scholarly journals Inoculum Size Effect in Dimorphic Fungi: Extracellular Control of Yeast-Mycelium Dimorphism in Ceratocystis ulmi

2004 ◽  
Vol 70 (3) ◽  
pp. 1356-1359 ◽  
Author(s):  
Jacob M. Hornby ◽  
Sarah M. Jacobitz-Kizzier ◽  
Donna J. McNeel ◽  
Ellen C. Jensen ◽  
David S. Treves ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Size Effect ◽  
Organic Solvent ◽  
Inoculum Size ◽  
Dutch Elm Disease ◽  
Sulfur Source ◽  
Dimorphic Fungus ◽  
Promoting Effect ◽  
Dimorphic Fungi ◽  
Methyl Donors

ABSTRACT We studied the inoculum size effect in Ceratocystis ulmi, the dimorphic fungus that causes Dutch elm disease. In a defined glucose-proline-salts medium, cells develop as budding yeasts when inoculated at ≥106 spores per ml and as mycelia when inoculated at <106 spores per ml. The inoculum size effect was not influenced by inoculum spore type, age of the spores, temperature, pH, oxygen availability, trace metals, sulfur source, phosphorous source, or the concentration of glucose or proline. Similarly, it was not influenced by added adenosine, reducing agents, methyl donors, amino sugars, fatty acids, or carbon dioxide. Instead, growing cells excreted an unknown quorum-sensing factor that caused a morphological shift from mycelia to budding yeasts. This yeast-promoting effect is abolished if it is extracted with an organic solvent such as ethyl acetate. The quorum-sensing activity acquired by the organic solvent could be added back to fresh medium in a dose-dependent fashion. The quorum-sensing activity in C. ulmi spent medium was specific for C. ulmi and had no effect on the dimorphic fungus Candida albicans or the photomorphogenic fungus Penicillium isariaeforme. In addition, farnesol, the quorum-sensing molecule produced by C. albicans, did not inhibit mycelial development of C. ulmi when present at concentrations of up to 100 μM. We conclude that the inoculum size effect is a manifestation of a quorum-sensing system that is mediated by an excreted extracellular molecule, and we suggest that quorum sensing is a general phenomenon in dimorphic fungi.

scholarly journals Diversity in yeast–mycelium dimorphism response of the Dutch elm disease pathogens: the inoculum size effect

2016 ◽  
Vol 62 (6) ◽  
pp. 525-529 ◽  
Author(s):  
Marie-Ève Wedge ◽  
Erika Sayuri Naruzawa ◽  
Martha Nigg ◽  
Louis Bernier
Keyword(s):  
Quorum Sensing ◽  
Size Effect ◽  
Inoculum Size ◽  
Dutch Elm Disease ◽  
Dimorphic Fungi ◽  
Ophiostoma Ulmi ◽  
Signalling Molecules ◽  
A Cell ◽  
Different Strains ◽  
External Stimuli

Dutch elm disease (DED) is caused by the dimorphic fungi Ophiostoma ulmi, Ophiostoma novo-ulmi, and Ophiostoma himal-ulmi. A cell population density-dependent phenomenon related to quorum sensing was previously shown to affect the reversible transition from yeast-like to mycelial growth in liquid shake cultures of O. novo-ulmi NRRL 6404. Since the response to external stimuli often varies among DED fungal strains, we evaluated the effect of inoculum size on 8 strains of the 3 species of DED agents by determining the proportion of yeast and mycelium produced at different spore inoculum concentrations in defined liquid shake medium. The results show that not all DED fungi strains respond similarly to inoculum size effect, since variations were observed among strains. It is thus possible that the different strains belonging to phylogenetically close species use different signalling molecules or molecular signalling pathways to regulate their growth mode via quorum-sensing mechanisms.

scholarly journals Quorum Sensing in the Dimorphic FungusCandida albicans Is Mediated by Farnesol

2001 ◽  
Vol 67 (7) ◽  
pp. 2982-2992 ◽  
Author(s):  
Jacob M. Hornby ◽  
Ellen C. Jensen ◽  
Amber D. Lisec ◽  
Joseph J. Tasto ◽  
Brandon Jahnke ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Chemical Nature ◽  
Tube Formation ◽  
Cross Reactivity ◽  
Inoculum Size ◽  
Cellular Growth ◽  
Farnesyl Pyrophosphate ◽  
Dimorphic Fungus ◽  
Fetal Bovine ◽  
Mycelial Development

