Abstract:[Objective] To decipher the functional mechanism of Tlp1 which is the only soluble chemoreceptor containing PAS domain in Sinorhizobium alkalisoli YIC4027. [Methods] We constructed the gene-deleted mutant strain based on the Red homologous recombination system and triparental conjugation. The growth rate, chemotaxis, aerotaxis, cell flocculation, biofilm formation, exopolysaccharide (EPS) production, colonization, and competitive nodulation of the wild type and the mutant strain were studied. [Results] Compared with the wild type, the mutant strain showed unaffected growth, weakened chemotaxis, aerotaxis, colonization, and competitive nodulation, and increased cell coagulation, biofilm formation, and EPS production. [Conclusion] This study confirmed that the soluble chemoreceptor Tlp1 in YIC4027 affected the chemotactic movement of the cells for the first time.