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Fungal Pathogens (fungal + pathogen)
Kinds of Fungal Pathogens Terms modified by Fungal Pathogens Selected AbstractsFungal pathogens associated with melon collapse in Spain,EPPO BULLETIN, Issue 2 2000J. García-Jiménez Spain produces 43 200 ha of melons with a considerable export to European markets. In the last 10 years, melon cultivation in Spain has decreased more than 40% due mainly to collapse of the vines caused by soil-borne diseases. Serious economic losses have resulted. In order better to understand the aetiology of this disease, a survey of 217 melon fields throughout the melon production areas of Spain was conducted from 1987 to 1996 to analyse the fungal population associated with roots. In addition, the presence of melon necrotic spot carmovirus (MNSV) was studied in 93 fields. This virus is present mainly in southeastern Spain. The predominant fungal species isolated from 82.5% of sampled fields with symptoms of collapse was Acremonium cucurbitacearum. Roots affected by this fungus show corky brown areas soon after transplanting. Small secondary roots and root hairs become necrotic, although there is continuous production of new rootlets. This process continues until the late stages of the disease. As the fruits approach maturity, the entire plant wilts and dies. Other fungal species associated with melon collapse are: Monosporascus cannonballus (isolated from 29.5% of sampled fields), Macrophomina phaseolina (32.7%) and Rhizoctonia solani (31.8%). Of these, the incidence of M. cannonballus isolated from diseased melons has increased substantially over the past 10 years. Melon collapse in Spain is complex because several fungi capable of causing collapse of the vines are prevalent and often isolated from roots in the same field. In addition, other minor pathogens, such as Rhizopycnis vagum and Plectosporium tabacinum, are frequently isolated from symptomatic vines and may also contribute to the death of the plants. [source] Calystegines in Calystegia sepium do not Inhibit Fungal Growth and Invertase Activity but Interact with Plant InvertasePLANT BIOLOGY, Issue 2 2004D. Höke Abstract: Calystegines are alkaloidal glycosidase inhibitors. They accumulate predominantly in young and meristemic parts of Calystegia sepium (Convolvulaceae). C. sepium, bindweed, infests meadows and cereal fields and is difficult to control chemically. Fungal pathogens against C. sepium are established as mycoherbicides. Stagonospora convolvuli LA39 attacks C. sepium and does not affect crop plants, but young plants of C. sepium are less susceptible to the fungus. The interaction of Stagonospora convolvuli with calystegines was investigated. Further, endophytic fungi of several classes were isolated from wild-grown Calystegia sepium leaves, and selected strains were tested for interaction with calystegines. Fungal growth on agar containing calystegines was not affected considerably. Plants in climate chambers were infected with an endophyte, Phomopsis, and with the fungal pathogen, Stagonospora convolvuli. Calystegine levels were measured in infected and non-infected plant tissues. Accumulation depended on developmental stage of the plant tissue and was not influenced by infection. Acid invertase was measured from fungal mycelia and from infected and non-infected plant tissues. Fungal acid invertase activity was not inhibited by 10 mM calystegine B2, while invertase from C. sepium leaves was inhibited. It is concluded that calystegines do not inhibit fungal development and sucrose consumption under the conditions of the present investigation, but may act by redirection of plant carbohydrate metabolism. [source] Phialemonium curvatum Prosthetic Valve Endocarditis with an Unusual Echocardiographic PresentationECHOCARDIOGRAPHY, Issue 6 2006Azriel Osherov M.D. Phialemonium species, an opportunistic fungal pathogen rarely causes invasive disease, have been described as opportunistic infection agents in humans, mainly as a result of immunosuppression and very rarely involves the heart. We present a case of a patient with Phialemonium curvatum prosthetic aortic valve endocarditis with an unusual initial transesophageal echocardiography (TEE) presentation, illustrating the important role of repeat TEE for the proper diagnosis and management of infective endocarditis. [source] Thermal biology of the meadow grasshopper, Chorthippus parallelus, and the implications for resistance to diseaseECOLOGICAL ENTOMOLOGY, Issue 6 2005Simon Springate Abstract., 1.,The thermal biology of the meadow grasshopper, Chorthippus parallelus, a common, habitat generalist acridid species found in the U.K., was characterised and the influence of thermoregulatory behaviour for resistance against a temperate (Beauveria bassiana) and tropical (Metarhizium anisopliae var. acridum) fungal pathogen was determined. 2.,Chorthippus parallelus was found to be an active behavioural thermoregulator, with a preferred temperature range of 32,35 °C. 3.,Both pathogens proved lethal to fifth instar and adult grasshoppers. No evidence of behavioural fever in response to infection by either pathogen was found, but normal thermoregulation was found to reduce virulence and spore production of B. bassiana. Normal thermoregulation did not appear to affect M. anisopliae var. acridum. 