability to survive with different food sources, and moved less.

Plasmids can be transferred from bacterium to bacterium through conjugation, which is called horizontal gene transfer. These DNA fragments often give microorganisms useful traits, such as the ability to survive in the presence of antibiotics or successfully colonize plants. The plasmid carrying the RsmQ gene is able to proliferate in bacterial populations, changing their behavior to a greater extent than previously thought.

According to the authors, RsmQ is the first known case confirming the existence of plasmid-encoded global regulators capable of turning other proteins on and off, thereby changing cell behavior. This indicates that there is a closer symbiotic relationship between plasmids and hosts than scientists thought.