Effects of anaerobic conditions on photosynthetic units of acaryochloris marina

Abstract

Acaryochloris marina is a unicellular oxygenic photosynthetic cyanobacteria. Its pigment composition (Chl d > 95%) and ability to adapt various environments (aerobic and anaerobic) make it a unique species. And from some aspects it is a candidature of evolution intermediate of non-oxygenic to oxygenic photosynthesis. Our experiment aims to study the relationship between anaerobic and aerobic metabolism of Acaryochloris marina and compare the photosynthetic apparatus under oxygen-stressed conditions. Acaryochloris marina MBIC 11017 was cultured in aerobic (normal cultural condition as control) and micro-anaerobic condition (achieved by constantly bubbling N2). Growth rate and pigment composition have been monitored during the time. Treated cultures grew slower than control, but it showed an increase in cell density. Oxygen evolution was measured with Clark oxygen electrode. Cells were harvested in one week after inoculation then broken using vortex the mixture of cells with silicon beads. Proteins were extracted and then fractionated with SDS-PAGE. The bands with different abundances between each sample were picked and analyzed with Mass-fingerprint. Several proteins were identified with high scores. Two of them were phycobilisome rod-core linker polypeptides which were important to membrane binding and energy transfer. Their bands were removed in the micro-anaerobic samples while they are clear in aerobic samples. Low temperature fluorescence result agreed with the results from protein analysis: The phycobiliprotein may be uncoupled from photosynthetic membrane by losing its linker polypeptides under oxygen-stressed condition.