Fermentative Escherichia coli makes a substantial contribution to H2 production in coculture with phototrophic Rhodopseudomonas palustris

Abstract

Individual species within microbial communities can combine their attributes to produce services that benefit society, such as the transformation of renewable resources into valuable chemicals. Under defined genetic and environmental conditions, fermentative Escherichia coli and phototrophic Rhodopseudomonas palustris exchange essential carbon and nitrogen, respectively, to establish a mutualistic relationship. In this relationship, each species produces H2 biofuel as a byproduct of its metabolism. However, the extent to which each species contributes to H2 production and the factors that influence their relative contributions were previously unknown. By comparing H2 yields in cocultures pairing R. palustris with either wild-type E. coli or a formate hydrogenlyase mutant that is incapable of H2 production, we determined the relative contribution of each species to total H2 production. Our results indicate that E. coli contributes between 32 and 86% of the H2 produced in coculture depending on the level of ammonium excreted by the R. palustris partner. The level of ammonium excretion influenced the time over which E. coliwas exposed to formate, the types of E. colifermentation products available to R. palustris, and the pH of the medium, all of which affected the contribution of each species to H2 production.

Enhanced nutrient uptake is sufficient to drive emergent cross-feeding between bacteria in a synthetic community

“…4C). Low formate yields could be explained in part by increased conversion of formate to H 2 and CO 2 by E. coli formate hydrogenlyase [42,43]. Consistent with this possibility, WT-based cocultures had the highest H 2 yields (Fig.…”

Reconstruction and optimization of a Pseudomonas putida-Escherichia coli microbial consortium for mcl-PHA production from lignocellulosic biomass

“…This indicates that the nitrogen-limited conditions affected xylose utilization by E. coli ∆4D (ACP-SCLAC) in the co-culture system. In order to further improve the utilization of xylose by the engineered E. coli , the nitrogen source concentration had to be increased, but nitrogen source limitation promotes the accumulation of mcl-PHA, so exploring the appropriate nitrogen source concentration to achieve a balance between the two engineered bacteria is crucial for the production of mcl-PHA ( Sangani et al, 2019 ). We therefore increased the concentration of the nitrogen source (NH 4 Cl) to 3 g/L, while using glucose and xylose at a 1:1 ratio as the carbon source.…”

Characteristics and Application of Rhodopseudomonas palustris as a Microbial Cell Factory

“…The efficiency of hydrogen production can be further improved via complementation of photo-fermentation and dark-fermentation. In this sequential two-stage dark- and photo-fermentation process, dark hydrogen production was conducted using acidogenic bacteria like Clostridium butyricum ( Su et al, 2009a ), C. pasteurianum ( Chen et al, 2008 ), Caldicellulosiruptor saccharolyticus ( Özgür et al, 2010 ), and E. coli ( Sangani et al, 2019 ), and photo hydrogen production was conducted using photosynthetic bacteria, like R. palustris . A sequential dark- and photo-fermentation system including C. pasteurianum and R. palustris has been constructed for hydrogen production using sucrose as a feedstock ( Chen et al, 2008 ).…”