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Tolaasins are lipodepsipeptides secreted by Pseudomonas tolaasii, the causal agent of brown blotch disease of mushroom, and are the toxins that cause the brown spots. We previously reported that Microbacterium foliorum NBRC 103072T is an effective tolaasin-detoxifying bacterium. In this study, we aimed to characterize the tolaasin-detoxification process of M. foliorum NBRC 103072T. The tolaasin detoxification by M. foliorum NBRC 103072T was carried out by hydrolyzation of tolaasins at two specific sites in the peptide moiety of tolaasins by its cells, and the resulting fragments were released from bacterial cells. The tolaasin-hydrolyzing activity can be extracted by a neutral detergent solution from M. foliorum NBRC 103072T cells. Moreover, tolaasin adsorption to the bacterial cells occurred prior to hydrolyzation of tolaasins, which might contribute to the effective tolaasin detoxification by M. foliorum NBRC 103072T. It is notable that the tolaasin-degradation process by M. foliorum NBRC 103072T is carried out by hydrolyzation at specific sites in the peptide moiety of lipopeptide by bacterial cells as a novel biological degradation process of cyclic lipopeptides. [Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Le niébé (Vigna unguiculata (L.) Walp.) est une légumineuse à graine très importante et constitue la principale source de protéines végétales pour l’alimentation des populations d’Afrique Subsaharienne. Sa production au Burkina Faso est entravée par la maladie des taches brunes provoquée par un champignon, Colletotrichum capsici (Syd.) Butler et Bisby. C’est dans la perspective d’accroître la productivité du niébé que nous avons entrepris de renforcer la lutte variétale contre cet agent pathogène. L’identification de marqueurs SNPs (Single Nucleotide Polymorphism) et QTL liés à la résistance à la maladie des taches brunes a été entrepris à partir d’une population biparentale F2 issus du croisement entre la variété sensible Tiligré et celle résistante KN-1. L’analyse QTL de la résistance du niébé à C. capsici à partir de la méthode ICIM add. a permis de confirmer et de valider respectivement un QTL majeur dénommé qBBDR2.1 et 9 marqueurs SNPs convertis, lesquels ont été cartographiés sur le chromosome Vu02 du niébé. Ce QTL dominant a présenté des effets additifs élevés liés aux allèles favorables de KN-1 et des valeurs de PVE de l’ordre de 51,50% et 55,33%, respectivement aux 21ème et 28ème JAI. English title: Confirmation of QTL mapping and validation of SNPs markers associated to cowpea resistance to Colletotrichum capsici, causal agent of brown blotch disease Cowpea (Vigna unguiculata (L.)Walp.) is one of the most important grain legume crops and constitutes the main source of plant protein for people food in sub-Saharan Africa. Cowpea production in Burkina Faso is constrained by brown blotch disease caused by a fungal, Colletotrichum capsici (Syd.) Butler and Bisby. In order to increase cowpea productivity we initiated a project to enhance host plant resistance to control the pathogen. The identification of SNP (Single Nucleotide Polymorphism) markers and QTL associated with brown blotch disease resistance was undertaken from a bi-parental F2 population resulting from a cross between the sensitive variety Tiligre and the resistant KN-1 to the disease. QTL analysis of cowpea resistance to C. capsici using the ICIM add method. Allowed to confirm and validate respectively a major QTL named qBBDR2.1 and 9 converted SNP markers, which were mapped on cowpea chromosome Vu02. This dominant QTL showed higher additive effects associated to alleles from KN-1 and PVE values of 51.50% and 55.33% respectively at 21 and 28 days after inoculation

Brown blotch disease (BBD) caused by Pseudomonas tolaasii is one of the most devastating diseases of Pleurotus spp. worldwide. Breeding for resistant strains is the most effective method for controlling BBD. To identify resistant germplasm for BBD management, 97 strains comprising 21 P. cf. floridanus, 20 P. ostreatus, and 56 P. pulmonarius were screened by two different methods, namely, inoculation of the pathogen on the mushroom pileus (IMP) and on the spawned substrate (IMSS) under controlled conditions. Out of the 97 strains screened, 22 P. pulmonarius, and four P. cf. floridanus were moderately resistant to BBD using the IMP method. Eleven P. pulmonarius, six P. cf. florida, and one P. ostreatus strains were highly resistant to BBD using the IMSS method. All of the 97 strains showed varying degrees of susceptibility using the IMP method, but eight strains were completely resistant using the IMSS method. Combining these two methods, five strains were highly resistant (four P. pulmonarius and one P. cf. floridanus) and 11 were moderately resistant (eight P. pulmonarius and three P. cf. floridanus). The resistance sources to P. tolaasii identified in P. pulmonarius and P. cf. floridanus could be used for further breeding of Pleurotus spp.

