Comparative Analysis of anaerobic metabolic pthaways in P.extremaustralis across Pseudomonas genomes

RAIGER IUSMAN LAURA; TRIBELLI PAULA M.; SORIA MARCELO; LOPEZ NANCY I.

Rosario

Congreso; IX Congreso de Microb[iologia General; 2013

SAMIGE

Metabolic versatility is a characteristic among Pseudomonas species that includes the use of different energy production strategies under low oxygen tension. Recently, we have studied some aspects of the microaerobic metabolism of P. extremaustralis, and obtained the whole genome of this species proceeding from an Antarctic environment. In this work, a comparative analysis of the main anaerobic pathways described in Pseudomonas, arginine and pyruvate fermentation and denitrification, was performed. Comparison was made using the genome sequences of 27 Pseudomonas strains available in the NCBI database, and including pathogenic, free-living environmental strains and P. extremaustralis, in order to assess the anaerobic metabolism in this genus and the evolutionary history of the involved genes. BLAST online resources, and tools included in SEED-Viewer within RAST Program and Pseudomonas Genome Database were used for sequence comparison. Mega 5.05 software for phylogenetic studies and Detrended Correspondence Analysis as a multivariate statistical analysis were also used. Denitrification involves the stepwise reduction of nitrate to nitrite,- nitric oxide, nitrous oxide , and, eventually, to dinitrogen. This metabolism presented high variability among Pseudomonas species. P. aeruginosa, P. mandelii, P. stutzeri and some P. fluorescens strains showed the complete machinery, while in others is absent. P. extremaustralis, were able to perform only nitrate reduction, and lacked the nitrite reductase machinery but, interestingly, presented the rest of the operons involved in nitric and nitrous oxides reduction, perhaps as a relictual metabolism. Pyruvate fermentation was conserved in this genus. The LdhA (fermentative lactate dehydrogenase) phylogenetic analysis showed that a common ancestor could be proposed for Proteobacteria and Pseudomonas. The ack gene, coding for acetate kinase and described as crucial for survival under anaerobic conditions, was found only in P. aeruginosa, P. extremaustralis (which presented two copies) and in P. stutzeri strains. Most of the analyzed Pseudomonas, except the plant pathogens P. syringae DC3000 and P. syringae T, showed at least one copy of the entire operon arcABCD encoding enzymes involved in arginine fermentation. Phylogenetic analysis of ArcA showed strong relationship of this metabolism among Pseudomonas species but seems to be not conserved among Proteobacteria. P. fluorescens, P. putida, P. stutzeri and P.extremaustralis showed one or more duplicated arc genes. Remarkably, our results showed that nitrate respiration, that confers higher amount of energy under anaerobic conditions, was the less conserved pathway among Pseudomonas genus. Pyruvate and arginine fermentation showed to be conserved anaerobic metabolisms, although not all the genes involved were present in the analyzed genomes.