The effect of heavy metals and other environmental conditions on the anaerobic phosphate metabolism of Acinetobacter johnsonii

Abstract

A strain of Acinetobacter with potential for bioremediation of heavy metalcontaminated waters was isoJated from a wastewater-treatment plant operating an enhanced biological phosphate removal process. N M R and extractive methods showed that polyphosphate accumulated aerobically was degraded under anaerobic conditions both in the presence and absence of cadmium or uranium (02-05 mM). N M R showed that free phosphate was formed at the expense of polyphosphate, and an extractive technique indicated that this reaction could be stimulated by the presence of UOi+ under these conditions. Energy-dispersive X-ray microanalysis demonstrated that only cadmium could enter the cells, and co-localized with intra-cellular granules containing phosphate and other divalent metals. The effects of other environmental parameters on the anaerobic phosphate metabolism were also investigated. Between pH 5 5 and 8.0, phosphate release increased with increasing pH. Between 4 "C and 37 "C, phosphate release increased with increasing temperature. The presence o f nitrate a t concentrations of 10 mM and above inhibited anoxic phosphate release, but supplying tungstate in the growth medium prior to anoxic incubation reduced the production o f active nitrate reductase and atleviated this effect.

Uranyl Precipitation byPseudomonas aeruginosavia Controlled Polyphosphate Metabolism

“…The use of Acinetobacter johnsonii, isolated from an enhanced biological phosphorus removal (EBPR) reactor, was effective in removing lanthanum from solution (4,5). In EBPR, biomass is cycled between an aerobic phase, in which phosphate is accumulated and stored as polyphosphate inside cells, and an anaerobic phase, in which phosphate is released from the microorganisms.…”

Unusual Versatility of the Filamentous, Diazotrophic Cyanobacterium Anabaena torulosa Revealed for Its Survival during Prolonged Uranium Exposure

“…The hydrolysis of polyphosphate induced in the presence of heavy metals and the free phosphate released at the expense of polyphosphate degradation have been shown to be involved in the extracellular precipitation of heavy metals, including uranium (23,24,44,45). Polyphosphate degradation and phosphate release were observed in an engineered strain of Pseudomonas aeruginosa overexpressing the polyphosphate kinase gene (ppk) under nutrient starvation conditions, resulting in the removal of 80% soluble U as uranyl phosphate precipitates (24).…”

“…Such intracellular sequestration within phosphate-rich granules or polyphosphates decreases the intracellular U concentration thereby protecting sensitive cytosolic molecules from U toxicity (6,20,21). On the other hand, the hydrolysis or degradation of polyphosphates in response to heavy metals or nutrient stress has been proposed to precipitate heavy metals extracellularly, enabling metal detoxification (23,24). The overexpression of the polyphosphate kinase (ppk) gene in Pseudomonas aeruginosa results in the significant accumulation of polyphosphates which degrade under carbon-starved conditions, and the phosphates released therefrom precipitate uranyl out of the solutions (24).…”

Microbially-induced Carbonate Precipitation for Immobilization of Toxic Metals

“…Radionuclides can be immobilized through interactions between microbially-produced sulfide (White, Sharman, & Gadd, 1998;Lebranz et al, 2000) and phosphate (Macaskie et al, 1992;Boswell, Dick, & Macaskie, 1999;Jeong & Macaskie, 1999), or through bacterial iron oxidation (Banfield et al, 2000) in the general process of biomineralization (Martinez et al, 2007). Uranium phosphate precipitation has been facilitated by diverse bacterial genera including Arthrobacter, BacillusI, Rahnella, Deinococcus, Escherichia and Pseudomonas (Basnakova et al,24 1998; Powers et al, 2002;Appukuttan, Rao, & Apte, 2006).…”