Flash oxygen yield patterns of autotrophically and photoheterotrophically grown Chlamydobotrys stellata in the presence and absence of lipophilic acceptors.

The obligate phototrophic green alga Chlamydobotrys stellata does not evolve oxygen when grown in CO2-free atmosphere on acetate. With the application of the lipophilic acceptor 2,6-dichloro-p-benzoquinone it was investigated whether this phenomenon is caused by the inactivation of the water-splitting system or by an inhibition of the electron transport chain. It was found that in the presence of DCQ, the photoheterotrophic alga exhibited a normal period-4 flash oxygen pattern, but the steady state yield was only 25% of that measured in the autotrophic cells. After DCQ addition, the initial distribution of S-states and the values of the transition probabilities proved to be the same in the autotrophic and photoheterotrophic algae. These results indicate that photoheterotrophic growth conditions inhibit the electron transport of Chl. stellata behind the acceptor site of DCQ, but the water-splitting system remains active with a reduced oxygen evolving capacity.