Germ Tube Research Articles

First Report of Powdery Mildew Caused by Podosphaera xanthii on Vernonia cinerea in China.

Vernonia cinerea (L.)Less. is an annual herbaceous plant of the Asteraceae family, which is widely distributed throughout Southeast Asia, India, and the tropical and subtropical regions of China. This herb is known to contain various bioactive compounds and is commonly used in traditional system of medicine in China and India (Singh et al. 2021). During the spring of 2022 and 2023, powdery mildew symptoms were observed on 70% of V. cinerea plants on the Hainan Medical University campus (19° 58' 53″ N; 110° 19' 47″ E) in Haikou, Hainan Province, China. Powdery mildew colonies covered the leaf surfaces and stems of affected plants, causing discoloration and defoliation. Mycelia were superficial and hyphal appressoria were nipple-shaped. Conidiophores (n =30) were unbranched, cylindrical, 104 to 188 × 11 to 15 µm, and produced three to five immature conidia in chains with a crenate outline. Foot cells (n =30) were cylindrical, straight or sometimes curved at the base, and 32 to 57 µm long. Conidia (n =100) were ellipsoid-ovoid to doliiform, 19 to 45 ×16 to 26 m (length/width ratio = 1.2 to 2.4), with well-developed fibrosin bodies, and produced germ tubes from the lateral position. Based on these morphological characteristics, the pathogen was provisionally identified as Podosphaera xanthii (Braun and Cook 2012). The teleomorph was not observed. A specimen was deposited in the Hainan Medical University Plant Pathology Herbarium as HMVC-22. To confirm the genus identification and ascertain a putative species, genomic DNA was extracted from mycelium, conidiophores, and conidia using a fungal DNA kit (Omega Bio-Tek, USA). The rDNA internal transcribed spacer (ITS) region was amplified with primers ITS1/ITS4 (White et al. 1990) and sequenced directly. The resulting 577-bp sequence was deposited in GenBank (accession no. OP765400). A BLASTn search in GenBank of this sequence showed 100% similarity with the ITS sequences of P. xanthii isolates from China (MT260063, MT739423 and MT131253), Thailand (LC270780), and Vietnam (KM260731). Additionally, the 28S rDNA region was amplified using the primer pairs NL1 and NL4 (O´Donnell 1993; accession no. OP765401). This region shared 100% similarity with P. xanthii isolates (LC371333, LC270780, and AB936277) as well. Powdery mildew from Hainan sample belonged to the P. xanthii group with strong bootstrap values support 99% in maximum likelihood phylogenetic tree based on ITS and 28S gene sequences. To confirm pathogenicity, five healthy potted plants of V. cinerea were inoculated by gently pressing a powdery mildew-infected leaf onto 15 young leaves. Five non-inoculated plants served as controls. All plants were maintained in a greenhouse at 24 to 30°C, 70% relative humidity, with a 16-h photoperiod. After 7 days, inoculated leaves showed powdery mildew symptoms whereas no symptoms were observed on control plants. The fungal colonies observed on inoculated plants were morphologically identical to those found on the originally infected leaves collected from Hainan Province. Based on the morphological characteristics and molecular identification, the fungus was identified as P. xanthii. In different countries and regions, Erysiphe cichoracearum has been previously reported on some Vernonia species, including V. Galamensis from southern parts of Ethiopia (Hundesa and Mekonnen 2017). To our knowledge, this is the first record of P. xanthii infecting V. cinerea in China. We are concerned that the pathogen could become a threat to the widespread planting of V. cinerea in the future.

Cytological studies reveal high variation in ascospore number and shape and conidia produced directly from ascospores in Morchella galilaea.

