Carotenoid accumulation in the psychrotrophic bacterium Arthrobacter agilis in response to thermal and salt stress

A psychrotrophic strain of Arthrobacter agilis, isolated from Antarctic sea ice, grows from 5 degreesC to 40 degreesC and in culture media containing 0-10% (w/v) NaCl. Maximum growth rate occurred at 30-35 degreesC with a dra stic decline as the cultivation temperatures diverged. Adaptation to extrem es of low temperature may be partially attributed to the production of the C-50 carotenoid bacterioruberin, and its glycosylated derivatives. Lowering of the cultivation temperature resulted in a concomitant increase in carot enoid production, which may contribute to membrane stabilisation at low tem perature. Maximum biomass accumulation occurred at 5-30 degreesC with a ten fold reduction at 40 degreesC. Changes in growth rates were minimal in cult ure media containing 0-2% (,w/v) NaCl at 10 degreesC while a gradual decrea se in growth rates occurred at higher salinity. Biomass accumulation at dif ferent salinity followed a trend similar to that observed with different cu ltivation temperatures. Maximum biomass accumulation was observed in cultur e media containing 0-5% (w/v) NaCl with a tenfold reduction at 10% (w/v) Na Cl. Carotenoid production also decreased as salinity increased.