Rapid Detection of Red Rot Disease Pathogens (Pythium chondricola and P. porphyrae) in Pyropia yezoensis (Rhodophyta) with PCR-RFLP.

Red rot disease is one of the best-known algal diseases infecting red algae Pyropia species. This disease decreases the quality and quantity of Pyropia aquaculture products in Korea, Japan, and China. Recently we found that Pythium chondricola (Oomycetes) infects blades of Pyropia yezoensis. Therefore, two Pythium species (P. chondricola and P. porphyrae) have been reported as red rot disease pathogens. In this study, we developed a species-specific molecular marker for distinguishing between the two red rot disease pathogens. Using a polymerase chain reaction restriction fragment length polymorphism method based on the mitochondrial cytochrome c oxidase subunit 2 (cox2) and nuclear ribosomal RNA large subunit regions, we classified these two Pythium species without a sequencing step. This new method had high specificity and efficiency for detecting red rot disease pathogens at the species level for both of the cultured and field samples. Therefore, the molecular markers developed in this study are effective for long-term monitoring of the infection and distribution pattern of each Pythium species in Pyropia aquaculture farms. Moreover, molecular monitoring can provide useful information for predicting infection and preventing mass mortality of Pyropia species by red rot disease.

Biocontrol Agents Reduce Progression and Mycotoxin Production of Fusarium graminearum in Spikelets and Straws of Wheat.

The aim of this study was to evaluate the interactions between wheat plant (spikelets and straws), a strain of mycotoxigenic pathogen Fusarium graminearum and commercial biocontrol agents (BCAs). The ability of BCAs to colonize plant tissue and inhibit the pathogen or its toxin production was observed throughout two phases of the life cycle of pathogens in natural conditions (colonization and survival). All evaluated BCAs showed effective reduction capacities of pathogenic traits. During establishment and the expansion stage, BCAs provoked an external growth reduction of F. graminearum (77-93% over the whole kinetic studied) and mycotoxin production (98-100% over the whole kinetic studied). Internal growth of pathogen was assessed with digital droplet polymerase chain reaction (ddPCR) and showed a very strong reduction in the colonization of the internal tissues of the spikelet due to the presence of BCAs (98% on average). During the survival stage, BCAs prevented the formation of conservation perithecia of the pathogen on wheat straw (between 88 and 98% of perithecia number reduction) and showed contrasting actions on the ascospores they contain, or perithecia production (-95% on average) during survival form. The mechanisms involved in these different interactions between F. graminearum and BCAs on plant matrices at different stages of the pathogen's life cycle were based on a reduction of toxins, nutritional and/or spatial competition, or production of anti-microbial compounds.

Insights into the Host Specificity of a New Oomycete Root Pathogen, Pythium brassicum P1: Whole Genome Sequencing and Comparative Analysis Reveals Contracted Regulation of Metabolism, Protein Families, and Distinct Pathogenicity Repertoire.

Pythium brassicum P1 Stanghellini, Mohammadi, Förster, and Adaskaveg is an oomycete root pathogen that has recently been characterized. It only attacks plant species belonging to Brassicaceae family, causing root necrosis, stunting, and yield loss. Since P. brassicum P1 is limited in its host range, this prompted us to sequence its whole genome and compare it to those of broad host range Pythium spp. such as P. aphanidermatum and P. ultimum var. ultimum. A genomic DNA library was constructed with a total of 374 million reads. The sequencing data were assembled using SOAPdenovo2, yielding a total genome size of 50.3 Mb contained in 5434 scaffolds, N50 of 30.2 Kb, 61.2% G+C content, and 13,232 putative protein-coding genes. Pythium brassicum P1 had 175 species-specific gene families, which is slightly below the normal average. Like P. ultimum, P. brassicum P1 genome did not encode any classical RxLR effectors or cutinases, suggesting a significant difference in virulence mechanisms compared to other oomycetes. Pythium brassicum P1 had a much smaller proportions of the YxSL sequence motif in both secreted and non-secreted proteins, relative to other Pythium species. Similarly, P. brassicum P1 had the fewest Crinkler (CRN) effectors of all the Pythium species. There were 633 proteins predicted to be secreted in the P. brassicum P1 genome, which is, again, slightly below average among Pythium genomes. Pythium brassicum P1 had only one cadherin gene with calcium ion-binding LDRE and DxND motifs, compared to Pythium ultimum having four copies. Pythium brassicum P1 had a reduced number of proteins falling under carbohydrate binding module and hydrolytic enzymes. Pythium brassicum P1 had a reduced complement of cellulase and pectinase genes in contrast to P. ultimum and was deficient in xylan degrading enzymes. The contraction in ABC transporter families in P. brassicum P1 is suggested to be the result of a lack of diversity in nutrient uptake and therefore host range.

