Isolation and characterization of heavy metals resistant Rhizobium isolates from different governorates in Egypt

Abstract

Contamination of soil with heavy metals is one of the major environmental problems in many countries that reach from many sources as power stations, application of metal pesticides, fertilizers, and sewage sludge. In this study, ten Rhizobium leguminosarum bv. viciae isolates were collected from different governorates in Egypt (Menoufia, Kafr El-Sheikh, Qalubia, Fayoum, Ismailia, Sharkya, Dakhalia, Behira and North Sinai) to evaluate their resistance to three heavy metals (Cu, Zn and Pb). The results showed that the isolates of RL3 and RL6 exhibited the best resistance toward the heavy metals tested. PCR based specific primers were used to screen the tested isolates for detection of some heavy metal resistant genes (copA, pbrA and czcD). The Pb-resistant gene pbrA was detected in most of tested isolates except RL7 and RL9 isolates, while, the Cu-resistant gene copA was found in all isolates except RL1, RL2, RL4 and RL8 isolates; however, the Zn-resistant gene czcD was detected only in the RL9 isolate. SDS-PAGE analysis was used to study the protein banding patterns for some tested isolates under lead stress and compared them with their untreated control.   Key words: CopA, pbrA and czcD genes, heavy metals, Rhizobium.