The aim of this study was to isolate and identify of some heavy
metals-tolerant bacteria from different heavy metals contaminated sites in Egypt to be used as bioremoval agents as well as plant growth promoters. Additionally, studying the efficiency of those strains on sorghum growth performance in heavy metals contaminated soil. This study was divided into two parts, the first part was achieved under laboratory conditions, while the second part was conducted under greenhouse conditions.
a) The first part
Five samples from heavy metals contaminated sites were
obtained for isolation purpose, three sediment samples (upstream,
midstream, downstream, Al-Rahawy drain, Giza Governorate) and two heavy metals contaminated agricultural soil samples (AL-Gabal AlAsfar region and Kafr Ilwan village, Qalyubia Governorate, Egypt.
A total of 703 heavy metals-tolerant bacterial isolates were recovered on Mueller-Hinton broth medium amended with four heavy metals individually, zinc (Zn2+
), cadmium (Cd2+), copper (Cu2+) and lead (Pb2+). Among these isolates, 37 were copper-tolerant, 37 were zinc-tolerant, 88 were lead-tolerant, 97 were cadmium tolerant. Then, MIC and MTC were achieved and resulted of 70 isolates were chosen as the most tolerant isolates for heavy metal. These ten selected isolates
were examined under four heavy metals at different concentrations and resulted of three isolates (UR54, MR77 and MR708) which identified as Alcaligenes faecalis MG24357757, Bacillus cereus MG24357557 and Alcaligenes faecalis MG79955057 according to the morphological, cultural, biochemical characteristics and 79S rDNA partial sequence.
Then, these strains were examined for their biosorption potentials under different pH values in media supplemented with four heavy metals (Cu2+, Cd2+, Zn2+ and Pb2+) at 7000 mg/l. After that, estimated their characterization in vitro as antioxidant agents and plant growth promoters.
b) The second part
The experimental soil was mixed with four heavy metals at
different concentrations either individually or in mixture. The
greenhouse experiment was designed in a randomized complete block design (RCBD) with 28 treatments and three replicates. The three identified strains were used as a heavy metals-tolerant plant growth promoting bacteria for enhancement of sorghum under contaminated
At the end of this experiment it was clear that sorghum
inoculation with heavy metals-tolerant plant growth promoting bacteria gave high results in all studied characteristics.