scholarly journals Repression of the Antifungal Activity of Pseudomonas sp. Strain DF41 by the Stringent Response

2011 ◽  
Vol 77 (16) ◽  
pp. 5635-5642 ◽  
Author(s):  
Jerrylynn Manuel ◽  
Chrystal Berry ◽  
Carrie Selin ◽  
W. G. Dilantha Fernando ◽  
Teresa R. de Kievit
Keyword(s):  
Antifungal Activity ◽  
Fungal Pathogen ◽  
Protease Activity ◽  
Biological Control Agent ◽  
Stringent Response ◽  
Control Agent ◽  
Wild Type ◽  
Content Type ◽  
Guanosine Tetraphosphate ◽  
Maximum Expression

ABSTRACTThe stringent response (SR) enables bacteria to adapt to nutrient limitation through production of the nucleotides guanosine tetraphosphate and guanosine pentaphosphate, collectively known as (p)ppGpp. Two enzymes are responsible for the intracellular pools of (p)ppGpp: RelA acts as a synthetase, while SpoT can function as either a synthetase or a hydrolase. We investigated how the SR affects the ability of the biological control agentPseudomonassp. strain DF41 to inhibit the fungal pathogenSclerotinia sclerotiorum(Lib.) de Bary. Strain DF41relAandrelA spoTmutants were generated and found to exhibit increased antifungal activity. Strain DF41 produces a lipopeptide (LP) molecule that is essential forSclerotiniabiocontrol. LP production and protease activity were both elevated in therelAandrelA spoTmutants. Addition ofrelAbut notspoTintransrestored the mutant phenotype to that of the parent. Next, we investigated whether an association exists between the SR and known regulators of biocontrol, including the Gac system and RpoS. AgacSmutant of strain DF41 produced less (p)ppGpp and exhibited a 1.7-fold decrease inrelAexpression compared to the wild type, suggesting thatrelAforms part of the Gac regulon. We discovered thatrpoStranscription was reduced significantly in the SR mutants. Furthermore,rpoSprovided intransrestored protease activity to wild-type levels but did not attenuate antifungal activity. Finally,relAexpression was decreased in the mutants, indicating that the SR is required for maximum expression ofrelA.

scholarly journals Behavior of a Wild-Type and Two Mutant Strains of Colletotrichum gloeosporioides f. sp. aeschynomene on Northern Jointvetch in the Field

Plant Disease ◽  
1998 ◽  
Vol 82 (4) ◽  
pp. 374-379 ◽  
Author(s):  
Y. Luo ◽  
D. O. TeBeest
Keyword(s):  
Population Density ◽  
Wild Type Strain ◽  
Colletotrichum Gloeosporioides ◽  
Biological Control Agent ◽  
Field Tests ◽  
The United States ◽  
Control Agent ◽  
Sampling Time ◽  
Wild Type ◽  
Mutant Strains

The fungus Colletotrichum gloeosporioides f. sp. aeschynomene causes an anthracnose on Aeschynomene virginica and has been used as a biological control agent to control this weed in the United States. The population dynamics of a wild-type strain (3-1-3) and two mutant strains of 3-1-3 of C. gloeosporioides f. sp. aeschynomene, a benomyl-resistant strain (B21) and nitrate-nonutilizing strain (Nit A), were studied in field tests on northern jointvetch in 1994 and 1995 to determine how the strains interacted on infected plants under field conditions. Plants were co-inoculated with strains 3-1-3 and B21, strains 3-1-3 and Nit A, and strains 3-1-3, B21, and Nit A at equal and unequal initial proportions. Plants were grown and maintained under flooded conditions in small wading pools. In co-inoculation of plants with 3-1-3 and B21 from equal initial proportions, the population of 3-1-3 increased slightly until it reached a proportion of 60 to 70%, whereas the population density of B21 reached 30 to 40% at the end of growing season. From unequal initial proportions, the population density of B21 decreased from 90 to about 50%, whereas the 3-1-3 increased from 10 to 50%. The population density of 3-1-3 increased from an equal initial proportion and was significantly greater than that of Nit A on every sampling time. From unequal initial proportions, the population density of 3-1-3 increased from 10 to 90%, whereas that of Nit A declined. In co-inoculation of plants with the three strains, the population density of 3-1-3 was significantly greater than those of the mutant strains at every sampling time. The proportions of mutant strains within the total population of C. gloeosporioides f. sp. aeschynomene on plants varied according to the test conditions and the number and types of strains co-inoculated.

