A bacterial endophyte exploits chemotropism of a fungal pathogen for plant colonization

Abstract Soil-inhabiting fungal pathogens use chemical signals released by roots to direct hyphal growth towards the host plant. Whether other soil microorganisms exploit this capacity for their own benefit is currently unknown. Here we show that the endophytic rhizobacterium Rahnella aquatilis locates hyphae of the root-infecting fungal pathogen Fusarium oxysporum through pH-mediated chemotaxis and uses them as highways to efficiently access and colonize plant roots. Secretion of gluconic acid (GlcA) by R. aquatilis in the rhizosphere leads to acidification and counteracts F. oxysporum-induced alkalinisation, a known virulence mechanism, thereby preventing fungal infection. Genetic abrogation or biochemical inhibition of GlcA-mediated acidification abolished biocontrol activity of R. aquatilis and restored fungal infection. These findings reveal a new way by which bacterial endophytes hijack hyphae of a fungal pathogen in the soil to gain preferential access to plant roots, thereby protecting the host from infection.

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Sick plants in grassland communities: a growth-defense trade-off is the main driver of fungal pathogen abundance and impact

10.1101/806299 ◽

2019 ◽

Cited By ~ 2

Author(s):

Seraina L. Cappelli ◽

Noémie A. Pichon ◽

Anne Kempel ◽

Eric Allan

Keyword(s):

Fungal Infection ◽

Biomass Production ◽

Fungal Pathogen ◽

Fungal Pathogens ◽

Nitrogen Addition ◽

Main Determinant ◽

Trade Off ◽

Main Driver ◽

Dilution Effects ◽

Plant Pathogen Interactions

ABSTRACTAboveground fungal pathogens can substantially reduce biomass production in grasslands. However, we lack a mechanistic understanding of the drivers of fungal infection and impact. Using a global change biodiversity experiment we show that the trade-off between plant growth and defense is the main determinant of fungal infection in grasslands. Nitrogen addition only indirectly increased infection via shifting plant communities towards more fast growing species. Plant diversity did not decrease infection, likely because the spillover of generalist pathogens or dominance of susceptible species counteracted dilution effects. There was also evidence that fungal pathogens reduced biomass more strongly in diverse communities. Further, fungicide altered plant-pathogen interactions beyond just removing pathogens, probably by removing certain fungi more efficiently than others. Our results show that fungal pathogens have large effects on plant functional composition and biomass production and highlight the importance of considering changes in pathogen community composition to understand their effects.

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Recent advances in understanding Candida albicans hyphal growth

F1000Research ◽

10.12688/f1000research.18546.1 ◽

2019 ◽

Vol 8 ◽

pp. 700 ◽

Cited By ~ 2

Author(s):

Robert A. Arkowitz ◽

Martine Bassilana

Keyword(s):

Candida Albicans ◽

Medical Research ◽

Filamentous Fungi ◽

Fungal Pathogen ◽

Fungal Pathogens ◽

Morphological Changes ◽

Hyphal Growth ◽

Yeast Form ◽

Intensive Research ◽

Human Fungal Pathogen

Morphological changes are critical for the virulence of a range of plant and human fungal pathogens. Candida albicans is a major human fungal pathogen whose ability to switch between different morphological states is associated with its adaptability and pathogenicity. In particular, C. albicans can switch from an oval yeast form to a filamentous hyphal form, which is characteristic of filamentous fungi. What mechanisms underlie hyphal growth and how are they affected by environmental stimuli from the host or resident microbiota? These questions are the focus of intensive research, as understanding C. albicans hyphal growth has broad implications for cell biological and medical research.

