Compartments formed by folded cell membrane might serve as gene archives:
The largest freshwater bacterium, Achromatium oxaliferum, is highly flexible in its requirements, as researchers led by the IGB have now discovered: It lives in places that differ extremely in environmental conditions such as hot springs and ice water. The bacterial strains from the different ecosystems do not differ in their gene content, but rather chose what to express. The adaptation is probably achieved by a process which is unique to these bacteria: only relevant genes are enriched in the genomes and transcribed, while others are archived in cell compartments.
Achromatium is special in many respects: It is 30,000 times larger than its “normal” counterparts that live in water and owing to its calcite deposits it is visible to the naked eye. It has several hundred chromosomes, which are most likely not identical. This makes Achromatium the only known bacterium with several different genomes.
The researchers have analyzed sequence data bases of sediments and show that Achromatium is universal. It is found in a broad range of environments: in shallow waters as well as in the ocean at a depth of 4000 metres. It can be found in hot springs and ice-cold water; in acidic and alkaline environments as well as in hypersaline waters.
Typically, such a wide range of environmental conditions would result in the establishment of new species, well-adapted to their specific environment. However, Achromatium defies this expectation. Though, equipped with equal functionality, the bacteria in the various ecosystems differ in their gene expression patterns by transcribing only relevant genes.Forschungsverbund Berlin, “Giant aquatic bacterium is a master of adaptation” at ScienceDaily
The paper is open access.