Exploring bacterial diversity in Arctic fjord sediments: a 16S rRNA-based metabarcoding portrait.

The frosty polar environment houses diverse habitats mostly driven by psychrophilic and psychrotolerant microbes. Along with traditional cultivation methods, next-generation sequencing technologies have become common for exploring microbial communities from various extreme environments. Investigations on glaciers, ice sheets, ponds, lakes, etc. have revealed the existence of numerous microorganisms while details of microbial communities in the Arctic fjords remain incomplete. The current study focuses on understanding the bacterial diversity in two Arctic fjord sediments employing the 16S rRNA gene metabarcoding and its comparison with previous studies from various Arctic habitats. The study revealed that Proteobacteria was the dominant phylum from both the fjord samples followed by Bacteroidetes, Planctomycetes, Firmicutes, Actinobacteria, Cyanobacteria, Chloroflexi and Chlamydiae. A significant proportion of unclassified reads derived from bacteria was also detected. Psychrobacter, Pseudomonas, Acinetobacter, Aeromonas, Photobacterium, Flavobacterium, Gramella and Shewanella were the major genera in both the fjord sediments. The above findings were confirmed by the comparative analysis of fjord metadata with the previously reported (secondary metadata) Arctic samples. This study demonstrated the potential of 16S rRNA gene metabarcoding in resolving bacterial composition and diversity thereby providing new in situ insights into Arctic fjord systems.

Metagenomic analysis of microbial communities in the sediments of a semi-intensive penaeid shrimp culture system.

The present study reports metagenomic sequencing and microbial diversity analysis of the sediment samples of a semi-intensive penaeid shrimp culture system. 16S rRNA gene-based high-throughput sequencing revealed distinct and diverse microbial communities in the analyzed sample. Analysis of the results showed a high abundance of Proteobacteria followed by Verrucomicrobia, Bacteroidetes, Planctomycetes, Firmicutes, Cyanobacteria, and Actinobacteria in the metagenome retrieved from the sediment sample. Unclassified bacteria also contributed a significant portion of the metagenome. Two potential shrimp pathogens viz Vibrio harveyi and Acinetobacter lwoffii detected in the sediment sample show the risk associated with the pond. Microbes that play essential roles in nutrient cycling and mineralization of organic compounds such as Bacteroidetes, Planctomycetes, Gammaproteobacteria, Firmicutes, Cyanobacteria, and Actinobacteria could also be identified. The present study provides preliminary data with respect to the microbial community present in the sediments of a shrimp culture system and emphasizes the application of metagenomics in exploring the microbial diversity of aquaculture systems, which might help in the early detection of pathogens within the system and helps to develop pathogen control strategies in semi-intensive aquaculture systems.