Gut microbiome-associated adaptability of suckermouth catfish inhabiting the polluted Buriganga River: insights into heavy-metal-remediating microorganisms

The suckermouth catfish (SMCF), known for its pollutant tolerance and high invasiveness, is prevalent in the heavily contaminated Buriganga River in Bangladesh. This waterway, contaminated with a variety of pollutants, including heavy metals, has experienced the near-complete disappearance of native fish populations; however, the suckermouth catfish demonstrates remarkable adaptability in this environment. One objective of this study is to elucidate the role of the gut microbiome in SMCFs' adaptation to this severely polluted habitat. We performed next-generation sequencing (NGS) of gut contents from SMCFs to analyze the gut microbial profiles of the fish samples. The results indicated that the suckermouth catfish's gut is enriched with microbial communities, including Paraclostridium, Klebsiella, Staphylococcus, Bacillus, and Pseudomonas, which have the potential to remediate pollutants, including heavy metals. The subsequent aim of this research is to isolate and identify bacteria from the SMCF gut capable of remediating multiple heavy metals. We isolated three isolates with the potential to remediate multiple heavy metals and identified them as Staphylococcus pasteuri SD, Morganella morganii SAS1, and Sporosarcina saromensis SAS using partial 16S rRNA gene amplicon sequencing and conventional techniques. All isolates showed distinct capabilities for remediating multiple heavy metals. Notably, S. pasteuri showed the highest lead (Pb) bioaccumulation (36.28%), S. saromensis showed the highest chromium (Cr) uptake (39.22%), and M. morganii showed the highest nickel (Ni) uptake (35.90%). Furthermore, these isolates exhibited remarkable metal-tolerance profiles, with maximum tolerable concentrations ranging from 125 ppm to 1000 ppm, and sustained healthy growth under metal-supplemented conditions throughout a 48-hour incubation period. This validates their potential to remediate multiple heavy metals. Collectively, the results underscore the ecological adaptability of suckermouth catfish in polluted aquatic environments, which is associated with their gut microbiome, and highlight the bioremediation potential of these gut-derived microbes as effective agents for mitigating heavy metal contamination.