4.,These results suggest that the effects of temperature on host resistance depend on the thermal sensitivity of the pathogen and, in this case, derive from direct effects of temperature on pathogen growth rather than indirect effects mediated by host immune response. 5.,The implications for possible risks of exotic pathogens and influence of climate change are discussed. [source] Behavioural changes in Schistocerca gregaria following infection with a fungal pathogen: implications for susceptibility to predationECOLOGICAL ENTOMOLOGY, Issue 3 2001Steven Arthurs Summary 1. Field observations have indicated that infection of locusts and grasshoppers by the fungal entomopathogen Metarhizium anisopliae var. acridum may result in a substantial increase in the host's susceptibility to predation, before death is caused directly by the disease. 2. Laboratory experiments were conducted to examine how the behaviour of the desert locust Schistocerca gregaria Forskål changes following infection by M. anisopliae var. acridum to explore some potential mechanisms underlying this phenomenon. 3. In the first experiment, which involved monitoring general locust activity in small cages throughout the disease incubation period, infected locusts were observed to increase locomotion and bodily movement from 3 days after infection until death (average survival time of 11 days). There was some evidence of reduced feeding and mating behaviour following infection. 4. In a second experiment, locusts were exposed individually to a simulated predator attack and the initiation and strength of any escape responses were measured. Infected locusts were observed to have a reduced escape capability (both the propensity to escape and the strength of the response). In contrast to the relatively early changes in general activity observed in the first experiment, this was only apparent at the late stages of infection shortly before death. 5. Both an increase in movement and general apparency early in the infection process, and reduced escape capability late on, suggest mechanisms whereby the susceptibility of locusts and grasshoppers to predation might be enhanced following infection with M. anisopliae var. acridum. [source] Temperature checks the Red Queen?ECOLOGY LETTERS, Issue 1 2003Resistance, virulence in a fluctuating environment Abstract Numerous studies have revealed genetic variation in resistance and susceptibility in host,parasite interactions and therefore the potential for frequency-dependent selection (Red Queen dynamics). Few studies, if any, have considered the abiotic environment as a mediating factor in these interactions. Using the pea aphid, Acyrthosiphon pisum, and its fungal pathogen, Erynia neoaphidis, as a model host,parasite system, we demonstrate how temperature can mediate the expression of genotypic variation for susceptibility and virulence. Whilst previous studies have revealed among-clone variation in aphid resistance to this pathogen, we show that resistance rankings derived from assessments at one temperature, are not conserved across differing temperature regimes. We suggest that variation in environmental temperature, through its nonlinear impact on parasite virulence and host defence, may contribute to the general lack of evidence for frequency-dependent selection in field systems. [source] Resting spore formation of aphid-pathogenic fungus Pandora nouryi depends on the concentration of infective inoculumENVIRONMENTAL MICROBIOLOGY, Issue 7 2008Zhi-Hong Huang Summary Resting spore formation of some aphid-pathogenic Entomophthorales is important for the seasonal pattern of their prevalence and survival but this process is poorly understood. To explore the possible mechanism involved in the process, Pandora nouryi (obligate aphid pathogen) interacted with green peach aphid Myzus persicae on cabbage leaves under favourable conditions. Host nymphs showered with primary conidia of an isolate (LC50: 0.9,6.7 conidia mm,2 4,7 days post shower) from air captures in the low-latitude plateau of China produced resting spores (azygospores), primary conidia or both spore types. Surprisingly, the proportion of mycosed cadavers forming resting spores (Pcfrs) increased sharply within the concentrations (C) of 28,240 conidia mm,2, retained high levels at 240,1760, but was zero or extremely low at 0.3,16. The Pcfrs,C relationship fit well the logistic equation Pcfrs = 0.6774/[1 + exp(3.1229,0.0270C)] (r2 = 0.975). This clarified for the first time the dependence of in vivo resting spore formation of P. nouryi upon the concentration of infective inoculum. A hypothesis is thus proposed that some sort of biochemical signals may exist in the host,pathogen interaction so that the fungal pathogen perceives the signals for prompt response to forthcoming host-density changes by either producing conidia for infecting available hosts or forming resting