Atypical Polyphosphate Accumulation by the Denitrifying Bacterium Paracoccus denitrificans

Abstract

Polyphosphate accumulation by Paracoccus denitrificans was examined under aerobic, anoxic, and anaerobic conditions. Polyphosphate synthesis by this denitrifier took place with either oxygen or nitrate as the electron acceptor and in the presence of an external carbon source. Cells were capable of poly-␤-hydroxybutyrate (PHB) synthesis, but no polyphosphate was produced when PHB-rich cells were incubated under anoxic conditions in the absence of an external carbon source. By comparison of these findings to those with polyphosphateaccumulating organisms thought to be responsible for phosphate removal in activated sludge systems, it is concluded that P. denitrificans is capable of combined phosphate and nitrate removal without the need for alternating anaerobic/aerobic or anaerobic/anoxic switches. Studies on additional denitrifying isolates from a denitrifying fluidized bed reactor suggested that polyphosphate accumulation is widespread among denitrifiers.Due to environmental problems associated with phosphorus discharge, phosphorus removal has become a standard treatment practice in wastewater purification plants. Enhanced biological phosphorus removal (EBPR) is the most common biological phosphorus removal method. The method is based on enrichment of so-called polyphosphate-accumulating organisms (PAOs) through recycling of the sludge between anaerobic and aerobic zones. Under these conditions, the PAOs release phosphorus in the anaerobic zone and store phosphorus as polyphosphate in the aerobic zone. Phosphorus is subsequently removed from the process stream by harvesting a fraction of the phosphorus-rich bacterial biomass (26).Recently, it was demonstrated that, not only under aerobic conditions but also under anoxic conditions, i.e., with nitrate as the electron acceptor, some PAOs are capable of polyphosphate accumulation (3,6,12,15). Since attempts to isolate bacteria with all characteristics attributed to PAOs have failed so far, information on these organisms is based on studies with crude sludge samples and enrichment cultures obtained from EBPR plants. On the basis of these studies, the following set of metabolic properties has been attributed to PAOs (22).Under anaerobic conditions, acetate or other low-molecularweight organic compounds are converted to polyhydroxyalkanoates (PHA), polyphosphate and glycogen are degraded, and phosphate is released. Under aerobic or anoxic conditions, PHA is converted to glycogen, phosphate is assimilated, and polyphosphate is intracellularly produced. Under the latter conditions, bacterial growth and phosphate uptake are regulated by the energy released from the breakdown of PHA.We studied the phosphorus dynamics in a prototype treatment system used for removal of organic matter and inorganic nitrogen from recirculating fish culture systems. The system comprised a nitrifying filter for oxidation of ammonia to nitrate, a digestion basin for anaerobic digestion of organic matter, and a denitrifying filter for reduction of nitrate to nitrogen gas (1). It was found that m...

Relationship between Nitrite Reduction and Active Phosphate Uptake in the Phosphate-Accumulating Denitrifier Pseudomonas sp. Strain JR 12

“…In a recent study (4), we demonstrated that the heterotrophic denitrifier Paracoccus denitrificans, as well other denitrifying isolates, exhibits the capability of polyP synthesis under either aerobic or anoxic conditions without the need for alternating aerobic and anaerobic (or anoxic) switches. Unlike PAO, these denitrifiers were unable to use polyhydroxyalkanoates as an energy source for polyP synthesis and derived energy from oxidation of external carbon sources.…”

Sorption and Release of Organics by Primary, Anaerobic, and Aerobic Activated Sludge Mixed with Raw Municipal Wastewater

“…This species has also been widely reported to uptake short chain fatty acid and store it as polyhydroxybutyrate (PHB) in both WWTP and single culture system [15,61]. However these microorganisms are unable to utilize PHB for Polyphosphate build up [8,15] which is also evident in the current study. As the microorganisms tend to show a different behaviour under various growth conditions, therefore the specific mechanism behind substrate utilization and growth is also subject to change under various operational parameters [8,15,[62][63][64][65][66][67].…”

Effects of Oxygen Loss on Carbon Processing and Heterotrophic Prokaryotes from an Estuarine Ecosystem: Results from Stable Isotope Probing and Cytometry Analyses

“…First, the O 2 content of many aquatic ecosystems is declining, and OM mineralization by pelagic microorganisms may be a major source of the P sustaining primary production during thermal stratification or when sediments have no or weak influence on upper water columns in terms of nutrient supply. Second, a study from engineered systems has shown that some denitrifying bacteria can remove P from the water and accumulate it in cells under anaerobic conditions (Barak and van Rijn 2000). Occurrence of such a process in water columns, when O 2 declines, may affect P availability.…”

“…crystal phosphate minerals (Goldhammer et al 2010). or by accumulating it into cells as polyphosphates (Barak and van Rijn 2000). This study by Barak and van Rijn (2000) showed, in an engineered system, that this accumulation was done by denitrifying bacteria using nitrate as electron acceptor when an external source of carbon was present.…”

“…or by accumulating it into cells as polyphosphates (Barak and van Rijn 2000). This study by Barak and van Rijn (2000) showed, in an engineered system, that this accumulation was done by denitrifying bacteria using nitrate as electron acceptor when an external source of carbon was present. These conditions (presence and decline of nitrate and presence of an external carbon source) were similar to those in our low-O 2 samples.…”