Microbiome pattern and diversity of an anadromous fish, hilsa shad (Tenualosa ilisha).

BACKGROUND: The host-microbe interactions are complex, dynamic and context-dependent. In this regard, migratory fish species like hilsa shad (Tenualosa ilisha), which migrates from seawater to freshwater for spawning, provides a unique system for investigating the microbiome under an additional change in fish's habitat. This work was undertaken to detect taxonomic variation of microbiome and their function in the migration of hilsa. METHODS AND RESULTS: The study employed 16S rRNA amplicon-based metagenomic analysis to scrutinize bacterial diversity in hilsa gut, skin mucus and water. Thus, a total of 284 operational taxonomic units (OTUs), 9 phyla, 35 orders and 121 genera were identified in all samples. More than 60% of the identified bacteria were Proteobacteria with modest abundance (> 5%) of Firmicutes, Bacteroidetes and Actinobacteria. Leucobacter in gut and Serratia in skin mucus were the core bacterial genera, while Acinetobacter, Pseudomonas and Psychrobacter exhibited differential compositions in gut, skin mucus and water. CONCLUSIONS: Representative fresh-, brackish- and seawater samples of hilsa habitats were primarily composed of Vibrio, Serratia and Psychrobacter, and their diversity in seawater was significantly higher (P < 0.05) than freshwater. Overall, salinity and water microbiota had an influence on the microbial composition of hilsa shad, contributing to host metabolism and adaptation processes. This pioneer exploration of hilsa gut and skin mucus bacteria across habitats will advance our insights into microbiome assembly in migratory fish populations.

Dysbiosis of Oral and Gut Microbiomes in SARS-CoV-2 Infected Patients in Bangladesh: Elucidating the Role of Opportunistic Gut Microbes.

Coronavirus disease-2019 (COVID-19) is an infectious disease caused by SARS-CoV-2 virus. The microbes inhabiting the oral cavity and gut might play crucial roles in maintaining a favorable gut environment, and their relationship with SARS-CoV-2 infection susceptibility and severity is yet to be fully explored. This study investigates the diversity and species richness of gut and oral microbiota of patients with COVID-19, and their possible implications toward the severity of the patient's illness and clinical outcomes. Seventy-four (n = 74) clinical samples (gut and oral) were collected from 22 hospitalized patients with COVID-19 with various clinical conditions and 15 apparently healthy people (served as controls). This amplicon-based metagenomic sequencing study yielded 1,866,306 paired-end reads that were mapped to 21 phyla and 231 classified genera of bacteria. Alpha and beta diversity analyses revealed a distinct dysbiosis of the gut and oral microbial communities in patients with COVID-19, compared to healthy controls. We report that SARS-CoV-2 infection significantly reduced richness and evenness in the gut and oral microbiomes despite showing higher unique operational taxonomic units in the gut. The gut samples of the patients with COVID-19 included 46 opportunistic bacterial genera. Escherichia, Shigella, and Bacteroides were detected as the signature genera in the gut of patients with COVID-19 with diarrhea, whereas a relatively higher abundance of Streptococcus was found in patients with COVID-19 having breathing difficulties and sore throat (BDST). The patients with COVID-19 had a significantly lower abundance of Prevotella in the oral cavity, compared to healthy controls and patients with COVID-19 without diabetes, respectively. The altered metabolic pathways, including a reduction in biosynthesis capabilities of the gut and oral microbial consortia after SARS-CoV-2 infection, were also observed. The present study may, therefore, shed light on interactions of SARS-CoV-2 with resilient oral and gut microbes which might contribute toward developing microbiome-based diagnostics and therapeutics for this deadly pandemic disease.