Environmental Control Of Growth And Bchl A Expression In Aerobic Anoxygenic Photosynthetic Bacterium

Aerobic anoxygenic phototrophic bacteria (AAPB) are facultative heterotrophs that can utilize light for photosynthesis. These unique-functioning bacteria are widely distributed in marine environments,,The widespread distribution and the significance of AAPB indicate an important role of these microorganisms in marine environments. To date, the corresponding mechanism has not been investigated throughly.In this study, typical strains of AAPB, Erythrobacter strain DSMZ6997 and Rosebacter strain DSMZ6996 was used for examination of the impact of carbon source, light intensity on its growth and BChl a expression in the batch culture and continuous culture,results showed that the expression of BChl a was regulated by carbon-source concentration and light conditions. The expression of BChl a in the experimental strain was stimulated by low availability of carbon-source but inhibited by light to certain extent at 300lux and completely at 1500lux. In contrast, cell abundance and even cell size of this strain was substantially enhanced under light/dark cycle cultivation conditions over dark cultivation conditions. Our results led to the conclusions that utilization of light through BChl a is helpful for AAPB to survive under carbon stress while light at high intensity is harmful for AAPB to synthesize BChl a, contributing to a better understanding of controlling mechanisms of AAPB in the marine environment.