The bugs are leading actors in the world of phytoplankton, the microscopic creatures that float on waves and currents on the uppermost layers of the sea, using sunlight to transform carbon dioxide (CO2) into energy.

CO2, the big culprit in global warming, is disgorged by the burning of oil, carbon and gas -- the fuels that have driven industrialisation.

Scientists believe that unbraked emissions of CO2 are causing a "greenhouse effect" in which the Earth's atmosphere is steadily warming, trapping heat from the Sun rather than let it radiate back into space.

One of the big areas of interest are carbon "sinks": living things that absorb CO2 from the air through photosynthesis, and can thus mitigate the climate-changing build-up of pollution.

Until recently, interest in "sinks" has focussed on planting forests, but increasingly scientists have become aware of an equally important role played by the sea, which accounts for two-thirds of the Earth's surface.

The two sequenced bacteria are Prochlorococcus marinus, the dominant phytoplankton in most tropical and temperate oceans, and Synechococcus, which is less abundant but has a broader global distribution.

Between them, these bugs account for as much as two-thirds of the atmospheric CO2 that is absorbed by the sea.

Understanding their genetic mechanisms should give vital clues as to their ability to take up CO2 and thus enable experts to get a clearer picture of the global warming dilemma.

The research is published in Thursday's issue of the British weekly Nature, and in next Wednesday's issue of the US publication Proceedings of the National Academy of Sciences (PNAS).

SPACE.WIRE