spores for surviving host absence in situ. [source] RAPID SPECIATION FOLLOWING RECENT HOST SHIFTS IN THE PLANT PATHOGENIC FUNGUS RHYNCHOSPORIUMEVOLUTION, Issue 6 2008Pascal L. Zaffarano Agriculture played a significant role in increasing the number of pathogen species and in expanding their geographic range during the last 10,000 years. We tested the hypothesis that a fungal pathogen of cereals and grasses emerged at the time of domestication of cereals in the Fertile Crescent and subsequently speciated after adaptation to its hosts. Rhynchosporium secalis, originally described from rye, causes an important disease on barley called scald, although it also infects other species of Hordeum and Agropyron. Phylogenetic analyses based on four DNA sequence loci identified three host-associated lineages that were confirmed by cross-pathogenicity tests. Bayesian analyses of divergence time suggested that the three lineages emerged between ,1200 to 3600 years before present (B.P.) with a 95% highest posterior density ranging from 100 to 12,000 years B.P. depending on the implemented clock models. The coalescent inference of demographic history revealed a very recent population expansion for all three pathogens. We propose that Rhynchosporium on barley, rye, and Agropyron host species represent three cryptic pathogen species that underwent independent evolution and ecological divergence by host-specialization. We postulate that the recent emergence of these pathogens followed host shifts. The subsequent population expansions followed the expansion of the cultivated host populations and accompanying expansion of the weedy Agropyron spp. found in fields of cultivated cereals. Hence, agriculture played a major role in the emergence of the scald diseases, the adaptation of the pathogens to new hosts and their worldwide dissemination. [source] NATURAL SELECTION ON A POLYMORPHIC DISEASE-RESISTANCE LOCUS IN IPOMOEA PURPUREAEVOLUTION, Issue 2 2007Joel M. Kniskern Although disease-resistance polymorphisms are common in natural plant populations, the mechanisms responsible for this variation are not well understood. Theoretical models predict that balancing selection can maintain polymorphism within a population if the fitness effects of a resistance allele vary from a net cost to a net benefit, depending upon the extent of pathogen damage. However, there have been a few attempts to determine how commonly this mechanism operates in natural plant,pathogen interactions. Ipomoea purpurea populations are often polymorphic for resistance and susceptibility alleles at a locus that influences resistance to the fungal pathogen, Coleosporium ipomoeae. We measured the fitness effects of resistance over three consecutive years at natural and manipulated levels of damage to characterize the type of selection acting on this locus. Costs of resistance varied in magnitude from undetectable to 15.5%, whereas benefits of resistance sometimes equaled, but never exceeded, these costs. In the absence of net benefits of resistance at natural or elevated levels of disease, we conclude that selection within individual populations of I. purpurea probably does not account completely for maintenance of this polymorphism. Rather, the persistence of this polymorphism is probably best explained by a combination of variable selection and meta-population processes. [source] High expression of a sucrose non-fermenting (SNF1)-related protein kinase from Colletotrichum gloeosporoides f. sp. malvae is associated with penetration of Malva pusilla,FEMS MICROBIOLOGY LETTERS, Issue 2 2002Paul H Goodwin Abstract A sucrose non-fermenting (SNF1)-related protein kinase homologue, cgsnf, from Colletotrichum gloeosporoides f. sp. malvae, a hemibiotrophic fungal pathogen of round-leaved mallow (Malva pusilla) was examined. During infection, cgsnf showed a large peak in expression relative to a constitutively expressed fungal actin gene when appressoria had formed during the penetration phase and then showed much lower expression levels during subsequent necrotrophic growth in the host. In pure culture with glucose or glycerol as sole carbon sources, expression levels were similar to that during necrotrophic growth. Expression was consistently higher in glycerol than in glucose cultures, which may reflect a lower cellular energy status in the fungus. These results are consistent with cgsnf having a role in transmitting nutritional signals, which may be involved with host penetration. [source] Identification of salivary components that induce transition of hyphae to yeast in Candida albicansFEMS YEAST RESEARCH, Issue 7 2009Jelani T.D. Leito Abstract Candida albicans, the major human fungal pathogen, undergoes a reversible morphological transition from single yeast cells to pseudohyphae and hyphae filaments. The hyphae form is considered the most invasive form of the fungus. The purpose of this study is to investigate the effect of saliva on hyphae growth of C. albicans. Candida albicans hyphae were inoculated in Roswell Park Memorial Institute medium with whole saliva, parotid saliva or buffer mimicking the