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

Abstract.

A psychrotrophic strain of Arthrobacter agilis, isolated from Antarctic sea ice, grows from 5°C to 40°C and in culture media containing 0–10% (w/v) NaCl. Maximum growth rate occurred at 30–35°C with a drastic decline as the cultivation temperatures diverged. Adaptation to extremes 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 carotenoid production, which may contribute to membrane stabilisation at low temperature. Maximum biomass accumulation occurred at 5–30°C with a tenfold reduction at 40°C. Changes in growth rates were minimal in culture media containing 0–2% (w/v) NaCl at 10°C while a gradual decrease in growth rates occurred at higher salinity. Biomass accumulation at different salinity followed a trend similar to that observed with different cultivation temperatures. Maximum biomass accumulation was observed in culture media containing 0–5% (w/v) NaCl with a tenfold reduction at 10% (w/v) NaCl. Carotenoid production also decreased as salinity increased.