Lichenological Practices for Monitoring Atmospheric Pollution and Climate Change in India

Abstract

Soil microflora is continuously changing with altered soil conditions. These soil alterations are a consequence of heavy metals entering and affecting every sphere of life. Heavy metals are not only hazardous for crops but also affect the soil microbial community. Soil bacteria with the potential of plant growth promotion and multiple metal resistances can be an instrument for crop improvement and heavy metal detoxification. In this study, predominant bacterial community associated with the heavy metal contaminated soil was studied using 16S rRNA gene sequencing in association with culture-based techniques. Elemental metal analysis of collected soil samples showed an elevated level of metal content in the soil. 16S rRNA gene analysis and phylogenetic analysis of 126 bacterial clones revealed the probable predominance of Pseudomonas (40.48%) followed by Flavisolibacter (13.49%). Based on morphological and biochemical characterization, nine Pseudomonas strains were selected from the soil and were further confirmed by 16S rRNA gene sequencing with 92%-100% similarity with Pseudomonas species. The minimum inhibitory concentration (MIC) and maximum tolerance capacity (MTC) of three essential metals Cu, Zn, and Fe were determined individually and in combinations. It was found that Zn is the most toxic metal among the three metals and the metal showed a synergistic effect in inhibiting microbial growth when used in combinations. Presence of three metal resistant/tolerant genes czcA, pcoA and copB were also determined in the isolated Pseudomonas sp. by PCR. The soil in this region has high concentrations of heavy metals. The indigenous Pseudomonas sp. has multiple metal resistances and can be used for bioremediation of heavy metals and microbe assisted phytoremediation.