Nep1-like proteins as a target for plant pathogen control.

The lack of efficient methods to control the major diseases of crops most important to agriculture leads to huge economic losses and seriously threatens global food security. Many of the most important microbial plant pathogens, including bacteria, fungi, and oomycetes, secrete necrosis- and ethylene-inducing peptide 1 (Nep1)-like proteins (NLPs), which critically contribute to the virulence and spread of the disease. NLPs are cytotoxic to eudicot plants, as they disturb the plant plasma membrane by binding to specific plant membrane sphingolipid receptors. Their pivotal role in plant infection and broad taxonomic distribution makes NLPs a promising target for the development of novel phytopharmaceutical compounds. To identify compounds that bind to NLPs from the oomycetes Pythium aphanidermatum and Phytophthora parasitica, a library of 587 small molecules, most of which are commercially unavailable, was screened by surface plasmon resonance. Importantly, compounds that exhibited the highest affinity to NLPs were also found to inhibit NLP-mediated necrosis in tobacco leaves and Phytophthora infestans growth on potato leaves. Saturation transfer difference-nuclear magnetic resonance and molecular modelling of the most promising compound, anthranilic acid derivative, confirmed stable binding to the NLP protein, which resulted in decreased necrotic activity and reduced ion leakage from tobacco leaves. We, therefore, confirmed that NLPs are an appealing target for the development of novel phytopharmaceutical agents and strategies, which aim to directly interfere with the function of these major microbial virulence factors. The compounds identified in this study represent lead structures for further optimization and antimicrobial product development.

Enhancing the Potentiality of Trichoderma harzianum against Pythium Pathogen of Beans Using Chamomile (Matricaria chamomilla, L.) Flower Extract.

Our present study was designed to investigate the role of both Trichoderma harzianum and chamomile (Matricaria chamomilla L.) flower extract in mutual reaction against growth of Pythium ultimum. In vitro, the activity of chamomile extract was found to reduce the radial growth of Pythium ultimum up to 30% compared to the control. Whereas, the radial growth reduction effect of T. harzianum against P. ultimum reached 81.6% after 120 h. Data also showed the productivity of total phenolics and total flavonoids by T. harzianum, was 12.18 and 6.33 mg QE/100 mL culture filtrate, respectively. However, these compounds were determined in chamomile flower extract at concentrations of 75.33 and 24.29 mg QE/100 mL, respectively. The fractionation of aqueous extract of chamomile flower using HPLC provided several polyphenolic compounds such as pyrogallol, myricetin, rosemarinic acid, catechol, p-coumaric acid, benzoic acid, chlorogenic acid and other minor compounds. In vivo, the potentiality of T. harzianum with chamomile flower extract against Pythium pathogen of bean was investigated. Data obtained showed a reduction in the percentage of rotted seed and infected seedling up to 28 and 8%, respectively. Whereas, the survival increased up to 64% compared to other ones. There was also a significant promotion in growth features, total chlorophyll, carotenoids, total polyphenols and flavonoids, polyphenol-oxidase and peroxidase enzymes compared to other ones. To the best of our knowledge, there are no reported studies that included the mutual association of fungus, T. harzianum with the extract taken from the chamomile flower against P. ultimum, either in vitro or in vivo. In conclusion, the application of both T. harzianum and/or M. chamomilla extracts in the control of bean Pythium pathogen showed significant results.

Efficacy of bioagents against Pythium deliense Meurs associated with yellowing of black pepper.