Thirty six Colletotrichum capsici (L.) single spore isolates associated with brown blotch disease in cowpea were collected from three agro-ecological zones of Burkina Faso from October to November 2014. To identify the most virulent strains, cowpea genotypes KVx61-1, KVx396-4-5-2-D and Moussa Local was inoculated with each isolate. The results showed that isolates 096-SA-2, 071-FA-6 and 079-PM-2 were the most virulent, respectively, in North Soudanian, Soudanian and Sahelian zones. To identify brown blotch disease resistant cowpea, each of the isolates was used to inoculate 41 different cowpea genotypes. Inoculated cowpea plants were evaluated for brown blotch disease severity at 7, 14 and 21 days after inoculation. Highly significant differences (P < 0.001) were found among genotypes, isolates and their interactions. Seven cowpea genotypes including KN-1, Moussa Local, Donsin Local and Melakh were identified as resistant and present specific resistance to the isolates. These genotypes can be used to improve cowpea resistance to brown blotch disease in Burkina Faso. Key words: Cultivars, pathotypes aggressiveness, disease resistance.

Symbiosis The white button mushrooms that many of us enjoy eating are subject to brown blotch disease caused by the bacterium Pseudomonas tolaasii . These bacteria are spread by means of biosurfactants, and damage is caused by a family of pore-forming cyclic lipopeptides called tolaasins. However, protective bacteria are also found on button mushrooms, and Hermenau et al. show how helper bacteria of the genus Mycetocola protect their host. Metabolic profiling, mass spectroscopy, structural characterization, and infection assays show that tolaasin is linearized by the helper bacteria. The authors also identify the enzyme responsible and show that a biosurfactant involved in pathogen spreading is also a cyclic lipopeptide that is neutralized by linearization. Understanding these protective mechanisms could allow the development of biocontrol strategies to stop spoilage. Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.2006109117 (2020).

Bacterial brown blotch disease, caused by Pseudomonas tolaasii, has been one of the most serious bacterial diseases of the oyster mushroom. Resistance to disease has been a priority in breeding programs for the oyster mushroom. In this study, a set of 37 Pleurotus ostreatus strains was tested for resistance to the pathogen P. tolaasii by two methods, with inoculations on pileus and spawned substrate under controlled environmental conditions. The results showed that the protocol with inoculation on spawned substrate was sensitive and adequate for testing resistance of oyster mushroom to brown blotch disease. According to the disease severity of fruiting bodies with inoculation on spawned substrates, strain ACCC50618 was resistant; ACCC50236 was moderate resistant; and the others were susceptible to the pathogen P. tolaasii (ACCC 01267). However, it was difficult to differentiate the resistance of P. ostreatus strains to P. tolaasii by inoculation on the pileus. This is the first report about resistance evaluation of P. ostreatus to brown blotch disease.

Brown blotch disease, caused by Colletotrichum capsici, is an important disease of cowpea with a significant yield losses ranging from 42 to 100% in West Africa. In this study, a specific polymerase chain reaction (PCR) primer set CC1F1/CcapR was used to characterize and to study the phylogenetic relationship of thirty eight strains of Colletotrichum species. This primer set is capable of amplifying only C. capsici from different fungal structures and provide a powerful tool for C. capsici detection in brown blotch disease in cowpea. Phylogenetic analysis from neighbor-joining (NJ) showed a high genetic variability in the rDNA-ITS region of the isolates. The isolates formed four groups or clusters on the basis of specific fragment analysis. Groups I, II, and III consist of strains containing specific region length of twenty one nucleotides and were considered as variant 1 of C. capsici. Group IV was a heterogeneous and consists of variants 1, 2, 3, and 4 of C. capsici. Key words: Cultivars, internal transcribed spacer (ITS) sequence, Colletotrichum species.

