Statistically significant differences (p < 0.05) observed between the removal efficiency for dead-microbial cells (Figure  3) and living

ones (Figure  2) indicated that the selected isolates were also removing heavy metals from the culture media by using active mechanisms. This was confirmed by the presence of certain specific heavy metal-resistance genes in test isolates (Figure  4). Bacterial isolates (Pseudomonas putida, Bacillus licheniformis and Brevibacillus laterosporus) contained the genes copC, chrB, cnrA3 and nccA encoding the resistance to Cu, Cr, Co-Ni and Co-Ni-Cd, respectively, but did not contain the genes copA, copB, cnrC2 and czcD. see more However, the presence of metal-resistant genes in Brevibacillus laterosporus and its growth inhibition could not be explained in the present study. Furthermore, protozoan isolates (Peranema sp., Trachelophyllum sp. and Aspidisca sp.) contained only the genes copC and chrB encoding the resistance of Cu and Cr, respectively. An exception was found with Peranema sp. that contained the gene cnrA3 encoding the resistance of Co and Ni. This is in agreement with Mohapatra [46], who reported that apart from the sensitivity of protozoa to metal toxicants, Peranema is one of the protozoan isolates that are generally resistant. In addition, Ruthven and Cairns [47] reported that Peranema could

tolerate approximately 1000 mg-Pb/l. The ability of Pseudomonas putida observed in this study to tolerate and remove several heavy metals from polluted CYT387 research buy industrial wastewater can be explained by the findings of Canovas and co-workers [10]. These authors reported that Branched chain aminotransferase the genome of Pseudomonas putida encodes an unexpected capacity to resist heavy metals and metalloids. This species in its different strains has been reported to exhibit high Semaxanib concentration maximal tolerant concentrations of a large spectrum

of divalent metals [35]. Contrary to the present findings, Pseudomonas putida has been previously reported to contain at least four Zn/Cd/Pb efflux transporters and two czc chemiosmotic transporters [11]. It has also been reported that Bacillus licheniformis produce extracellular polymers with great affinity for metals; these polymers are able to complex with and accumulate metals such as Fe, Ni, Cd, etcetera [23, 48]. This study corroborates the findings reported elsewhere that microorganisms can use several mechanisms to simultaneously remove metals [11, 20, 33]. In addition, the removal efficiency of test microorganisms mostly depended on the availability and concentrations of heavy metals in industrial wastewaters. No individual isolate showed a high removal rate of all the heavy metals from the polluted industrial wastewaters (Figure  2). High removal efficiency for only certain heavy metals was also observed in the culture media inoculated with protozoan isolates such as Peranema sp.