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Updated: Sep 9, 2025

Assembly and Quantification of Co-Cultures Combining Heterotrophic Yeast with Phototrophic Sugar-Secreting Cyanobacteria
Published on: December 27, 2024
Co-Culture of Cyanobacteria and Rhizobia, Increasing Biomass Under Nitrogen-Starvation Conditions
Akari Takagi1, Nanako Machida1, Misato Nagao1,2
1College of Agriculture, Ibaraki University, 3-21-1 Ami, Ibaraki, 300-0332, Japan.
Abstract:
A pair of new strains was obtained from a natural environment and identified as the filamentous non-heterocystous cyanobacterium SZ2 and the rhizobia Ensifer/Sinorhizobium sp. ST1. This pair was of particular interest because it could potentially perform both photosynthesis and nitrogen fixation. Interactions and material production were investigated in a new co-culture system using the "natural pair" of these strains. Cocultivation was favorable under both mixotrophic (coMC) and autotrophic conditions (coAC) when material production was assessed using heptadecane (C17H36) from the SZ2 strains. Under coAC, where nitrogen is depleted, some soluble factor(s) produced by the co-culture-possibly including ammonium ions-appear to function as biomass-increasing factors (BIFs), contributing to the enhanced accumulation of chlorophyll a in SZ2, along with extracellular polysaccharides, lipids, carbohydrates, and proteins in the total biomass. A notable feature of this "aquatic" coAC system is that it overcomes biomass reduction under nitrogen-deficient conditions, which is difficult in monoculture systems and can contribute to economic material production for biorefineries.
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