Yuuka Chieda
Kyushu University
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Featured researches published by Yuuka Chieda.
Applied and Environmental Microbiology | 2007
Kazuhiro Iiyama; Yuuka Chieda; Jae Man Lee; Takahiro Kusakabe; Chisa Yasunaga-Aoki; Susumu Shimizu
ABSTRACT To investigate the role of superoxide dismutase (SOD) in virulence against the silkworm, Bombyx mori, mutants of Pseudomonas aeruginosa PAO1 lacking manganese-SOD (PAO1sodM), iron-SOD (PAO1sodB), or both (PAO1sodMB) were generated. The mutants were injected into the hemocoel of B. mori. The virulence decreased in the order PAO1 = PAO1sodM > PAO1sodB > PAO1sodMB. In particular, PAO1sodMB was avirulent at a dose of 105 cells or less. The sod double mutant PAO1sodMB was then complemented with either pSodM or pSodB in trans. In both the complemented strains, the virulence was partially restored. Of the two plasmids, pSodB contributed more to the virulence of P. aeruginosa against B. mori. The results of growth in B. mori hemolymph broth and microscopic analysis suggested that a longer lag phase and superoxide sensitivity correlated with decreased virulence in sod mutants. In conclusion, the SODs are required for full virulence of P. aeruginosa against B. mori and Fe-SOD is more important than Mn-SOD in the infection process.
Journal of Applied Entomology | 2009
I. Egami; Kazuhiro Iiyama; Pingbo Zhang; Yuuka Chieda; N. Ino; K. Hasegawa; Jae Man Lee; Takahiro Kusakabe; Chisa Yasunaga-Aoki; Susumu Shimizu
Twenty bacteria were isolated from four ant lion larvae. The isolates were classified into three groups by biological characteristics. Since Group I, Group II and Group III were isolated from individual larvae Kuo1, Kuo3, 4 and Kuo2, respectively, with exception of one isolate Kuo2‐1, each ant lion tested had its own dominant bacterial flora. Groups I and II were closer to Serratia liquefaciens and Enterobacter cloacae, respectively, whereas Group III could not be identified by the test used. The phylogenetic analysis of GroEL amino acid sequences revealed that Group I, II and III were related to those of Serratia spp., E. cloacae and Salmonella spp. –Escherichia/Shigella spp., respectively. Among these groups, Group I was highly virulent against Bombyx mori and Periplaneta americana, and caused 100% mortality within 24 h. The other two groups (Group II and III) were avirulent to these insect species. The culture filtrate of Group I caused killing activity to B. mori larvae and the insecticidal substance was purified from culture filtrate of Group I bacterium. Since the insecticidal activity highly correlated with proteolytic activity in the chromatographies, Group I bacterium may secret insecticidal proteinase in vitro.
Journal of Eukaryotic Microbiology | 2004
Kazuhiro Iiyama; Yuuka Chieda; Chisa Yasunaga-Aoki; Shoji Hayasaka; Susumu Shimizu
ABSTRACT Ribosomal DNA (rDNA) containing small subunit (SSU) rDNA and both flanking regions in the entomopathogenic microsporidian Nosema bombycis NIS 001 was amplified from genomic DNA with a primer set based on the sequence of an inverse polymerase chain reaction (PCR) ‐derived fragment. In this fragment, SSU rDNA was divided by a 618‐bp insert at nt 599, and 5S rDNA was located downstream of the SSU rDNA, fragmented by 284‐bp intergenic spacer. In addition, the 48‐bp 3′‐end of large subunit (LSU) rDNA was located 118 bp upstream of the fragmented SSU rDNA. In the amplicon, the region upstream of the LSU rDNA was a homologue of the C‐terminal CHARLIES transposon‐like element of human GTF2IRD2. In this organism, another fragmented SSU rDNA, which was divided by a 231‐bp insert at nt 50, was also detected. Both the intact (insertless) and fragmented SSU rDNAs clustered with LSU rDNA and 5S rDNA and the intergenic sequences between SSU rDNA and 5S rDNA were divergent in an organism. Reverse transcription (RT)‐PCR assay indicated that not only the intact SSU rDNA but also the fragmened SSU rDNA were transcribed in N. bombycis.