saliva ion composition, and cultured for 18 h at 37 °C under aerobic conditions with 5% CO2. Whole saliva and parotid saliva induced transition to yeast growth, whereas the culture with buffer remained in the hyphae form. Parotid saliva was fractionated on a reverse-phase C8 column and each fraction was tested for inducing transition to yeast growth. By immunoblotting, the salivary component in the active fraction was identified as statherin, a phosphoprotein of 43 amino acids that has been implicated in remineralization of the teeth. Synthetically made statherin induced transition of hyphae to yeast. By deletion of five amino acids at the negatively charged N-terminal site (DpSpSEE), yeast-inducing activity and binding to C. albicans were increased. In conclusion, statherin induces transition to yeast of C. albicans hyphae and may thus contribute to the oral defense against candidiasis. [source] Promoter regulation in Candida albicans and related speciesFEMS YEAST RESEARCH, Issue 1 2009Sabine E. Eckert Abstract Regulation of gene expression has been studied extensively in Saccharomyces cerevisiae and Schizosaccharomyces pombe. Some, but by far not all, of the findings are also applicable to Candida albicans, an important ascomycete fungal pathogen of humans. Areas of research in C. albicans include the influence of key signal transduction cascades on morphology, and the response to host-generated influences, such as host immune effector cells, blood, pH or elevated carbon dioxide. The resistance to antifungal agents and response to stress are also well researched. Conditional gene expression and reporter genes adapted to the codon usage of C. albicans are now widely used in C. albicans. Here we present a comprehensive overview of the current techniques used to investigate regulation mechanisms for promoters in C. albicans and other Candida species. In addition, we discuss reporter genes used for the study of gene expression. [source] Analysis of the Paracoccidioides brasiliensis triosephosphate isomerase suggests the potential for adhesin functionFEMS YEAST RESEARCH, Issue 8 2007Luiz Augusto Pereira Abstract Paracoccidioides brasiliensis is an important fungal pathogen. The disease it causes, paracoccidioidomycosis (PCM), ranges from localized pulmonary infection to systemic processes that endanger the life of the patient. Paracoccidioides brasiliensis adhesion to host tissues contributes to its virulence, but we know relatively little about molecules and the molecular mechanisms governing fungal adhesion to mammalian cells. Triosephosphate isomerase (TPI: EC 5.3.1.1) of P. brasiliensis (PbTPI) is a fungal antigen characterized by microsequencing of peptides. The protein, which is predominantly expressed in the yeast parasitic phase, localizes at the cell wall and in the cytoplasmic compartment. TPI and the respective polyclonal antibody produced against this protein inhibited the interaction of P. brasiliensis to in vitro cultured epithelial cells. TPI binds preferentially to laminin, as determined by peptide inhibition assays. Collectively, these results suggest that TPI is required for interactions between P. brasiliensis and extracellular matrix molecules such as laminin and that this interaction may play an important role in the fungal adherence and invasion of host cells. [source] Yeast diversity sampling on the San Juan Islands reveals no evidence for the spread of the Vancouver Island Cryptococcus gattii outbreak to this localeFEMS YEAST RESEARCH, Issue 4 2006James A. Fraser Abstract Biological diversity has been estimated for various phyla of life, such as insects and mammals, but in the microbe world is has been difficult to determine species richness and abundance. Here we describe a study of species diversity of fungi with a yeast-like colony morphology from the San Juan Islands, a group of islands that lies southeast of Vancouver Island, Canada. Our sampling revealed that the San Juan archipelago biosphere contains a diverse range of such fungi predominantly belonging to the Basidiomycota, particularly of the order Tremellales. One member of this group, Cryptococcus gattii, is the etiological agent of a current and ongoing outbreak of cryptococcosis on nearby Vancouver Island. Our sampling did not, however, reveal this species. While the lack of recovery of C. gattii does not preclude its presence on the San Juan Islands, our results suggest that the Strait of Juan de Fuca may be serving as a geographical barrier to restrict the dispersal of this primary human fungal pathogen into the United States. [source] Upward range extension of Andean anurans and chytridiomycosis to extreme elevations in response to tropical deglaciationGLOBAL CHANGE BIOLOGY, Issue 1 2007TRACIE A. SEIMON Abstract High-alpine life forms and ecosystems exist at the limits of habitable environments, and thus, are especially sensitive to environmental change. Here we report a recent increase in the elevational limit of anurans following glacial retreat in the tropical Peruvian Andes. Three species have colonized ponds in recently deglaciated terrain at new record