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The Destructive Fungal Pathogen Botrytis cinerea—Insights from Genes Studied with Mutant Analysis

Pathogens ◽

10.3390/pathogens9110923 ◽

2020 ◽

Vol 9 (11) ◽

pp. 923

Author(s):

Nicholas Cheung ◽

Lei Tian ◽

Xueru Liu ◽

Xin Li

Keyword(s):

Botrytis Cinerea ◽

Fungal Pathogen ◽

Fungal Pathogens ◽

Gene Annotation ◽

Hyphal Growth ◽

Biological Processes ◽

Biological Mechanisms ◽

Crop Species ◽

Mutant Analysis ◽

Sclerotial Formation

Botrytis cinerea is one of the most destructive fungal pathogens affecting numerous plant hosts, including many important crop species. As a molecularly under-studied organism, its genome was only sequenced at the beginning of this century and it was recently updated with improved gene annotation and completeness. In this review, we summarize key molecular studies on B. cinerea developmental and pathogenesis processes, specifically on genes studied comprehensively with mutant analysis. Analyses of these studies have unveiled key genes in the biological processes of this pathogen, including hyphal growth, sclerotial formation, conidiation, pathogenicity and melanization. In addition, our synthesis has uncovered gaps in the present knowledge regarding development and virulence mechanisms. We hope this review will serve to enhance the knowledge of the biological mechanisms behind this notorious fungal pathogen.

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Microsporidian and fungal infections in Lepidoptera and Orthoptera in Bulgaria

Annual of Natural Sciences Department ◽

10.33919/ansd.19.1.11 ◽

2021 ◽

Vol 5 ◽

pp. 100-107

Author(s):

Daniela Pilarska ◽

Diana Gadzhalova ◽

Danail Takov

Keyword(s):

Fungal Infection ◽

Infection Rate ◽

Fungal Pathogen ◽

Fungal Pathogens ◽

Fungal Infections ◽

Biological Agent ◽

Perennial Plants ◽

Lepidopteran Species ◽

Microsporidian Infection ◽

Erannis Defoliaria

Fourteen hundred and sixty three larvae of 10 lepidopteran species collected from trees and bushes in the spring and summer of 2017, 2018 and 2019 from 5 localities in Northwest and South Bulgaria were investigated for presence of microsporidian and fungal pathogens. Also, 77 grasshopper individuals of Poecilimon thoracicus (Orthoptera, Tettiigoniidae) collected from various shrubs and perennial plants in the spring and summer of 2017 were examined. Conducted microscopic analyses showed the presence of microsporidian infection caused by Endoreticulatis poecilimonae in P. thoracicus and fungal infection in the larvae of mottled umber, Erannis defoliaria caused by Entomophaga auliciae. The studies showed that the average infection rate with the microsporidium E. poecilimonae was 57.1%. The prevalence of the fungus Entomophaga auliciae was 100% during the observed epizootic. E. auliciae is an efficient fungal pathogen which causes strong epizootics and can be used as classical or augmentation biological agent.

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Genome Mining and Evaluation of the Biocontrol Potential of Pseudomonas fluorescens BRZ63, a New Endophyte of Oilseed Rape (Brassica napus L.) against Fungal Pathogens

International Journal of Molecular Sciences ◽

10.3390/ijms21228740 ◽

2020 ◽

Vol 21 (22) ◽

pp. 8740

Author(s):

Daria Chlebek ◽

Artur Pinski ◽

Joanna Żur ◽

Justyna Michalska ◽

Katarzyna Hupert-Kocurek

Keyword(s):

Brassica Napus ◽

Plant Growth ◽

Pseudomonas Fluorescens ◽

Oilseed Rape ◽

Plant Growth Promotion ◽

Fungal Pathogens ◽

Growth Promotion ◽

Genome Mining ◽

Plant Colonization ◽

Brassica Napus L

Endophytic bacteria hold tremendous potential for use as biocontrol agents. Our study aimed to investigate the biocontrol activity of Pseudomonas fluorescens BRZ63, a new endophyte of oilseed rape (Brassica napus L.) against Rhizoctonia solani W70, Colletotrichum dematium K, Sclerotinia sclerotiorum K2291, and Fusarium avenaceum. In addition, features crucial for biocontrol, plant growth promotion, and colonization were assessed and linked with the genome sequences. The in vitro tests showed that BRZ63 significantly inhibited the mycelium growth of all tested pathogens and stimulated germination and growth of oilseed rape seedlings treated with fungal pathogens. The BRZ63 strain can benefit plants by producing biosurfactants, siderophores, indole-3-acetic acid (IAA), 1-aminocyclopropane-1-carboxylate (ACC) deaminase, and ammonia as well as phosphate solubilization. The abilities of exopolysaccharide production, autoaggregation, and biofilm formation additionally underline its potential to plant colonization and hence biocontrol. The effective colonization properties of the BRZ63 strain were confirmed by microscopy observations of EGFP-expressing cells colonizing the root surface and epidermal cells of Arabidopsis thaliana Col-0. Genome mining identified many genes related to the biocontrol process, such as transporters, siderophores, and other secondary metabolites. All analyses revealed that the BRZ63 strain is an excellent endophytic candidate for biocontrol of various plant pathogens and plant growth promotion.

