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- Differential expression of the major catalase, KatA in the two wild type Pseudomonas aeruginosa strains, PAO1 and PA14
- Bi-o Kim , In-Young Chung , You-Hee Cho
- J. Microbiol. 2019;57(8):704-710. Published online June 11, 2019
- DOI: https://doi.org/10.1007/s12275-019-9225-1
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- 9 Citations
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Abstract
- KatA is the major catalase required for hydrogen peroxide (H2O2) resistance and acute virulence in Pseudomonas aeruginosa PA14, whose transcription is governed by its dual promoters (katAp1 and katAp2). Here, we observed that KatA was not required for acute virulence in another wild type P. aeruginosa strain, PAO1, but that PAO1 exhibited higher KatA expression than PA14 did. This was in a good agreement with the observation that PAO1 was more resistant than PA14 to H2O2 as well as to the antibiotic peptide, polymyxin B (PMB), supposed to involve reactive oxygen species (ROS) for its antibacterial activity. The higher KatA expression in PAO1 than in PA14 was attributed to both katAp1 and katAp2 transcripts, as assessed by S1 nuclease mapping. In addition, it was confirmed that the PMB resistance is attributed to both katAp1 and katAp2 in a complementary manner in PA14 and PAO1, by exploiting the promoter mutants for each -10 box (p1m, p2m, and p1p2m). These results provide an evidence that the two widely used P. aeruginosa strains display different virulence mechanisms associated with OxyR and Anr, which need to be further characterized for better understanding of the critical virulence pathways that may differ in various P. aeruginosa strains.
- Expansion of antibacterial spectrum of xanthorrhizol against Gram-negatives in combination with PMBN and food-grade antimicrobials
- Man Su Kim , Ha-Rim Kim , Haebom Kim , Soo-Keun Choi , Chang-Hwan Kim , Jae-Kwan Hwang , Seung-Hwan Park
- J. Microbiol. 2019;57(5):405-412. Published online February 22, 2019
- DOI: https://doi.org/10.1007/s12275-019-8511-2
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- 8 Citations
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Abstract
- Xanthorrhizol (XTZ), isolated from Curcuma xanthorrhiza, has potent antifungal and antibacterial activity. It shows very strong activity against Gram-positive bacteria, such as Streptococcus mutans and Staphylococcus aureus, but is generally not active against Gram-negative bacteria. In this study, we explored the possibility of using a combination strategy for expanding the antimicrobial spectrum of XTZ against Gram-negative bacteria. To take advantage of XTZ being a food-grade material, 10 food-grade or generally recognized as safe (GRAS) antimicrobial compounds with low toxicities were selected for combination therapy. In addition, polymyxin B nonapeptide (PMBN), which is less toxic than polymyxin B, was also selected as an outer membrane permeabilizer. The antibacterial activity of various double or triple combinations with or without XTZ were assayed in vitro against four Gram-negative bacterial species (Escherichia coli, Salmonella enterica serovar Typhi, Salmonella enterica serovar Typhimurium, and Vibrio cholerae), with synergistic combinations exhibiting clear activity subjected to further screening. The combinations with the greatest synergism were XTZ + PMBN + nisin, XTZ + PMBN + carvacrol, and XTZ + PMBN + thymol. These combinations also showed potent antimicrobial activity against Shigella spp., Yersinia enterocolitica, and Acinetobacter baumannii. In time-kill assays, the three combinations achieved complete killing of E. coli within 2 h, and S. Typhi and V. cholera within 15 min. This is the first report on expanding the activity spectrum of XTZ against Gram-negative bacteria through combination with PMBN and food-grade or GRAS substances, with the resulting findings being particularly useful for increasing the industrial and medical applications of XTZ.
Research Support, Non-U.S. Gov't
- Inactivation of MuxABC-OpmB Transporter System in Pseudomonas aeruginosa Leads to Increased Ampicillin and Carbenicillin Resistance and Decreased Virulence
- Liang Yang , Lin Chen , Lixin Shen , Michael Surette , Kangmin Duan
- J. Microbiol. 2011;49(1):107-114. Published online March 3, 2011
- DOI: https://doi.org/10.1007/s12275-011-0186-2
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- 34 Citations
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Abstract
- Resistance-Nodulation-Cell Division (RND) pumps play important roles in bacterial resistance to antibiotics. Pseudomonas aeruginosa is an important human pathogen which exhibits high level resistance to antibiotics. There are total of 12 RND pumps present in the P. aeruginosa PAO1 genome. The recently characterized MuxABC-OpmB system has been shown to play a role in resistance to novobiocin, aztreonam, macrolides, and tetracycline in a multiple knockout mutation. In this study, we examined the expression levels of all the 12 RND pump gene clusters and tested the involvement of MuxABC-OpmB in pathogenicity. The results indicated that in addition to the four known constitutively expressed RND pumps, mexAB-oprM, mexGHIopmD, mexVW, and mexXY, relatively high levels of expression were observed with mexJK and muxABCopmB in the conditions tested. Inactivation of muxA in the muxABC-opmB operon resulted in elevated resistance to ampicillin and carbenicillin. The mutant also showed attenuated virulence in both Brassica rapa pekinensis and Drosophila melanogaster infection models. The decreased virulence at least in part was due to decreased twitching motility in the mutant. These results indicate that the RND pump MuxABC-OpmB is associated with ampicillin and carbenicillin susceptibility and also involved in pathogenesis in P. aeruginosa.
- Construction of Multiple Mutant Strains by Mating Procedures for the Cloning of pmn and pmb Genes Encoding Amino Acid Permeases in Neurospora crassa
- Han, Hyo Young , Min, Kyung Hee
- J. Microbiol. 1995;33(2):142-145.
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Abstract
- The pmb gene encoding a basic amino acid transport protein in Neurospora crassa could be cloned by using a mutant strain defective in pmb gene as a host strain, using a negative selection on the media containing amino acid analogue canavanine. To select positive transformants of the genes for cloning, an auxotrophic marker (his-2) was added to a pmb mutant strain by mating ; a triple mutant (pmn : pmb : his-2) was constructued by crossing a strain defective in basic amino acid transport system (# 1683-bat um 535 "A") to a double mutant strain defective in neutral amino acid transport and histidine production (mitr6r : his-2 "a"). Crossing was performed on synthetic crossing (SC) media containing histidine. The pmn : pmb and pmn :pmb : his-2 strains were selected among the progeny colonies from crosses on plates containing 50㎍/㎖ para-fluoro-phenylalanine (PFPA), 200㎍/㎖ canavanine, and 500㎍/㎖ histidine. The selected colonies were cultured on minimal media with or without histidine for discarding pmn : pmb strain, because the pmn : pmb : his -2 strain grows only on histidine containing media. The pmn :pmb : his-2 strain selected can be used as a host strain for the cloning of the pmb and the pmn genes from a Neurospora genomic library by means of positive selections.
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