Phosphine generation by mixed- and monoseptic-cultures of anaerobic bacteria

A microbial basis for bioreductive generation of phosphine is proposed, whi ch could account at least in part for the presence of this toxic gas in nat ural anaerobic environments and in sewage and landfill gases. Phosphine gen eration under anaerobic growth conditions was dependent upon both the cultu re inoculum source (animal faeces) and enrichment culture conditions. Phosp hine was detected in headspace gases from mixed cultures under conditions p romoting fermentative growth of mixed acid and butyric acid bacteria, eithe r in the presence or absence of methane generation. Monoseptic cultures of certain mixed acid fermenters (Escherichia coli, Salmonella gallinarum, and Salmonella arizonae) and solvent fermenters (Clostridium sporogenes, Clost ridium acetobutyricum and Clostridium cochliarium) also generated phosphine . Such fermentative bacteria participate in the multi-stage process of meth anogenesis in nature. Generation of phosphine by these bacteria, rather tha n by methanoarchaea themselves, could explain the apparent correlation betw een methanogenesis and the formation of phosphine in nature. (C) 2000 Elsev ier Science B.V. All rights reserved.