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 non-consumers, but the synergistic mechanisms remain unknown. Here, we found that two bacterial strains isolated from Chinese oilfields, Dietzia sp. DQ12-45-1b and Pseudomonas stutzeri SLG510A3-8, had a synergistic effect on hexadecane (C16) biodegradation, even though P. stutzeri could not utilize C16 individually. To gain a better understanding of the roles of the alkane non-consumer P. stutzeri in the C16-degrading consortium, we reconstructed a two-species stoichiometric metabolic model iBH1908, and integrated in silico prediction with the following in vitro validation, a comparative proteomics analysis, and extracellular metabolomic detections. Metabolic interactions between P. stutzeri and Dietzia sp. were successfully revealed for the importance in efficient C16 degradation. In the process, P. stutzeri survived on C16 metabolic intermediates from Dietzia sp., including hexadecanoate, 3-hydroxybutanoate, and α-ketoglutarate. In return, P. stutzeri reorganized its metabolic flux distribution to fed back acetate and glutamate to Dietzia sp. to enhance its C16 degradation efficiency by improving Dietzia cell accumulation and by regulating the expression of Dietzia succinate dehydrogenase. By using the synergistic microbial consortium of Dietzia sp. and P. stutzeri with the addition of the in silico predicted key exchanged metabolites, diesel oil was effectively disposed in 15 days with the removal fraction of 85.54±6.42%, leaving low amounts of C15-C20 isomers. Our finding provided a novel microbial assembling mode for the efficient bioremediation or chemical production in the future.IMPORTANCE Many natural and synthetic microbial communities are composed of not only species whose biological properties are in consistent with their corresponding communities, but also the ones whose chemophysical characteristics do not directly contribute to the performance of their communities. Even though the latter ones are often essential to the microbial communities, their roles are unclear yet. Here, by investigation of an artificial two-member microbial consortium in n-alkane biodegradation, we showed that the microbial member without the n-alkane degrading capability had a cross-feeding interaction with and the metabolic regulation to the leading member for the synergistic n-alkane biodegradation. Our study improves the current understanding of microbial interactions. As "assistant' microbes displayed their importance in communities besides the functional microbes, our findings also suggest a useful 'assistant' microbe principle in the design of microbial communities for either bioremediation or chemical production.