Carbon cloth stimulates direct interspecies electron transfer in syntrophic co-cultures

Abstract

h i g h l i g h t sConductive carbon cloth stimulated syntrophic metabolism in DIET co-cultures. Carbon cloth did not stimulate metabolism in a co-culture that relied on H 2 transfer. Non-conductive cotton cloth did not facilitate DIET. Carbon cloth restored DIET in Geobacter strains missing pili or OmcS cytochrome. a r t i c l e i n f o t r a c tThis study investigated the possibility that the electrical conductivity of carbon cloth accelerates direct interspecies electron transfer (DIET) in co-cultures. Carbon cloth accelerated metabolism of DIET co-cultures (Geobacter metallireducens-Geobacter sulfurreducens and G. metallireducens-Methanosarcina barkeri) but did not promote metabolism of co-cultures performing interspecies H 2 transfer (Desulfovibrio vulgaris-G. sulfurreducens). On the other hand, DIET co-cultures were not stimulated by poorly conductive cotton cloth. Mutant strains lacking electrically conductive pili, or pili-associated cytochromes participated in DIET only in the presence of carbon cloth. In co-cultures promoted by carbon cloth, cells were primarily associated with the cloth although the syntrophic partners were too far apart for cell-to-cell biological electrical connections to be feasible. Carbon cloth seemingly mediated interspecies electron transfer between the distant syntrophic partners. These results suggest that the ability of carbon cloth to accelerate DIET should be considered in anaerobic digester designs that incorporate carbon cloth.

Interspecies electron transfer in syntrophic methanogenic consortia: From cultures to bioreactors

“…One way to increase the efficiency of DIET is to add conductive materials such as granular activated carbon (GAC), carbon cloth, graphite, biochar, magnetite (Fe 3 O 4 ) particles, etc., into methanogenic digesters [79][80][81][82]. When GAC was added, aggregation became weaker, but metabolism was substantially accelerated.…”

Role and Potential of Direct Interspecies Electron Transfer in Anaerobic Digestion

“…Chen et al [11] successfully confirmed the accelerating effect on DIET metabolism of carbon cloth addition in co-cultures of G. metallireducens with G. sulfurreducens or M. barkeri. The DIET metabolism between these species was not stimulated in co-cultures with poorly conductive cotton cloth, indicating that the electrically conductive characteristic of the carbon cloth is the major reason for the enhancement in metabolism.…”

“…However, DIET can also occur through conductive materials as nonbiological electric conduits, as shown in Figure 2C [11]. Under a conductive-materialsupplemented environment, microorganisms do not form tight aggregates of the kind that are necessary for direct physical contact or electrical connection through pili between cells; instead, they seem to be tightly attached to the surface of the conductive materials [11,12,14] (Figure 3). Furthermore, important biological tools for DIET, such as pili and cytochrome OmcS, are not required for electron exchange if conductive materials exist.…”

“…We demonstrated that its use enhanced organic degradation and methanogenesis rates. Several other conductive materials, such as granular activated carbon (GAC), biochar, and carbon cloth, have also been reported to promote DIET in mixed cultures and defined co-cultures [6,[11][12][13][14].…”

Development of a Photosynthetic Microbial Electrochemical Cell (PMEC) Reactor Coupled with Dark Fermentation of Organic Wastes: Medium Term Perspectives

“…was ruled out because the electrode was poised at a potential that was too high for appreciable hydrogen production [26]. Also G. metallireducens is not able to use hydrogen as an electron donor, and a strain of G. sulfurreducens in which a gene for the hydrogenase required for hydrogen uptake had been deleted reduced fumarate as well as wild-type cells [24,27,28].…”