Diminished redundancy of outer membrane factor proteins in rhizobiales: a nodT homolog is essential for free-living Rhizobium etli

• Published in: Journal of molecular microbiology and biotechnology Vol. 13; no. 1-3; p. 22
• Main Authors: Hernández-Mendoza, Armando, Nava, Noreide, Santana, Olivia, Abreu-Goodger, Cei, Tovar, Anibal, Quinto, Carmen
• Format: Journal Article
• Language: English
• Published: Switzerland 01-01-2007
• Subjects: Alphaproteobacteria - genetics; Alphaproteobacteria - metabolism; Anti-Bacterial Agents - pharmacology; Bacterial Outer Membrane Proteins - genetics; Bacterial Outer Membrane Proteins - metabolism; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Chromosomes, Bacterial; Gene Expression Regulation, Bacterial; Molecular Sequence Data; Operon; Plasmids - genetics; Restriction Mapping; Reverse Transcriptase Polymerase Chain Reaction; Rhizobium etli - drug effects; Rhizobium etli - genetics; Rhizobium etli - metabolism
• ISSN: 1464-1801
• DOI: 10.1159/000103594

Rhizobium etli is a gram-negative soil bacterium that induces nitrogen-fixing nodules on common bean roots (Phaseolus vulgaris). R. etli encodes two genes homologous to nodT of Rhizobium leguminosarum. nodTch is chromosomal and forms an operon with new genes resembling a multi-drug efflux pump of the resistance-nodulation-cell division (RND) family. nodTch is the last gene of this operon and can also be independently transcribed; the gene product is located in the bacterial outer membrane. Cell survival requires nodTch under all conditions tested. A second nodT gene, nodTpc, is encoded by plasmid c; it is constitutively transcribed but does not complement the essential function encoded by nodTch. NodT proteins belong to the outer membrane efflux proteins of the TolC superfamily. The number of duplications in the tolC gene family positively correlates with genome size in gram-negative bacteria. Nonetheless, some alpha-proteobacteria, including R. etli, encode fewer outer membrane factor exporters than expected suggesting further roles in addition to detoxification.