Assessment of Thermal, Salinity and Heavy Metal Tolerance of Avicennia marina Associated Endophytic and Soil Fungi and Evaluation of their Hydrolytic Activity

Abstract

Stress conditions in many unique habitats represent a selecting force for the biological forms found in these niches. Organisms in such habitats cope up with these unfavorable conditions and modify their life machinery to maintain a successful life. Mangrove ecosystem is mainly characterized by high salinity beside the high affinity of its sediments to retain heavy metals. In a trial to explore the microbial life found in such unique ecosystems, the endophytic and soil fungi associated with Avicennia marina growing on Red sea coast at Ras-Mohammad area in Egypt have been studied. Such studies not only play a role in understanding how a successful life is maintained in these niches, but also helps in exploring microbial enzymes with promising characters needed potentially in many industrial applications. It has been found that, the investigated isolates are mesophiles with a remarkable halotolerant behavior and a variable tolerance behavior for Mn++, Zn++, Fe++ and Cu++. Soil isolates have recorded halotolerance behavior higher than that of endophytic isolates. One endophytic isolate, Chaetomium globosum, showed low removal capacity for Cu++ from the broth medium, however its growth was slightly inhibited in presence of this metal (100 ppm). Also, a soil isolate, Aspergillus flavipes, has recorded enhanced growth in presence of Fe++ (100 ppm) although no removal capacity has been detected. That reflects their possible ability to produce extracellular enzymes retaining considerable stability and activity under the presence of these heavy metals. Aspergillus flavipes showed a promising hydrolytic profile and the endophytic isolates showed acceptable profiles.