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Isolation and Characterization of Root-Associated Bacterial Endophytes and Their Biocontrol Potential against Major Fungal Phytopathogens of Rice (Oryza sativa L.)

Pathogens ◽

10.3390/pathogens9030172 ◽

2020 ◽

Vol 9 (3) ◽

pp. 172

Author(s):

Maqsood Ahmed Khaskheli ◽

Lijuan Wu ◽

Guoqing Chen ◽

Long Chen ◽

Sajid Hussain ◽

...

Keyword(s):

Oryza Sativa ◽

Fungal Pathogens ◽

Oryza Sativa L ◽

Defense Responses ◽

Growth And Yield ◽

Bacterial Endophytes ◽

16S Rrna Sequence ◽

Resistance Response ◽

Isolation And Characterization ◽

Fungal Phytopathogens

Rice (Oryza sativa L.) is a major cereal food crop worldwide, and its growth and yield are affected by several fungal phytopathogens, including Magnaporthe oryzae, Fusarium graminearum, F. moniliforme, and Rhizoctonia solani. In the present study, we have isolated and characterized root-associated bacterial endophytes that have antifungal activities against rice fungal phytopathogens. A total of 122 root-associated bacterial endophytes, belonging to six genera (Bacillus, Fictibacillus, Lysinibacillus, Paenibacillus, Cupriavidus, and Microbacterium) and 22 species were isolated from three rice cultivars. Furthermore, the 16S rRNA sequence-based phylogeny results revealed that Bacillus was the most dominant bacterial genera, and that there were 15 different species among the isolates. Moreover, 71 root-associated endophytes showed antagonistic effects against four major fungal phytopathogens, including M. oryzae, F. graminearum, F. moniliforme, and R. solani. Additionally, the biochemical, physiological, and PCR amplification results of the antibiotic-related genes further supported the endophytes as potential biocontrolling agents against the rice fungal pathogens. Consequently, the findings in this study suggested that the isolated bacterial endophytes might have beneficial roles in rice defense responses, including several bioactive compound syntheses. The outcomes of this study advocate the use of natural endophytes as an alternative strategy towards the rice resistance response.

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#78: Use of Isavuconazonium for Treatment Of Invasive Fungal Infection in Immunocompromised Pediatric Patients

Journal of the Pediatric Infectious Diseases Society ◽

10.1093/jpids/piaa170.006 ◽

2021 ◽

Vol 10 (Supplement_1) ◽

pp. S2-S2

Author(s):

Sindhu Mohandas ◽

Kanokporn Mongkolrattanothai ◽

Leslie Stach ◽

Regina Orbach ◽

Michael Neely

Keyword(s):