ABSTRACT The inoculum size effect in the dimorphic fungus Candida albicans results from production of an extracellular quorum-sensing molecule (QSM). This molecule prevents mycelial development in both a growth morphology assay and a differentiation assay using three chemically distinct triggers for germ tube formation (GTF): l-proline, N-acetylglucosamine, and serum (either pig or fetal bovine). In all cases, the presence of QSM prevents the yeast-to-mycelium conversion, resulting in actively budding yeasts without influencing cellular growth rates. QSM exhibits general cross-reactivity within C. albicans in that supernatants from strain A72 are active on five other strains ofC. albicans and vice versa. The QSM excreted by C. albicans is farnesol (C15H26O; molecular weight, 222.37). QSM is extracellular, and is produced continuously during growth and over a temperature range from 23 to 43�C, in amounts roughly proportional to the CFU/milliliter. Production is not dependent on the type of carbon source nor nitrogen source or on the chemical nature of the growth medium. Both commercial mixed isomer and (E,E)-farnesol exhibited QSM activity (the ability to prevent GTF) at a level sufficient to account for all the QSM activity present in C. albicans supernatants, i.e., 50% GTF at ca. 30 to 35 μM. Nerolidol was ca. two times less active than farnesol. Neither geraniol (C10), geranylgeraniol (C20), nor farnesyl pyrophosphate had any QSM activity.

scholarly journals Quorum-Sensing Mechanisms Mediated by Farnesol in Ophiostoma piceae: Effect on Secretion of Sterol Esterase

2015 ◽  
Vol 81 (13) ◽  
pp. 4351-4357 ◽  
Author(s):  
Felipe de Salas ◽  
María Jesús Martínez ◽  
Jorge Barriuso
Keyword(s):  
Quorum Sensing ◽  
Cell Density ◽  
Transcriptional Analysis ◽  
Morphological Transition ◽  
Dimorphic Fungus ◽  
Dimorphic Fungi ◽  
Content Type ◽  
Ophiostoma Piceae ◽  
Enhanced Production ◽  
Sterol Esterase

ABSTRACTOphiostoma piceaeCECT 20416 is a dimorphic wood-staining fungus able to produce an extracellular sterol-esterase/lipase (OPE) that is of great biotechnological interest. In this work, we have studied the morphological change of this fungus from yeast to hyphae, which is associated with the cell density-related mechanism known as quorum sensing (QS), and how this affects the secretion of OPE. The data presented here confirm that the moleculeE,E-farnesol accumulates as the cell number is growing within the population. The exogenous addition of this molecule or spent medium to the cultures increased the extracellular activity of OPE 2.5 times. This fact was related not to an increase in microbial biomass or in the expression of the gene coding for OPE but to a marked morphological transition in the cultures. Moreover, the morphological transition also occurred when a high cell density was inoculated into the medium. The results suggest thatE,E-farnesol regulates through QS mechanisms the morphological transition in the dimorphic fungusO. piceaeand that it is associated with a higher extracellular esterase activity. Furthermore, identification and transcriptional analysis of genestup1andcyr1, which are involved in the response, was carried out. Here we report enhanced production of a sterol-esterase/lipase of biotechnological interest by means of QS mechanisms. These results may be useful in increasing the production of secreted enzymes of other dimorphic fungi of biotechnological interest.

scholarly journals An Efficient Strategy for Obtaining Mutants by Targeted Gene Deletion in Ophiostoma novo-ulmi

2021 ◽  
Vol 12 ◽  
Author(s):  
Jorge Luis Sarmiento-Villamil ◽  
Thais Campos de Oliveira ◽  
Erika Sayuri Naruzawa ◽  
Louis Bernier
Keyword(s):  
Molecular Mechanisms ◽  
Gene Deletion ◽  
High Efficiency ◽  
Pathogenic Fungi ◽  
Gene Replacement ◽  
Dutch Elm Disease ◽  
Large Set ◽  
Purine Nucleotide ◽  
Dimorphic Fungus ◽  
Dimorphic Fungi

