PHYSICAL GROWTH AND BIOMASS CHARACTERIZATION OF BACTERIAL CELLS EXPOSED TO Cd(II), Cr(VI), Cu(II), Ni(II), AND Pb(II)

Abstract

This paper describes the growth characterization of consortium culture (CC) comprising an acclimatized mixed bacterial culture in aqueous solution containing heavy metal ions, namely Cd(II), Cr(VI), Cu(II), Ni(II), and Pb(II). Microscopy and biochemical tests performed revealed that consortium culture (CC), an environmental mixed bacterial culture to predominantly consist of six Gram negative (Pseudomonas sp, Serratia sp, Flavobacterium sp, Chryseomonas sp, Xanthomonas sp, and Agrobacterium sp) and three Gram positive (Bacillus sp, Arthrobacter sp, and Micrococcus sp) bacteria. The isolates are combination of strains that have been screened intensively and developed from a pool of mixed cultures isolated from point and non-point sources of areas related to metal-based activities. As the extent of heavy metal removal by CC has been characterized elsewhere, we focused into factors that contribute to efficient and effective metal loading. Physiological changes were apparent in CC as significant increase in flocculation index (IF) and decrease in degree of hydrophobicity were observed (p < 0.05) in cells grown in the presence of metals, determined from the flocculation test and bacterial adhesion to hydrocarbon (BATH) method. Analysis by Fourier transformed infra-red (FTIR) not only revealed the existence of an array of functional groups (i.e. amides, amines, carboxyls, carbonates, phosphates, sulfhydryls, and sulfates) that are known to facilitate metal binding but also the emergence of two new peaks in the presence of metals, one that corresponds to C=O stretch, possibly of carboxyl or carbonate in nature, and a second yet to be identified peak. The information is useful for bioremediation applications of wastewater treatment by understanding the effects exerted by the presence of heavy metals towards growth of bacterial cells.