Yellowing and wilting of black pepper vines is a serious concern in many black pepper growing tracts where Pythium deliense was recently emerged as a pathogen from the rhizosphere of affected vines, which is proved to be pathogenic by Koch's postulates. As a measure to manage the symptoms, bioagents were evaluated against infection by P. deliense. Among the seven bioagents tested, Trichoderma harzianum and Streptomyces albulus showed 100% inhibition in vitro followed by one Streptomyces sp. and S. rimosus (75.33%). The potential ones were further evaluated under the hydroponic system in vivo by challenge inoculation. No root infection was noticed with T. harzianum and S. albulus inoculation, instead, the inoculated plants showed root regeneration. This suggests the efficiency of these bioagents on plant growth promotion as well as on disease suppression. Biochemical analysis of the hydroponic medium showed an increase in membrane conductivity in all the treatments except in T. harzianum. The release of phenolic compounds into the medium was lowest with T. harzianum indicating the prevention of pathogen invasion. In planta evaluation under greenhouse condition and field evaluation also showed the protective effect of T. harzianum and S. albulus with a reduction in the intensity of yellowing to an extent of 73.1% and 71.2%, respectively. The study revealed that T. harzianum and the actinomycete S. albulus had the potential to prevent the root rot caused by P. deliense.

Control of damping-off in tomato seedlings exerted by Serratia spp. strains and identification of inhibitory bacterial volatiles in vitro.

Serratia marcescens can be a plant growth promoting bacteria (PGPB) and an opportunistic human and plant pathogen. We have identified and characterized strains of related species of Serratia and evaluated their biological control of damping-off of tomato seeds caused by Pythium cryptoirregulare. Serratia ureilytica, S. bockelmannii and S. nevei were identified by phylogenetic analysis of partial gyrB gene sequence and average nucleotide identity (ANI). Tomato seeds inoculated with S. ureilytica ILBB 145 showed higher germination percentage and reduced damping-off in greenhouse experiment resembling a commercial operation, and volatiles produced by this strain caused the nearly complete inhibition in vitro of P. cryptoirregulare. Analysis of volatile organic compounds (VOCs) showed that ILBB 145 produced dimethyl disulfide (DMDS), which can partially account for this inhibition. Serratia bockelmannii ILBB 162 performance against damping-off was intermediate and the inhibition of P. cryptoirregulare in vitro was lower and explained by volatile and diffusible metabolites. Both strains augmented DMDS production in the presence of P. cryptoirregulare, suggesting this compound may play a role in the context of interspecific competition. Serratia nevei ILBB 219 showed the lowest inhibition of P. cryptoirregulare in vitro, no DMDS production, and no biocontrol in planta. Draft genomes of the three strains were annotated and individual genes and biosynthesis gene clusters were identified in relation with the observed phenotypes. We report S. ureilytica - a low risk species- with activity as a biological control agent and DMDS produced by this bacterial species putatively involved in seed and seedling protection against P. cryptoirregulare.

Feasibility of Volatile Biomarker-Based Detection of Pythium Leak in Postharvest Stored Potato Tubers Using Field Asymmetric Ion Mobility Spectrometry.

The study evaluates the suitability of a field asymmetric ion mobility spectrometry (FAIMS) system for early detection of the Pythium leak disease in potato tubers simulating bulk storage conditions. Tubers of Ranger Russet (RR) and Russet Burbank (RB) cultivars were inoculated with Pythium ultimum, the causal agent of Pythium leak (with negative control samples as well) and placed in glass jars. The headspace in sampling jars was scanned using the FAIMS system at regular intervals (in days up to 14 and 31 days for the tubers stored at 25 °C and 4 °C, respectively) to acquire ion mobility current profiles representing the volatile organic compounds (VOCs). Principal component analysis plots revealed that VOCs ion peak profiles specific to Pythium ultimum were detected for the cultivars as early as one day after inoculation (DAI) at room temperature storage condition, while delayed detection was observed for tubers stored at 4 °C (RR: 5th DAI and RB: 10th DAI), possibly due to a slower disease progression at a lower temperature. There was also some overlap between control and inoculated samples at a lower temperature, which could be because of the limited volatile release. Additionally, data suggested that the RB cultivar might be less susceptible to Pythium ultimum under reduced temperature storage conditions. Disease symptom-specific critical compensation voltage (CV) and dispersion field (DF) from FAIMS responses were in the ranges of -0.58 to -2.97 V and 30-84% for the tubers stored at room temperature, and -0.31 to -2.97 V and 28-90% for reduced temperature, respectively. The ion current intensities at -1.31 V CV and 74% DF showed distinctive temporal progression associated with healthy control and infected tuber samples.

Cyclic lipopeptide-producing Pseudomonas koreensis group strains dominate the cocoyam rhizosphere of a Pythium root rot suppressive soil contrasting with P. putida prominence in conducive soils.