The dimorphic fungus Ophiostoma novo-ulmi is the highly aggressive pathogen responsible for the current, highly destructive, pandemic of Dutch elm disease (DED). Genome and transcriptome analyses of this pathogen previously revealed that a large set of genes expressed during dimorphic transition were also potentially related to plant infection processes, which seem to be regulated by molecular mechanisms different from those described in other dimorphic pathogens. Then, O. novo-ulmi can be used as a representative species to study the lifestyle of dimorphic pathogenic fungi that are not shared by the “model species” Candida albicans and Ustilago maydis. In order to gain better knowledge of molecular aspects underlying infection process and symptom induction by dimorphic fungi that cause vascular wilt disease, we developed a high-throughput gene deletion protocol for O. novo-ulmi. The protocol is based on transforming a Δmus52 O. novo-ulmi mutant impaired for non-homologous end joining (NHEJ) as the recipient strain, and transforming this strain with the latest version of OSCAR plasmids. The latter are used for generating deletion constructs containing the toxin-coding Herpes simplex virus thymidine kinase (HSVtk) gene which prevents ectopic integration of the T-DNA in Ophiostoma DNA. The frequency of gene deletion by homologous recombination (HR) at the ade1 locus associated with purine nucleotide biosynthesis was up to 77.8% in the Δmus52 mutant compared to 2% in the wild-type (WT). To validate the high efficiency of our deletion gene methodology we deleted ade7, which also belongs to the purine nucleotide pathway, as well as bct2, ogf1, and opf2 which encode fungal binuclear transcription factors (TFs). The frequency of gene replacement by HR for these genes reached up to 94%. We expect that our methodology combining the use of NHEJ deficient strains and OSCAR plasmids will function with similar high efficiencies for other O. novo-ulmi genes and other filamentous fungi.

scholarly journals Organization and Evolutionary Trajectory of the Mating Type (MAT) Locus in Dermatophyte and Dimorphic Fungal Pathogens

2009 ◽  
Vol 9 (1) ◽  
pp. 46-58 ◽  
Author(s):  
Wenjun Li ◽  
Banu Metin ◽  
Theodore C. White ◽  
Joseph Heitman
Keyword(s):  
Mating Type ◽  
Fungal Pathogens ◽  
Control Cell ◽  
Gene Arrangement ◽  
Microsporum Canis ◽  
Microsporum Gypseum ◽  
Last Common Ancestor ◽  
Dimorphic Fungus ◽  
Dimorphic Fungi ◽  
Evolutionary Trajectory

ABSTRACT Sexual reproduction in fungi is governed by a specialized genomic region, the mating type (MAT) locus, whose gene identity, organization, and complexity are diverse. We identified the MAT locus of five dermatophyte fungal pathogens (Microsporum gypseum, Microsporum canis, Trichophyton equinum, Trichophyton rubrum, and Trichophyton tonsurans) and a dimorphic fungus, Paracoccidioides brasiliensis, and performed phylogenetic analyses. The identified MAT locus idiomorphs of M. gypseum control cell type identity in mating assays, and recombinant progeny were produced. Virulence tests in Galleria mellonella larvae suggest the two mating types of M. gypseum may have equivalent virulence. Synteny analysis revealed common features of the MAT locus shared among these five dermatophytes: namely, a small size (∼3 kb) and a novel gene arrangement. The SLA2, COX13, and APN2 genes, which flank the MAT locus in other Ascomycota are instead linked on one side of the dermatophyte MAT locus. In addition, the transcriptional orientations of the APN2 and COX13 genes are reversed compared to the dimorphic fungi Histoplasma capsulatum, Coccidioides immitis, and Coccidioides posadasii. A putative transposable element, pogo, was found to have inserted in the MAT1-2 idiomorph of one P. brasiliensis strain but not others. In conclusion, the evolution of the MAT locus of the dermatophytes and dimorphic fungi from the last common ancestor has been punctuated by both gene acquisition and expansion, and asymmetric gene loss. These studies further support a foundation to develop molecular and genetic tools for dermatophyte and dimorphic human fungal pathogens.

scholarly journals Spectrum and Inoculum Size Effect of a Rapid Antigen Detection Test for Group A Streptococcus in Children with Pharyngitis

PLoS ONE ◽  
2012 ◽  
Vol 7 (6) ◽  
pp. e39085 ◽  
Author(s):  
Jérémie F. Cohen ◽  
Martin Chalumeau ◽  
Corinne Levy ◽  
Philippe Bidet ◽  
Franck Thollot ◽  
...  
Keyword(s):  
Size Effect ◽  
Group A Streptococcus ◽  
Inoculum Size ◽  
Antigen Detection ◽  
Rapid Antigen Detection Test ◽  
Group A

scholarly journals Inoculum size effects in blaIMP-6 and plasmid-mediated quinolone resistance gene-positive Enterobacteriaceae in Japan

