In addition, the iron chelator 2, 2′-dipyridyl was able to kill the mioC mutant strain (Fig. 1b). Subsequently, bacterial sensitivities were tested with three different metals: As, Zn and Cu (Fig. 1c). Consistent with the PM assay, the mutant was notably sensitive to As and Zn. Although Cu was not used in the PM assay, we performed the sensitivity test using Cu because it is known to promote cell death. However, the sensitivity of the mutant to Cu was not different from that of the
other two strains. To summarize, we confirmed the results observed with the Biolog PM system using sensitivity tests. The mioC mutant strain displayed significant reductions in biofilm formation during static aerobic growth (Fig. 2a). Therefore, we thought that the mutant might be able to reduce BMN 673 manufacturer cell aggregation of P. aeruginosa under biofilm conditions. Interestingly, aggregation of the mutant cell was reduced during
static Idasanutlin ic50 aerobic growth (Supporting Information, Fig. S1). Under iron excess condition, biofilm formations of the mutant and over-expressed complementation strains were reduced compared with that of the wild type (Fig. 2a and Fig. S2). Thus, the balance of the mioC gene product may be important for maintaining biofilm formation ability under iron excess condition. Interestingly, biofilm formation of the mutant was significantly induced by the iron chelator 2,2′-dipyridyl compared with the other two strains (Fig. 2a and Fig. S2). The growth mutant appeared to be slower under the iron chelator than was the wild type (Fig. 1b), whereas biofilm formation ability was enhanced by
0.5 mM dipyridyl (Fig. 2a and Fig. S2). No biofilm formation occurred in the absence of dipyridyl, but robust biofilm formation occurred in the presence of dipyridyl, which clearly demonstrated that dipyridyl Glycogen branching enzyme treatment increased biofilm formation of the mutant (Fig. S2). In addition, biofilm formation was increased in the mioC mutant cell under Zn and As stresses (Fig. 2b). Consistent with sensitivity data, biofilm formation under Cu stress was similar to that under normal conditions (Fig. 2b). Subsequently, the colony morphology test was performed using Congo red and Brilliant blue (Fig. 2c–e). Congo red and Brilliant blue, a constituent of the agar used in the experiments, are known to bind the glucose-rich exopolysaccharide pellicle and proteins, respectively (Dietrich et al., 2008). Interestingly, red color formation was not observed in the mioC mutant strain, compared with the wild type under iron-rich conditions (Fig. 2d). Red color was recovered in the mioC over-expressed complementation strain under iron excess (Fig. 2d). However, this pellicle appeared in the mutant but disappeared in the other two strains under iron depletion (Fig. 2e). We also performed motility tests (Fig. S3). Interestingly, the swarming motility of the mioC mutant strain had a branch form.