Researchers discover the smallest aquatic bacterium ever described

The research results, published recently in the journal Nature Scientific Reports, are important both for the discovery of a whole new group of bacteria with different genetic characteristics, and the possible ecological significance of this group of bacteria called for the time, 'Candidatus Actinomarinidae', since "are associated with the highest production of the oceans, recorded at depths around 50 meters between spring and autumn," said Camacho.

Researchers have studied the so-called DCM-Deep Chlorophyll Maximum in several areas of the planet and, more in detail, in the Mediterranean Sea, and they have described, with massive sequencing techniques, all inhabiting microbiota in such areas of the seas and oceans. These techniques "allow shelling whole microbial diversity of an ecosystem -millions of gene sequences that identify all the organisms that live there are obtained-, and to identify key genes that may explain the ecological role of microorganisms in the ecosystem; results which are later compared with environmental data taken in the study and allow for more detail on the functioning of biogeochemical cycles, "explains Camacho, who recalls that considering that microorganisms accumulate more than 90% of the biomass of the oceans" the importance of deepening in their knowledge is clear. "

Molecular analysis techniques have allowed more specifically characterize this new group of bacteria and, combined with other sophisticated analysis and microscopic techniques such as cell-situ hybridisation and flow cytometry, to determine that these are "smallest free-living microorganisms described so far, not only in terms of cell measure, but also with respect to the size of its genome, which is quite close to the theoretical limits on the minimum size of a living being independent, "said Antonio Camacho.

A record size

With biovolumes from 0'006 to 0'024 μm3 (average of 0'013 μm) and an average diameter of 0'292 μm, these bacteria are considerably smaller than the free-living organism which held that record up to now, Pelagibacter ubico, a marine bacterium also with a range of biovolume between 0'019 and 0'039 μm, nearly double that Candidatus Actinomarina minuta. Compared with commonly known bacterium, Escherichia cuele, the bacteria described in this paper has a size approximately 150 times lower.

The collaboration between these two research groups from Valencian universities, the University of Valencia and the University Miguel Hernandez, who bring together their expertise in genomics and microbial ecology, has made it possible to move forward together in the knowledge of microbial diversity in aquatic ecosystems. A few months ago provided new data on the Albufera of Valencia and the Mar Menor and in this case, key details of these marine areas of great importance from the point of view of the functioning of the oceans. The aforementioned collaboration continues in the search for explanatory mechanisms of microbial biodiversity patterns on aquatic ecosystems and knowing microbial metabolisms that dominate in these environments, which are crucial to the functioning of biogeochemical cycles at regional and planetary scale.

The research team of Professor Antonio Camacho, belonging to the Cavanilles Institute of Biodiversity and Evolutionary Biology of the University of Valencia, has accumulated experience of decades in the study of ecological patterns that govern the functioning of aquatic ecosystems as well as the biodiversity that they contain.