Indigenous plasmids of Bacillus megaterium WSH-002 involved in mutualism with Ketogulonicigenium vulgare WSH-001

- Elimination of all the plasmids had no obvious impact on the cell growth of B. megaterium.
- Elimination of pBME2 and pBME3 affected 2-KLG production by K. vulgare.
- Potential genes involved in mutualism process on the indigenous plasmids were annotated.

In the two-step vitamin C fermentation process, the precursor 2-keto-l-gulonic acid (2-KLG) was synthesized using a mixed culture of Ketogulonicigenium vulgare WSH-001 and Bacillus megaterium WSH-002, which contained three plasmids, pBME1, pBME2 and pBME3. The cell growth of B. megaterium was not affected by the elimination of these plasmids. However, elimination of pBME2 and pBME3 significantly affected l-sorbose uptake and 2-KLG production. Sequence analysis of the plasmids showed that many of the pBME2 and pBME3 genes were of unknown function or could not be assigned to a specific metabolic pathway. The current work showed that the indigenous plasmids pBME2 and pBME3 of B. megaterium WSH-002 involved in mutualism with K. vulgare WSH-001. The results provided a promising new route to further demonstrate the mutualism process between the two bacteria.