Mechanosensing in E. coli – similarities with vertebrates uncovered

Researchers from University of Colorado Boulder (CO, USA) have discovered that individual Escherichia coli can sense the external environment via voltage-induced calcium flux – a mechanism similar to vertebrate’s neurons. This suggests the mechanism is highly conserved, and may also be implicated in infection as many bacterial species rely on mechanical contact in pathogenicity.

First author, Giancarlo Bruni (University of Colorado Boulder) commented: “People typically think that [bacteria]are these little things, that all they are doing is trying to divide and create more energy. [But] we’re not all that different.”

It has previously been understood that bacteria can react to a variety of chemical cues; however, more recently research into physical cues has been undertaken. This study, published recently in the Proceedings of the National Academy of Sciences, is believed to be the first to document electrical excitability in response to mechanical stimulation in individual bacterial cells.

The researchers inserted genetically-encoded calcium sensors into the E. coli and observed the bacteria’s response to mechanical stimuli using microscopy. The team discovered that when the E. coli were mechanically stimulated with a hydrogel, cytoplasmic calcium levels increased. In addition, the bacteria altered protein concentrations dependent on physical environment.

The group went on to demonstrate that inhibiting calcium flux stopped the change in bacterial protein concentrations, whilst inducing voltage-induced calcium flux reproduced the protein alterations. This suggests calcium relays cues about the physical environment, as senior author, Joel Kralj (University of Colorado Boulder) explained: “What we think could be happening is that they’re using these electrical signals to modify their lifestyle.”

These findings suggest there may be a conserved mechanism of mechanotransduction from bacteria right up to vertebrates. Moreover, mechanical contact has been implicated in the pathogenicity of some bacterial species, and these results could shed new light on this phenomenon.

Kralj concluded: “If we can block bacterial electrical activity, they may be less likely to infect, because now they don’t know that they have landed on your soft delicious gut cell. We could cut their hands off so they can no longer feel.”

Sources: Bruni GN, Weekley RA, Dodd BJT & Kralj JM. Voltage-gated calcium flux mediates Escherichia coli mechanosensation Proc. Natl Acad. Sci. doi:10.1073/pnas.1703084114 (2017) (Epub ahead of print);


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