Comparison of biofilm formation by strains N16961 and N169-dtatABC cultured under aerobic and anaerobic conditions. For each strain (N16961 and n169-dtatABC), under each condition (aerobic and anaerobic), and at each time point, 7 wells were measured for repeat in one test. And the tests were repeated for three times. T-test was used for the comparison of strains N16961 and N169-dtatABC at each time point and under each condition. P values are less than 0.05 in all of the comparisons.