Pseudomonas isolates from tropical environments have been underexplored and may form an untapped reservoir of interesting secondary metabolites. In this study, we compared Pseudomonas and cyclic lipopeptide (CLP) diversity in the rhizosphere of a cocoyam root rot disease (CRRD) suppressive soil in Boteva, Cameroon with those from four conducive soils in Cameroon and Nigeria. Compared with other soils, Boteva andosols were characterized by high silt, organic matter, nitrogen and calcium. Besides, the cocoyam rhizosphere at Boteva was characterized by strains belonging mainly to the P. koreensis and P. putida (sub)groups, with representations in the P. fluorescens, P. chlororaphis, P. jessenii and P. asplenii (sub)groups. In contrast, P. putida isolates were prominent in conducive soils. Regarding CLP diversity, Boteva was characterized by strains producing 11 different CLP types with cocoyamide A producers, belonging to the P. koreensis group, being the most abundant. However, putisolvin III-V producers were the most dominant in the rhizosphere of conducive soils in both Cameroon and Nigeria. Furthermore, we elucidated the chemical structure of putisolvin derivatives-putisolvin III-V, and described its biosynthetic gene cluster. We show that high Pseudomonas and metabolic diversity may be driven by microbial competition, which likely contributes to soil suppressiveness to CRRD.

Pythiosis in cats in northeastern Brazil.

The epidemiological, clinical and anatomopathological aspects of pythiosis in cats in northeastern Brazil are described. From January 2000 to December 2018 the Laboratory of Animal Pathology of the Federal University of Campina Grande received 1928 tissue samples of cats, three of which were diagnosed as pythiosis. Grossly, the cats showed a multinodular mass in the oral cavity associated with facial deformity (case 1), a large multinodular mass thickening the jejunum wall (case 2), and an ulcerated nodule in the skin at the base of the tail (case 3). Histologically, pyogranulomatous inflammation and necrosis, with intralesional predominantly negatively stained hyphae, were observed in all cases. Immunohistochemistry for Pythium insidiosum revealed strong immunolabelling of the hyphae. The diagnosis of pythiosis was based on the epidemiological, clinical and anatomopathological findings, and was confirmed by immunohistochemistry. Although uncommon in cats, pythiosis should be readily considered as a differential diagnosis of chronic pyogranulomatous infections of the gastrointestinal tract and skin, especially in endemic areas, where the disease is often diagnosed in other animal species.

Prediction and Characterization of RXLR Effectors in Pythium Species.

RXLR effectors, a class of secreted proteins that are transferred into host cells to manipulate host immunity, have been reported to widely exist in oomycetes, including those from genera Phytophthora, Hyaloperonospora, Albugo, and Saprolegnia. However, in Pythium species, no RXLR effector has yet been characterized, and the origin and evolution of such virulent effectors are still unknown. Here, we developed a modified regular expression method for de novo identification of RXLRs and characterized 359 putative RXLR effectors in nine Pythium species. Phylogenetic analysis revealed that all oomycetous RXLRs formed a single superfamily, suggesting that they might have a common ancestor. RXLR effectors from Pythium and Phytophthora species exhibited similar sequence features, protein structures, and genome locations. In particular, there were significantly more RXLR proteins in the mosquito biological control agent P. guiyangense than in the other eight Pythium species, and P. guiyangense RXLRs might be the result of gene duplication and genome rearrangement events, as indicated by synteny analysis. Expression pattern analysis of RXLR-encoding genes in the plant pathogen P. ultimum detected transcripts of the majority of the predicted RXLR genes, with some RXLR effectors induced in infection stages and one RXLR showing necrosis-inducing activity. Furthermore, all predicted RXLR genes were cloned from two biocontrol agents, P. oligandrum and P. periplocum, and three of the RXLR genes were found to induce a defense response in Nicotiana benthamiana. Taken together, our findings represent the first evidence of RXLR effectors in Pythium species, providing valuable information on their evolutionary patterns and the mechanisms of their interactions with diverse hosts.

Efficacy of miltefosine therapy against subcutaneous experimental pythiosis in rabbits.

We evaluated the in vitro activity of miltefosine against 29 Pythium spp. and the in vivo therapeutic response of 2mg/kg/day of miltefosine given orally to rabbit with pythiosis induced experimentally. The MICs (in µg/mL) of miltefosine was medium-dependent and ranged from 0.5 to 2 and 32-64 on RPMI 1640 and Mueller Hinton broth, respectively. The treatment with miltefosine demonstrated significantly lower subcutaneous lesion areas compared to the control group but was not sufficient for the complete remission of the lesions. This study indicates that miltefosine has limited efficacy against pythiosis and furthers in vitro and in vivo studies are necessary to determine the possible potential of this drug in the treatment of pythiosis.

