Comparative proteomics reveals essential mechanisms for osmotolerance in Gluconacetobacter diazotrophicus

Plant growth-promoting bacteria are a promising alternative to improve agricultural sustainability. Gluconacetobacter diazotrophicus is an osmotolerant bacterium able to colonize several plant species, including sugarcane, coffee, and rice. Despite its biotechnological potential, the mechanisms controlling such osmotolerance remain unclear. The present study investigated the key mechanisms of resistance to osmotic stress in G. diazotrophicus. The molecular pathways regulated by the stress were investigated by comparative proteomics, and proteins essential for resistance were identified by knock-out mutagenesis. Proteomics analysis led to identify regulatory pathways for osmotic adjustment, de novo saturated fatty acids biosynthesis, and uptake of nutrients. The mutagenesis analysis showed that the lack of AccC protein, an essential component of de novo fatty acid biosynthesis, severely affected G. diazotrophicus resistance to osmotic stress. Additionally, knock-out mutants for nutrients uptake (Delta tbdr and Delta oprB) and compatible solutes synthesis (Delta mtlK and Delta otsA) became more sensitive to osmotic stress. Together, our results identified specific genes and mechanisms regulated by osmotic stress in an osmotolerant bacterium, shedding light on the essential role of cell envelope and extracytoplasmic proteins for osmotolerance. (C) 2020 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.

Automated summary

This study investigated the key mechanisms of resistance to osmotic stress in Gluconacetobacter diazotrophicus. Proteomics analysis identified regulatory pathways for osmotic adjustment, de novo saturated fatty acids biosynthesis, and uptake of nutrients, while mutagenesis analysis showed the essential role of specific proteins in osmotolerance. The findings shed light on the importance of cell envelope and extracytoplasmic proteins for osmotolerance in this osmotolerant bacterium.