Secreted indole serves as a signal for expression of type III secretion system translocators in enterohaemorrhagic Escherichia coli O157 : H7

Hirakawa, Hidetada; Kodama, Takao; Takumi-Kobayashi, Asuka; Honda, Takeshi; Yamaguchi, Akihito

doi:10.1099/mic.0.020420-0

Cited by 90 publications

(75 citation statements)

References 34 publications

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“…The downstream flanking DNA included the last four amino acid codons for uhpT, the last three amino acid codons for fnr, the last two amino acid codons for arcA, the stop codon, and 450 bp of additional DNA. These deletion constructs were ligated into the BamHI-and SalI-digested temperature-sensitive vector pKO3 (26) and introduced into HH-H7-008, the parent strain (23). We selected sucrose-resistant, chloramphenicol-sensitive colonies at 30°C and confirmed the resulting mutant strains by PCR analysis and DNA sequencing.…”

Section: Methodsmentioning

confidence: 99%

Elevated Expression of GlpT and UhpT via FNR Activation Contributes to Increased Fosfomycin Susceptibility in Escherichia coli under Anaerobic Conditions

Kurabayashi

Tanimoto

Fueki

et al. 2015

Antimicrob Agents Chemother

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Because a shortage of new antimicrobial agents is a critical issue at present, and with the spread of multidrug-resistant (MDR) pathogens, the use of fosfomycin to treat infections is being revisited as a "last-resort option." This drug offers a particular benefit in that it is more effective against bacteria growing under oxygen-limited conditions, unlike other commonly used antimicrobials, such as fluoroquinolones and aminoglycosides. In this study, we showed that Escherichia coli strains, including enterohemorrhagic E. coli (EHEC), were more susceptible to fosfomycin when grown anaerobically than when grown aerobically, and we investigated how the activity of this drug was enhanced during anaerobic growth of E. coli. Our quantitative PCR analysis and a transport assay showed that E. coli cells grown under anaerobic conditions had higher levels of expression of glpT and uhpT, encoding proteins that transport fosfomycin into cells with their native substrates, i.e., glycerol-3-phosphate and glucose-6-phosphate, and led to increased intracellular accumulation of the drug. Elevation of expression of these genes during anaerobic growth requires FNR, a global transcriptional regulator that is activated under anaerobic conditions. Purified FNR bound to DNA fragments from regions upstream of glpT and uhpT, suggesting that it is an activator of expression of glpT and uhpT during anaerobic growth. We concluded that the increased antibacterial activity of fosfomycin toward E. coli under anaerobic conditions can be attributed to elevated expression of GlpT and UhpT following activation of FNR, leading to increased uptake of the drug.

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Section: Methodsmentioning

confidence: 99%

Elevated Expression of GlpT and UhpT via FNR Activation Contributes to Increased Fosfomycin Susceptibility in Escherichia coli under Anaerobic Conditions

Kurabayashi

Tanimoto

Fueki

et al. 2015

Antimicrob Agents Chemother

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“…In enterohaemorrhagic E. coli (EHEC), a tnaA mutant had decreased EspA and EspB (type III secreted proteins) secretion and reduced its ability to form attaching and effacing (A/E) lesions in HeLa cells. However, those abilities were restored upon exogenous addition of indole [35]. It was therefore concluded that indole regulated the expression of the espA and espB genes and were involved in the formation of A/E lesions in EHEC.…”

Section: Effect Of Indole On V Cholerae Virulencementioning

confidence: 98%

Role of Indole Production on Virulence of Vibrio cholerae Using Galleria mellonella Larvae Model

et al. 2016

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Cell to cell communication facilitated by chemical signals plays crucial roles in regulating various cellular functions in bacteria. Indole, one such signaling molecule has been demonstrated to control various bacterial phenotypes such as biofilm formation and virulence in diverse bacteria including Vibrio cholerae. The present study explores some key factors involved in indole production and the subsequent pathogenesis of V. cholerae. Indole production was higher at 37°C than at 30°C, although the growth at 37°C was slightly higher. A positive correlation was observed between indole production and biofilm formation in V. cholerae. Maximum indole production was detected at pH 7. There was no significant difference in indole production between clinical and environmental V. cholerae isolates, although indole production in one environmental isolate was significantly different. Both growth and indole production showed relevant changes with differences in salinity. An indole negative mutant strain was constructed using transposon mutagenesis and the direct effect of indole on the virulence of V. cholerae was evaluated using Galleria mellonella larvae model. Comparison to the wild type strain, the mutant significantly reduced the mortality of G. mellonella larvae which regained its virulence after complementation with exogenous indole. A gene involved in indole production and the virulence of V. cholerae was identified.

