An espionage in bacteria - new knowledge about fight against infections
Free-living bacteria typically encounter large fluctuations in their environment such as the transition from nutrient abundance to scarcity, i.e. feast and famine cycle. When growth substrates are exhausted, bacteria initiate specific developmental programs that prepare them for a long period of dormancy.
Much less is known about recovery from dormancy when nutrients become available again. It is now clear that cells display considerable phenotypic heterogeneity in the timing of recovery – in clonal population some cells start growing rather quickly while others stay dormant for longer and initiate growth only later. The timing of growth resumption has been suggested to rely on a stochastic process, but some reports also describe different states of dormancy (shallow and deep dormancy) and suggest that growth resumption from shallow dormancy is quicker. Scientists at University of Tartu Institute of Technology have shown that the order of cells resuming growth under some conditions is determined by the order they enter stationary phase, indicating a long-term memory effect in E. coli.
When nutrients run out, bacteria enter a dormant metabolic state. This low or undetectable metabolic activity helps bacteria to preserve their scant reserves for the future needs, yet it also diminishes their ability to scan the environment for new growth-promoting substrates. However, neighboring microbial growth is a reliable indicator of a favorable environment and can thus serve as a cue for exiting dormancy. We report that for Escherichia coli and Pseudomonas aeruginosa this cue is provided by the basic peptidoglycan unit (i.e. muropeptide). Scientists show that several forms of muropeptides from a variety of bacterial species can stimulate growth resumption of dormant cells and the sugar – peptide bond is crucial for this activity. These results, together with previous research that identifies muropeptides as a germination signal for bacterial spores, and their detection by mammalian immune cells, show that muropeptides are a universal cue for bacterial growth.
Read more in Scientific Reports!