Spores are important as dispersal and survival propagules in fungi. In this study we investigated the variation in number, shape, size and germination mode of ascospores in Morchella galilaea, the only species of the genus Morchella known to fruit in the autumn. Based on the observation of five samples, we first discovered significant variation in the shape and size of ascospores in Morchella. One to sixteen ascospores were found in the asci. Ascospore size correlated negatively with ascospore number, but positively with ascus size, and ascus size was positively correlated with ascospore number. We noted that ascospores, both from fresh collections and dried specimens, germinated terminally or laterally either by extended germ tubes, or via the production of conidia that were formed directly from ascospores at one, two or multiple sites. The direct formation of conidia from ascospores takes place within asci or after ascospores are discharged. Using laser confocal microscopy, we recorded the number of nuclei in ascospores and in conidia produced from ascospores. In most ascospores of M. galilaea, several nuclei were observed, as is typical of species of Morchella. However, nuclear number varied from zero to around 20 in this species, and larger ascospores harbored more nuclei. One to six nuclei were present in the conidia. Nuclear migration from ascospores to conidia was observed. Conidia forming directly from ascospores has been observed in few species of Pezizomycetes; this is the first report of the phenomenon in Morchella species. Morphological and molecular data show that conidial formation from ascospores is not found in all the specimens of this species and, hence, is not an informative taxonomic character in M. galilaea. Our data suggest that conidia produced from ascospores and successive mitosis within the ascus may contribute to asci with more than eight spores. The absence of mitosis and/or nuclear degeneration, as well as cytokinesis defect, likely results in asci with fewer than eight ascospores. This study provides new insights into the poorly understood life cycle of Morchella species and more broadly improves knowledge of conidia formation and reproductive strategies in Pezizomycetes.

The polyphenolic suberized peridermal skin of the Sikkim cucumber acts as an effective chemical barrier against Botrytis cinerea infection

Certain species of fleshy fruit that undergo skin cracking are capable of forming a specialized polyphenolic periderm to seal the wounded skin. Some of the genetic and metabolic components pertaining periderm formation have been identified, however it remains unknown if, and to what extent, this specialized tissue can act as an efficient barrier against the invasion of pathogenic fungi. We monitored the infection process of Botrytis cinerea on the cuticle-coated skin of the common cucumber (Cucumis sativus) or on the polyphenolic suberized peridermal skin of the Sikkim cucumber (C. sativus var. sikkimensis). In vivo inoculation assays inferred that while B. cinerea can successfully penetrate and form necrotic lesions on sativus fruit, it is incapable of penetrating the peridermal skin of sikkimensis fruit. Gas chromatography-mass spectrometry (GC-MS) profiling of fruit skin extracts, in vitro conidial germination and germ tube elongation assays, and qRT-PCR cutinase-encoding gene expression analyses, inferred that the accumulation of suberin monomers in the peridermal skin of sikkimensis fruit stimulate increased elongation of B. cinerea germ tubes and significantly alters the differential expression of cutinase-encoding genes. Among them, Bcin0607010, Bcin08g01580 and Bcin07g06480, three yet unidentified cutinases, whose expression is specifically increased in the presence of sikkimensis fruit skin extracts. Our data demonstrate that a polyphenolic suberized peridermal skin in cucumber fruit can shape the interactions with B. cinerea and implies that suberization of fleshy fruit may provide a means for reducing damage imposed by this and other pathogens.

Activity of propolis from Mexico on the proliferation and virulence factors of Candida albicans

BackgroundThis research evaluated the anti-Candida albicans effect of Mexican propolis from Chihuahua.Chemical composition of the ethanolic extract of propolis was determined by GC-MS, HPLC-DAD, and HPLC-MS. The presence of anthraquinone, aromatic acid, fatty acids, flavonoids, and carbohydrates was revealed.ResultsThe anti-Candida activity of propolis was determined. The inhibitions halos were between 10.0 to 11.8 mm; 25% minimum inhibitory concentration (0.5 mg/ml) was fungistatic, and 50% minimum inhibitory concentration (1.0 mg/ml) was fungicidal.The effect of propolis on the capability of C. albicans to change its morphology was evaluated. 25% minimum inhibitory concentration inhibited to 50% of germ tube formation.Staining with calcofluor-white and propidium iodide was performed, showing that the propolis affected the integrity of the cell membrane.INT1 gene expression was evaluated by qRT-PCR. Propolis significantly inhibited the expression of the INT1 gene encodes an adhesin (Int1p).Chihuahua propolis extract inhibited the proliferation of Candida albicans, the development of the germ tube, and the synthesis of adhesin INT1.ConclusionsGiven the properties demonstrated for Chihuahua propolis, we propose that it is a candidate to be considered as an ideal antifungal agent to help treat this infection since it would not have the toxic effects of conventional antifungals.