A GacS deficiency does not affectPseudomonas chlororaphisPA23 fitness when growing on canola, in aged batch culture or as a biofilm

2006 ◽  
Vol 52 (12) ◽  
pp. 1177-1188 ◽  
Author(s):  
N Poritsanos ◽  
C Selin ◽  
W G.D Fernando ◽  
S Nakkeeran ◽  
T.R. de Kievit
Keyword(s):  
Antifungal Activity ◽  
Batch Culture ◽  
Hydrogen Cyanide ◽  
Fungal Pathogen ◽  
Biocontrol Agent ◽  
Antifungal Compounds ◽  
Pseudomonas Chlororaphis ◽  
Wild Type ◽  
Biocontrol Activity ◽  
Competition Assays

Pseudomonas chlororaphis PA23 is a biocontrol agent that protects against the fungal pathogen Sclerotinia sclerotiorum. Employing transposon mutagenesis, we isolated a gacS mutant that no longer exhibited antifungal activity. Pseudomonas chlororaphis PA23 was previously reported to produce the nonvolatile antibiotics phenazine 1-carboxylic acid and 2-hydroxyphenazine. We report here that PA23 produces additional compounds, including protease, lipase, hydrogen cyanide, and siderophores, that may contribute to its biocontrol ability. In the gacS mutant background, generation of these products was markedly reduced or delayed with the exception of siderophores, which were elevated. Not surprisingly, this mutant was unable to protect canola from disease incited by S. sclerotiorum. The gacS mutant was able to sustain itself in the canola phyllosphere, therefore, the loss of biocontrol activity can be attributed to a reduced production of antifungal compounds and not a declining population size. Competition assays between the mutant and wild type revealed equivalent fitness in aged batch culture; consequently, the gacS mutation did not impart a growth advantage in the stationary phase phenotype. Under minimal nutrient conditions, the gacS-deficient strain produced a tenfold less biofilm than the wild type. However, no difference was observed in the ability of the mutant biofilm to protect cells from lethal antibiotic challenge.Key words: Pseudomonas, biocontrol, gacS, fitness, biofilms.

scholarly journals ThemtfATranscription Factor Gene Controls Morphogenesis, Gliotoxin Production, and Virulence in the Opportunistic Human Pathogen Aspergillus fumigatus

2014 ◽  
Vol 13 (6) ◽  
pp. 766-775 ◽  
Author(s):  
Timothy D. Smith ◽  
Ana M. Calvo
Keyword(s):  
Aspergillus Fumigatus ◽  
Protease Activity ◽  
Galleria Mellonella ◽  
Molecular Genetic ◽  
Colony Growth ◽  
Infection Model ◽  
Slight Reduction ◽  
Wild Type ◽  
Content Type ◽  
Factor Gene

ABSTRACTAspergillus fumigatusis the leading causative agent of invasive aspergillosis (IA). The number of cases is on the rise, with mortality rates as high as 90% among immunocompromised patients. Molecular genetic studies inA. fumigatuscould provide novel targets to potentially set the basis for antifungal therapies. In the current study, we investigated the role of the transcription factor genemtfAinA. fumigatus. Our results revealed thatmtfAplays a role in the growth and development of the fungus. Deletion or overexpression ofmtfAleads to a slight reduction in colony growth, as well as a reduction in conidiation levels, in the overexpression strain compared to the wild-type strain. Furthermore, production of the secondary metabolite gliotoxin increased whenmtfAwas overexpressed, coinciding with an increase in the transcription levels of the gliotoxin genesgliZandgliPwith respect to the wild type. In addition, our study showed thatmtfAis also necessary for normal protease activity inA. fumigatus; deletion ofmtfAresulted in a reduction of protease activity compared to wild-type levels. Importantly, the absence ofmtfAcaused a decrease in virulence in theGalleria mellonellainfection model, indicating thatmtfAis necessary forA. fumigatuswild-type pathogenesis.

scholarly journals Cryptococcus neoformans Evades Pulmonary Immunity by Modulating Xylose Precursor Transport

