Genome sequencing and annotation have revealed a putative cellulose biosynthetic operon in the strain Pseudomonas
syringae pv. syringae UMAF0158, the causal agent of bacterial apical necrosis. Bioinformatics analyses and experimental
methods were used to confirm the functionality of the cellulose biosynthetic operon. In addition, the results showed the
contribution of the cellulose operon to important aspects of P. syringae pv. syringae biology, such as the formation of biofilms
and adhesion to the leaf surface of mango, suggesting that this operon increases epiphytic fitness. However, based on the
incidence and severity of the symptoms observed in tomato leaflets, cellulose expression reduces virulence, as
cellulose-deficient mutants increased the area of necrosis, whereas the cellulose-overproducing strain decreased the area
of necrosis compared with the wild type. In conclusion, the results of this study show that the epiphytic and pathogenic
stages of the P. syringae pv. syringae UMAF0158 lifestyle are intimately affected by cellulose production.