Postharvest biocontrol of green mold (Penicillium digitatum) in citrus by Bacillus velezensis strain S161 and its mode of action

Green mold caused by Penicillium digitatum is a major postharvest disease of citrus that can result in significant losses during storage. Synthetic chemical fungicides typically used to control this disease have raised potential concerns regarding environmental pollution, human health, and the development of fungicide resistance. Biological control of postharvest diseases has been demonstrated to be an effective alternative to chemical control. In the present study, we investigated the postharvest biocontrol efficacy of Bacillus velezensis strain S161 against P. digitatum and its potential mechanisms of action. Results indicated that a cell-free supernatant (CFS) obtained from liquid culture of S161 strongly inhibited the mycelial growth, spore germination, and germ tube elongation of P. digitatum in vitro. The CFS effectively protected citrus fruit against P. digitatum, providing 95.6 % control. Further investigations revealed that the CFS degraded and ruptured hyphal membranes and spores and induced the excessive accumulation of reactive oxygen species (ROS) in hyphal cells resulting in oxidative damage. CFS exposure also resulted in the downregulation of genes associated with spore germination, growth, reproduction, and virulence. antiSMASH analysis of biosynthetic gene clusters (BGCs) in B. velezensis indicated that B. velezensis possesses several core clusters, encoding the synthesis of surfactin, bacillomycin D, fengycin, bacilysin, bacillibactin, macrolactin, difficidin, bacillaene, and amylocycicin. Further analysis using Liquid Chromatography Tandem Mass Spectrometry (LC-MS) revealed the presence of four of these metabolites (surfactin, iturin, fengycin, and bacillibactin) in the CFS of B. velezensis. Additional bioassays conducted in sealed plates revealed that volatile organic compounds (VOCs) produced by S161 also inhibited the growth of P. digitatum. A total of 24 VOCs were found to be produced by S161 using headspace solid-phase microextraction/gas chromatography-mass spectrometry (HS-SPME/GC-MS). The identified VOCs were mainly ketones and alcohols. Collectively, our results indicate that B. velezensis strain S161 is an effective biocontrol agent of P. digitatum on citrus and inhibits pathogen germination and growth through a range of mechanisms, including the downregulation of genes associated with spore germination and growth, induction of oxidative stress, and the antimicrobial activity of VOCs.

Exogenous myristate promotes the colonization of arbuscular mycorrhizal fungi in tomato.

Arbuscular mycorrhizal fungi (AMF) can establish symbiotic associations with the roots of most terrestrial plants, thereby improving the tolerance of the host plants to biotic and abiotic stresses. Although AMF cannot synthesize lipids de novo, they can obtain lipids from the root cells for their growth and development. A recent study reveals that AMF can directly take up myristate (C14:0 lipid) from the environment and produce a large amount of hyphae in asymbiotic status; however, the effect of environmental lipids on AM symbiosis is still unclear. In this study, we inoculated tomato (Solanum lycopersicum) with AMF in an in vitro dual culture system and a sand culture system, and then applied exogenous myristate to the substrate, in order to explore the effect of exogenous lipids on the mycorrhizal colonization of AMF. We investigated the hyphae growth, development, and colonization of AMF, and examined the gene expression involved in phosphate transport, lipid biosynthesis, and transport. Results indicate that exogenous lipids significantly stimulated the growth and branching of hyphae, and significantly increased the number of hyphopodia and mycorrhizal colonization of AMF, with arbuscular abundance and intraradical spores or vesicles being the most promoted. In contrast, exogenous myristate decreased the growth range and host tropism of the germ tubes, and largely inhibited the exchange of nutrition between symbionts. As a result, exogenous myristate did not affect the plant growth. This study suggests that lipids promote mycorrhizal colonization by enhancing the growth and development of AMF hyphae and increasing their contact opportunities with plant roots. To the best of our knowledge, this is the first report that shows that lipids promote the colonization of AMF. Our study highlights the importance of better understanding the roles of environmental lipids in the establishment and maintenance of AM symbiosis and, thus, in agricultural production.