Fungal Infection ◽

Invasive Fungal Infection ◽

Liposomal Amphotericin ◽

Fungal Pathogens ◽

Pediatric Patients ◽

Therapeutic Option ◽

Dual Therapy ◽

Primary Diagnosis ◽

Cardiac Transplant ◽

Serum Concentrations

Abstract Background Isavuconazole (ISZ), dosed as the pre-drug isavuconazonium (ISM), is active against a wide variety of clinically important fungal pathogens. ISM is approved for the treatment of invasive aspergillosis and mucormycosis in adults ≥18 years of age. We present our experience with ISM to treat proven or probable fungal infection in immunocompromised pediatric patients. Methods Retrospective review of patients who received ISM at our institution between April 2016 and April 2019, we abstracted demographic information, primary diagnosis, indication for ISM therapy, ISZ serum concentrations if available, and outcomes. Results Of 14 patients who received ISM, 11 were ≤18 years of age (range 6–18 years). Underlying conditions included leukemia (n = 7), lymphoma (n = 1), post BMT (n = 1), diabetes (n = 1), and cardiac transplant (n = 1). Nine (82%) had proven invasive fungal infection (IFI) with aspergillosis (n = 2), zygomycosis (n = 3), mixed aspergillosis and zygomycosis (n = 2), mixed Rhizopus and Scedosporium (n = 1), and pathology only (n = 1) and 2 had probable IFI. Five of these 11 patients received combination ISM and liposomal amphotericin initially and the other 6 received liposomal amphotericin with or without other azoles prior to changing to ISM monotherapy. This was followed by monotherapy with ISM in 10 patients after a mean of 26 days (range 6–63) and continued dual therapy in the one. ISM dosing was 10 mg/kg q8h on days 1 and 2, followed by q24 thereafter, up to a maximum of 372 mg/dose. There were 19 measured ISZ serum concentrations obtained from 8 patients after >1 week of verified inpatient dosing, ranging from 1.0 to 7.5 mg/L, above the MIC in all cases when known. Three (27%) patients died of underlying non-mycological causes, 1 (9%) died of progressive scedosporiosis, and 7 (64%) improved. ISM was well tolerated with no dose-limiting, drug-related toxicities noted. Conclusions ISM is a well-tolerated therapeutic option in pediatric patients at risk for or with invasive mycosis. Only 1 of our 11 patients died from progressive fungal disease.

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Responses of soil microorganisms to volatile exudates from germinating pea seeds

Canadian Journal of Botany ◽

10.1139/b85-142 ◽

1985 ◽

Vol 63 (6) ◽

pp. 1040-1045 ◽

Cited By ~ 19

Author(s):

J. M. Norton ◽

G. E. Harman

Keyword(s):

Soil Microorganisms ◽

Sclerotium Rolfsii ◽

Hyphal Growth ◽

Soil Microbial Activity ◽

Soil Microflora ◽

Natural Soil ◽

Soil Microbial ◽

Aged Seed ◽

Seed Rot ◽

Pea Seeds

Responses of soil microorganisms to volatile exudates from germinating pea seeds of differing quality were determined. Germination of sclerotia of Rhizoctonia solani and Sclerotium rolfsii and subsequent hyphal growth were stimulated by exposure to volatiles from aged but not nonaged pea seeds. Hyphae grew preferentially toward aged seeds. In natural soil, bacterial and fungal populations showed significant increases after exposure to volatiles from aged seed. For example, Fusarium spp. and Pseudomonas spp. showed increases of 79 and 2200%, respectively, over their original population levels after a 48-h exposure to volatiles. Conversely, Pythium populations and associated seed-rotting potential of soil decreased in natural soils exposed to volatiles. In autoclaved soils infested with P. ultimum (PHP4), Pythium populations increased dramatically after exposure to volatiles from aged pea seeds. In soils infested with either soil fungi or bacteria in addition to P. ultimum, Pythium levels remained constant or decreased, respectively, with time of exposure. Exposure to the volatiles from aged pea seeds stimulated soil microbial activity. These results suggest that Pythium germlings, when unable to reach a host, are subjected to microbial antagonism in the presence of the native soil microflora. A decrease in cucumber seed rot coincided with decreases in Pythium numbers.

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Nanoscale adhesion forces between the fungal pathogen Candida albicans and macrophages

Nanoscale Horizons ◽

10.1039/c5nh00049a ◽

2016 ◽

Vol 1 (1) ◽

pp. 69-74 ◽

Cited By ~ 15

Author(s):

Sofiane El-Kirat-Chatel ◽

Yves F. Dufrêne

Keyword(s):

Atomic Force Microscopy ◽

Candida Albicans ◽

Immune Cells ◽

Fungal Pathogen ◽

Fungal Pathogens ◽

Adhesion Forces ◽

Force Microscopy ◽

Atomic Force

We establish atomic force microscopy as a new nanoscopy platform for quantifying the forces between fungal pathogens and immune cells.

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

Canadian Journal of Microbiology ◽

10.1139/w06-079 ◽

2006 ◽

Vol 52 (12) ◽

pp. 1177-1188 ◽

Cited By ~ 37

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.

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