elevations for amphibians worldwide (5244,5400 m). Two of these species were also found to be infected with Batrachochytrium dendrobatidis (Bd), an emerging fungal pathogen causally associated with global amphibian declines, including the disappearance of several Latin American species. The presence of this pathogen was associated with elevated mortality rates of at least one species. These results represent the first evidence of upward expansion of anurans to newly available habitat brought about by recent deglaciation. Furthermore, the large increase in the upper limit of known Bd infections, previously reported as 4112 m in Ecuador, to 5348 m in this study, also expands the spatial domain of potential Bd pathogenicity to encompass virtually all high elevation anuran habitats in the tropical Andes. [source] Cutaneous Hyalohyphomycosis Secondary to Paecilomyces Species Treated with Voriconazole in an Immune Compentent HostJOURNAL OF CUTANEOUS PATHOLOGY, Issue 1 2005H. Skelton Paecilomyces, a hyalohyphomycosis, is an uncommon cause of cutaneous and subcutaneous infections. Most cases reported have occurred in patients with impaired host defenses or following a surgical procedure, and have proven highly resistant to anti fungal therapies. A 60-year-old man presented with scattered non-healing verrucous lesions as well as ulcers and excoriations on the upper extremities and trunk. The lesion had begun shortly after the patient was scratched by prickly okra. The patient had no underlying health problems and he was on no medication. Histology revealed epidermal hyperkeratosis, acanthosis, with papillomatosis with intraepidermal micro-abscess formation. Within the dermis there was a mixed acute and chronic granulomatous infiltrate. With GMS stain numerous pleomorphic yeast forms and pseudohyphael forms were seen. Cultures confirmed Paecilomyces species. The patient was treated with Voriconazole with complete resolution of his lesion. Paecilomyces is an emerging fungal pathogen, which in our immune competent patient manifest as widespread cutaneous disease. [source] Conservation biological control with the fungal pathogen Pandora neoaphidis: implications of aphid species, host plant and predator foragingAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 1 2005S. Ekesi Abstract 1,Pandora neoaphidis is an important aphid-specific fungal pathogen in temperate agroecosystems. Laboratory studies were carried out to obtain baseline data on factors that may affect its performance in conservation biological control. 2,Virulence of P. neoaphidis was assessed in dose,response bioassays against Microlophium carnosum on nettle, Uroleucon jaceae on knapweed, Acyrthosiphon pisum on bean and bird's-foot trefoil Lotus corniculatus, and Metopolophium dirhodum on barley and Yorkshire fog Holcus lanatus. The most susceptible aphid was A. pisum feeding on bean with an LD50 of 19 conidia per mm2, whereas U. jaceae had an LD50 of 104 conidia per mm2 and was least susceptible to infection. 3,The presence of foraging adult ladybirds, Coccinella septempunctata, increased transmission of P. neoaphidis from infected cadavers to apterae of M. carnosum, U. jacea, and A. pisum by 7,30% at the largest cadaver density tested. Adult coccinellids that had previously foraged on nettle, knapweed, bean or bird's-foot trefoil transfered conidia to A. pisum on bean and induced infections in 2,13% of aphids. 4,Conidia of P. neoaphidis dispersed passively in the airstream from sporulating M. carnosum cadavers on nettle plants and initiated infections in A. pisum colonies feeding on bean (4,33%) or M. dirhodum on barley (3%) located within 1.0 m of the nettle source. 5,The results suggest that M. carnosum and A. pisum may be more useful as reservoirs for P. neoaphidis in noncrop and crop areas than U. jaceae or M. dirhodum, and infection and dispersal between habitats could be enhanced in the presence of coccinellids. [source] Analysis of the Italian Dutch Elm Disease Fungal PopulationJOURNAL OF PHYTOPATHOLOGY, Issue 2 2005A. Santini Abstract Sixty-two Ophiostoma ulmi sensu lato strains have been collected from symptomatic trees in seven areas of Central Italy. Isolates were compared with 10 reference strains, belonging to the species O. ulmi and to the two subspecies of O. novo-ulmi, in order to establish the genetic variability within the Italian population of this fungal pathogen. The structure of the population has been analysed by means of morpho-physiological features and of the direct amplification of minisatellite-region DNA polymerase chain reaction (DAMD-PCR) by using the M13 core sequence. The DNA profiles have been compared with taxonomic parameters (growth rate, culture aspect and fertility barriers). Taxa could thus be well separated. None of the isolates collected was recognized as O. ulmi. Isolates assigned to the two subspecies of O. novo-ulmi (novo ulmi and americana) by means of the fertility test, showed short genetic distances with the respective reference strains and they constituted subgroups according to their geographical origin. The high level of variation