Genotyping and phylogenetic analysis of Pythium insidiosum causing human corneal ulcer.

Pythium insidiosum belongs to the Oomycetes, which are known to cause serious life-threatening infectious condition in humans and animals. Corneal infections caused by P. insidiosum are rare and difficult to treat. The molecular-based diagnosis of Pythium is employed for the species identification and to study molecular phylogenetic relationship. Based on Cytochrome oxidase II (cox II) gene, P. insidiosum is categorized into three clades or groups: Clade-I or ATH (American strains), Clade-II or BTH (American, Asian, and Australian strains), and Clade-III or CTH (mostly Thailand strains). This study focused on the molecular identification of Pythium insidiosum from patients with corneal ulcer using ITS regions and clade identification by cox II gene sequencing and correlated with the clinical outcome. The isolates were collected from Aravind Eye Hospital, Madurai, India, from April to December 2018. Through the microbiological laboratory reports, 15 isolates of Pythium sp. from keratitis patient were selected, followed by DNA extraction, ITS, and cox II gene sequencing and phylogenetic analysis using the reference sequences from NCBI database. All 15 P. insidiosum isolates were phylogenetically clustered together as a single group and where also placed distantly from other Pythium species (outgroup). Most ocular isolates fell into either clade BTH or clade CTH, and none of our ocular isolates were in clade ATH. Two of the strains were very distinct and did not match any of the clusters indicating different lineages. There was no significant difference between clinical outcome and genotype of P. insidiosum.

The glycoside hydrolase 18 family chitinases are associated with development and virulence in the mosquito pathogen Pythium guiyangense.

Chitinases, the enzymes responsible for the biological degradation of chitin, participate in numerous physiological processes such as nutrition, parasitism, morphogenesis and immunity in various organisms. However, the genome-wide distribution, evolution and biological functions of chitinases are rarely reported in oomycetes. This study systematically investigated the glycoside hydrolase 18 (GH18) family of chitinases from the mosquito pathogenic oomycete, Pythium guiyangense using bioinformatics and experimental assays. A total of 3 pairs of GH18 chitinase genes distributed in three distinct phylogenic clusters were identified from P. guiyangense genome, which is consistent with the ones in plant pathogenic oomycetes. Further transcriptional analysis revealed that Pgchi1/2 was highly expressed at the development stages, while Pgchi3/4 and Pgchi5/6 were up-regulated at the infection stages. The biological function analysis of chitinase genes using genetic transformation silencing method showed that silencing of Pgchi1/2 resulted in reduced zoospore production, without affecting the virulence. However, attenuation of Pgchi3/4 and Pgchi5/6 genes regulated not only oxidative stress responses, but also led to decreased infection rates to mosquito larvae. Taken together, this study provides a comprehensive overview of P. guiyangense chitinase family and reveals their diverse roles in the development, stress response, and virulence, which would elucidate insightful information on the molecular mechanism of chitinase in entomopathogenic pathogens.

Talaromyces variabilis interferes with Pythium aphanidermatum growth and suppresses Pythium-induced damping-off of cucumbers and tomatoes.

Pythium-induced damping-off disease is a major disease limiting cucumber and tomato production in different parts of the world. The current study investigated the efficiency of Talaromyces variabilis and its bioactive metabolites in suppressing Pythium-induced damping-off of cucumbers and tomatoes. T. variabilis inhibited the in vitro growth of P. aphanidermatum in solid and liquid media. In addition, abnormalities in P. aphanidermatum hyphae were observed as a result of T. variabilis. Extracts from T. variabilis induced cellular leakage and suppressed oospore production of P. aphanidermatum. Biochemical analyses of T. variabilis metabolites showed that T. variabilis produces glucanase, cellulase and siderophores, suggesting the contribution of these metabolites in the inhibition of P. aphandermatum growth and in hyphal abnormalities. Treating cucumber seeds with spore and mycelial suspension of T. variabilis isolates led to a significant improvement in the seedling survival of P. aphanidermatum-inoculated seedlings from 18 to 52% (improvement by 34%) for isolate 48 P and from 30-66% (improvement by 36%) for isolate 28 R. Similarly, treating tomato seeds with spore and mycelial suspension of T. variabilis isolates led to a significant improvement in the seedling survival of P. aphanidermatum-inoculated seedlings from 7 to 36% (improvement by 29%) for isolate 28 R and from 20 to 64% (improvement by 44%) for isolate 48 P. Differences in the percent improvement in seedling survival between experiments may be related to difference in the efficacy of the two different isolates or their interaction with the hosts and pathogen. The use of T. variabilis in the biocontrol of Pythium-induced diseases may offer alternatives to the currently used chemical control.

