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

Abstract

Phosphate uptake by the phosphate-accumulating denitrifier Pseudomonas sp. JR12 was examined with different combinations of electron and carbon donors and electron acceptors. Phosphate uptake in acetate-supplemented cells took place with either oxygen or nitrate but did not take place when nitrite served as the final electron acceptor. Furthermore, nitrite reduction rates by this denitrifier were shown to be significantly reduced in the presence of phosphate. Phosphate uptake assays in the presence of the H ؉ -ATPase inhibitor N,N-dicyclohexylcarbodiimide (DCCD), in the presence of the uncoupler carbonyl cyanide 3-chlorophenylhydrazone (CCCP), or with osmotic shock-treated cells indicated that phosphate transport over the cytoplasmic membrane of this bacterium was mediated by primary and secondary transport systems. By examining the redox transitions of whole cells at 553 nm we found that phosphate addition caused a significant oxidation of a c-type cytochrome. Based on these findings, we propose that this c-type cytochrome serves as an intermediate in the electron transfer to both nitrite reductase and the site responsible for active phosphate transport. In previous studies with this bacterium we found that the oxidation state of this c-type cytochrome was significantly higher in acetate-supplemented, nitrite-respiring cells (incapable of phosphate uptake) than in phosphate-accumulating cells incubated with different combinations of electron donors and acceptors. Based on the latter finding and results obtained in the present study it is suggested that phosphate uptake in this bacterium is subjected to a redox control of the active phosphate transport site. By means of this mechanism an explanation is provided for the observed absence of phosphate uptake in the presence of nitrite and inhibition of nitrite reduction by phosphate in this organism. The implications of these findings regarding denitrifying, phosphate removal wastewater plants is discussed.Biological phosphate removal from wastewater is a generally accepted, less costly alternative to chemical phosphate removal (27). Microorganisms involved in this process are capable of phosphate uptake in excess of their metabolic requirements and store phosphate internally as polyphosphate (polyP) polymers. Microorganisms thought to underlie phosphate removal in wastewater plants are collectively known as phosphate accumulating organisms (PAO). The general consensus concerning their metabolism is that they require alternating aerobic and anaerobic (or anoxic) conditions. Under such conditions phosphate is released in the anaerobic zone and stored as polyP in the aerobic or anoxic zone. Phosphorus is subsequently removed from the process stream by harvesting a fraction of the phosphorus-rich bacterial biomass (26). Isolation of bacterial isolates with all characteristics attributed to PAO have failed so far, and information on these organisms is based on studies with crude sludge samples or enrichment cultures obtained from biological phosphate removing plants. T...

Biological nitrogen removal with nitrification and denitrification via nitrite pathway

“…In this case, the presence of phosphate, rather than its absence, has also a profound effect on denitrification and causes nitrite accumulation. Nitrite reduction rate decreased from 4.9 to 2.7 mg NO 2 -N/g protein min as phosphate concentration was increased from 0 to 15.5 mg P/l (Barak et al 2000).…”

Origin, causes and effects of increased nitrite concentrations in aquatic environments

“…Nitrite reduction rates by a Pseudomonas sp. strain decreased from 4.9 to 2.7 mg NO − 2 -N g −1 protein min −1 as phosphate concentration was increased from 0 to 15.5 mg P L −1 (Barak & Van Rijn 2000). According to Barak and Van Rijn (2000) the latter could be caused by a competitive use of a c-type cytochrome, needed for electron transport to both nitrite reductase and the site responsible for active phosphate transport.…”

Effects of phosphorus on polyphosphate accumulation by Cunninghamella elegans

“…Under natural conditions, the amount of phosphorus available for biosynthetic purposes will depend not only on the total amount of phosphate in the environment, but also on its solubility, which is dictated by others chemical and physical factors of the environment (4,5,18,24,33,49).…”

“…Metabolic changes related to pH of the culture medium, phosphorus content and polyP chain size in cells on stationary and logarithmic growth phases were demonstrated in different microorganisms, including fungi (4,5,18,24,42,65,72).…”

“…Besides being an important constituent of organic molecules, phosphorus can be present not only as orthophosphate (Pi) but also as condensed inorganic phosphates (4,5,22,23,24,28,31,32).…”