detected indicates a postepidemic situation in Italy. Some inconsistency was found within the subspecies clusters. Several isolates, assigned to subspecies americana using fertility test, were in the novo-ulmi cluster and vice versa. A possible explanation is that these isolates are americana,novo-ulmi hybrids. [source] Screening method to identify inhibitors of siderophore biosynthesis in the opportunistic fungal pathogen, Aspergillus fumigatusLETTERS IN APPLIED MICROBIOLOGY, Issue 1 2009L.J. Pinto Abstract Aims:,Aspergillus fumigatus is the most common cause of airborne mould infections in immunocompromised patients worldwide. Our aim was to develop a method to identify agents that inhibit siderophore biosynthesis because this pathway is unique to the fungus and is essential for virulence. Methods and Results:, A high-throughput two-step screening assay was developed using 96-well plates in which fungal growth and siderophore production is assessed spectrophotometrically. If a compound inhibits growth only in iron-limited medium (screen 1), its effect on siderophore production is then determined (screen 2). The proof of concept was demonstrated using a known antifungal agent, amphotericin B, and a strain of A. fumigatus deficient in siderophore production. Conclusions:, The two-stage screening method clearly identified growth defects in A. fumigatus related specifically to siderophore biosynthesis. Significance and Impact of the Study:, The increasing incidence of life-threatening fungal infections has produced an urgent need for novel antifungal agents. The method described in this report will facilitate the identification of novel antifungal compounds that inhibit a pathway critical for A. fumigatus virulence and have a reduced probability of affecting host metabolism. [source] Microsatellite loci for the fungus Ascosphaera apis: cause of honey bee chalkbrood diseaseMOLECULAR ECOLOGY RESOURCES, Issue 3 2009STEPHEN A. REHNER Abstract The fungus Ascosphaera apis is a worldwide fungal pathogen of honey bees. To provide tools for understanding the dispersal history of this pathogen, strain differences in virulence, and host,pathogen interactions, we used the draft genome assembly of A. apis to develop microsatellite loci for this species. We present testing results for 25 scorable loci revealing two to eight alleles per locus in a survey of Maryland isolates of this fungus. [source] Microsatellite markers for the red band needle blight pathogen, Dothistroma septosporumMOLECULAR ECOLOGY RESOURCES, Issue 5 2008I BARNES Abstract Twelve microsatellite markers were developed for population analyses of the fungal pathogen, Dothistroma septosporum. Intersimple sequence repeat polymerase chain reaction (ISSR-PCR) and an enrichment protocol (fast isolation by amplified fragment length polymorphism of sequences containing repeats [FIASCO]) were both used to identify 28 unique microsatellite regions in the genome. From 22 primer pairs designed, 12 were polymorphic. These markers, screened on two populations representing 42 isolates, produced 40 alleles across all loci with an allelic diversity of 0.09,0.76 per locus. Cross-species amplification showed variable success with Dothistroma rhabdoclinis and Mycosphaerella dearnessi and some sequence variation within isolates of Dothistroma pini. These markers will be used to further study the population structure and diversity of D. septosporum. [source] Development of polymorphic markers for the root pathogen Thielaviopsis basicola using ISSR-PCRMOLECULAR ECOLOGY RESOURCES, Issue 4 2004MARIA M. GELDENHUIS Abstract Thielaviopsis basicola is a soil-borne fungal pathogen affecting many important agricultural crops. Little is known regarding the population biology or origin of this pathogen. Polymorphic markers developed for Ceratocystis fimbriata, a species complex phylogenetically closely related to T. basicola, were tested and found not to be useful for T. basicola. In this study 14 primer pairs, seven of which resulted in the amplification of single polymorphic fragments in T. basicola were developed. These primers will enable further studies on this economically important pathogen, and will result in an enhanced understanding of its population structure in different parts of the world. [source] Development and characterization of microsatellite markers for the fungus Ceratocystis fimbriataMOLECULAR ECOLOGY RESOURCES, Issue 2 2004J. Steimel Abstract Ceratocystis fimbriata is a serious fungal pathogen on a wide range of plants, but many cryptic species within C. fimbriata are apparently host-specialized. Anchor polymerase chain reaction (PCR) and simple sequence repeat (SSR) enriched libraries were used to develop 16 microsatellite markers for C. fimbriata. All markers were polymorphic when tested against isolates from four host-specialized lineages of the pathogen. These markers will be valuable for phylogenetic and population genetic studies, as well as for tracking accidental introductions of host-specialized forms of the pathogen. [source] PMT family of Candida albicans: five protein mannosyltransferase isoforms affect growth, morphogenesis and antifungal resistanceMOLECULAR MICROBIOLOGY, Issue 2 2005Stephan K.