Biochemical and molecular evidence of a Δ9 fatty acid desaturase from Ensifer meliloti 1021

Abstract

It has been reported that Ensifer meliloti presents a high proportion of monounsaturated fatty acids and has a putative desaturase gene designated as PhFAD12 (National Centre for Biotechnology Information), encoding a putative Δ12 desaturase-like protein. In this work, we report the desaturation capacity and characterisation of this gene encoding the putative fatty acid desaturase of E. meliloti 1021. This gene was also isolated from the rhizobial strain and overexpressed in Escherichia coli. Compared to a control, the expression of this gene in the transformed strain decreased the levels of palmitic and stearic acids, enhanced palmitoleic and cis-vaccenic levels, and allowed for the detection of oleic acid. E. coli overexpressing the putative desaturase gene was capable of desaturating palmitic and stearic acids to monounsaturated fatty acids, similarly to the rhizobial strain. Our studies show that AAK64726 encodes a Δ9 desaturase instead of a Δ12 desaturase as previously indicated. This work describes evidence for the presence of a desaturase-mediated mechanism in monounsaturated fatty acid synthesis in E. meliloti 1021, which is modified by high growth temperature. This mechanism supplements the anaerobic mechanism for unsaturated fatty acid synthesis.

Investigating the Role of the Stringent Response in Lipid Modifications during the Stationary Phase in E. coli by Direct Analysis with Time-of-Flight-Secondary Ion Mass Spectrometry

“…5 Yet, wild type E. coli does not produce any fatty acid desaturase and has also therefore been used as a model system for recombinant expression of desaturases. 53 We currently cannot explain the mechanism behind the observed desaturation. Our results suggest that the production of the enzyme(s) involved in desaturation is not regulated by ppGpp.…”

“…Other types of bacteria exhibit desaturases that modify existing phospholipids . Yet, wild type E. coli does not produce any fatty acid desaturase and has also therefore been used as a model system for recombinant expression of desaturases . We currently cannot explain the mechanism behind the observed desaturation.…”

Phosphatidylcholine‐deficient suppressor mutant of Sinorhizobium meliloti, altered in fatty acid synthesis, partially recovers nodulation ability in symbiosis with alfalfa (Medicago sativa)

“…Levels similar to that of OG10017 were observed in M15 and derivatives (Figure S6a; Table S1), suggesting that FabA might not contribute to the formation of this fatty acid. Notably, a desaturase that exists in S. meliloti (Paulucci et al., 2014) might constitute an additional pathway for introducing unsaturations into fatty acyl chains of phospholipids. Clearly, strains with a mutated fabA gene produce less PE(36:2) and more PE(34:1), PE(32:1), PE(32:0), and PE(33:1) than wild type, and therefore indicate a tendency to form less unsaturated and more saturated as well as shorter chain fatty acyl residues.…”

Membrane Homeoviscous Adaptation in Sinorhizobium Submitted to a Stressful Thermal Cycle Contributes to the Maintenance of the Symbiotic Plant–Bacteria Interaction

“…Lipid components of the bacterial cell envelope largely influence the bacteria-plant symbiotic interaction process (Siebers et al, 2016). Phosphatidylcholine (PC) is a PL present in the membranes of bacteria of the rhizobiaceae family (Sohlenkamp et al, 2003;Basconcillo et al, 2009;Paulucci et al, 2011Paulucci et al, , 2013Paulucci et al, , 2014Paulucci et al, , 2015 and is essential for symbiotic interactions of rhizobia with legumes. For example, root nodule formation on soybean with efficient N fixation after infection with Bradyrhizobium japonicum depends on the presence of PC in the bacterium (Hacker et al, 2008).…”