We also tested the selleck chemical possibility that arginine might improve the growth of strain CFNX186-24 due to the presence of a putative N-acetylornithinase (EC 3.5.1.16) encoded in the plasmid p42f. In the Enterobactericeae this enzyme catalyzes the conversion of N-acetylornithine to ornithine, a key step in the arginine biosynthesis pathway [20]. However, the growth deficiency of strain CFN186-24 in MM was not Saracatinib clinical trial corrected by the addition of 1, 5, 10 or 15 mM arginine (data not shown). Furthemore, we constructed an argE mutant strain (ReTV3, Table 1) that was able to grow in MM without exogenous arginine at

the same rate as parental strain CFN42 (data not shown), confirming that this gene is not essential for arginine synthesis. Discussion Seminal studies on the phenotypic characterisation of plasmid-cured strains of R. leguminosarum and R. etli revealed that the absence of several plasmids cause a growth deficiency in rich and minimal medium [18, 21]. These findings suggested that undefined metabolic traits are present on rhizobial plasmids.

The bioinformatic analysis of 897 bacterial genomes performed by Harrison et al [13] revealed the presence of extrachromosomal core genes in 82 genomes mainly belonging to the Proteobacteria. In contrast with these in silico data, there is little experimental information on the contribution of these core genes to bacterial metabolism or cellular process. The few genes that have been functionally characterized encode

redundant functions and are totally dispensable for the cell [7–9, 12]. Our selleck study provides experimental evidence that the enzymes MOHMT (EC 2.1.2.11) and PBAL (EC 6.3.2.1) encoded on plasmid p42f are indispensable for the synthesis of pantothenate. Moreover, our results showed that the cluster of panCB, katG and oxyR genes was insufficient to restore full growth capacity to the p42f cured derivative CFNX186, implying that in addition to pantothenate synthesis, there are more functions encoded on plasmid p42f required for growth in MM. Obvious candidates for these functions could not be identified a priori among the 567 proteins encoded in p42f Etofibrate even though their predicted functions were recently updated with KAAS (KEGG Automatic Annotation Server and Pathway Reconstruction Server). We discarded arginine limitation as the cause for the growth deficiency of strain CFNX186-24. The arginine prototrophy displayed by a mutation in the p42f encoded argE suggests that in R. etli the conversion of N-acetylornithine to ornithine is catalyzed by the chromosome-encoded ArgJ, an ornithine acetyltransferase (OATase, EC 2.3.1.35), which transfers the acetyl group of N-acetylornithine to glutamate to produce ornithine and N-acetylglutamate. Functional OATases have been found in the majority of bacteria [20].