Microbial Pathogenesis | 2011
Yuuka Chieda; Kazuhiro Iiyama; Jae Man Lee; Takahiro Kusakabe; Chisa Yasunaga-Aoki; Susumu Shimizu
We studied the contribution of exotoxin A to the virulence of Pseudomonas aeruginosa against the silkworm, Bombyx mori. First, an exotoxin A-deficient mutant strain (PAO1toxA) was created, and its virulence compared with that of the parental PAO1 strain. In a short-term mortality assay, the mutant harboring pBBR1MCS2 did not kill B. mori until 120 h after inoculation and complementation of the corresponding gene in trans restored the strains virulence. Next, to ascertain whether or not it lost all virulence, PAO1toxA (pBBR1MCS2, pGFP) was used in a long-term mortality assay. B. mori inoculated with the mutant strain did not die until early in the 5th instar (240 h after inoculation). However, 50% of the inoculated B. mori died late in the 5th instar or in the early pupal stage (408 h after inoculation). All had died by the pupal stage (600 h after inoculation). The mutant strain was isolated from dead larvae and cocoons. The bacterial population of PAO1toxA in hemolymph reached 4.77 × 10(7) cfu/ml. These results indicated that exotoxin A acts as a virulence factor in B. mori and that other virulence factor(s) are involved during the late stages of infection.
Plasmid | 2016
Eigo Takahashi; Jae Man Lee; Hiroaki Mon; Yuuka Chieda; Chisa Yasunaga-Aoki; Takahiro Kusakabe; Kazuhiro Iiyama
Pseudomonas aeruginosa PAO1 organisms harbouring different plasmids were cultured in broths containing appropriate antibiotic(s). Extracellular proteins were more abundant in the presence of tetracycline or kanamycin than in the presence of other antibiotics. Zymography revealed that alkaline protease (AprA) production was interfered by these antibiotics. Extracellular proteins were not observed at the same level when AprA-deficient EG03 strains were cultured in the presence of different antibiotics. The extracellular protein levels were dependent on the antibiotics and plasmid derivative groups. Levels of extracellular protein were not significantly different between PAO1 (pBBR1MCS-5) and EG03 (pAprcomp-MCS5), and profiles of the extracellular proteome were comparable. In contrast, the level of EG03 (pBBR1MCS-MCS5) extracellular protein was higher than those observed in the other two strains. These results suggested that although AprA partially contributes to the alteration of extracellular protein level, the effect is limited.
Fems Microbiology Letters | 2005
Yuuka Chieda; Kazuhiro Iiyama; Chisa Yasunaga-Aoki; Jae Man Lee; Takahiro Kusakabe; Susumu Shimizu
Fems Microbiology Letters | 2008
Yuuka Chieda; Kazuhiro Iiyama; Jae Man Lee; Takahiro Kusakabe; Chisa Yasunaga-Aoki; Susumu Shimizu
Journal of insect biotechnology and sericology | 2012
Fusako Kaibara; Kazuhiro Iiyama; Yuuka Chieda; Jae Man Lee; Takahiro Kusakabe; Chisa Yasunaga-Aoki; Susumu Shimizu
Journal of insect biotechnology and sericology | 2013
Kazuhiro Iiyama; Kazuki Mori; Hiroaki Mon; Yuuka Chieda; Jae Man Lee; Takahiro Kusakabe; Kousuke Tashiro; Shin Ichiro Asano; Chisa Yasunaga-Aoki; Susumu Shimizu
Journal of insect biotechnology and sericology | 2007
Yuuka Chieda; Kazuhiro Iiyama; Jae Man Lee; Takahiro Kusakabe; Chisa Yasunaga-Aoki; Susumu Shimizu