Laboratório de Biotecnologia (Setor de Biologia Integrativa), Universidade Estadual do Norte Fluminense Darcy Ribeiro (UENF), Campos dos Goytacazes, Rio de Janeiro, Brazil.
Res Microbiol. 2021 Jan-Feb;172(1):103785. doi: 10.1016/j.resmic.2020.09.005. Epub 2020 Oct 6.
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 (Δtbdr and ΔoprB) and compatible solutes synthesis (ΔmtlK and ΔotsA) 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.
植物促生菌是提高农业可持续性的一种有前途的替代方法。氧化葡糖醋杆菌是一种耐渗透压的细菌，能够定殖于包括甘蔗、咖啡和水稻在内的几种植物物种上。尽管具有生物技术潜力，但控制这种耐渗透压性的机制仍不清楚。本研究调查了氧化葡糖醋杆菌抵抗渗透压胁迫的关键机制。通过比较蛋白质组学研究了应激调节的分子途径，并通过敲除突变体鉴定了抵抗所必需的蛋白质。蛋白质组学分析确定了渗透压调节、从头合成饱和脂肪酸和营养物质吸收的调控途径。突变体分析表明，从头合成脂肪酸所必需的 AccC 蛋白的缺失严重影响了氧化葡糖醋杆菌对渗透压胁迫的抵抗能力。此外，营养物质吸收（Δtbdr 和 ΔoprB）和相容性溶质合成（ΔmtlK 和 ΔotsA）的敲除突变体对渗透压胁迫更为敏感。总之，我们的研究结果确定了耐渗透压细菌中受渗透压胁迫调节的特定基因和机制，揭示了细胞包膜和细胞外蛋白在耐渗透压性中的重要作用。
