Biology subjects

Lopez-Lara, I. M.

Publications and source records attributed to Lopez-Lara, I. M..

3 recordsLinked to original sources

bioRxiv2025

The effect of Sinorhizobium meliloti volatilomes and synthetic long-chain methylketones on soil and Medicago truncatula microbiomes

Bacterial volatile compounds play important roles in intra- and interkingdom interactions but very little is known about their effects on soil and plant microbiomes. The legume symbiont Sinorhizobium meliloti (Sm) releases volatile methylketones (MKs), one of which acts as an infochemical in bacteria and hampers plant-bacteria interactions. MK production in Sm is modestly increased in the absence of the long-chain-fatty-acyl-coenzyme-A (CoA) synthetase FadD. To explore further the ecological role of MKs on soil and plant bacterial communities, we aimed at obtaining an MK-overproducer Sm strain by deleting the 3-oxo-acyl-CoA-thiolase-encoding fadA gene. Analyses of the Sm wild type (wt), and fad mutant volatilomes identified seventeen compounds consisting mostly of MKs and fatty acid methyl esters (FAMEs) and revealed that the fadA mutant produced more MKs than the fadD mutant and much more than the wt, while in the fadD mutant FAME emission was increased. When natural soil or the rhizosphere of Medicago truncatula were exposed to wt and fadA volatilomes or synthetic MKs, bacterial alpha- or beta-diversity were not strongly affected but specific genera were identified which responded differentially to each condition. Interestingly, Sm volatilomes had a significant effect on root endosphere Ensifer/Sinorhizobium populations by maintaining their abundance over time in contrast to control conditions or exposure to synthetic MKs. This study provides new insights on the synthesis of rhizobial volatile compounds and represents the first exploration of the effects of bacterial volatilomes on plant bacterial communities, contributing to increase our knowledge on the complex molecular bases underlying plant-bacteria interactions.

microbiology↗

bioRxiv2024

Genes required for the formation of virulence-provoking bacterial sphingolipids

Sphingolipids are ubiquitous in membranes of eukaryotes and are associated with important cellular functions. Although sphingolipids occur scarcely in bacteria, for some of them they are essential and, in other bacteria, they contribute to fitness and stability of the outer membrane, such as in the well-studied -proteobacterium Caulobacter crescentus. We previously defined five structural genes for ceramide synthesis in C. crescentus. However, other mutants affected in genes of this same genomic region show cofitness with a mutant deficient in serine palmitoyltransferase. Here we show that at least two phospho-sphingolipids are produced in C. crescentus and that at least another six gene products are needed for the decoration of ceramide upon phospho-sphingolipid formation. All eleven genes participating in phospho-sphingolipid formation are also required in C. crescentus for membrane stability and for displaying sensitivity towards the antibiotic polymyxin B. The genes for the formation of complex phospho-sphingolipids are also required for C. crescentus virulence on Galleria mellonella insect larvae. Author SummarySphingolipids participate in the formation of biological membranes and molecular signaling in higher organisms. Many bacteria also accommodate sphingolipids in their membranes. Here we report that eleven genes participate in the synthesis of complex bacterial phospho-sphingolipids. Our data show that these lipids contribute to membrane stability, but also confer sensitivity towards certain antibiotics. The bacterium Caulobacter crescentus is widely distributed in fresh water lakes and streams and was considered to be non-virulent. However, we demonstrate that complex phospho-sphingolipids are the main virulence contributors in this bacterium.

microbiology↗

bioRxiv2022

Formation of sulfoquinovosyl diacylglycerol by acylation of sulfoquinovosyl glycerol

Sulfoquinovosyl diacylglycerol (SQDG) is a membrane-forming lipid present in photosynthetic organisms as well as in distinct bacteria growing in phosphate-limited environments. Four genes for SQDG biosynthesis were previously identified in Rhodobacter sphaeroides, the operon sqdBDC and sqdA. In this work, we found that SMc02490 of Sinorhizobium meliloti is an SqdA orthologue. Expression of the S. meliloti sqdBDC operon in Escherichia coli results in formation of sulfoquinovosyl glycerol (SQGro), while co-expression of this operon together with smc02490 (sqdA) results in formation of SQDG. Furthermore, SqdA allows for incorporation of exogenous SQGro into SQDG in S. meliloti and in E. coli cultures, suggesting that presence of SqdA in bacteria permit them to use environmental SQGro for the biosynthesis of the membrane lipid SQDG. An in vitro enzymatic assay for the acyltransferase SqdA was developed. Cell-free crude extracts of E. coli expressing sqdA can efficiently convert [35S]-sulfoquinovosyl monoacylglycerol into SQDG using as acyl donor acyl carrier protein. Bioinformatic analyses reveal that this sulfoquinovose acylation pathway for SQDG biosynthesis is delimited to the Hyphomicrobiales (Rhizobiales) and Rhodobacterales orders of Alphaproteobacteria.

microbiology↗