JGH, YJ, and WJY helped in sampling and data this website collection. All the authors read and approved the final manuscript.”
“Background Burkholderia pseudomallei is a Gram-negative bacillus and the causative agent of melioidosis, BKM120 a severe disease endemic in Southeast Asia and northern Australia [1]. The organism is an environmental saprophyte
found in soil and water. It infects humans and animals mostly by direct contact with wet soil [1, 2]. The incidence of melioidosis is high in northeastern Thailand, where saline soil and water are abundant [3, 4]. The salt concentration in soil in this region ranges from 40 to 1,000 mM NaCl – significantly higher than the 20 mM NaCl average in other parts of the country (Development ATM/ATR activation Department, Ministry of Interior,
Thailand). It has been suggested that high salt or osmotic stress in northeast Thailand may be a key factor for B. pseudomallei alteration for survival in the natural environment, and it may enable the bacteria to establish the infection in respective hosts. The relationship between high salt concentration and susceptibility to bacterial infection is described in cystic fibrosis (CF) patients [5]. The lung airway surface liquid of CF sufferers has twice the NaCl concentration of healthy lungs [6]. Opportunistic infections of CF lungs have been linked with a variety of pathogens, including B. cepacia complex [7, 8] and B. pseudomallei[9]. However, the impact of salt and osmotic stress on B. pseudomallei and the related mechanisms underlying B. pseudomallei pathogenesis in CF patients are unknown. An earlier
study demonstrated that the killing efficiency of Burkholderia species, including B. pseudomallei, against the nematode Caenorhabditis elegans is enhanced in condition containing 300 mM NaCl [10]. We also showed that B. pseudomallei grown under salt stress invades a lung epithelial cell line A549 [11] more efficiently, and exhibits significantly greater Chlormezanone resistance to ceftazidime, an antibiotic used to treat melioidosis [12]. Our transcriptional analysis revealed B. pseudomallei pre-exposed to salt stress up-regulates a 10-fold increase of a gene associated with short-chain dehydrogenase/oxidoreductase (SDO) [11]. A different study by Bhatt & Weingart [13] also showed that an oxidoreductase encoding gene (bsrA) was up-regulated in B. cenocepacia in response to increased NaCl concentrations. However, the role of SDO for B. pseudomallei adaptation to osmotic or salt stress remains unknown. In the present study, we analyzed the protein sequence and predicted structure of B. pseudomallei SDO using bioinformatics analysis, to provide information about the possible functions of SDO. We further investigated its functional roles by constructing a SDO deletion mutant strain, and examined the interaction between mutant and host cells. The results suggest that SDO is an adaptive determinant of B.