2020 ◽  
Vol 88 (8) ◽  
Author(s):  
Lucy X. Li ◽  
Camaron R. Hole ◽  
Javier Rangel-Moreno ◽  
Shabaana A. Khader ◽  
Tamara L. Doering
Keyword(s):  
Cryptococcus Neoformans ◽  
Mutant Strain ◽  
Fungal Pathogen ◽  
Wild Type ◽  
Content Type ◽  
Helper Cell Type ◽  
Lymphoid Structures ◽  
Type Infection

ABSTRACT Cryptococcus neoformans is a fungal pathogen that kills almost 200,000 people each year and is distinguished by abundant and unique surface glycan structures that are rich in xylose. A mutant strain of C. neoformans that cannot transport xylose precursors into the secretory compartment is severely attenuated in virulence in mice yet surprisingly is not cleared. We found that this strain failed to induce the nonprotective T helper cell type 2 (Th2) responses characteristic of wild-type infection, instead promoting sustained interleukin 12p40 (IL-12p40) induction and increased IL-17A (IL-17) production. It also stimulated dendritic cells to release high levels of proinflammatory cytokines, a behavior we linked to xylose expression. We further discovered that inducible bronchus-associated lymphoid tissue (iBALT) forms in response to infection with either wild-type cryptococci or the mutant strain with reduced surface xylose; although iBALT formation is slowed in the latter case, the tissue is better organized. Finally, our temporal studies suggest that lymphoid structures in the lung restrict the spread of mutant fungi for at least 18 weeks after infection, which is in contrast to ineffective control of the pathogen after infection with wild-type cells. These studies demonstrate the role of xylose in modulation of host response to a fungal pathogen and show that cryptococcal infection triggers iBALT formation.

scholarly journals VibA, a Homologue of a Transcription Factor for Fungal Heterokaryon Incompatibility, Is Involved in Antifungal Compound Production in the Plant-Symbiotic Fungus Epichloë festucae

2014 ◽  
Vol 14 (1) ◽  
pp. 13-24 ◽  
Author(s):  
Jennifer T. Niones ◽  
Daigo Takemoto
Keyword(s):  
Transcription Factor ◽  
Antifungal Activity ◽  
Critical Role ◽  
Antifungal Compound ◽  
Symbiotic Association ◽  
Wild Type ◽  
Exogenous Dna ◽  
Content Type ◽  
Type Isolate ◽  
Epichloë Festucae

ABSTRACT Symbiotic association of epichloae endophytes ( Epichloë/Neotyphodium species) with cool-season grasses of the subfamily Pooideae confers bioprotective benefits to the host plants against abiotic and biotic stresses. While the production of fungal bioprotective metabolites is a well-studied mechanism of host protection from insect herbivory, little is known about the antibiosis mechanism against grass pathogens by the mutualistic endophyte. In this study, an Epichloë festucae mutant defective in antimicrobial substance production was isolated by a mutagenesis approach. In an isolated mutant that had lost antifungal activity, the exogenous DNA fragment was integrated into the promoter region of the vibA gene, encoding a homologue of the transcription factor VIB-1. VIB-1 in Neurospora crassa is a regulator of genes essential in vegetative incompatibility and promotion of cell death. Here we show that deletion of the vibA gene severely affected the antifungal activity of the mutant against the test pathogen Drechslera erythrospila . Further analyses showed that overexpressing vibA enhanced the antifungal activity of the wild-type isolate against test pathogens. Transformants overexpressing vibA showed an inhibitory activity on test pathogens that the wild-type isolate could not. Moreover, overexpressing vibA in a nonantifungal E. festucae wild-type Fl1 isolate enabled the transformant to inhibit the mycelial and spore germination of D. erythrospila . These results demonstrate that enhanced expression of vibA is sufficient for a nonantifungal isolate to obtain antifungal activity, implicating the critical role of VibA in antifungal compound production by epichloae endophytes.

scholarly journals Bacillus amyloliquefaciens ALB65 Inhibits the Growth of Listeria monocytogenes on Cantaloupe Melons

