Identification and characterization of eight cadmium resistant bacterial isolates from a cadmium-contaminated sewage sludge

Abstract

CHOVANOVA ,K ., S LADEKOVA ,D ., K MEŤ ,V ., P ROKSOVA ,M ., H ARICHOVA, J., PUSKAROVA ,A ., P OLEK ,B . F ISSN 0006-3088. (Biologia). ISSN 1335-6399 (Biologia. Section Cellular and Molecular Biology). Cadmium-resistant bacterial community, isolated from sewage sludge contaminated by cadmium ions, was characterized by biochemical reactions, amplified ribosomal DNA restriction analysis (ARDRA) and in physiological terms. Between bacteria from bacterial community short cadmium-resistant Gram-negative rods predominated. Eight of them were biochemically profiled using either API 20 E, API 20 NE systems or ENTEROtests, and by key conventional and confirmation tests. Biochemical tests assigned the eight isolates to six bacterial species, Alcaligenes xylosoxidans, Comamonas testosteroni, Klebsiella planticola, Pseudomonas putida, Pseudomonas fluorescens, and Serratia liquefaciens. The ARDRA analysis of each of the eight isolates enabled five different ARDRA patterns to be recognized. P. putida and P. fluorescens, identified by biochemical tests as two different species, ARDRA analysis clustered these two strains to the same cluster indicating only one species. Differentiation among strains of the same ARDRA group was shown by analysis of whole cell protein patterns. Cadmium-resistant bacterial isolates were able to remove cadmium from solution and the efficiency of cadmium removal correlated with the amount of additionally synthesized proteins in the cell fractions. Analysis of plasmid content revealed that only two K. planticola strains harbored plasmids. The ability of biochemical and molecular methods to identify and characterize natural culturable bacterial community isolated from polluted environment, and the potential exploitation of cadmium-resistant bacterial strains in bioremediation processes aimed at heavy metal removal from contaminated environments, is discussed in this study.