Involvement of a SDR enzyme on the survival of Ochrobactrum sp. 11a under ionic and thermal stress

PRINCIPE, A.; JOFRÉ, E; CASTRO, M.; FISCHER, S; MORI, G

Tucuman

Congreso; XLV Reunión anual de SAIB; 2009

SAIB

The plant growth-promoting rhizobacterium Ochrobactrum sp. 11a is able to use a variety of substrates, including sugars, phenolic compounds and heavy metals. This ability to utilize a wide spectrum of substrates probably contributes to cell survival and proliferation in the nutritionally complex soil and rhizosphere environments. In this study, we have analyzed the function of a short chain dehydrogenase/reductase (SDR) from an Ochrobactrum sp. 11a- Tn5-B21 mutant. This mutant appeared to be sensitive to saline (300 mM NaCl) and thermal (40 ºC) stress. The introduction of plasmid pJN105 containing a copy of the gene encoding the SDR protein fully restored the ability of the mutant strain to tolerate both saline and thermal stresses, indicating that these observed changes were caused by the inactivation of this gene. Multiple alignment analysis of the predicted protein sequence showed a high similarity to SDR proteins from different symbiotic bacteria such as Sinorhizobium meliloti 1021 (84 %) and Mesorhizobium loti MAFF303099 (64 %). In addition, this protein showed a conserved domain corresponding to 3-ketoacyl-(acylcarrier- protein) reductase, an enzyme of fatty acid biosynthesis found in many bacterial species. Therefore, it is likely that this SDR protein may contribute to the catabolic ability and stress survival in Ochrobactrum.