Fluorescence properties of the chlorophyll d-dominated cyanobacterium Acaryochloris sp. strain Awaji

Abstract

Fluorescence properties of the newly discovered chlorophyll (Chl) d-dominated cyanobacterium, Acaryochloris sp. strain Awaji were examined by a combination of steady state and the time-resolved fluorescence measurements. Acaryochloris sp. strain Awaji, in contrast to Acaryochloris marina MBIC11017, exhibited photosystem (PS) II fluorescence at 745 nm at room temperature and at 750 nm at −196 °C with a few Chl d components in the shorter wavelength region of the maxima. PS I fluorescence was not detected by steady state measurements but was by time-resolved spectroscopy as a transient component. The results clearly indicated diversity in the antenna systems in the genus Acaryochloris that contains Chl d as major pigments. Delayed fluorescence was observed only in the Chl a fluorescence region, consistent with A. marina. This strongly suggested that the primary electron donor for the PS II reaction center should be Chl a, which is identical to all other oxygenic photosynthetic organisms.