Monounsaturated fatty acid aerobic synthesis inBradyrhizobiumTAL1000 peanut-nodulating is affected by temperature

Abstract

Aims The aim of this work was to clarify the mechanism of monounsaturated fatty acid (MUFA) synthesis in Bradyrhizobium TAL1000 and the effect of high temperature on this process. Methods and Results Bradyrhizobium TAL1000 was exposed to a high growth temperature and heat shock, and fatty acid composition and synthesis were tested. To determine the presence of a possible desaturase, a gene was identify and overexpressed in Escherichia coli. The desaturase expression was detected by RT‐PCR and Western blotting. In B. TAL1000, an aerobic mechanism for MUFA synthesis was detected. Desaturation was decreased by high growth temperature and by heat shock. Two hours of exposure to 37°C were required for the change in MUFA levels. A potential ∆9 desaturase gene was identified and successfully expressed in E. coli. A high growth temperature and not heat shock reduced transcript and protein desaturase levels in rhizobial strain. Conclusions In B. TAL1000, the anaerobic MUFA biosynthetic pathway is supplemented by an aerobic mechanism mediated by desaturase and is down‐regulated by temperature to maintain membrane fluidity under stressful conditions. Significance and Impact of the Study This knowledge will be useful for developing strategies to improve a sustainable practice of this bacterium under stress and to enhance the bioprocess for the inoculants' manufacture.

Response of cellular fatty acids to environmental stresses in endophytic Micrococcus spp.

“…High contents of iso-C 15:0 and anteiso fatty acids are characteristic of Gram positive bacteria, and dominance of odd numbered branched chain fatty acids in Micrococcus shows agreement with previous findings (Kaur et al 2005) Similar to our findings, accumulation of saturated fatty acids and a declined level of unsaturated fatty acid content with increasing temperature has been reported in several other groups of organisms (Denich et al 2003;Canion et al 2013). It has been found that temperature not only affects the activity of fatty acid desaturates, but also affects the formation and availability of primers required for biosynthesis of fatty acids, and consequently affects the membrane fluidity and stability (Paulucci et al 2013). Increased saturation and chain length with increasing temperatures and accumulation of short-chain, unsaturated and branched-chain fatty acids at lower temperatures are in fact essential to maintain the homeoviscous adaptation of the membrane during temperature stress (Sinensky 1974;Chihib et al 2003;Mrozik et al 2004).…”

Reorganization of Azospirillum brasilense cell membrane is mediated by lipid composition adjustment to maintain optimal fluidity during water deficit

“…In fact, normal cellular function requires membrane lipid that are largely fluid and the bilayers of most organisms are entirely or mostly fluid at physiological temperatures (Paulucci et al . ). The fluidity of biological membranes may be modulated by metabolic regulation of lipid composition (Thompson ).…”

“…The primary lipid components of the bilayer are phospholipids (PL), with fatty acids (FAs) being the major component (Paulucci et al . ). The major membrane‐forming PL in bacteria are phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylglycerol (PG) and cardiolipin (CL) (Denich et al .…”

“…; Paulucci et al . , ). However, little is known about the function of cytoplasmic membrane and its components in response to different environmental conditions in A. brasilense .…”

“…UFA has an important effect on the fluidity and function of biological membranes (Aguilar and de Mendoza 2006). Numerous studies have demonstrated that FA plays a role in the adaptive response in many micro-organisms and is therefore an important factor in maintenance of biological activity (Drouin et al 2000;Paulucci et al 2011Paulucci et al , 2013. However, little is known about the function of cytoplasmic membrane and its components in response to different environmental conditions in A. brasilense.…”