Characteristics of intracellular polyphosphate granules and phosphorus-absorption of a marine polyphosphate-accumulating bacterium, Halomonas sp. YSR-3

Abstract

Halomonas sp. YSR-3 was isolated from the Yellow Sea and identified as a polyphosphate-accumulating bacterium and the characteristics of its intracellular polyphosphate (polyP) granules and phosphorus absorption were studied. Most YSR-3 cells stored one or two polyP granules in regular appearance and high-density. The diameter of the granules was about 400 nm measuring by a transmission electron microscope (TEM). After stained with 4,6-diamidino-2-phenylindole (DAPI) and visualized by a fluorescence microscope, the cells turned blue and the granules were bright yellow. The composition of granules includes P (major ingredient), Mg, S, K, and Ca as detected by an energy dispersive X-ray spectrometer (EDS). When inorganic phosphorus (PO3−4) and ferric ion (Fe 3+) were added into media, the biomass increased and the cells formed intracellular polyP granules owing to the phosphorus assimilation from media. The YSR-3 obtained higher biomass by adding 0.02 g/L FePO 4 than 0.005 g/L and 0.01 g/L FePO 4; however, the phosphorus absorption was higher with 0.01 g/L FePO 4 than 0.005 g/L and 0.02 g/L FePO 4 The optical density at wavelength 480 nm (OD 480 nm) was 0.79 and 100% cells could form intracellular polyP granules. These results show that strain YSR-3 is able to acquire higher biomass and absorb more inorganic phosphorus when 0.01 g/L FePO 4 is added. The characteristics of absorbing and storing phosphorus as intracellular inorganic polyP granules have a potential for application in high-efficiency phosphorus removal in wastewater treatment.