Skp1 isoforms are differentially modified by a dual function prolyl 4-hydroxylase/N-acety lglucosaminyltransferase in a plant pathogen.

Skp1 is hydroxylated by an O2-dependent prolyl hydroxylase (PhyA) that contributes to O2-sensing in the social amoeba Dictyostelium and the mammalian pathogen Toxoplasma gondii. HO-Skp1 is subject to glycosylation and the resulting pentasaccharide affects Skp1 conformation in a way that influences association of Skp1 with F-box proteins, and potentially the assembly of E3(SCF) ubiquitin ligase complexes that mediate the polyubiquitination of target proteins that are degraded in the 26S-proteasome. To investigate the conservation and specificity of these modifications, we analyzed proteins from the oomycete Pythium ultimum, an important crop plant pathogen. Putative coding sequences for Pythium's predicted PhyA and first glycosyltransferase in the predicted five-enzyme pathway, a GlcNAc-transferase (Gnt1), predict a bifunctional enzyme (Phgt) that, when expressed in Dictyostelium, rescued a knockout of phyA but not gnt1. Though recombinant Phgt was also unable to glycosylate Dictyostelium HO-Skp1, it could hydrolyze UDP-GlcNAc and modify a synthetic hydroxypeptide from Dictyostelium Skp1. Pythium encodes two highly similar Skp1 isoforms, but only Skp1A was efficiently hydroxylated and glycosylated in vitro. While kinetic analysis revealed no evidence for processive processing of Skp1, the physical linkage of the two activities implies dedication to Skp1 in vivo. These findings indicate a widespread occurrence of the Skp1 modification pathway across protist phylogeny, suggest that both Gnt1 and PhyA are specific for Skp1 and indicate that the second Skp1 provides a bypass mechanism for O2-regulation in Pythium and other protists that conserve this gene.

Genome mining identifies cepacin as a plant-protective metabolite of the biopesticidal bacterium Burkholderia ambifaria.

Beneficial microorganisms are widely used in agriculture for control of plant pathogens, but a lack of efficacy and safety information has limited the exploitation of multiple promising biopesticides. We applied phylogeny-led genome mining, metabolite analyses and biological control assays to define the efficacy of Burkholderia ambifaria, a naturally beneficial bacterium with proven biocontrol properties but potential pathogenic risk. A panel of 64 B. ambifaria strains demonstrated significant antimicrobial activity against priority plant pathogens. Genome sequencing, specialized metabolite biosynthetic gene cluster mining and metabolite analysis revealed an armoury of known and unknown pathways within B. ambifaria. The biosynthetic gene cluster responsible for the production of the metabolite cepacin was identified and directly shown to mediate protection of germinating crops against Pythium damping-off disease. B. ambifaria maintained biopesticidal protection and overall fitness in the soil after deletion of its third replicon, a non-essential plasmid associated with virulence in Burkholderia cepacia complex bacteria. Removal of the third replicon reduced B. ambifaria persistence in a murine respiratory infection model. Here, we show that by using interdisciplinary phylogenomic, metabolomic and functional approaches, the mode of action of natural biological control agents related to pathogens can be systematically established to facilitate their future exploitation.

Assessment of temperature-dependent proteomes of Pythium insidiosum by using the SWISS-PROT database.

Pythium insidiosum causes the life-threatening disease, called pythiosis. Information on microbial pathogenesis could lead to an effective method of infection control. This study aims at assessing temperature-dependent proteomes, and identifying putative virulence factors of P. insidiosum. Protein extracts from growths at 25°C and 37°C were analyzed by mass spectrometry and SWISS-PROT database. A total of 1052 proteins were identified. Upon exposure to increased temperature, 219 proteins were markedly expressed, eight of which were putative virulence factors of P. insidiosum. These temperature-dependent proteins should be further investigated for their roles in pathogenesis, and some of which could be potential therapeutic targets.