-H. Summary Protein O -mannosyltransferases (Pmt proteins) initiate O- mannosylation of secretory proteins. The PMT gene family of the human fungal pathogen Candida albicans consists of PMT1 and PMT6, as well as three additional PMT genes encoding Pmt2, Pmt4 and Pmt5 isoforms described here. Both PMT2 alleles could not be deleted and growth of conditional strains, containing PMT2 controlled by the MET3- or tetOScHOP1- promoters, was blocked in non-permissive conditions, indicating that PMT2 is essential for growth. A homozygous pmt4 mutant was viable, but synthetic lethality of pmt4 was observed in combination with pmt1 mutations. Hyphal morphogenesis of a pmt4 mutant was defective under aerobic induction conditions, yet increased in embedded or hypoxic conditions, suggesting a role of Pmt4p-mediated O- glycosylation for environment-specific morphogenetic signalling. Although a PMT5 transcript was detected, a homozygous pmt5 mutant was phenotypically silent. All other pmt mutants showed variable degrees of supersensitivity to antifungals and to cell wall-destabilizing agents. Cell wall composition was markedly affected in pmt1 and pmt4 mutants, showing a significant decrease in wall mannoproteins. In a mouse model of haematogenously disseminated infection, PMT4 was required for full virulence of C. albicans. Functional analysis of the first complete PMT gene family in a fungal pathogen indicates that Pmt isoforms have variable and specific roles for in vitro and in vivo growth, morphogenesis and antifungal resistance. [source] Phospholipase C-mediated calcium signalling is required for fungal development and pathogenicity in Magnaporthe oryzaeMOLECULAR PLANT PATHOLOGY, Issue 3 2009HEE-SOOL RHO SUMMARY Calcium signalling has profound implications in the fungal infection of plants and animals, during which a series of physiological and morphological transitions are required. In this article, using a model fungal pathogen, Magnaporthe oryzae, we demonstrate that the regulation of the intracellular calcium concentration ([Ca2+]int) is essential for fungal development and pathogenesis. Imaging of [Ca2+]int showed that infection-specific morphogenesis is highly correlated with the spatiotemporal regulation of calcium flux. Deletion of the fungal phospholipase C gene (M. oryzae phospholipase C 1, MoPLC1) suppressed calcium flux, resulting in a fungus defective in developmental steps, including appressorium formation and pathogenicity. Surprisingly, the PLC-,1 gene of mouse was able to functionally substitute for MoPLC1 by restoring the calcium flux, suggesting the evolutionary conservation of the phospholipase C-mediated regulation of calcium flux. Our results reveal that MoPLC1 is a conserved modulator of calcium flux that is essential for the regulation of key steps in fungal development and pathogenesis. [source] Characterisation of the CipC-like protein AFUA_5G09330 of the opportunistic human pathogenic mould Aspergillus fumigatusMYCOSES, Issue 4 2010Bettina Bauer Summary,Aspergillus fumigatus is currently the major airborne fungal pathogen that menaces immunocompromised individuals. Germination of inhaled conidia is a hallmark of the early infection process, but little is known about the underlying mechanisms. The intention of our ongoing studies is the identification of A. fumigatus proteins that are differentially expressed during germination and may provide insights in the germination process. Using a proteomic approach, we identified AFUA_5G09330 as a major hyphal-specific protein. This result was confirmed using monoclonal antibodies generated in this study. AFUA_5G09330 belongs to a fungal-specific protein family. The eponymous CipC protein of A. nidulans has been shown to be induced by concanamycin A, and transcriptional data from Cryptococcus neoformans demonstrate a strong up-regulation of the expression of a homologous gene during infection. Our data provide evidence that AFUA_5G09330 is a monomeric, cytoplasmic protein. We found no evidence for an overexpression of AFUA_5G09330 induced by concanamycin A or other stress conditions. AFUA_5G09330 is exclusively found in the hyphal morphotype that enables an invasive growth of A. fumigatus during infection. Further studies are required to define the biological function of this hyphae-specific protein and its potential relevance for the pathogenicity of A. fumigatus. [source] Community lifestyle of Candida in mixed biofilms: a mini reviewMYCOSES, Issue 6 2009Z. M. Thein Summary Candida is the most common human fungal pathogen that causes a variety of afflictions from superficial mucosal infections to deep mycoses. Biofilm formation is a major virulence factor of Candida, and more than 300 articles have been published on Candida biofilms over the past two decades. However, most of these data are on monospecies biofilms of Candida, and information on mixed-species Candida biofilms or bacteria,Candida combinations is still scarce. Yet, in nature, the yeast exist in a mixed milieu either in