2020 ◽  
Vol 87 (1) ◽  
Author(s):  
Thao D. Tran ◽  
Celia Del Cid ◽  
Robert Hnasko ◽  
Lisa Gorski ◽  
Jeffery A. McGarvey
Keyword(s):  
United States ◽  
Biological Control ◽  
Listeria Monocytogenes ◽  
Bacillus Amyloliquefaciens ◽  
Biological Control Agent ◽  
Gene Clusters ◽  
The United States ◽  
Control Agent ◽  
Content Type

ABSTRACT Listeria monocytogenes is a foodborne pathogen that causes high rates of hospitalization and mortality in people infected. Contamination of fresh, ready to eat produce by this pathogen is especially troubling because of the ability of this bacterium to grow on produce under refrigeration temperatures. In this study, we created a library of over 8,000 plant phyllosphere-associated bacteria and screened them for the ability to inhibit the growth of L. monocytogenes in an in vitro fluorescence-based assay. One isolate, later identified as Bacillus amyloliquefaciens ALB65, was able to inhibit the fluorescence of L. monocytogenes by >30-fold in vitro. B. amyloliquefaciens ALB65 was also able to grow, persist, and reduce the growth of L. monocytogenes by >1.5 log CFU on cantaloupe melon rinds inoculated with 5 × 103 CFU at 30°C and was able to completely inhibit its growth at temperatures below 8°C. DNA sequence analysis of the B. amyloliquefaciens ALB65 genome revealed six gene clusters that are predicted to encode genes for antibiotic production; however, no plant or human virulence factors were identified. These data suggest that B. amyloliquefaciens ALB65 is an effective and safe biological control agent for the reduction of L. monocytogenes growth on intact cantaloupe melons and possibly other types of produce. IMPORTANCE Listeria monocytogenes is estimated by the Centers for Disease Control and Prevention and the U.S. Food and Drug Administration to cause disease in approximately 1,600 to 2,500 people in the United States every year. The largest known outbreak of listeriosis in the United States was associated with intact cantaloupe melons in 2011, resulting in 147 hospitalizations and 33 deaths. In this study, we demonstrated that Bacillus amyloliquefaciens ALB65 is an effective biological control agent for the reduction of L. monocytogenes growth on intact cantaloupe melons under both pre- and postharvest conditions. Furthermore, we demonstrated that B. amyloliquefaciens ALB65 can completely inhibit the growth of L. monocytogenes during cold storage (<8°C).

scholarly journals Draft Genome Sequence of Bacillus velezensis Strain E68, Isolated from an Oil Battery

2020 ◽  
Vol 9 (24) ◽  
Author(s):  
Nathan Liang ◽  
Suha Jabaji
Keyword(s):  
Biological Control ◽  
Fungal Pathogens ◽  
Biological Control Agent ◽  
Draft Genome ◽  
Gene Clusters ◽  
Control Agent ◽  
Biosynthetic Gene ◽  
Bacillus Velezensis ◽  
Biosynthetic Gene Clusters ◽  
Content Type

ABSTRACT Bacillus velezensis strain E68 is a biosurfactant-producing bacterium isolated from an oil battery near Chauvin, Alberta, Canada. Strain E68 exhibited antimicrobial activity against fungal pathogens and could potentially serve as a biological control agent. Its genome was sequenced and annotated, revealing the presence of multiple lipopeptide biosynthetic gene clusters.

scholarly journals Novel Cell-Killing Mechanisms of Hydroxyurea and the Implication toward Combination Therapy for the Treatment of Fungal Infections

2017 ◽  
Vol 61 (11) ◽  
Author(s):  
Amanpreet Singh ◽  
Ameeta Agarwal ◽  
Yong-jie Xu
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Fungal Pathogen ◽  
Fungal Infections ◽  
Genetic Data ◽  
Heme Biosynthesis ◽  
Wild Type ◽  
Content Type ◽  
Ergosterol Synthesis ◽  
Opportunistic Fungal Pathogen ◽  
Cell Lethality

ABSTRACT We have previously reported that an erg11 mutation affecting ergosterol synthesis and a hem13 mutation in the heme synthesis pathway significantly sensitize the fission yeast Schizosaccharomyces pombe to hydroxyurea (HU) (1, 2). Here we show that treatment with inhibitors of Erg11 and heme biosynthesis phenocopies the two mutations in sensitizing wild-type cells to HU. Importantly, HU synergistically interacts with the heme biosynthesis inhibitor sampangine and several Erg11 inhibitors, the antifungal azoles, in causing cell lethality. Since the synergistic drug interactions are also observed in the phylogenetically divergent Saccharomyces cerevisiae and the opportunistic fungal pathogen Candida albicans, the synergism is likely conserved in eukaryotes. Interestingly, our genetic data for S. pombe has also led to the discovery of a robust synergism between sampangine and the azoles in C. albicans. Thus, combinations of HU, sampangine, and the azoles can be further studied as a new method for the treatment of fungal infections.

