meliloti on a proteomic as well as a transcriptomic scale [12–15]. But the cellular response of S. meliloti to acid stress has so far not been investigated on a genome-wide level. pH stress can affect cells in several ways and therefore different responses exist. Acid tolerance in general is a mechanism of the cell to face an unfavourable acidic condition, whereas
an adaptive AZD1480 chemical structure acid tolerance (ATR) is defined as increased tolerance against low pH after growing cells in moderately low pH media  (for review see ). For rhizobia most studies about genes involving the acid stress response have been conducted with S. medicae (formerly classified as S. meliloti WSM 419). By using a transposon mutagenesis system  a functionally diverse set of pH responsive and acid tolerance related genes could be identified . Gene products required for acid tolerance in S. medicae are for example ActP, a CPx heavy metal transporting ATPase Nutlin-3a in vitro , and ActA, an apolipoprotein acyl transferase . A gene coding for a regulatory protein known to be
required for the acid tolerance in S. medicae is actR . The encoded response regulator ActR is activated by its corresponding sensor histidine kinase ActS, whose loss also leads to sensitivity to low pH. The cbbS gene involved in CO2 fixation and the narB gene involved in nitrate assimilation as well as the nitrogen fixation regulator genes fixK and nifA could be identified as target genes for the regulator ActR . Along with the genes required for low pH tolerance some further genes up-regulated by low pH were identified for S. medicae [19, 24]. Among these was lpiA, a gene found to be necessary for the adaptive acid tolerance (ATR). In Rhizobium tropici, the bacterial symbiont of Phaseolus vulgaris, this gene was also up-regulated by low pH and was found to be necessary for an increased nodulation competitiveness . In this study the transcriptional response of S. meliloti strain 1021 following a pH shift from pH 7.0 to pH 5.75 Selleckchem Venetoclax was
analysed on a genome wide level. Using whole-genome Sm6kOligo microarrays  the expression of S. meliloti genes responding to this environmental change was monitored over a period of one hour. The data obtained was filtered and clustered to obtain groups of genes with a similar behaviour. Results and Discussion Growth analysis of S. meliloti 1021 cultures exposed to neutral and acidic pH The aim of this study was to analyse the transcriptional response of S. meliloti 1021 following a shift from a neutral to an acidic pH. Since adaptation to new environmental conditions means passing through an evolving process of cellular responses until reaching a steady state balance, it was decided to monitor the transcriptional response over a certain period of time. One critical point concerns the https://www.selleckchem.com/products/elacridar-gf120918.html correct choice of parameters for the pH shift. The pH stress should be applied to S.