ISOLATION AND DIAGNOSIS OF CADMIUM-RESISTANT BACTERIA AND ITS POTENTIAL PHYTOREMEDIATION WITH THE BROAD BEAN PLANT

Abstract

Results of the study proved that phytoremediation can be a promising technique to treat cadmium (Cd)-contaminated soil. Four bacteria types were isolated from the soil; two are autotrophic and others are heterotrophic. Autotrophic bacteria were dominant in soils with 42 mg Cd Kg-1. The total count and diversity of both bacteria types decreased with the increase of Cd in media and reached their minimum limit of tolerance at 60 mg Cd L-1 in terms of the heterotrophic bacteria, while the minimum limit of tolerance in the case of autotrophic bacteria was at 110 mg Cd L-1. The four isolates can form biofilms that ranged in thickness between 2.8–4.3 mm. The tolerant isolates belong to Rhizobium leguminosarum, Pseudomonas fluorescens, Actinobacteria, and Corynebacterium. Shoot and dry weight significantly varied according to the changes in Cd concentrations and isolate types. The level in either shoot or root exceeded critical levels, however, its concentration was higher in the root compared with the shoot. The effect of Cd on broad bean plants began at 80 and 100 mg Cd L-1. The broad bean plant was resistant to growing in the contaminated area by Cd even at 120 mg Cd Kg-1 DW. The presence of heterotrophic bacteria was noticeably useful for autotrophic bacteria, as well as, for enhancing Cd resistance. The study showed that cooperative phytoremediation could be a safe and active technique to apply in the field soil contaminated with heavy metals.