Lipopeptides constitute a structurally diverse group of metabolites produced by various bacterial and fungal genera. In the past decades, research on lipopeptides has been fueled by their antimicrobial, antitumour, immunosuppressant and surfactant activities. However, the natural functions of lipopeptides in the lifestyles of the producing microorganisms have received considerably less attention. The substantial structural diversity of lipopeptides suggests that these metabolites have different natural roles, some of which may be unique to the biology of the producing organism. This review gives a detailed overview of the versatile functions of lipopeptides in the biology of Pseudomonas and Bacillus species, and highlights their role in competitive interactions with coexisting organisms, including bacteria, fungi, oomycetes, protozoa, nematodes and plants. Their functions in cell motility, leading to colonization of novel habitats, and in the formation and development of highly structured biofilms are discussed in detail. Finally, this review provides an update on lipopeptide detection and discovery as well as on novel regulatory mechanisms and genes involved in lipopeptide biosynthesis in these two bacterial genera.

A toxin produced by Pseudomonas tolaasii, tolaasin, causes brown blotch disease in mushrooms. Tolaasin forms pores on the cellular membrane and destroys cell structure. Inhibiting the ability of tolaasin to form ion channels may be an effective method to protect against attack by tolaasin. However, it is first necessary to elucidate the three-dimensional structure of the ion channels formed by tolaasin. In this study, the structure of the tolaasin ion channel was determined in silico based on data obtained from nuclear magnetic resonance experiments.

The names of all plant pathogenic bacteria which have been effectively and validly published in terms of the international. Code of Nomenclature of Bacteria and the Standards for Naming Pathovars are listed to provide an authoritative register of names for use by authors, journal editors and others who require access to currently correct nomenclature. Included are species, subspecies and pathovar names and details of type and pathotype strains reported from 1980 to 2007. An explanation of how to use this list is provided. In recent years the taxonomy of plant pathogenic bacteria has been extensively revised. For some taxa there are several valid synonyms. Unless otherwise stated, the most recently published name is used in this list as the reference name (in bold italic) to which all other synonyms are referred. This does not mean that the reference name is always to be preferred. A synonym, i.e., a previously published name for the same organism, may represent a classification considered by individual scientists or groups to give a more coherent taxonomy and may be used. This list is presented by the International Society of Plant Pathology Committee on the Taxonomy of Plant Pathogenic Bacteria, Carolee T. Bull Convener.

Cyclic lipopeptides (CLPs) are versatile molecules produced by a variety of bacterial genera, including plant-associated Pseudomonas spp. CLPs are composed of a fatty acid tail linked to a short oligopeptide, which is cyclized to form a lactone ring between two amino acids in the peptide chain. CLPs are very diverse both structurally and in terms of their biological activity. The structural diversity is due to differences in the length and composition of the fatty acid tail and to variations in the number, type, and configuration of the amino acids in the peptide moiety. CLPs have received considerable attention for their antimicrobial, cytotoxic, and surfactant properties. For plant-pathogenic Pseudomonas spp., CLPs constitute important virulence factors, and pore formation, followed by cell lysis, is their main mode of action. For the antagonistic Pseudomonas sp., CLPs play a key role in antimicrobial activity, motility, and biofilm formation. CLPs are produced via nonribosomal synthesis on large, multifunctional peptide synthetases. Both the structural organization of the CLP synthetic templates and the presence of specific domains and signature sequences within peptide synthetase genes will be described for both pathogenic and antagonistic Pseudomonas spp. Finally, the role of various genes and regulatory mechanisms in CLP production by Pseudomonas spp., including two-component regulation and quorum sensing, will be discussed in detail. Additional keywords: Bacillus, nonribosomal peptide synthesis

