ISOLATION AND CHARACTERIZATION OF A RHODOPSEUDOMONAS SP. STRAIN

Among the known subgroups of anoxygenic phototrophic bacteria, the Purple Nonsulfur Bacteria were widely investigated for their versatile metabolisms. This study isolated and identified an anoxygenic phototrophic bacterium of strain PUF1 from the East Lake, Wuhan, using the colony morphology, cell ultrathin structure, characteristic absorption spectra and phylogenetic analysis. The isolated strain was identified as Rhodopseudomonas sp. The bacterial cells are straight or slightly curved rod-shaped, 3.05—10.06 µm in length, 0.32—0.68 µm in diameter, with laminar membranes. The bacterial culture appears dark purple-red with major pigments being Bchl. a and carotenoids. With an initial pH of 6.0 to 8.0 and light intensity of 500 to 3000 lx, cell biomass at the stationary phase measured by the optical density (OD) showed no obvious difference, but pH higher than 8.0 in the liquid culture indeed decreased the maximal quantum yield of PS II (F_v/F_m). PUF1 had inconstant protein contents in its growth with the highest protein content of more than 60% related to the cellular dry weight in the stationary growth phase. The activity of ATPase continuously declined over the culture time. A plot of F_v/F_m fitted the single peak Gauss model with peak values in the log phase that showed certain relationships between the F_v/F_m and bacterial growing status. These findings provide important references for the study of physiological and biochemical characteristics of phototrophic bacteria.