Journal Articles
- Regulator of ribonuclease activity modulates the pathogenicity of Vibrio vulnificus
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Jaejin Lee , Eunkyoung Shin , Jaeyeong Park , Minho Lee , Kangseok Lee
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J. Microbiol. 2021;59(12):1133-1141. Published online November 9, 2021
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DOI: https://doi.org/10.1007/s12275-021-1518-5
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Abstract
- RraA, a protein regulator of RNase E activity, plays a unique
role in modulating the mRNA abundance in Escherichia coli.
The marine pathogenic bacterium Vibrio vulnificus also possesses
homologs of RNase E (VvRNase E) and RraA (VvRraA1
and VvRraA2). However, their physiological roles have not
yet been investigated. In this study, we demonstrated that
VvRraA1 expression levels affect the pathogenicity of V. vulnificus.
Compared to the wild-type strain, the VvrraA1-deleted
strain (ΔVvrraA1) showed decreased motility, invasiveness,
biofilm formation ability as well as virulence in mice; these
phenotypic changes of ΔVvrraA1 were restored by the exogenous
expression of VvrraA1. Transcriptomic analysis indicated
that VvRraA1 expression levels affect the abundance
of a large number of mRNA species. Among them, the halflives
of mRNA species encoding virulence factors (e.g., smcR
and htpG) that have been previously shown to affect VvrraA1
expression-dependent phenotypes were positively correlated
with VvrraA1 expression levels. These findings suggest that
VvRraA1 modulates the pathogenicity of V. vulnificus by regulating
the abundance of a subset of mRNA species.
- Characterization of a novel dsRNA mycovirus of Trichoderma atroviride NFCF377 reveals a member of “Fusagraviridae” with changes in antifungal activity of the host fungus
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Jeesun Chun , Byeonghak Na , Dae-Hyuk Kim
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J. Microbiol. 2020;58(12):1046-1053. Published online October 23, 2020
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DOI: https://doi.org/10.1007/s12275-020-0380-1
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Abstract
- Trichoderma atroviride is a common fungus found in various
ecosystems that shows mycoparasitic ability on other fungi.
A novel dsRNA virus was isolated from T. atroviride NFCF377
strain and its molecular features were analyzed. The viral
genome consists of a single segmented double-stranded RNA
and is 9,584 bp in length, with two discontinuous open reading
frames (ORF1 and ORF2). A mycoviral structural protein
and an RNA-dependent RNA polymerase (RdRp) are encoded
by ORF1 and ORF2, respectively, between which is found a
canonical shifty heptameric signal motif (AAAAAAC) followed
by an RNA pseudoknot. Analysis of sequence similarity
and phylogeny showed that it is closely related to members
of the proposed family “Fusagraviridae”, with a highest similarity
to the Trichoderma atroviride mycovirus 1 (TaMV1).
Although the sequence similarity of deduced amino acid to
TaMV1 was evident, sequence deviations were distinctive at
untranslated regions (UTRs) due to the extended size. Thus,
we inferred this dsRNA to be a different strain of Trichoderma
atroviride mycovirus 1 (TaMV1-NFCF377). Electron
microscopy image exhibited an icosahedral viral particle of
40 nm diameter. Virus-cured isogenic isolates were generated
and no differences in growth rate, colony morphology, or
conidia production were observed between virus-infected and
virus-cured strains. However, culture filtrates of TaMV1-
NFCF377-infected strain showed enhanced antifungal activity
against the plant pathogen Rhizoctonia solani but not to
edible mushroom Pleurotus ostreatus. These results suggested
that TaMV1-NFCF377 affected the metabolism of the fungal
host to potentiate antifungal compounds against a plant pathogen,
but this enhanced antifungal activity appeared to be
species-specific.
