Advances in marine group II archaea research

Abstract:

Marine Group II (MGII) is the most abundant archaeal group in surface ocean waters. At present, no pure culture of the group has been isolated successfully since they were discovered in 1992. Analysis of the 16S rRNA genes has revealed that MGII mainly consist of two groups, MGIIa and MGIIb, which perform photoheterotrophy and potentially play an important role in marine carbon cycle. Phylogenetic classification based on the 16S rRNA gene assigned MGIIa and MGIIb as two families within an order-level lineage under Thermoplasmata. The phylogenetic position of a third group, MGIIc, is ambiguous due to the lack of their 16S rRNA gene sequences and absence in the metagenome data. This mini-review aims to provide the latest information on the distribution, abundance and diversity, metabolic capabilities and potential ecological functions, as well as efforts being made in enrichment and isotope labeling studies of MGII. Insights on future research directions are also provided.