Full Paper Production of EPS under Cr(VI) challenge in two indigenous bacteria isolated from a tannery effluent Rida Batool 1,2 , Kim Yrj € al € a 2 , Kamran Shaukat 3 , Nazia Jamil 1 and Shahida Hasnain 1 1 Department of Microbiology and Molecular Genetics, Quaid-e-Azam Campus, University of the Punjab, Lahore, Pakistan 2 Department of Biosciences, MEM-Group, University of Helsinki, Finland 3 Department of Applied Sciences, University of Huddersfield, United Kingdom Indigenous Cr(VI) reducing bacterial strains Pseudomonas aeruginosa Rb-1 and Ochrobactrum intermedium Rb-2 were evaluated for EPS production under Cr(VI) challenged and free conditions. Strain Rb-2 was more efficient in total EPS production (13.63 mg g 1 ) than Rb-1 (4.15 mg g 1 ) under Cr(VI) stress. Thick covering of capsular material around the cells of both bacterial strains was detected by electron microscopy. Transmission electron micrographs showed the appearance of pilli like structures under chromium stress by two bacteria suggested the possible involvement of this in exchange of hereditary material to increase their chances of survival under stress conditions. FTIR study showed involvement of sulphonate and hydroxyl groups in the binding with Cr(VI) ions. Solid-state 13 C NMR spectra revealed that EPS produced by both strains exhibited structural similarity with the glucan. The partial psl gene sequences of Rb-1 and Rb-2 showed homology with psl gene of Pseudomonas aeruginosa PAO1 and capsular polysaccharide biosynthesis protein of various strains of Pseudomonas. This is the first report on the identification of psl gene from Ochrobacterum in NCBI GenBank database up to our knowledge. Keywords: Exopolysaccharide / Cr(VI) reducing bacteria / Electron microscopy / FTIR / NMR / psl gene Received: November 18, 2014; accepted: March 13, 2015 DOI 10.1002/jobm.201400885 Introduction Extra cellular polymeric substances (EPS) are the major metabolites produced by the microbes that not only provide protection from harsh environmental condi- tions but also aid in the attachment of the organisms to a vast variety of biotic and abiotic surfaces [30, 31]. In bacteria, EPS are localized either on the cell surface or outside the cell surface, regardless of their origin. Bacterial EPS are a complex mixture of high molecular weight polymeric macromolecules such as polysacchar- ides, proteins, uronic acids, lipids together with some other non-polymeric low molecular weight compo- nents [29]. EPS facilitate the bacteria in cell-to-cell aggregation, biofilm formation, protection from desiccation, and resistance to destructive exogenous substances. Additionally, EPS played an important role in scavenging heavy metals from the contaminated environment by precipitating heavy metal ions in polymeric mass [29, 37]. The ionizable groups of EPS form complexes with metal ions resulting in metal chelation [19]. Previously, many microbes such as bacteria, algae or fungi have been reported for the removal of Cr(VI) from the environment due to their EPS producing ability [13, 15, 27]. These microbes might be exploited to remove Cr(VI) from contaminated sites [19]. Bacterial extracellular polymeric substances (EPS) are quite heterogeneous in nature controlled by a set of different genes. The psl (polysaccharide synthesis locus) is the major component of the biofilm produced by Pseudomonas aeruginosa. Pseudomonas produces at least three different types of polysaccharides, which contrib- ute towards the matrix alginate, e.g., pel (referring to pellicle) and psl. Alginate is found as the major component of polysaccharides of the biofilm matrix produced by mucoid P. aeruginosa, controlled by alg Correspondence: Dr. Rida Batool, Department of Microbiology and Molecular Genetics, University of the Punjab, Quaid-e-Azam Campus, Lahore-54590, Pakistan E-mail: ridazaidi_1@yahoo.com Phone: þ92 42 35952811 Fax: þ92 42 99230481 Environment  Health  Techniques EPS Production under Cr(VI) stressed condition 1 ß 2015 WILEY-VCH Verlag GmbH & Co. KGaA,Weinheim www.jbm-journal.com J. Basic Microbiol. 2015, 54,1–11