scholarly journals Horizontal Transmission of the Entomopathogenic Fungal Isolate INRS-242 of Beauveria bassiana (Hypocreales: Cordycipitaceae) in Emerald Ash Borer, Agrilus planipennis (Coleoptera: Buprestidae)

2019 ◽  
Author(s):  
Narin Srei ◽  
Robert Lavallée ◽  
Claude Guertin
Keyword(s):  
Beauveria Bassiana ◽  
Fungal Pathogen ◽  
Biological Control Agent ◽  
Horizontal Transmission ◽  
Emerald Ash Borer ◽  
Control Agent ◽  
Agrilus Planipennis ◽  
Fungal Isolate ◽  
Ash Trees ◽  
Fungus Beauveria Bassiana

Abstract Emerald ash borer (EAB), Agrilus planipennis Fairmaire, is an invasive and destructive beetle that causes extensive damage to ash trees in North America. The entomopathogenic fungus Beauveria bassiana Vuillemin is considered as an effective biological control agent for EAB adult populations. Using an autodissemination device with a fungal isolate of B. bassiana, our research aims to investigate the possibility of horizontal transmission of the fungal disease from infected to uninfected EAB adults during mating. Results show that the efficiency of fungal transmission is significantly related to the sex of EAB carrying the fungal pathogen. EAB males are the promising vector to transmit mycosis to their partners during mating. Results strengthen the potential of the fungal autodissemination device as a powerful biological strategy to control EAB populations.

scholarly journals The Burkholderia contaminans MS14ocfCGene Encodes a Xylosyltransferase for Production of the Antifungal Occidiofungin

2013 ◽  
Vol 79 (9) ◽  
pp. 2899-2905 ◽  
Author(s):  
Kuan-Chih Chen ◽  
Akshaya Ravichandran ◽  
Adam Guerrero ◽  
Peng Deng ◽  
Sonya M. Baird ◽  
...  
Keyword(s):  
Antifungal Activity ◽  
Gene Cluster ◽  
Mass Spectroscopy ◽  
Type Strain ◽  
Wild Type Strain ◽  
Activity Level ◽  
Antifungal Compound ◽  
Wild Type ◽  
Content Type ◽  
Burkholderia Contaminans

ABSTRACTBurkholderia contaminansstrain MS14 produces the antifungal compound occidiofungin, which is responsible for significant antifungal activities against a broad range of plant and animal fungal pathogens. Occidiofungin is a cyclic glycolipopeptide made up of eight amino acids and one xylose. A 56-kbocfgene cluster was determined to be essential for occidiofungin production. In this study, theocfCgene, which is located downstream ofocfDand upstream of theocfBgene in theocfgene cluster, was examined. Antifungal activity of theocfCgene mutant MS14KC1 was reduced against the indicator fungusGeotrichum candidumcompared with that of the wild-type strain. Furthermore, the analysis of the protein sequence suggests that theocfCgene encodes a glycosyltransferase. Biochemical analyses using nuclear magnetic resonance (NMR) and mass spectroscopy revealed that theocfCmutant produced the occidiofungin without the xylose. The purifiedocfCmutant MS14KC1 product had a level of bioactivity similar to that of the wild-type product. The revertant MS14KC1-R of theocfCmutant produced the same antifungal activity level on plate assays and the same antifungal compound based on high-performance liquid chromatography (HPLC) and mass spectroscopy analysis as wild-type strain MS14. Collectively, the study demonstrates that theocfCgene encodes a glycosyltransferase responsible to add a xylose to the occidiofungin molecule and that the presence of the xylose is not important for antifungal activity againstCandidaspecies. The finding provides a novel variant for future studies aimed at evaluating its use for inhibiting clinical and agricultural fungi, and the finding could also simplify the chemical synthesis of occidiofungin variants.

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