Transcriptome profiling of a Sinorhizobium meliloti fadD mutant reveals the role of rhizobactin 1021 biosynthesis and regulation genes in the control of swarmingReport as inadecuate




Transcriptome profiling of a Sinorhizobium meliloti fadD mutant reveals the role of rhizobactin 1021 biosynthesis and regulation genes in the control of swarming - Download this document for free, or read online. Document in PDF available to download.

BMC Genomics

, 11:157

First Online: 08 March 2010Received: 16 September 2009Accepted: 08 March 2010

Abstract

BackgroundSwarming is a multicellular phenomenom characterized by the coordinated and rapid movement of bacteria across semisolid surfaces. In Sinorhizobium meliloti this type of motility has been described in a fadD mutant. To gain insights into the mechanisms underlying the process of swarming in rhizobia, we compared the transcriptome of a S. meliloti fadD mutant grown under swarming inducing conditions semisolid medium to those of cells grown under non-swarming conditions broth and solid medium.

ResultsMore than a thousand genes were identified as differentially expressed in response to growth on agar surfaces including genes for several metabolic activities, iron uptake, chemotaxis, motility and stress-related genes. Under swarming-specific conditions, the most remarkable response was the up-regulation of iron-related genes. We demonstrate that the pSymA plasmid and specifically genes required for the biosynthesis of the siderophore rhizobactin 1021 are essential for swarming of a S. meliloti wild-type strain but not in a fadD mutant. Moreover, high iron conditions inhibit swarming of the wild-type strain but not in mutants lacking either the iron limitation response regulator RirA or FadD.

ConclusionsThe present work represents the first transcriptomic study of rhizobium growth on surfaces including swarming inducing conditions. The results have revealed major changes in the physiology of S. meliloti cells grown on a surface relative to liquid cultures. Moreover, analysis of genes responding to swarming inducing conditions led to the demonstration that iron and genes involved in rhizobactin 1021 synthesis play a role in the surface motility shown by S. meliloti which can be circumvented in a fadD mutant. This work opens a way to the identification of new traits and regulatory networks involved in swarming by rhizobia.

AbbreviationsAHLN-acyl-homoserine lactones

TTSStype III secretion system

MMminimal medium

EPSexopolysaccharide

RT-qPCRreverse transcription-quantitative polymerase chain reaction

SmStreptomycin

SpSpectinomycin

KmKanamycin

ApAmpicillin

RifRifampin

NmNeomycin sulphate

ODoptical density

CASChrome azurol S.

Electronic supplementary materialThe online version of this article doi:10.1186-1471-2164-11-157 contains supplementary material, which is available to authorized users.

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Author: Joaquina Nogales - Ana Domínguez-Ferreras - Carol V Amaya-Gómez - Pieter van Dillewijn - Virginia Cuéllar - Juan Sanjuá

Source: https://link.springer.com/article/10.1186/1471-2164-11-157







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