Interactions between autotrophic and heterotrophic strains improve CO₂ fixing efficiency of non-photosynthetic microbial communities

Five autotrophic strains isolated from non-photosynthetic microbial communities (NPMCs), which were screened from oceans with high CO₂ fixing capability, were identified as Ochrobactrum sp. WH-2, Stenotrophomonas sp. WH-11, Ochrobactrum sp. WH-13, Castellaniella sp. WH-14, and Sinomicrobium oceani WH-15. The CO₂ fixation pathways of all these strains were Calvin-Benson-Bassham pathway. These strains could metabolize multifarious organic compounds, which allowed switching them to autotrophic culture after enrichment in heterotrophic culture. The central composite response surface method indicated that these strains possessed many interactive effects, which increased the CO₂ fixing efficiency of a combined community composed of these strains by 56 %, when compared with that of the single strain. Furthermore, another combined community composed of these autotrophic strains and NPMC had richer interactive relationships, with CO₂ fixing efficiency being 894 % higher than that of the single strain and 148 % higher than the theoretical sum of the CO₂ fixing efficiency of each of its microbial components. The interaction between strictly heterotrophic bacteria in NPMC and isolated autotrophic strains played a crucial role in improving the CO₂ fixing efficiency, which not only eliminated self-restraint of organic compounds generated during the growth of autotrophic bacteria but also promoted its autotrophic pathway. Copyright © 2015 Springer Science+Business Media New York.