Metabolic Exchange with Non-Alkane-Consuming Pseudomonas stutzeri SLG510A3-8 Improves -Alkane Biodegradation by the Alkane Degrader sp. Strain DQ12-45-1b.

Biodegradation of alkanes by microbial communities is ubiquitous in nature. Interestingly, the microbial communities with high hydrocarbon-degrading performances are sometimes composed of not only hydrocarbon degraders but also nonconsumers, but the synergistic mechanisms remain unknown. Here, we found that two bacterial strains isolated from Chinese oil fields, sp. strain DQ12-45-1b and SLG510A3-8, had a synergistic effect on hexadecane (C compound) biodegradation, even though could not utilize C individually. To gain a better understanding of the roles of the alkane nonconsumer in the C-degrading consortium, we reconstructed a two-species stoichiometric metabolic model, BH1908, and integrated prediction with the following validation, a comparative proteomics analysis, and extracellular metabolomic detection. Metabolic interactions between and sp. were successfully revealed to have importance in efficient C degradation. In the process, survived on C metabolic intermediates from sp., including hexadecanoate, 3-hydroxybutanoate, and α-ketoglutarate. In return, reorganized its metabolic flux distribution to fed back acetate and glutamate to sp. to enhance its C degradation efficiency by improving cell accumulation and by regulating the expression of succinate dehydrogenase. By using the synergistic microbial consortium of sp. and with the addition of the -predicted key exchanged metabolites, diesel oil was effectively disposed of in 15 days with a removal fraction of 85.54% ± 6.42%, leaving small amounts of C to C isomers. Our finding provides a novel microbial assembling mode for efficient bioremediation or chemical production in the future. Many natural and synthetic microbial communities are composed of not only species whose biological properties are consistent with their corresponding communities but also ones whose chemophysical characteristics do not directly contribute to the performance of their communities. Even though the latter species are often essential to the microbial communities, their roles are unclear. Here, by investigation of an artificial two-member microbial consortium in -alkane biodegradation, we showed that the microbial member without the -alkane-degrading capability had a cross-feeding interaction with and metabolic regulation to the leading member for the synergistic -alkane biodegradation. Our study improves the current understanding of microbial interactions. Because "assistant" microbes showed importance in communities in addition to the functional microbes, our findings also suggest a useful "assistant-microbe" principle in the design of microbial communities for either bioremediation or chemical production.