Cadmium resistance in extremely halophilic archaeon Haloferax strain BBK2

Abstract

Halophilic archaea are prevalent in highly saline habitats. Haloferax strain BBK2 is an orange pigmented, exopolysaccharide (EPS) producing extremely halophilic archaeon, isolated from solar salterns of Ribandar, Goa, India. It grew in varying pH (5–10) and NaCl concentration (10–30%). The isolate grew well in complex (NTYE) and minimal media (NGSM) in presence of heavy metal cadmium (Cd) up to 4.0mM (805.28mgL−1) concentration. The optimum growth in the presence and absence of Cd was seen at a pH range of 7–9 and salinity of 15–25%. The growth kinetics of the isolate in NTYE showed a specific growth rate (μmax) of 0.352 with generation time of 1.968days. In presence of 1mM Cd, the μmax was 0.325day−1 and generation time was 2.132days. In NGSM, the μmax decreased from 0.517day−1 (in control) to 0.265day−1 in 1mM Cd while, the doubling time increased from 1.34days in control to 2.615days in presence of 1mM Cd. SDS PAGE of the whole cell protein extracts showed overexpressed proteins of 74.14 and 40kDa. The scanning electron microscopy, energy dispersive X-ray spectroscopy (SEM–EDX) analysis of the intact cells and cells disrupted by dialysis revealed that Cd was bound onto the cells, which was further confirmed by AAS, FTIR and XRD analysis.