the oral cavity or in other habitats with a multitude of bacteria colonising mucosal surfaces within a shared community. This mini review describes the current knowledge on candidal,candidal or bacterial,candidal interactions in mixed-species biofilms. The underlying mechanisms of these interactions appear to depend on several factors relating to biofilm development, such as species and strains of organisms, nutritional factors, aerobiosis and related environmental factors. Although the fundamental nature of these interactions appears to be commensalism and antagonism, the emerging evidence based on novel molecular, proteomic and imaging tools indicates these biological mechanisms to be far more complex than hitherto recognised. Demystifying the mechanisms underlying the growth and development of mixed-species communities involving Candida will undoubtedly yield useful data for the effective management of microbial infections in general. [source] Candida dubliniensis: first identification in Sfax hospital, TunisiaMYCOSES, Issue 2 2009M. Khlif Summary Candida dubliniensis, a newly described fungal pathogen associated mainly to immunocompromised host's infection, is phenotypically closely related to C. albicans. In this study, we report for the first time, isolation and identification, in Tunisia, of 14 isolates of C. dubliniensis from 12 human immunodeficiency virus-negative patients hospitalised in the intensive care unit (ICU) at Habib Bourguiba Sfax Hospital. Our study was firstly based on the failure to grow at 45 °C. This presumptive identification was completed by other tests: chlamydospore production, culture on Candiselect4 (Bio-Rad) and the commercial test Bichro-Dubli fumouze®, which specifically identify C. dubliniensis. The confirmation of the discrimination between both species was performed by PCR, targeting the hyphal wall protein (HWP1) gene. The recovery of C. dublinensis by routine laboratory diagnosis is recommended for elucidating the epidemiology of this novel pathogen. [source] Complement and fungal pathogens: an updateMYCOSES, Issue 6 2008Cornelia Speth Summary Fungal infections are a serious complication in immunocompromised patients such as human immunodeficiency virus-infected individuals, patients with organ transplantations or with haematological neoplasia. The lethality of opportunistic fungal infection is high despite a growing arsenal of antimycotic drugs, implying the urgent need for supportive immunological therapies to strengthen the current inefficient antimicrobial defences of the immunocompromised host. Therefore, increasing effort has been directed to investigating the interplay between fungi and the host immunity and thus to find starting points for additional therapeutic approaches. In this article, we review the actual state of the art concerning the role of complement in the pathogenesis of fungal infections. Important aspects include the activation of the complement system by the fungal pathogen, the efficiency of the complement-associated antimicrobial functions and the arsenal of immune evasion strategies applied by the fungi. The twin functions of complement as an interactive player of the innate immunity and at the same time as a modulator of the adaptive immunity make this defence weapon a particularly interesting therapeutic candidate to mobilise a more effective immune response and to strengthen in one fell swoop a broad spectrum of different immune reactions. However, we also mention the ,Yin-Yang' nature of the complement system in fungal infections, as growing evidence assigns to complement a contributory part in the pathogenesis of fungus-induced allergic manifestations. [source] POPULATION EXTINCTION IN DETERMINISTICAND STOCHASTIC DISCRETE-TIME EPIDEMIC MODELS WITH PERIODIC COEFFICIENTS WITH APPLICATIONS TO AMPHIBIAN POPULATIONSNATURAL RESOURCE MODELING, Issue 2 2006KEITH E. EMMERT ABSTRACT. Discrete-time deterministic and stochastic epidemic models are formulated for the spread of disease in a structured host population. The models have applications to a fungal pathogen affecting amphibian populations. The host population is structured according to two developmental stages, juveniles and adults. The juvenile stage is a post-metamorphic, nonreproductive stage, whereas the adult stage is reproductive. Each developmental stage is further subdivided according to disease status, either susceptible or infected. There is no recovery from disease. Each year is divided into a fixed number of periods, the first period represents a time of births and the remaining time periods there are no births, only survival within a stage, transition to another stage or transmission of infection. Conditions are derived for population extinction and for local stability of the disease-free equilibrium and the endemic equilibrium. It is shown that high transmission rates can destabilize the disease-free equilibrium and low survival probabilities can lead to population extinction. Numerical simulations illustrate the dynamics of the deterministic and stochastic models. [source] | |||||||||||||||||||||||||||||||||||||