Deciphering the dysbiosis caused in the fish microbiota by emerging contaminants and its mitigation strategies-A review.

The primary barrier to nutrient absorption in fish is the intestinal epithelium, followed by a community of microorganisms known as the gut microbiota, which can be thought of as a hidden organ. The gastrointestinal microbiota of fish plays a key role in the upholding of overall health by maintaining the homeostasis and disease resistance of the host. However, emerging contaminants as the result of anthropogenic activities have significantly led to disruptions and intestinal dysbiosis in fish. Which probably results in fish mortalities and disrupts the balance of an ecosystem. Therefore, we comprehensively seek to compile the effects and consequences of emerging contaminations on fish intestinal microbiota. Additionally, the mitigation strategies including prebiotics, probiotics, plant-based diet, and Biofloc technology are being outlined. Biofloc technology (BFT) can treat toxic materials, i.e., nitrogen components, and convert them into a useful product such as proteins and demonstrated promising elevating technique for the fish intestinal bacterial composition. However, it remains unclear whether the bacterial isolate is primarily responsible for the BFT's removal of nitrate and ammonia and the corresponding removal mechanism. To answer this, real time polymerase chain reaction (RT-PCR) with metagenomics, transcriptomics, and proteomics techniques probably provides a possible solution.

Bio-reductive synthesis of silver nanoparticles, its antibacterial efficiency, and possible toxicity in common carp fish (Cyprinus carpio).

The biological synthesis of nanoparticles is an emerging field of study that seeks to synthesize nanoparticles using non-chemical mechanisms such as microorganisms, plants, and animal blood serum. Among these, plants have gained particular attention due to their ease of handling, availability, and ability to synthesize a wide range of nanoparticles. Therefore, the current study aimed to fabricate the silver nanoparticles (AgNPs) using Chinese medicinal plants (CMP) for their possible toxicity in common carp fish (Cyprinus carpio). For this purpose, CMP was dried, ground, and used as a bio-reductive agent. The fabricated AgNPs were characterized and a well dispersed AgNPs were obtained. Moreover, the C. carpio was exposed to the AgNPs for bioaccumulation and histological alterations. The obtained findings revealed that the AgNPs were mostly accumulated in the intestines followed by the gills, muscles, liver, and brain. The accumulated AgNPs caused histological alterations in gills and intestines at the highest concentration (0.08 mg/L). However, very less alterations were caused by the lowest concentration, especially in the intestine. In conclusion, further in-depth research is needed to determine the risks associated with the usage of nanoparticles to reveal their harmful impacts on fish and the aquatic environment. HIGHLIGHTS: The biological fabrication of AgNPs is considered eco-friendly. Chinese medicinal plants play a significant role in AgNPs synthesis. AgNPs have excellent antibacterial activity. AgNPs are bioaccumulated in various organs of fish.