ABSTRACT: Alginate, a major exopolysaccharide (EPS) produced by P. putida, is known to create hydrated environments and alleviate the effect of water limitation. In addition to alginate, P. putida is capable of producing cellulose (bcs), putida exopolysaccharide a (pea), and putida exopolysaccharide b (peb). However, unlike alginate, not much is known about their roles under water limitation. Hence, in this study we examined the role of different EPS under water stress. To create environmentally realistic water stress conditions as observed in soil, we used Pressurized Porous Surface Model (PPSM). Our main hypothesis was that under water stress, absence of alginate would be compensated by the other EPS. To test our hypothesis, we investigated colony morphologies and whole genome transcriptomes of P. putida KT2440 WT and its mutants deficient in either alginate or all known EPS A custom-made Nimblegen (WI, USA) whole genome one-color oligonucleotide expression array (12x135K with 45-60 mer probes) of P. putida KT2440 was used to investigate effect of water stress on the differential expression of the whole genome. In this study Pseudomonas putida KT2440 wild type (WT) and two of its mutants deficient either in alginate (Alg-), or all known EPS (EPS-) production were used and grown under dry (water stress) and wet (without water stress) conditions. (Deleted genes in Alg-: PP1277-PP128; in EPS-: PP1277-1288 (alg) + PP2634-2638 (bcs) + PP3132-3142 (pea) + PP1795-1788 (peb)) (Nilsson et al., 2011).39. Nilsson, M., Chiang, W.C., Fazli, M., Gjermansen, M., Givskov, M., and Tolker-Nielsen, T. (2011) Influence of putative exopolysaccharide genes on Pseudomonas putida KT2440 biofilm stability. Environ Microbiol. 13 (5):1 357-1369
