ABSTRACT
A bacterium capable of utilizing the alkyl chains of didecyldimethylammonium salt was isolated from activated sludge. In addition, the isolate also utilized didodecyldimethylammonium salt, ditetradecyldimethylammonium salt and alkyltrimethylammonium salts (C10 to C18) as sole source of carbon and energy. The broad substrate with respect to the alkyl chain length was also demonstrated with oxidation rates of various quaternary ammonium salts by didecyldimethylammonium chloride-grown cells. The oxidation rate decreased with increasing alkyl chain lengths. The main factor impeding the biodegradation of dialkyldimethylammonium salts with long alkyl chains is probably the low bioavailability of water-insoluble chemicals. The biodegradability of dialkyldimethylammonium salts was therefore determined in flow-through columns at concentrations below their aqueous solubility. Dialkyldimethylammonium salts adsorbed on silica gel particles packed in flow-through columns were immediately metabolized by the isolate when dissolved. Microorganisms present in river water pumped through a sterile column degraded dissolved dicocodimethylammonium salts within a week.
Subject(s)
Quaternary Ammonium Compounds/metabolism , Water Pollutants/metabolism , Water Purification/methods , Biodegradation, Environmental , Oxidation-Reduction , Quaternary Ammonium Compounds/chemistry , Water Microbiology , Water MovementsABSTRACT
Three man, aged 66, 60 and 26 years with bipolar disorder and long periods (20-5 years) of effective lithium prophylaxis had relapses on lithium discontinuation. Once the drug was reinstituted, it was no longer effective. Combinations of lithium with a classical MAO inhibitor or a second mood stabilizer (valproic acid and carbamazepine, respectively) ultimately proved to be successful. The risk of refractoriness should be kept in mind before considering to stop lithium therapy. A better compliance can be achieved by informing patients about the risks of discontinuing lithium, by maintaining a minimal maintenance dose and by adequately coping with possible side effects.
