Sphingopyxis alaskensis RB2256

S. alaskensis is an obligate aerobe isolated as one of the most numerically abundant bacteria from Alaskan waters over a period spanning ten years, demonstrating it is one of the most common culturable inhabitants from these environments. Its capacity to thrive in oligotrophic environments at 4-10 degrees Celsius is linked to unique genetic and physiological properties which are fundamentally different from those of the well studied bacteria such as Escherichia coli. It has a constant ultramicro-size (its volume is 0.1 um 3), irrespective of whether it is growing or starved, that provides it with a mechanism for avoiding predation, and a high surface to volume ratio to enhance nutrient uptake. This is coupled with the ability to utilize low concentrations of nutrients using high affinity, broad specificity uptake systems ( e.g. highest reported rates of alanine transport for any bacterium) and the ability to simultaneously take up mixed substrates. It is likely to be an important contributor in terms of biomass and nutrient cycling in marine environments. Ultramicrobacteria (nanobacteria), such as S. alaskensis, have been reported in a range of aquatic, terrestrial and clinical samples, and in fossils; many of which are controversial. The reports have raised questions about the minimum size of a free-living cell. The astrobiology community has been particularly interested, as the minimum cell-size has important implications for cellular evolution and for the search for extraterrestrial life. S. alaskensis is a useful model for these purposes, as it has been shown, for example, to achieve maximum rates of growth with 200 ribosomes per cell. (EBI Integr8)