In non-industrialized parts of the world today cholera remains common. It persists in part because V. cholera, the bacteria that causes the disease, is able to survive in diverse environments ranging from the intestinal lumen, to fresh water, to estuaries, to the sea.
A study in The Journal of General Physiology
provides new insights about the membrane components of V. cholera
that enable it to withstand otherwise deadly increases in osmotic pressure resulting from changes in its surrounding environment.
Like other bacteria, V. cholera
utilizes mechanosensitive channels to respond to rapid shifts in the external osmolarity. But the specific details of how it does so are unclear. Now, researchers from the University of Maryland utilize techniques previously used on E. coli
to analyze the functional properties of V. cholera
. Sergei Sukharev and colleagues performed the first patch-clamp analysis of channels in the plasma membrane of V. cholera
and compared them with those in E. coli
. They found that the gating and conductive properties of V. cholerae
channels were comparable to those of their E. coli
counterparts. A further comparison of the responses of channels in the two species indicated that, whereas small-conductance MscS-like channels were less dense in V. cholerae
than in E. coli
, large conductance MscL-type channels were present at higher density. Surprisingly, however, V. cholerae
was more sensitive than E. coli
to abrupt decreases in osmolarity. The findings suggest that the increased number of MscL channels might help compensate for other traits rendering V. cholerae
vulnerable to osmotic shock.