2019 ◽  
Author(s):  
Yoshihiko Ogawa ◽  
Ryuichi Nakano ◽  
Kei Kasahara ◽  
Tomoki Mizuno ◽  
Nobuyasu Hirai ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Drug Resistance ◽  
Klebsiella Pneumoniae ◽  
Size Effect ◽  
Resistance Gene ◽  
Size Effects ◽  
Antimicrobial Agents ◽  
Inoculum Size ◽  
Experimental Strains

AbstractThe aim of this study was to examine the resistance genes in clinical isolates which produced IMP-6 type metallo-β-lactamase lactamase (MBL) and had mildly reduced susceptibilities to levofloxacin and/or amikacin. The inoculum size effect was also assessed. A total of 14 Enterobacteriaceae isolates (2 Escherichia coli and 12 Klebsiella pneumoniae) which produced IMP-6 MBL, and had mild increases in their MICs for levofloxacin and amikacin were examined. Thirteen out of 14 isolates harbored CTX-M-2, with the remaining isolate co-harboring CTX-M-2 and CTX-M-1 as ESBLs. All isolates carried one or more PMQRs; aac(6′)-Ib-cr was the most prevalent (92.8%), followed by oqxA (64.3%), qnrS (42.9%), oqxAB (21.4%), and qnrB (14.3%). The inoculum size effects were significant in all strains for meropenem, 13 for imipenem, 7 for levofloxacin, and 3 for amikacin. Conjugation was successfully performed with 8 isolates and 11 strains were obtained. Eleven of the experimental strains (100%), and 8 strains (72.7%) showed inoculum size effects for meropenem and imipenem, respectively. No inoculum size effect was seen for levofloxacin. Four strains harbored qnr genes and 2 strains harbored qnr genes and QRDR mutations concurrently. blaIMP-6 positive Enterobacteriaceae with mildly reduced susceptibilities to levofloxacin and/or amikacin also harbored at least one plasmid-mediated drug resistance gene. These represent an unrecognized threat, capable of compromising the in vitro activity of many classes of antimicrobial agents. We conclude that IMP-6 MBL plays an important role in decreasing the MIC for carbapenems, whereas qnr does not for levofloxacin.

scholarly journals Striking up the conversation: quorum sensing in fungi

Fine Focus ◽  
2015 ◽  
Vol 1 (2) ◽  
pp. 139-151
Author(s):  
Brooke Martini ◽  
Cody Orr ◽  
Ginny Webb
Keyword(s):  
Quorum Sensing ◽  
Fungal Infections ◽  
Large Population ◽  
Pantothenic Acid ◽  
Opportunistic Pathogen ◽  
Fungal Species ◽  
Cellular Growth ◽  
Growth Morphology ◽  
Dimorphic Fungus ◽  
Diploid Cells

Quorum sensing is a form of communication observed in different species of microbes. Numerous studies have shown the ability of bacteria and fungi to carry out quorum sensing by releasing specific molecules to enable communication in a large population. Quorum sensing has been shown to influence growth, morphology, and other factors pertaining to virulence in pathogenic microbes. In this review, we address three important fungal species and explain how each fungus has a unique and dynamic way of communicating. Candida albicans is an opportunistic pathogen, or one that is part of the normal microbiota that can become pathogenic and cause several diseases. Here, we address two quorum sensing molecules (QSMs) identified by investigators. These chemicals are tyrosol and farnesol, which act together to control cellular growth, morphology and biofilm production. Another opportunistic fungal pathogen, Cryptococcus neoformans, has been shown to display quorum sensing activity by using pantothenic acid as well as a peptide called quorum sensing-like peptide 1. These molecules have both been shown to control growth rates of C. neoformans. Saccharomyces cerevisiae is another dimorphic fungus that uses QSMs, although it is nonpathogenic. Using two aromatic alcohols, phenylethanol and tryptophol, S. cerevisiae can alter pseudohyphal growth in diploid cells as well as invasive growth in haploid cells. By understanding more about the ways these organisms communicate, we present the potential for new and better targets for the treatment of fungal infections.

scholarly journals In Vitro Antifungal Activity of Micafungin (FK463) against Dimorphic Fungi: Comparison of Yeast-Like and Mycelial Forms

2003 ◽  
Vol 47 (4) ◽  
pp. 1376-1381 ◽  
Author(s):  
Toru Nakai ◽  
Jun Uno ◽  
Fumiaki Ikeda ◽  
Shuichi Tawara ◽  
Kazuko Nishimura ◽  
...  
Keyword(s):  
Antifungal Activity ◽  
Amphotericin B ◽  
Growth Form ◽  
Paracoccidioides Brasiliensis ◽  
Penicillium Marneffei ◽  
Apparent Difference ◽  
Dimorphic Fungus ◽  
Mycelial Form ◽  
Dimorphic Fungi

