Toxicity risks associated with heavy metals to fish species in the Transboundary River - Linked Ramsar Conservation Site of Tanguar Haor, Bangladesh.

The presence of trace metals in aquatic ecosystems can have detrimental effects on fish survival. The Tanguar haor, a Ramsar conservation wetland, receives sediment and water from multiple transboundary rivers. However, there have been limited studies on the metal concentrations in fish species in this sediment-rich wetland. This study aimed to analyze the concentrations of iron (Fe), manganese (Mn), chromium (Cr), copper (Cu), zinc (Zn), cadmium (Cd), and lead (Pb) in water, sediment, and fish tissues. Higher concentrations of Cd and Pb were found in the water and sediment. All these metals were detected in eight fish species, including benthic and pelagic species. Among them, Systomus sarana, a pelagic fish that also consumes benthic organisms, exhibited a higher metal pollution index than other fish, particularly benthic species. The release of higher metal concentrations from sediment into the water has the potential to impact the accumulation of metals in fish. SYNOPSIS: This study on metal concentrations in fish species will aid policymaking on ecotoxicology research for transboundary river-connected wetlands.

Global stress response in Pseudomonas aeruginosa upon malonate utilization.

Versatility in carbon source utilization assists Pseudomonas aeruginosa in its adaptation to various niches. Recently, we characterized the role of malonate, an understudied carbon source, in quorum sensing regulation, antibiotic resistance, and virulence factor production in P. aeruginosa . These results indicate that global responses to malonate metabolism remain to be uncovered. We leveraged a publicly available metabolomic dataset on human airway and found malonate to be as abundant as glycerol, a common airway metabolite and carbon source for P. aeruginosa . Here, we explored and compared adaptations of P. aeruginosa UCBPP-PA14 (PA14) in response to malonate or glycerol as a sole carbon source using transcriptomics and phenotypic assays. Malonate utilization activated glyoxylate and methylcitrate cycles and induced several stress responses, including oxidative, anaerobic, and metal stress responses associated with increases in intracellular aluminum and strontium. Some induced genes were required for optimal growth of P. aeruginosa in malonate. To assess the conservation of malonate-associated responses among P. aeruginosa strains, we compared our findings in strain PA14 with other lab strains and cystic fibrosis isolates of P. aeruginosa . Most strains grew on malonate as a sole carbon source as efficiently as or better than glycerol. While not all responses to malonate were conserved among strains, formation of biomineralized biofilm-like aggregates, increased tolerance to kanamycin, and increased susceptibility to norfloxacin were the most frequently observed phenotypes. Our findings reveal global remodeling of P. aeruginosa gene expression during its growth on malonate as a sole carbon source that is accompanied by several important phenotypic changes. These findings add to accumulating literature highlighting the role of different carbon sources in the physiology of P. aeruginosa and its niche adaptation. Importance: Pseudomonas aeruginosa is a notorious pathogen that causes local and systemic infections in immunocompromised individuals. Different carbon sources can uniquely modulate metabolic and virulence pathways in P. aeruginosa , highlighting the importance of the environment that the pathogen occupies. In this work, we used a combination of transcriptomic analysis and phenotypic assays to determine how malonate utilization impacts P. aeruginosa, as recent evidence indicates this carbon source may be relevant to certain niches associated within the human host. We found that malonate utilization can induce global stress responses, alter metabolic circuits, and influence various phenotypes of P. aeruginosa that could influence host colonization. Investigating the metabolism of malonate provides insight into P. aeruginosa adaptations to specific niches where this substrate is abundant, and how it can be leveraged in the development of much-needed antimicrobial agents or identification of new therapeutic targets of this difficult-to-eradicate pathogen.

Monitoring of selected pesticides residue levels in water samples of paddy fields and removal of cypermethrin and chlorpyrifos residues from water using rice bran.

Consumption of pesticides associated foods increased in recent decades in Bangladesh. Most of the pesticides come from paddy, as rice is the main food items here and about 70 % pesticides are used only on paddy fields. Water samples of paddy fields and Kaliganga River of Manikganj district were analyzed to provide base line data on cypermethrin, chlorpyrifos and diazinon residue by using high performance liquid chromatography. Levels of Cypermethrin, chlorpyrifos and diazinon detected in the paddy field water samples were (0.605 ± 0.011 µg/L), (0.06 ± 0.001 µg/L) and (0.039 ± 0.002 µg/L), respectively. 0.11 ± 0.003 µg/L of cypermethrin and 0.012 ± 0.0006 µg/L of chlorpyrifos were also identified in the water samples of Kaligonga River. Diazinon residue was not detected in the river water samples. The detected concentrations of pesticide residues in the river water were below the accepted maximum residue limit (MRL) value of drinking water (0.1 µg/l) adopted by the FAO/WHO Codex Alimentarius Commission. Cypermethrin and chlorpyrifos were chosen for decontamination through rice bran, as it was found in river water. Two gm rice bran could easily decontaminated 95.6 % and 96.4 % of cypermethrin and chlorpyrifos. The result of this study showed that pesticide residue was detected in water samples were below the MRLs value, which can easily be decontaminated through absorption of rice bran.