Parvez, M. A. K. | Search bioRxiv

bioRxiv2026

Heavy Metal-Resistant, Plastic-Degrading Bacillus sp. Isolated from Landfill Leachate: Identification and Characterization

Landfill leachates in rapidly urbanizing regions like Dhaka present a complex ecological challenge owing to the concurrent buildup of heavy metals and plastic waste. Despite the severity of this pollution, the role of indigenous multi-functional bacteria in mitigating these mixed contaminants remains poorly understood. This research sought to isolate and characterize bacteria resistant to heavy metals and capable of degrading plastics from the Aminbazar and Matuail landfills and evaluate their bioremediation potential. Physicochemical analysis confirmed extreme contamination, with heavy metal levels (Pb, Cr, Cd, Cu) significantly exceeding WHO safety limits. Out of 81 isolates, nearly half exhibited multi-metal resistance and polyethylene (PE) degradation capacity. Statistical analysis showed a significant correlation between plastic degradation and multi-metal tolerance, suggesting a linked evolutionary adaptation. Enzymatic assays confirmed enzymes (e.g., urease, catalase, citrate and esterase) as drivers of both plastic degradation and heavy metal tolerance in leading isolates. Molecular screening identified the resistance genes pbrA and alkB, while the high prevalence of Class 1 integrons (80% in pbrA-positive isolates) points to a high potential for horizontal gene transfer in these environments. Furthermore, MALDI-TOF MS identified the functional isolates as Bacillus sp. with FTIR verifying the contribution of specific cell-surface functional groups to metal biosorption. These results underscore the promise of native Bacillus strains as promising agents for the development of sustainable, integrated biotechnologies for landfill restoration and complex waste management.

microbiology↗

bioRxiv2023

Phylogenetic diversity and functional potential of large and cell-associated viruses in the Bay of Bengal

The Bay of Bengal (BoB), the largest bay in the world, provides valuable ecosystem services such as fishing and recreation to millions of people living along its coast and has a significant economic value. The BoB is impacted by various environmental factors such as seasonal monsoons and multiple freshwater inputs, and this region is particularly vulnerable to sea-level rise and increased frequency of devastating cyclones that are predicted to be exacerbated due to global climate change. These factors are also compounded by anthropogenic influences from tourism and development, making it an important ecosystem to understand and study from a global change perspective. Despite its importance, microbial diversity and ecology have remained largely understudied in this region. In this study, we describe the diversity and putative functional importance of large and cell-associated (that is, originating from the cellular size fraction) viruses from two coastal sites in the BoB, with an emphasis on giant viruses and large phages. Sites chosen for this study include Coxs Bazar, a populated beach with multiple freshwater inputs, and Saint Martin Island, a resort island that has considerably less human influence compared to Coxs Bazar. Through metagenomic sequencing, we were able to identify a more abundant and more diverse viral community at Coxs Bazar consisting of many viruses that are indicators of freshwater intrusion and runoff. Overall, 1962 putative phage genome bins were obtained ranging from 10 - 655 kilobase pairs (kbp) in sizes. Of these genomes, 16 from Saint Martin were found to be larger than 100kbp which we deemed "large" phages, and we were able to reconstruct a phylogeny of these large phages using the TerL gene as a marker. This phylogeny revealed clades enriched in large phages and a high diversity of large phage candidates in the Bay of Bengal coast. Protein annotation analysis showed a wide variety of functionality from both sites with more auxiliary metabolic genes (AMGs) found in the Coxs Bazar viral community. Five giant virus (Phylum Nucleocytoviricota) genomes were also reconstructed from Coxs Bazar and identified as belonging to the orders Imitervirales and Pandoravirales. These genomes ranged from 83 - 876 kbp in size and contained a wide range of encoded functionalities. To the best of our knowledge, our study represents the first insights on the phylogenetic and functional diversity of viruses in the Bay of Bengal. These results thus provide an important foundation for further studies on the impact of host-virus interactions on biogeochemical cycles and microbial food web in this understudied marine environment.

microbiology↗