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“…Indole also acts as an intracellular and extracellular signal for virulence, biofilm formation, acid resistance, drug resistance, and sporulation in bacteria (74)(75)(76)(77)(78)(79). Phenol, on the other hand, is toxic in its free form but is found as a functional group in many secondary metabolites of plants (80).…”

Section: Discussionmentioning

confidence: 99%

Requirements for In Vitro Germination of Paenibacillus larvae Spores

Alvarado

Phui

Elekonich

et al. 2012

Journal of Bacteriology

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Paenibacillus larvae is the causative agent of American foulbrood (AFB), a disease affecting honey bee larvae. First-and secondinstar larvae become infected when they ingest food contaminated with P. larvae spores. The spores then germinate into vegetative cells that proliferate in the midgut of the honey bee. Although AFB affects honey bees only in the larval stage, P. larvae spores can be distributed throughout the hive. Because spore germination is critical for AFB establishment, we analyzed the requirements for P. larvae spore germination in vitro. We found that P. larvae spores germinated only in response to L-tyrosine plus uric acid under physiologic pH and temperature conditions. This suggests that the simultaneous presence of these signals is necessary for spore germination in vivo. Furthermore, the germination profiles of environmentally derived spores were identical to those of spores from a biochemically typed strain. Because L-tyrosine and uric acid are the only required germinants in vitro, we screened amino acid and purine analogs for their ability to act as antagonists of P. larvae spore germination. Indole and phenol, the side chains of tyrosine and tryptophan, strongly inhibited P. larvae spore germination. Methylation of the N-1 (but not the C-3) position of indole eliminated its ability to inhibit germination. Identification of the activators and inhibitors of P. larvae spore germination provides a basis for developing new tools to control AFB.A merican foulbrood (AFB) is a bacterial disease of honey bees that kills the developing larvae (1, 2). Paenibacillus larvae spores are the infectious agents for AFB, but it is the vegetative cells that cause disease (3, 4). In 2005, a survey of almond-pollinating bee colonies indicated that 4% of colonies had a significant AFB load (5). Once a beekeeping operation is contaminated, the bacterial spores are not easily removed (6). Although autoclaving and high concentrations of chemical disinfectants effectively kill the spores, these treatments are not viable for the beekeeping industry (7). Traditionally, Terramycin and other antibiotics have been used for the treatment and prevention of AFB. However, antibiotic treatment is ineffective in the spore stage of P. larvae, and overuse of the antibiotics leads to resistant strains (8, 9). Presently, the only accepted practice for controlling the spread of AFB is burning both the infected colonies and beekeeping equipment (3, 6).AFB occurs when first-or second-instar larvae (within 48 h after the egg hatches) ingest food that is contaminated with the P. larvae spores (10). Twelve hours after ingestion, P. larvae spores germinate and the new vegetative cells start to proliferate inside the larval gut (11). Several days postinfection, extreme bacteremia causes the death of the honey bee larvae (12-14). After the nutrient levels of the honey bees are depleted, P. larvae cells stop dividing and then sporulate. As a result, billions of spores are found in the dead remains of each bee larva (15, 16). Within the col...

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Secreted indole serves as a signal for expression of type III secretion system translocators in enterohaemorrhagic Escherichia coli O157 : H7

Cited by 90 publications

References 34 publications

Elevated Expression of GlpT and UhpT via FNR Activation Contributes to Increased Fosfomycin Susceptibility in Escherichia coli under Anaerobic Conditions

Elevated Expression of GlpT and UhpT via FNR Activation Contributes to Increased Fosfomycin Susceptibility in Escherichia coli under Anaerobic Conditions

Role of Indole Production on Virulence of Vibrio cholerae Using Galleria mellonella Larvae Model

Requirements for In Vitro Germination of Paenibacillus larvae Spores

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