The 5' upstream region of the cellulose synthase operon (bcs operon) has been isolated by cloning from Escherichia coli. A gene encoding YhjQ is located 1.0 kb upstream of the bcs operon in E. coli. The function of YhjQ remains unknown. Insertional inactivation of the yhjQ gene causes abnormal cell division, resulting in incomplete partition of the chromosome and filamentous cells of various sizes. These results suggest that the product of yhjQ may affect normal doubling and cellular morphology. Salmonella enteritidis, and Escherichia coli strains also produce cellulose (Zogaj et al. 2001). This multicellularity is a common behavior of bacteria at certain developmental stages, offering strategic advantages in comparison with single cells (Shapiro 1998). Here, we report the cloning of the yhjQ gene that exists in the upstream region of the bcs operon involved in cellulose synthesis in E. coli. Insertional inactivation of this gene hinders cell division, and results in filamentous cells of various sizes.