This review discusses several research studies that employed comet assay to evaluate the environmental impact of genotoxins in aquatic environments. It focuses on in vivo and in situ studies of aquatic animals. New chemicals are being added each year to the existing burden of toxic substances in the environment. Excessive agricultural and industrial activities adversely affect biodiversity, threatening the survival of species in a particular habitat, as well as posing disease risks to humans. Some of the chemicals, e.g., pesticides and heavy metals, may be genotoxic to the sentinel species and/or to non-target species, causing deleterious effects in somatic or germ cells. Comet assay is a quick, sensitive, and low-cost technique for detecting DNA strand breakage. However, the comet assay has much more to offer than being an assay for testing DNA strand breaks in animal organs. The use of repair enzymes increases the range of DNA lesions that can be detected with the assay. Comparing data from studies that employed different approaches, such as empirical scoring or comet tail lengths, comet assay is one of the challenging techniques to be utilized in environmental studies. The relative amount of DNA in the comet tail indicates DNA break intensity. The assay has been modified to detect various base alterations by including the digestion of nucleoids with a lesion-specific endonuclease. The determination of DNA damage in these indicator species using the comet test would thus offer information on the genotoxic potential of their habitat at an early stage. This would enable intervention techniques to prevent or mitigate adverse health impacts in sentinel animals and humans.

The yaks that inhabit the Tibetan plateau are a rare breed that is closely related to local economic development and human civilization. This ancient breed may have evolved a unique gut microbiota due to the hypoxic high-altitude environment. The gut microbiota is susceptible to external factors, but research regarding the effects of different feeding models on the gut fungal community in yaks remains scarce. In this study, we compared and analyzed the composition and variability of the gut fungal community among wild yaks (WYG), house-feeding domestic yaks (HFG), and grazing domestic yaks (GYG). The results revealed that Basidiomycota and Ascomycota were the most preponderant phyla in the gut fungal community, regardless of feeding models. Although the types of dominant fungal phyla did not change, their abundances did. Intergroup analysis of fungal diversity showed that the Shannon and Simpson indices of WYG and GYG were significantly higher than those of HFG. Fungal taxonomic analysis showed that there were 20 genera (Sclerostagonospora and Didymella) that were significantly different between WYG and GYG, and 16 genera (Thelebolus and Cystobasidium) that were significantly different between the WYG and HFG. Furthermore, the proportions of 14 genera (Claussenomyces and Papiliotrema) significantly decreased, whereas the proportions of eight genera (Stropharia and Lichtheimia) significantly increased in HFG as compared to GYG. Taken together, this study indicated that the gut fungal composition and structure differ significantly between yaks raised in different breeding groups.

This study aimed to investigate the effects of different feeding patterns on meat quality, gut microbiota and its metabolites of Tibetan pigs. Tibetan pigs with similar body weight were fed the high energy diets (HEP, 20 pigs) and the regular diets (RFP, 20 pigs), and free-ranging Tibetan pigs (FRP, 20 pigs) were selected as the reference. After 6 weeks of experiment, meat quality indexes of semitendinosus muscle (SM) and cecal microbiota were measured. The results of meat quality demonstrated that the shear force of pig SM in FRP group was higher than that in HEP and RFP groups (p < 0.001); the pH-value of SM in HEP pigs was higher at 45 min (p < 0.05) and lower at 24 h (p < 0.01) after slaughter than that in FRP and RFP groups; the SM lightness (L* value) of FRP pigs increased compared with RFP and HEP groups (p < 0.001), while the SM redness (a* value) of FRP pigs was higher than that of RFP group (p < 0.05). The free fatty acid (FA) profile exhibited that the total FAs and unsaturated FAs of pig SM in HEP and RFP groups were higher than those in FRP group (p < 0.05); the RFP pigs had more reasonable FA composition with higher n-3 polyunsaturated FAs (PUFAs) and lower n-6/n-3 PUFA ratio than HEP pigs (p < 0.05). Based on that, we observed that Tibetan pigs fed high energy diets (HEP) had lower microbial α-diversity in cecum (p < 0.05), and distinct feeding patterns exhibited a different microbial cluster. Simultaneously, the short-chain FA levels in cecum of FRP and RFP pigs were higher compared with HEP pigs (p < 0.05). A total of 11 genera related to muscle lipid metabolism or meat quality, including Alistipes, Anaerovibrio, Acetitomaculun, etc., were identified under different feeding patterns (p < 0.05). Spearman correlation analysis demonstrated that alterations of free FAs in SM were affected by the genera Prevotellaceae_NK3B31_group, Prevotellaceae UCG-003 and Christensenellaceae_R-7_group (p < 0.05). Taken together, distinct feeding patterns affected meat quality of Tibetan pigs related to gut microbiota alterations.

