An axenic cyclostat of Prochlorococcus PCC 9511 with a simulator of natural light regimes

A cyclostat was designed for growing the oceanic oxyphotobacterium Prochlorococcus PCC 9511. Culture of this organism, known to be difficult to grow, was mastered for a large volume. Prochlorococcus grew well and axenic conditions were maintained for up to 15 days. We designed an illumination system allowing a smooth bell-shaped irradiance curve reaching almost 1000 mu mol quanta m(-2) s(-1) to be obtained. Cell division was strongly synchronised under these illumination conditions, which were close to those found at low latitude in the upper layer of ocean. The described device is particularly well suited to make experiments requiring up to 6 L per day of well synchronised, exponentially-growing Prochlorococcus culture.