title: Phosphate uptake and release by Acinetobacter johnsonii in continuous culture and coupling of phosphate release to heavy metal accumulation.
abstract: A strain of polyphosphate-synthesizing, phosphate-releasing Acinetobacter johnsonii was isolated from a wastewater treatment plant operating enhanced biological phosphate removal (EBPR) and was used to remove La(3+) from solution via precipitation of cell-bound LaPO(4). The effect of repeated aerobic-anaerobic cycles on the carbon and phosphate metabolism of the organism was studied in attempts to promote increased phosphate flux using a three-stage, continuous bioreactor comprising aerobic, anaerobic and settling vessels. The bioreactor was operated in two modes: In flow-through mode, cells were grown aerobically with acetate as the sole carbon source, promoting excess phosphate uptake (up to 5.0 mmol/l=3.0 mmol/g protein). Cells were diluted into the anaerobic vessel where phosphate was released (up to 1.0 mmol/l=0.3 mmol/g protein), and thence to waste. The system was initially operated to steady state in flow-through mode, then switched to recycle mode. Here the anaerobic vessel output passed to a settling vessel from which settled cells were returned to the aerobic vessel. Carbon source (acetate) was supplied only to the anaerobic vessel; increased anaerobic acetate uptake was observed during recycle, which was sustained when the system was returned to flow-through mode and was related to increased cellular lipid inclusions by flow cytometry and electron microscopy. These phenomena may represent adaptation of cells to aerobic-anaerobic cycling with aerobic carbon/energy limitation. Addition of La(3+) to the anaerobic vessel during recycle mode promoted removal of 95% of the La(3+) from a 0.1 to 0.3 mM (14-42 ppm) solution at the expense of biogenic phosphate.
authors.affiliation: School of Biosciences, The University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
authors.forename: C D
authors.initials: CD
authors.lastname: Boswell
authors.forename: R E
authors.initials: RE
authors.lastname: Dick
authors.forename: H
authors.initials: H
authors.lastname: Eccles
authors.forename: L E
authors.initials: LE
authors.lastname: Macaskie
mesh_terms: D000085:Acetates / Q000378:metabolism; D000150:Acinetobacter / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure; D000332:Aerobiosis; D000693:Anaerobiosis; D001673:Biodegradation, Environmental; D018533:Biomass; D019149:Bioreactors; D005434:Flow Cytometry; D006863:Hydrogen-Ion Concentration; D007220:Industrial Waste; D007811:Lanthanum / Q000378:metabolism*; D019216:Metals, Heavy / Q000378:metabolism*; D008854:Microscopy, Electron; D009566:Nitrates / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism*; D018508:Water Purification
chemical_list: D000085:Acetates; D007220:Industrial Waste; D019216:Metals, Heavy; D009566:Nitrates; D010710:Phosphates; D007811:Lanthanum