IIT –Madras shows how specific bacterial proteins act as molecular sensors of salt concentration, temperature

Chennai: In one of the latest findings, the Indian Institute of Technology (Madras) has shown how specific bacterial proteins act as molecular sensors of salt concentration and temperature.


The research would be helpful for developing treatment for bacterial infection and understanding fundamental mechanisms by which bacteria resist treatment.


The results of the IIT-Madras researchers, which involved both experiments and simulations, is now published in the prestigious peer-reviewed journal Nature Communications.


This research was conducted by Dr. Athi Narayanan Naganathan of the premiere institute and the work is significant as it explains in detail the structural changes that occur in bacterial proteins in response to stimulus.


“Bacterial systems displays incredible adaptability which is primarily driven by proteins that respond in an intricate manner to changing environmental conditions,” said Narayanan said speaking about the research.


He said that the study unveils the basic molecular forces that hold the protein together can go a long way in understanding pathogenicity.


“The susceptibility to and intensity of bacterial infection are directly related to the virulence of the bacteria. Bacterial virulence is in turn affected by external environmental conditions such as heat, presence of salts etc. Bacteria have developed regulatory mechanisms that enable their survival under hostile conditions in the host or outside,” she said.


Citing an example she said E. coli, a common bacterium that results in severe diarrhoea, fever, and dehydration, has to decide when and whether to express the virulence factors (molecules produced by bacteria) so that a host can be successfully invaded.


They primarily sense their location (say, whether they are in the soil or in a human host) by monitoring the external salt concentration and temperature.


Bacterial systems have evolved molecular sensors that can inform them whether a host has been invaded or if the environment is hostile or friendly.


“Such sensors, a majority of which are proteins, undergo structural changes proportional to the prevailing environmental conditions. These changes then determine the extent to which they interact with other proteins that in turn drives expression or silencing of specific genes,” she said.


The molecular mechanism by which bacterial proteins sense changes in salt concentrations was not clearly known.


To answer this, his research team has chosen a specific protein, Cnu, that is known to have osmo-regulatory (salt-regulatory) properties.




Cnu binds to another protein called H-NS and confers salt and temperature adaptability to the bacterium.


“We have investigated the role of solution osmolarity conditions in modulating the structure, stability, and conformational properties of Cnu and have shown that it acts as an exquisite molecular sensor of solvent ionic strength.” Narayanan said.




The array of conformations that Cnu populates in response to changes in salt concentration are remarkably matched in the binding partner, H-NS, resulting in large changes in the binding properties and hence function.


“Such molecular symphonies happen not just in bacteria but in all cell types, and what we show here is just one of the many mechanisms that are possible,” he said on the nature of this ground-breaking work. ENDS

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