ABSTRACT The characteristics of in vitro micafungin (FK463) antifungal activity against six species of dimorphic fungi were investigated in accordance with the NCCLS M27-A microdilution methods. MICs of micafungin, amphotericin B, itraconazole, and fluconazole for Histoplasma capsulatum var. capsulatum, Blastomyces dermatitidis, Paracoccidioides brasiliensis, Penicillium marneffei, and Sporothrix schenckii were determined both for the yeast-like form and mycelial form. Coccidioides immitis was tested only in its mycelial form. We have clearly demonstrated that the in vitro activity of micafungin depends considerably on the growth form of dimorphic fungi. Micafungin exhibited potent activity against the mycelial forms of H. capsulatum, B. dermatitidis, and C. immitis (MIC range, 0.0078 to 0.0625 μg/ml), while it was very weakly active against their yeast-like forms (MIC range, 32 to >64 μg/ml). Micafungin was also more active against the mycelial forms than the yeast-like forms of Paracoccidioides brasiliensis, Penicillium marneffei, and S. schenckii. The MICs of amphotericin B were 2 to 5 dilutions lower for the mycelial forms than for the yeast-like forms of B. dermatitidis and Paracoccidioides brasiliensis. There was no apparent difference in the activity of itraconazole between the two forms. The MICs of fluconazole for the yeast-like forms were generally lower than those for the mycelial forms, and considerably so for B. dermatitidis. These results suggest that the growth form employed in antifungal susceptibility testing of dimorphic fungi can considerably influence the interpretation of results. At present, it cannot be judged whether micafungin has clinical usefulness for dimorphic fungus infections, since for most fungi it remains uncertain which growth form correlates better with therapeutic outcome. However, the results of this study warrant further investigations of micafungin as a therapeutic agent for infections caused by dimorphic fungi.

scholarly journals Comparison of Phylogenetically Distinct Histoplasma Strains Reveals Evolutionarily Divergent Virulence Strategies

mBio ◽  
2014 ◽  
Vol 5 (4) ◽  
Author(s):  
Victoria E. Sepúlveda ◽  
Corinne L. Williams ◽  
William E. Goldman
Keyword(s):  
Cell Wall ◽  
North America ◽  
Phylogenetic Analyses ◽  
Clinical Manifestations ◽  
Inoculum Size ◽  
Sublethal Dose ◽  
Dimorphic Fungus ◽  
Content Type ◽  
Wide Range

ABSTRACTInfection with the dimorphic fungusHistoplasma capsulatumresults from the inhalation of contaminated soil. Disease outcome is variable and depends on the immune status of the host, number of organisms inhaled, and theH. capsulatumstrain.H. capsulatumis divided into seven distinct clades based on phylogenetic analyses, and strains from two separate clades have been identified in North America (denoted as NAm strains). We characterized anH. capsulatumisolate (WU24) from the NAm 1 lineage in relation to two other well-characterizedHistoplasmaisolates, the Panamanian strain G186A and the NAm 2 strain G217B. We determined that WU24 is a chemotype II strain and requires cell wall α-(1,3)-glucan for successfulin vitroinfection of macrophages. In a mouse model of histoplasmosis, WU24 exhibited a disease profile that was very similar to that of strain G186A at a high sublethal dose; however, at this dose G217B had markedly different kinetics. Surprisingly, infection with a lower dose mitigated many of the differences during the course of infection. The observed differences in fungal burden, disease kinetics, symptomology, and cytokine responses all indicate that there is a sophisticated relationship between host and fungus that drives the development and progression of histoplasmosis.IMPORTANCEHistoplasmosis has a wide range of clinical manifestations, presenting as mild respiratory distress, acute respiratory infection, or a life-threatening disseminated disease most often seen in immunocompromised patients. Additionally, the outcome appears to be dependent on the amount and strain of fungus inhaled. In this study, we characterized a recent clinicalH. capsulatumisolate that was collected from an HIV+individual in North America. In contrast to other isolates from the same lineage, this strain, WU24, infected both macrophages and wild-type mice. We determined that in contrast to many other North American strains, WU24 infection of macrophages is dependent on the presence of cell wall α-(1,3)-glucan. Surprisingly, comparison of WU24 with two previously characterized isolates revealed that many conclusions regarding relative strain virulence and certain hallmarks of histoplasmosis are dependent on the inoculum size.

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