- Two novel synthetic peptides inhibit quorum sensing-dependent biofilm formation and some virulence factors in Pseudomonas aeruginosa PAO1
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Mostafa N. Taha , Amal E. Saafan , A. Ahmedy , Eman El Gebaly , Ahmed S. Khairalla
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J. Microbiol. 2019;57(7):618-625. Published online June 27, 2019
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DOI: https://doi.org/10.1007/s12275-019-8548-2
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Abstract
- Quorum sensing (QS) regulates virulence factor expression
in Pseudomonas aeruginosa. Inhibiting the QS-controlled virulence
factors without inhibiting the growth of P. aeruginosa
is a promising approach for overcoming the widespread
resistance of P. aeruginosa. This study was proposed to investigate
the effects of two novel synthetic peptides on the biofilm
development and virulence factor production of P. aeruginosa.
The tested strain was P. aeruginosa PAO1. The results
indicated that both of the synthetic peptides (LIVRHK and
LIVRRK) inhibited (P < 0.05) the formation of biofilms and
the production of virulence factors, including pyocyanin, protease,
and rhamnolipids, without inhibiting the growth of
PAO1. Additionally, we detected transcriptional changes related
to QS and found a significant reduction in the levels of
gene expression of lasI, lasR, rhlI, and rhlR. This study demonstrates
that LIVRRK and LIVRHK are novel synthetic peptides
that can act as potent inhibitors of QS-regulated virulence
factors in P. aeruginosa. Moreover, these synthetic peptides
have potential applications in the treatment of biofilmrelated
diseases. Both peptides may be able to control chronic
infections and biofilm-associated problems of P. aeruginosa.
- The antimicrobial potential of a new derivative of cathelicidin from Bungarus fasciatus against methicillin-resistant Staphylococcus aureus
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Mercedeh Tajbakhsh , Abdollah Karimi , Abolghasem Tohidpour , Naser Abbasi , Fatemeh Fallah , Maziar Mohammad Akhavan
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J. Microbiol. 2018;56(2):128-137. Published online February 2, 2018
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DOI: https://doi.org/10.1007/s12275-018-7444-5
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Abstract
- Cathelicidins are a family of antimicrobial peptides which exhibit
broad antimicrobial activities against antibiotic-resistant
bacteria. Considering the progressive antibiotic resistance,
cathelicidin is a candidate for use as an alternative approach
to treat and overcome the challenge of antimicrobial resistance.
Cathelicidin-BF (Cath-BF) is a short antimicrobial peptide,
which was originally extracted from the venom of Bungarus
fasciatus. Recent studies have reported that Cath-BF and some
related derivatives exert strong antimicrobial and weak hemolytic
properties. This study investigates the bactericidal
and cytotoxic effects of Cath-BF and its analogs (Cath-A and
Cath-B). Cath-A and Cath-B were designed to increase their
net positive charge, to have more activity against methicillin
resistant S. aureus (MRSA). The results of this study show
that Cath-A, with a +17-net charge, has the most noteworthy
antimicrobial activity against MRSA strains, with minimum
inhibitory concentration (MIC) ranging between 32–128
μg/ml. The bacterial kinetic analysis by 1 × MIC concentration
of each peptide shows that Cath-A neutralizes the clinical
MRSA isolate for 60 min. The present data support the
notion that increasing the positive net charge of antimicrobial
peptides can increase their potential antimicrobial activity.
Cath-A also displayed the weakest cytotoxicity effect
against human umbilical vein endothelial and H9c2 rat cardiomyoblast
cell lines. Analysis of the hemolytic activity reveals
that all three peptides exhibit minor hemolytic activity
against human erythrocytes at concentrations up to 250 μg/ml.
Altogether, these results suggest that Cath-A and Cath-B are
competent candidates as novel antimicrobial compounds
against MRSA and possibly other multidrug resistant bacteria.
