Effect of sulfate on the osmoregulatory and physio-biochemical responses of GIFT (Oreochromis niloticus) juveniles reared in potassium-deficient medium saline waters

The inland saline waters were continuously observed to have low potassium concentrations compared to their seawater counterpart of the same salinity. We hypothesize that the toxic effect of sulfate may manifest in low potassium saline (LPSW) waters compared to brackish water of the same salinity. Thus, LC50 trials were performed in GIFT (genetically improved farmed tilapia) fry (0.5 ± 0.02 g) to determine the acute sulfate toxicity in freshwater (FW, 0.5 g L-1), artificial seawater (ASW, 10 g L-1), and LPSW (10 g L-1). The median lethal concentrations (96h LC50) of sulfate ion in FW, LPSW, and ASW for the GIFT were 5.30 g L-1, 2.56 g L-1, and 2.98 g L-1, respectively. A second experiment was conducted for 21 days, exposing fish to a sub-lethal level of sulfate ion (SO42-) concentration (1000 mg L-1, one-fifth of FW LC50) with different types of waters (FW, freshwater, 0.5 g L-1; ASW, artificial seawater, 10 g L-1; LPSW, low potassium saline water, 10 g L-1) with and without sulfate inclusion to constitute the treatments as follows, (FW, FW + SO4, ASW, ASW + SO4, LPSW, LPSW + SO4). The effect of sulfate on GIFT reared in sulfate-rich potassium-deficient medium saline water was evaluated by focusing on the hematological adjustments, stress-induced oxidative damage, and osmoregulatory imbalances. The survival was not altered due to the sulfate concentration and K+ deficiency; however, there were significant changes in branchial NKA (Na+/K+-ATPase) activity and osmolality. The increase in NKA was highest in LPSW treatment, suggesting that internal ionic imbalance was triggered due to an interactive effect of sulfate and K+ deficiency. The cortisol levels showed a pronounced increase due to sulfate inclusion irrespective of K+ deficiency. The antioxidant enzymes, i.e., SOD (superoxide dismutase), catalase, GST (glutathione-S-transferase), and GPX (glutathione peroxidase), reflected a similar pattern of increment in the gills and liver of the LPSW + SO4 groups, suggesting a poor antioxidant status of the exposed group. The hepatic peroxidation status, i.e. TBARS (thiobarbituric acid reactive substances), and the peroxide values were enhanced due to both K+ deficiency and sulfate inclusion, suggesting a possible lipid peroxidation in the liver due to handling the excess sulfate anion concentration. The hematological parameters, including haemoglobin, total erythrocyte count, and hematocrit level, reduced significantly in the LPSW + SO4 group, indicating a reduced blood oxygen capacity due to the sulfate exposure and water potassium deficiency. The hepatic acetylcholine esterase activity was suppressed in all the treatments with sulfate inclusion, while the highest suppression was observed in the LPSW + SO4 group. Thus, it is concluded that sulfate-induced physiological imbalances manifest more in potassium-deficient water, indicating that environmental sulfate is more detrimental to inland saline water than freshwater or brackish water of the same salinity.

Co-exposure of microplastics and heavy metals in the marine environment and remediation techniques: a comprehensive review

Microplastics (MPs) and heavy metals are significant pollutants in the marine environment, necessitating effective remediation strategies to prevent their release into the sea through sewage and industrial effluent. This comprehensive review explores the current understanding of the co-exposure of MPs and heavy metal-enriched MPs, highlighting the need for effective remediation methods. Various mechanisms, including surface ion complexation, hydrogen bonding, and electrostatic forces, contribute to the adsorption of heavy metals onto MPs, with factors like surface area and environmental exposure duration playing crucial roles. Additionally, biofilm formation on MPs alters their chemical properties, influencing metal adsorption behaviors. Different thermodynamic models are used to explain the adsorption mechanisms of heavy metals on MPs. The adsorption process is influenced by various factors, including the morphological characteristics of MPs, their adsorption capacity, and environmental conditions. Additionally, the desorption of heavy metals from MPs has implications for their bioavailability and poses risks to marine organisms, emphasizing the importance of source reduction and remedial measures. Hybrid approaches that combine both conventional and modern technologies show promise for the efficient removal of MPs and heavy metals from marine environments. This review identifies critical gaps in existing research that should be addressed in future studies including standardized sampling methods to ensure accurate data, further investigation into the specific interactions between MPs and metals, and the development of hybrid technologies at an industrial scale. Overall, this review sheds light on the adsorption and desorption mechanisms of heavy metal-enriched MPs, underscoring the necessity of implementing effective remediation strategies.

Evaluation of Leuconostoc mesenteroides YML003 as a probiotic against low-pathogenic avian influenza (H9N2) virus in chickens

AIM

  The aims of the study were to isolate anti-H9N2 bacteria from Korean Kimchi isolates and to evaluate its performance in cell line, egg and in specific pathogen-free (SPF) chickens.

METHODS AND RESULTS

  Using Madin-Darby canine kidney (MDCK) cell line, 220 bacterial isolates were screened and the isolate YML003 was selected having pronounced antiviral activity against H9N2 virus. This isolate was identified as Leuconostoc mesenteroides by 16S rRNA gene sequencing. Anti-H9N2 activity of the strain was also evaluated by hemagglutination assay. Leuconostoc mesenteroides YML003 was assessed for its survival in gastric juice and 5% bile acid and the antibiotic susceptibility. Both live and heat-killed cells were selected for in vivo chicken feeding experiment. Body weight, immune index, serobiochemical parameters and splenic IFN-γ production were assessed during selected intervals. Viral population in the trachea and cloacae were calculated by quantitative real-time reverse transcriptase PCR (qRT-PCR).

CONCLUSIONS

  Leuconostoc mesenteroides YML003 exhibited anti-H9N2 activity both in in vitro cell line as well as in vivo SPF chickens.

SIGNIFICANCE AND IMPACT OF THE STUDY

  This is a primary report on the anti-H9N2 activity by a Leuconostoc strain. Amid the increasing reports of avian influenza virus occurrence resulting in severe losses to the poultry industry, prophylactic administration of such probiotic strains are highly significant.