FermentativeEscherichia colimakes a substantial contribution to H₂production in coculture with phototrophicRhodopseudomonas palustris

Abstract

15Individual species within microbial communities can combine their attributes to produce services 16 that benefit society, such as the transformation of renewable resources into valuable chemicals. 17Under defined genetic and environmental conditions, fermentative Escherichia coli and 18phototrophic Rhodopseudomonas palustris exchange essential carbon and nitrogen, respectively, 19to establish a mutualistic relationship. In this relationship, each species produces H2 biofuel as a 20 byproduct of their metabolism. However, the extent to which each species contributes to H2 21 production and the factors that influence their relative contributions were previously unknown. 22By comparing H2 yields in cocultures pairing R. palustris with either wild-type E. coli or a 23 formate hydrogenlyase mutant that is incapable of H2 production, we determined the relative 24 contribution of each species to total H2 production. Our results indicate that E. coli contributes 25 between 32% and 86% of the H2 produced in coculture depending on the level of ammonium 26 excreted by the R. palustris partner. An R. palustris strain that stimulated rapid E. coli growth 27 through a high level of ammonium excretion resulted in earlier accumulation of formate and 28 acidic conditions that allowed E. coli to be the major contributor to H2 production. 29 30

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 the E. coli formate hydrogenlyase (28, 29). Consistent with this possibility, WT-based cocultures had higher H 2 yields at G17 and G146 (Fig.…”

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

“…This indicates that the nitrogenlimited conditions affected xylose utilization by E. coli Δ4D (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.…”