Review
- MINIREVIEW] Nontraditional Therapies to Treat Helicobacter pylori Infection
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Morris O. Makobongo , Jeremy J. Gilbreath , D. Scott Merrell
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J. Microbiol. 2014;52(4):259-272. Published online March 29, 2014
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DOI: https://doi.org/10.1007/s12275-014-3603-5
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Abstract
- The Gram-negative pathogen Helicobacter pylori is increasingly more resistant to the three major antibiotics (metronidazole, clarithromycin and amoxicillin) that are most commonly used to treat infection. As a result, there is an increased rate of treatment failure; this translates into an overall higher cost of treatment due to the need for increased length of treatment and/or the requirement for combination or sequential
therapy. Given the rise in antibiotic resistance, the complicated treatment regime, and issues related to patient compliance that stem from the duration and complexity of treatment, there is clearly a pressing need for the development of novel therapeutic strategies to combat H. pylori infection. As such, researchers are actively investigating the utility of antimicrobial peptides, small molecule inhibitors and naturopathic therapies. Herein we review and discuss each of these novel approaches as a means to target this important gastric pathogen.
Journal Article
- Cyclic Lipopeptide Profile of Three Bacillus subtilis Strains; Antagonists of Fusarium Head Blight
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Christopher A. Dunlap , David A. Schisler , Neil P. Price , Steven F. Vaughn
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J. Microbiol. 2011;49(4):603-609. Published online September 2, 2011
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DOI: https://doi.org/10.1007/s12275-011-1044-y
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Abstract
- The objective of the study was to identify the lipopetides associated with three Bacillus subtilis strains.
The strains are antagonists of Gibberella zeae, and have been shown to be effective in reducing Fusarium
head blight in wheat. The lipopeptide profile of three B. subtilis strains (AS43.3, AS43.4, and OH131.1)
was determined using mass spectroscopy. Strains AS43.3 and AS43.4 produced the anti-fungal lipopeptides
from the iturin and fengycin family during the stationary growth phase. All three strains produced the
lipopeptide surfactin at different growth times. Strain OH131.1 only produced surfactin under these conditions.
The antifungal activity of the culture supernatant and individual lipopeptides was determined by the inhibition
of G. zeae. Cell-free supernatant from strains AS43.3 and AS43.4 demonstrated strong antibiosis of G. zeae,
while strain OH131.1 had no antibiosis activity. These results suggest a different mechanism of antagonism
for strain OH131.1, relative to AS43.3 and AS43.4.
Research Support, Non-U.S. Gov't
- Evaluation of Antagonistic Activities of Bacillus subtilis and Bacillus licheniformis Against Wood-Staining Fungi: In Vitro and In Vivo Experiments
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Natarajan Velmurugan , Mi Sook Choi , Sang-Sub Han , Yang-Soo Lee
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J. Microbiol. 2009;47(4):385-392. Published online September 9, 2009
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DOI: https://doi.org/10.1007/s12275-009-0018-9
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Abstract
- The antifungal activity of bacterial strains Bacillus subtilis EF 617317 and B. licheniformis EF 617325 was demonstrated against sapstaining fungal cultures Ophiostoma flexuosum, O. tetropii, O. polonicum, and O. ips in both in vitro and in vivo conditions. The crude active supernatant fractions of 7 days old B. subtilis and B. licheniformis cultures inhibited the growth of sapstaining fungi in laboratory experiments. Thermostability and pH stability of crude supernatants were determined by series of experiments. FT-IR analysis was performed to confirm the surface structural groups of lipoproteins present in the crude active supernatant. Partial purification of lipopeptides present in the crude supernatant was done by using Cellulose anion exchange chromatography and followed by Sephadex gel filtration chromatography. Partially purified compounds significantly inhibited the sapstaining fungal growth by in vitro analysis. The lipopeptides responsible for antifungal activity were identified by electrospray ionization mass spectrometry after partial purification by ion exchange and gel filtration chromatography. Four major ion peaks were identified as m/z 1023, 1038, 1060, and 1081 in B. licheniformis and 3 major ion peaks were identified as m/z 1036, 1058, and 1090 in B. subtilis. In conclusion, the partially purified lipopeptides may belong to surfactin and iturin family. In vivo analysis for antifungal activity of lipopeptides on wood was conducted in laboratory. In addition, the potential of extracts for fungal inhibition on surface and internal part of wood samples were analyzed by scanning electron microscopy.