Infection of Agaricus bisporus with Pseudomonas tolaasii or treatment with a tolaasin containing preparation resulted in the activation of tyrosinase and the development of a brown discolouration of the fruitbody. In order to investigate whether tolaasin is responsible for these reactions, mushrooms were treated with different concentrations of HPLC-purified tolaasin. Tolaasin was found to induce both browning and the activation of tyrosinase, with the level of activation being related to the concentration of toxin applied. In water-treated controls, active tyrosinase isoforms with pIs of 4.5 and 4.4 were the main isoforms found but tolaasin treatment resulted in the activation of a tyrosinase isoform with a pI of 5.7. The different active isoforms could be distinguished as the tolaasin activated isoforms had a higher affinity for catechol as a substrate (Km0.82 m m ) than the active isoforms in the control (Km2.86 m m ). In mushrooms inoculated with P. tolaasii or treated with tolaasin containing extracts no significant differences were found in the mechanism of oxidation of tyrosine, γ-glutaminyl-4-hydroxybenzene or γ-glutaminyl-3,4-dihydroxybenzene to form melanin. In tolaasin treated samples, a constant total amount of melanin and sum of the three phenols was found.

Pseudomonas tolaasii is a bacterium endemic to the compost beds where common mushroom (Agaricus bisporus) is cultivated. Under some environmental conditions still not well-determined, but influenced by temperature and relative humidity, the bacterium can become pathogenic and provoke the brown blotch disease. This review describes the interaction between P. tolaasii and A. bisporus that results in the appearance of brown spots on the mushroom caps, typical symptoms of the disease. Firstly, P. tolaasii is studied, the changes in pathogenicity are explained, the compounds that provoke the damage are enumerated as well as various experimental methods to identify the pathogenic form of the bacteria. Secondly, mechanisms involved in the formation of the brown colour on the A. bisporus caps upon infection are briefly mentioned, taking into account the enzymes that catalyse the reaction, their mechanism, substrates and reaction products. Afterwards, a detailed description of the infection process is presented step by step, starting by the chemotactical attraction, fixation, secretion of the toxins, membrane breakdown, effect of the toxin on mushroom polyphenol oxidases and on the discolouration reaction. A possible mechanism of infection is hypothesised at the molecular level. Finally, the strategies tested until now to control the disease are discussed.

Brown blotch disease of mushrooms is caused by the Gram-negative bacterium Pseudomonas tolaasii [1-3]. The disease symptoms are characteristic brown sunken lesions on the mushroom cap and stipe, which make affected mushrooms unmarketable. These lesions arise due to collapse of fungal hyphae and the consequent release of tyrosinase activity [4]. The mushroom crop is a very lucrative protected horticultural commodity with an estimated world-wide value of over £1 billion per annum. Up to 20% of this crop is lost or downgraded as a result of P. tolaasii infection. P. tolaasii is thus an important biotic factor responsible for mushroom crop loss and is endemic in many mushroom farms [3]. Development of new methods of disease control, through an understanding of the disease process, is therefore an important aim.

The alpha-helix is a common element of secondary structure in proteins and peptides. In eukaryotic organisms, which exclusively incorporate L-amino acids into such molecules, stereochemical interactions make such alpha-helices, invariably right-handed. Pseudomonas tolaasii Paine is the causal organism of the economically significant brown blotch disease of the cultivated mushroom Agaricus bisporus (Lange) Imbach. P. Tolaasii proceduces an extracellular lipodepsipeptide toxin, tolaasin, which causes the brown pitted lesions on the mushroom cap. Circular dichroism studies on tolaasin in a membrane-like environment indicate the presence of a left-handed alpha-helix, probably formed by a sequence of 7 D-amino acids in the peptide. P. tolaasii represents the first reported example of an organism which has evolved the ability to biosynthesize a left-handed alpha-helix.

A brown blotch disease of cultivated mushrooms, caused byPseudomonas Tolaasi Paine, has been studied. To get infection under artificial conditions the bacteria had to be grown on media containing extracts from meat or mushrooms. The mushroom extracts were obtained from pilei and pure culture mycelium, with hot as well as with cold water. Under natural conditions old mycelium in the casing soil and stumps of mushrooms left on the beds after picking may provide for the active substances, which probably are extracted and splashed by the water used in spraying the beds. Trashing the beds will cut down the rate of blotched mushrooms.Pseudomonas Tolaasi proved to be resistant to the bactericides tested.