Table 1.
Antimicrobial susceptibilities of S. maltophilia KJ and its derived deletion mutants.
Figure 1.
Growth of KJ, KJΔJ, KJΔK, and KJΔIJK in Luria-Bertani (LB) and Mueller-Hinton (MH) media.
(A) Growth curves of KJ, KJΔJ, KJΔK, and KJΔIJK in LB and MH broth. (B) The growth curve of 24-h MH-cultured KJ and KJΔIJK cells subcultured into the MH or LB media.
Figure 2.
The role of SmeIJK pump in the tolerance to hypo-osomolarity and casein hydrolysate.
The data are the average of the measurements made in triplicate. (A) The relative survival of KJΔIJK, KJΔJ, and KJΔK to the wild-type KJ in the LB medium containing different concentrations of NaCl. The relative survival percentage of individual mutant to the wild-type KJ, at each cultured condition, was calculated using the OD450 nm of the wild-type KJ as 100%. (B) The relative survival of KJΔIJK, KJΔJ, and KJΔK to the wild-type KJ in the MH medium containing different concentrations of NaCl. The relative survival percentage of individual mutant to the wild-type KJ, at each cultured condition, was calculated using the OD450 nm of the wild-type KJ as 100%. (C) The sensitivities of KJ to SDS in LB or LB containing casein hydrolysate, beef infusion, or starch were determined by the OD450 nm measurement. The percentage of survival was defined as the OD450 nm ratio of the SDS-additive group to the SDS-free counterpart. (D) Growth curves of KJΔIJK grown in the media of the LB, the LB without NaCl, the LB with casein hydrolysate, and the MH, respectively.
Figure 3.
Assessment of the cell envelope integrity of S. maltophilia KJ and its derived mutants in different cultured conditions.
(A) Sodium dodecyl sulfate (SDS) survival analysis. The survival of KJ, KJΔIJK, KJΔJ, and KJΔK in LB or MH broth without or with 0.02% SDS was determined by the A450 nm measurement. The percentage of survival was defined as the A450 nm ratio of the SDS-additive group to the SDS-free counterpart. (B) Polymyxin E susceptibility. The polymyxin E susceptibility of KJ, KJΔIJK, KJΔJ, and KJΔK in LB or MH broth was determined by the disc diffusion assay.
Figure 4.
Determination of PrpoE activities in different strains and culture conditions.
Plasmid containing a transcriptional fusion of the upstream region of rpoE to the xylE gene (pRpoExylE) was transferred into the wild-type KJ and its derived mutants. The C23O activities of the logarithmic-phase cultures of these strains were determined. Each bar represents the mean of three independent experiments. Error bars, where visible, indicate the average deviation. *, p≤0.01 significance calculated by a Student's t-test. (A) The impacts of resA mutant and rseA/rpoE double mutant on the promoter activity of rpoE gene. (B) The impacts of smeIJK mutant and culture media on the promoter activity of rpoE gene.
Figure 5.
The expression of smeIJK operon in different stresses and culture media.
Plasmid containing a transcriptional fusion of the upstream region of smeI to the xylE gene (pSmeIxylE) was transferred into the wild-type KJ. The C23O activities of the logarithmic-phase cultures of KJ(pSmeIxylE) were determined. Each bar represents the mean of three independent experiments. Each bar represents the mean of three independent experiments. *, p≤0.01 significance calculated by a Student's t-test. (A) The expression of smeIJK operon in different stresses. The concentrations of the stressors added were: Triton X-100, 100 µg/ml; benzalkonium chloride (BC), 10 µg/ml; cetyltributylammonium bromide (CTAB), 10 µg/ml; gentamicin (Gm), 1 µg/ml; amikacin (Ami), 1 µg/ml; and leucomycin (Leu), 0.5 µg/ml. (B) The expression of smeIJK operon in different culture media, including the LB, the LB without NaCl, the LB with casein hydrolysate, and the MH.
Figure 6.
Determination of PsmeI activities in different strains.
Plasmid containing a transcriptional fusion of the upstream region of smeI to the xylE gene (pSmeIxylE) was transferred into the wild-type KJ and its derived mutants. The C23O activities of the logarithmic-phase cultures of these strains were determined. Each bar represents the mean of three independent experiments. Error bars, where visible, indicate the average deviation. *, p≤0.01 significance calculated by a Student's t-test. (A) The impacts of resA mutant and rseA/rpoE double mutant on the promoter activity of smeIJK operon. (B) The impacts of MDAs treatment on the promoter activity of smeIJK operon in the wild-type and rpoE mutant.
Figure 7.
The involvement of smeIJK and membrane damaging agents (MDAs) in the σE-mediated envelope stress response (ESR) of S. maltophilia.
(A) Deletion of smeIJK compromises the cell envelope integrity and activates the rpoE to alleviate the envelope stress. (B) The treatment of MDAs on the wild-type cells activates rpoE system and upregualtes smeIJK expression. SmeIJK operon is a member of rpoE regulon.