Abstract
The ability of bacteria to adapt to external osmotic changes is fundamental for their survival. Halotolerant microorganisms, such as Tistlia consotensis, have to cope with continuous fluctuations in the salinity of their natural environments which require effective adaptation strategies against salt stress. Changes of extracellular protein profiles from Tistlia consotensis in conditions of low and high salinities were monitored by proteogenomics using a bacterial draft genome. At low salinity, we detected greater amounts of the HpnM protein which is involved in the biosynthesis of hopanoids. This may represent a novel, and previously unreported, strategy by halotolerant microorganisms to prevent the entry of water into the cell under conditions of low salinity. At high salinity, proteins associated with osmosensing, exclusion of Na+ and transport of compatible solutes, such as glycine betaine or proline are abundant. We also found that, probably in response to the high salt concentration, T. consotensis activated the synthesis of flagella and triggered a chemotactic response neither of which were observed at the salt concentration which is optimal for growth. Our study demonstrates that the exoproteome is an appropriate indicator of adaptive response of T. consotensis to changes in salinity because it allowed the identification of key proteins within its osmoadaptive mechanism that had not previously been detected in its cell proteome.
Highlights
All living microorganisms are exposed to a variety of environmental parameters that define their habitats
This study revealed that T. consotensis combined different adaptive strategies to counteract the changes in the environmental salinity
This study identified proteins that play an important role in the osmoregulatory mechanisms of T. consotensis under hypo-osmotic and hyperosmotic conditions, information found regarding secreted proteins involved in salinity stress response was limited
Summary
All living microorganisms are exposed to a variety of environmental parameters that define their habitats. To survive they must be able to sense environmental changes and react to with various adaptive mechanisms [1]. One of the most important environmental factors for halotolerant organisms is the salt concentration of the surrounding water while osmotic stress is a PLOS ONE | DOI:10.1371/journal.pone.0135065. This work was carried out under MAVDT Research Permit Resolution No 0168, 2009 and MAVDT Contract No 56, 2013 for Access to Genetic Resources
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