4b). Therefore, the mioC mutant cells may strongly inhibit iron acquisition with mutant CFS. We speculated that some chemicals of the wild-type CFS may have stimulated production of pellicle and that mutant CFS may have inhibited production of pellicle and iron utilization in P. aeruginosa. Subsequently, we performed biofilm assay using CFS of the wild-type and mutant cells (Fig. 4c). BTK inhibitor Interestingly, biofilm formation of the mioC mutant cells was induced by 10% wild-type CFS, a result that coincided with data of colony morphology (Fig. 4a and c). Therefore, the wild-type CFS may contain chemicals that
can stimulate production of pellicle EPS and biofilm formation. The swarming motility test was conducted with CFS. Interestingly, the swarming motility using the mioC mutant CFS had a branch form in the wild-type and mioC over-expressed cells (Fig. S4). However, the swarming motility using the wild-type CFS was not changed (data not shown). Therefore, the wild-type and mioC over-expressed cells may have sensed the strong iron depletion and interfered with the iron utilization by mutant CFS. Fld has been found in prokaryotes of all major taxa (Zurbriggen et al., 2007). Fld is typically induced as an adaptive resource under environmental or nutritional hardships such as iron limitation (Zurbriggen et al., 2007). Interestingly,
CHIR-99021 ic50 Fld expression confers tolerance to iron deficit and abiotic stress when introduced in plants (Zurbriggen et al., 2007). Suplatast tosilate Therefore, Fld may be important to the resistance of various stresses in bacteria. We performed PM analysis to investigate the Fld function and our result suggested that the mioC gene mutation changed the physiology
of P. aeruginosa in response to oxidative, metal and antibiotic stresses. Interestingly, the mioC mutant was significantly sensitive to norfloxacin and colistin, whereas the mutant was resistant to ampicillin, polymyxin B and gentamicin. Norfloxacin is a fluoroquinolone antibiotic and functions by inhibiting DNA gyrase (Leigh & Emmanuel, 1984). The mioC gene of P. aeruginosa was induced 1.5-fold under norfloxacin (GDS2317, GEO database), which suggested that the mioC gene might be important for defense against norfloxacin. Each antibiotic has a different mode of action. It remains unclear why different antibiotics work differently to the mutant sensitivity. Because the function of MioC has been characterized for first time, we believed that our global phenotypic analysis will be useful resource to the scientific field. Our data demonstrated that Fld may be linked to biofilm, aggregation and motility under various stresses. It has been reported that flavodoxin gene was induced under biofilm condition of P. aeruginosa (Anderson et al., 2008). The flavodoxin A gene was also induced 5.3-fold in the biofilms of E. coli (Hancock & Klemm, 2007).