The yak (Bos grunniens) exhibits exceptional regional adaptability, enabling it to thrive in the distinctive ecological niches of the Qinghai–Tibet Plateau. Its survival relies on the intricate balance of its intestinal microbiome, essential for adapting to harsh environmental conditions. Despite the documented significance of bacteria and fungi in maintaining intestinal homeostasis and supporting immune functions, there is still a substantial gap in understanding how the composition and functionality of yak gut microbiota vary along altitude–temperature gradients. This study aims to fill this gap by employing 16S rRNA and ITS amplicon sequencing techniques to analyze and compare the intestinal microbiome of yaks residing at different elevations and exposed to varying temperatures. The findings demonstrate subtle variations in the diversity of intestinal bacteria and fungi, accompanied by significant changes in taxonomic composition across various altitudes and temperature gradients. Notably, Firmicutes, Actinobacteriota, and Bacteroidota emerged as the dominant phyla across all groups, with Actinobacteriota exhibiting the highest proportion (35.77%) in the LZF group. Functional prediction analysis revealed significant associations between the LZF group and metabolic pathways related to amino acid metabolism and biosynthesis. This suggests a potential role for actinomycetes in enhancing nutrient absorption and metabolism in yaks. Furthermore, our findings suggest that the microbiota of yaks may enhance energy metabolism and catabolism by modulating the Firmicutes-to-Bacteroidota ratio, potentially mitigating the effects of temperature variations. Variations in gut bacterial and fungal communities among three distinct groups were analyzed using metagenomic techniques. Our findings indicate that microbial genera exhibiting significant increases in yaks at lower altitudes are largely beneficial. To sum up, our research investigated the changes in gut bacterial and fungal populations of yaks residing across diverse altitude and temperature ranges. Moreover, these results enhance comprehension of gut microbial makeup and variability, offering perspectives on the environmental resilience of dry lot feeding yaks from a microbial angle.

Due to the ecotoxicity of 17β-estradiol (E2), residual E2 in the environment poses potential risks to human and animal health and ecosystems. Biodegradation is considered one of the most effective strategies to remove E2 from the environment. Here, a novel, efficient E2-degrading bacterial strain Microbacterium resistens MZT7 was isolated from activated sludge and characterized. The genome of strain MZT7 contained 4,011,347 bp nucleotides with 71.26% G + C content and 3785 coding genes. There was 86.7% transformation efficiency of 10 mg/L E2 by strain MZT7 after incubation for 5 d at optimal temperature (30 °C) and pH (7.0). This strain was highly tolerant to ranges in pH (5.0–11.0), temperature (20–40 °C), and salinity (2–8%). Adding sources of carbon (glucose, maltose, sucrose, or lactose) or nitrogen sources (urea, peptone, or beef extract) promoted the degradation of E2 by strain MZT7. However, when yeast extract was added as a nitrogen source, the degradation efficiency of E2 was inhibited. Metabolites were analyzed by LC-MS and three metabolic pathways of E2 degradation were proposed. Further, the intermediates dehydroepiandrosterone and androsta-1,4-diene-3,17-dione were detected, as well as identification of kshB and fadD3 genes by KEGG, confirming one E2 degradation pathway. This study provided some insights into E2 biodegradation.

Despite the crucial role of the gut microbiota in different physiological processes occurring in the animal body, reports regarding the gut microbiota of animals residing in different environmental conditions like high altitude and different climate settings are limited. The Qinghai–Tibetan Plateau is renowned for its extreme climatic conditions that provide an ideal environment for exploring the effects of high altitude and temperature on the microbiota of animals. Yaks have unique oxygen delivery systems and genes related to hypoxic response. Damxung, Nyêmo, and Linzhou counties in Tibet have variable altitudes and temperatures that offer distinct settings for studying yak adaptation to elevated terrains. The results of our study suggest that amplicon sequencing of V3-V4 and internal transcribed spacer 2 (ITS2) regions yielded 13,683 bacterial and 1912 fungal amplicon sequence variants (ASVs). Alpha and beta diversity indicated distinct microbial structures. Dominant bacterial phyla were Firmicutes, Bacteroidota, and Actinobacteriota. Genera UCG-005, Christensenellaceae_R-7_group, and Rikenellaceae_RC9_gut_group were dominant in confined yaks living in Damxung county (DXS) and yaks living in Linzhou county (LZS), whereas UCG-005 prevailed in confined yaks living in Nyêmo county (NMS). The linear discriminant analysis effect size (LEfSe) analysis highlighted genus-level differences. Meta-stat analysis revealed significant shifts in bacterial and fungal community composition in yaks at different high altitudes and temperatures. Bacterial taxonomic analysis revealed that two phyla and 32 genera differed significantly (p < 0.05). Fungal taxonomic analysis revealed that three phyla and four genera differed significantly (p < 0.05). Functional predictions indicated altered metabolic functions, especially in the digestive system of yaks living in NMS. This study reveals significant shifts in yak gut microbiota in response to varying environmental factors, such as altitude and temperature, shedding light on previously unexplored aspects of yak physiology in extreme environments.