Bacteria Genomes - SYNECHOCOCCUS

Marine unicellular cyanobacteria of the synechococcus group occupy an important position at the base of the marine food chain. They are abundant in the world's oceans and as a result are one of the most numerous genomes on earth. They have the ability to acquire major nutrients and trace metals from the submicromolar concentrations found in the oligotrophic open seas and their light-harvesting apparatus is uniquely adapted to the spectral quality of light in the ocean.

A third of the open ocean isolates of synechococcus possess a unique type of swimming motility not seen in any other type of microorganism, they propel themselves through seawater at speeds of up to 25 mm/sec despite their lack of external propelling devices. They do not use their motility to respond to light gradients, but instead to respond to extremely small gradients of nitrogenous compounds.

Synechococcus sp. strain WH8102 is a motile strain that can be grown in both natural and artificial seawater liquid media as well as on plates and is amenable to biochemical and genetic manipulation. The availability of the complete sequence of the genome of synechococcus WH8102 will provide insights not only into the unique adaptations of this cyanobacterial group to the marine environment, including mechanisms of nutrient and metal transport, chemotaxis, motility, and viral interactions but also into what factors might be ultimately important in controlling primary productivity in the oceans.

Marine synechococcus spp. coexist with the other abundant unicellular marine cyanobacterial group, prochlorococcus . A major difference between the synechococcus and prochlorococcus groups lies in their light-harvesting apparatus, with synechococcus utilising chlorophyll A, and prochlorococcus relying on divinyl chlorophylls A and B. A comparative analysis of their genomes should allow insights not only into the evolution of light-harvesting complexes, but also into cyanobacterial diversification in the oceans, including adaptations to different marine niches.

Marine unicellular cyanobacteria are responsible for an estimated 20-40% of chlorophyll biomass and carbon fixation in the oceans.

References:

Nature 424:1037-1042 (2003)
http://www.genomenewsnetwork.com/sequenced_genomes/genome_guide_p3.shtml
http://genome.jgi-psf.org/finished_microbes/synw8/synw8.home.html
http://bioresearch.ac.uk/browse/mesh/C0085538L0087331.html