Rare biosphere

The species of rare biosphere can offer the gene pool that can be activated under changing conditions, thus keeping the ecosystem functional.

[4] Members of the rare biosphere have been recognised as important drivers of many key ecosystem functions, for example providing bioavailable nitrogen in marine and soil environment.

[5][6] Previous attempts to characterize in situ abundance of different microbial species in specific environment have been made through culturing and molecular biology techniques.

[7] Culturing produces a very narrow picture of some of the rarer species present, especially when studying an environment where only less than 0,1% of all microbes are cultivable with standard methods.

The current state of the art practice is the use of high-throughput sequencing techniques, pioneered by Dr. Mitchell Sogin of the Marine Biological Laboratory.

Using this method, Sogin et al.’s study of microbial diversity in North Atlantic deep water produced an estimate of 5266 different taxa.

[11] As these less abundant species are limited in number, viral infection and ultimately death by lysis is more unlikely as the viruses depend on high concentrations of host organisms to persist.

For example, recent evidence implicates that a rare minority may be responsible for fixing more cumulative nitrogen than the abundant majority of microbial cells in marine environment.

[7][5] A subtle and less direct manner the rare biosphere may be affecting ecosystems, in terms of biodiversity and biogeochemical cycles, is by acting as an unlimited source of genetic diversity and material.

[11] The rare biosphere could be seen as a seed bank, transferring genes resulting in fitter recombinants that rise to become the dominant majority.

This suggests that populations within the rare biosphere experience evolutionary forces specific to the location they are found, such as selection, speciation, and extinction.