Assessing the impact of heavy metals on bacterial diversity in coastal regions of Southeastern India.

Globally, there is growing concern over the environmental contamination of coastal ecosystems caused by anthropogenic activities. Here,we performed a study to evaluate the degree of heavy metal contamination in 5 different sediment samples collected from five sites along the Southeastern coast of India. Additionally, the research aims to explore the potential ecological implications of heavy metal contamination on the bacterial diversity, a crucial factor in upholding a sustainable ecosystem. A total of  seven heavy metals, i.e., chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), mercury (Hg), cadmium (Cd) and arsenic (As), were assessed and quantified using inductively coupled plasma mass spectrometry. Targeted amplicon sequencing revealed that phylum Proteobacteria (36.9%) was the most dominating followed by Halobacterota (25.5%), Actinobacteriota (15%), Firmicutes (6.7%), Bacteroidota (4.0%), Thermoplasmatota (2.3%), Acidobacteriota (2.0%), Chloroflexi (1.6%), Planctomycetota (1.2%) and Crenarchaeota (1.1%). According to the alpha diversity estimate, lesser bacterial diversity was observed in areas with high pollution levels. Moreover, the physicochemical parameters of the sediments were analyzed. The contamination levels of the sediments were evaluated using the geo-accumulation index (Igeo), contamination factor (CF) and pollution loading index (PLI) to ascertain the comprehensive toxicity status of the sediments. The Igeo values revealed sediment pollution with metals such as Hg and Cd. The sediments obtained from the sampling site PU-01 showed the highest concentration of Hg pollution. Considering the ecotoxicological aspect, the estimated risk index (RI) values indicated a range from low to significant ecological risk.

Revealing bacterial and fungal communities of the untapped forest and alpine grassland zones of the Western-Himalayan region.

The Western Himalayas offer diverse environments for investigating the diversity and distribution of microbial communities and their response to both the abiotic and biotic factors across the entire altitudinal gradient. Such investigations contribute significantly to our understanding of the complex ecological processes that shape microbial diversity. The proposed study focuses on the investigation of the bacterial and fungal communities in the forest and alpine grasslands of the Western Himalayan region, as well as their relationship with the physicochemical parameters of soil. A total of 185 isolates were obtained using the culture-based technique belonging to Bacillus (37%), Micrococcus (16%), and Staphylococcus (7%). Targeted metagenomics revealed the abundance of bacterial phyla Pseudomonadota (23%) followed by Acidobacteriota (20.2%), Chloroflexota (15%), and Bacillota (11.3%). At the genera level, CandidatusUdaeobacter (6%), Subgroup_2 (5.5%) of phylum Acidobacteriota, and uncultured Ktedonobacterales HSB_OF53-F07 (5.2%) of Choloroflexota phylum were found to be preponderant. Mycobiome predominantly comprised of phyla Ascomycota (54.1%), Basidiomycota (24%), and Mortierellomycota (19.1%) with Archaeorhizomyces (19.1%), Mortierella (19.1%), and Russula (5.4%) being the most abundant genera. Spearman's correlation revealed that the bacterial community was most influenced by total nitrogen in the soil followed by soil organic carbon as compared to other soil physicochemical factors. The study establishes a fundamental relationship between microbial communities and the physicochemical properties of soil. Furthermore, the study provides valuable insights into the complex interplay between biotic and abiotic factors that influence the microbial community composition of this unique region across various elevations.