Syntrophy in microbial fuel cells

摘要: Syntrophy has a pivotal role in the microbial degradation of organic compounds methanogenic ecosystems (McInerney et al., 2009). Methanogenic is sequential process: series organisms involved various conversion steps these into methane and carbon dioxide (Dolfing, 1988). Typically, product one step substrate for next organism chain; each lives off waste product(s) its predecessor. Their defining characteristic as it relates to syntrophy that many associations producer critically dependent on activities consumer (Schink Stams, 2006): short chain volatile fatty acids like propionate butyrate only sustainable if electrons produced process are removed by other 2013). This concept was first put forward Bryant al. (1967) who famously invoked thermodynamics rationalize their observation ethanol could sustain growth an degrader hydrogen hydrogenotrophic methanogen. Since then we have learned interspecies transfer not mechanism facilitate syntrophy: formate direct electron (DIET) distinct alternatives classical pathway (Stams Plugge, 2009; Summers 2010). Obviously, very core value syntrophy—the critical interdependency between consumer—has been challenged this changing perspective. That is, until recently. Earlier year Kimura Okabe (2013) reported Geobacter sulfurreducens PCA can oxidize acetate what authors labelled ‘a syntrophic cooperation' with Hydrogenophaga sp. strain AR20 conjunction electrode final acceptor. However, close reading paper reveals G. does require presence activity perform feat: pure culture also acceptor; grow reaction, expected (Bond Lovley, 2003). Thus depend partner, association two therefore syntrophic. For co-culture be syntrophic, would ceases electrogen, or more precisely able use electrodes The data provide no evidence indeed case, though they do indicate benefits from AR20. It will interesting see extent anode potential modulates interactions electrogens, tempting speculate applying ‘optimal' may coax syntrophy. Morris recently noted literature anaerobic traditionally described detailed mechanistic terms, making explanations rather wordy. They propose define ‘obligately mutualistic metabolism'. definition covers highlighted above—the consumer—but alleviate need highlight (thermodynamic) rational behind ecosystems. Interestingly, host–bacterial mutualism human intestine (Backhed 2005) area much current research (for recent review, example Sommer Backhed, 2013) seems fall within realm syntrophy. It eye-openers DIET DIET-based (Summers 2010; Shrestha lead exciting work but give new impetus biochemical thermodynamical-oriented via Sieber 2012). Surprisingly, little known about kinetics interplay (Dolfing Tiedje, 1986; Dwyer 1988; Stams 2006). Microbial fuel cells promising tools tackle those issues, traditional chemostat studies offer perspective well, types acetogenesis methanogenesis (Lever, 2012; Oren, Given long running times needed obtain comprehensive sets systems, prudent start such some modelling delineate at which dilution rates insightful results (Xu 2011; Dolfing Xu,