Figure Attachment 1 A: PCR validation of sdrC amplification fragment, with A and B fragments as templates, overlapping PCR amplification was performed to fuse AB fragments. B: Amplification of sdrC homologous arm fragments. C: 1% agarose gel electrophoresis amplification map was amplified by pKOR1 vector framework. D: The electrophoresis results of sdrC-JD-F/JD-R wild bacteria and knockout bacteria showed that 1 refers to the amplification product of knockout strain RN4220 △ sdrc, and 2 refers to the control of wild bacteria RN4220.