Deteksi Kandiduria Pada Wanita Penderita Diabetes Melitus Di Puskesmas I Denpasar Barat

Diabetes mellitus is a disease associated with metabolic disorders in the body with the characteristics of an increase in the body's blood sugar levels. In people with diabetes mellitus, candiduria infection can occur due to excessive growth of Candida fungi in the urinary tract. Patients are declared candiduria if Candida is found in the urine >103 CFU/mL. The study ao aimed to determine whether candiduria occurred in women with diabetes mellitus who were examined at the West Denpasar Health Center I. The sampling technique used purposive sampling. The sample used was 53 urine using the patient's medical record data for December 2022. Sample analysis was carried out at the Parasitology and Mycology Laboratory STIKES Wira Medika Bali. Candiduria was detected by examining the number of colonies per ml of urine on Sabouraud Dextrose Agar. Identification of causative species was carried out by Gram microscopy and germ tube test. Based on the examination results, 2 samples (3.8%) were positive for candiduria and 51 samples (96.3%) were negative. Identification of Candida species known to cause candiduria in both samples was caused by C. albicans. With the characteristics of an oval, gram-positive blastospore, and a germ tube test, the formation of blastospores is like germinating cells. Based on the results of the study, it is expected that respondents maintain body immunity, blood sugar levels, and cleanliness of the genital area so as to reduce the risk of candiduria.

Isolation, identification, and antifungal resistance of Candida species from various samples

This study in Aden, Yemen, collected 67 samples from patients attending hospitals and laboratories. Samples were taken from different body areas, covering various age groups and genders. Fungal infections, particularly Candida species, are a significant cause of death worldwide. The emergence of azole-resistant Candida has raised concerns and highlighted the need for better antifungal agents.In the study, 68.66% of the collected samples contained pathogenic Candida fungi. Some samples also showed bacterial growth or both bacteria and fungi. Suspected Candida growth on corn meal agar exhibited chlamydospore formation and germ tubes on human serum. Carbohydrate fermentation tests were positive for Glucose, Maltose, Galactose, and Xylose, while Sucrose and Lactose were negative. All Candida isolates (100%) were accurately identified to the species level using CHROM agar Candida. Candida's pathogenicity was linked to various virulence factors, including hydrolytic enzyme secretion. Nystatin was the most effective antifungal agent (100% sensitivity), while Fluconazole (73.92%) and Amphotericin B (52.17%) showed varying levels of sensitivity. However, Voriconazole, ketoconazole, and Miconazole displayed high resistance rates (89.13%, 84.78%, and 80.44%, respectively) against the isolated Candida.This study concluded that Candida spp., particularly Candida albicans, were frequently found in the samples from patients, with vaginal swaps being a common site of infection. The identification of Candida isolates to the species level using CHROM agar Candida was accurate. Nystatin, Fluconazole, and Amphotericin B were the most effective antifungal agents against Candida spp.

The pathology of canine mammary candidiasis with embolic dissemination in a dog

Candidiasis is a fungal disease caused by Candida albicans or other members of the genus Candida. Descriptions of candidiasis are comparatively reduced in veterinary relative to human medicine, with no cases of mammary candidiasis being identified in pet animals. This report presents the cytological, pathological, and molecular findings of mammary candidiasis with embolic dissemination in a postpartum dog. A 1-year-old, female Shih-tzu dog that had recently given birth was admitted to a veterinary teaching hospital in Southern Brazil after repeated episodes of intermittent mammary disease and a neurological syndrome. The dog was euthanized due to worsened clinical status and poor prognosis despite adequate clinical therapy and was submitted for routine post-mortem evaluation to determine the cause of the neurological manifestations. Cytological analysis of purulent mastitis identified intralesional fungal hyphae. Gross evaluation revealed multiple masses within the kidneys, liver, myocardium, pancreas, and brain. Routine histopathology and histochemistry identified fungal nephritis, hepatitis, myocarditis, pancreatitis, and encephalitis associated with intralesional fungal hyphae, frequently with fungal emboli and vasculitis. Pure cultures of C. albicans were obtained from fragments of the masses observed at the myocardium and kidneys, with the typical germ tube of C. albicans being identified by microscopic evaluation. A PCR assay that targeted the ITS1 and 4 generic regions of fungi, amplified the desired amplicon, and direct sequencing confirmed C. albicans. Immunohistochemical and molecular assays designed to identify common infectious disease pathogens of dogs did not confirm the participation of canine distemper virus, canine parvovirus, or canine adenovirus in the target tissues of this dog. These findings suggest that this dog suffered an initial cutaneous lesion, that probably served as portal of entry to the mammary gland, resulting in mammary candidiasis with subsequent embolic dissemination to multiple organs. This report represent the first description of mammary candidiasis in pet animals and probably one of the few pathological descriptions of mammary candidiasis in domestic animals. In this case, the cause of the fungal infection was probably associated with factors intrinsic to abdominal surgery, pregnancy, and the utilization of antibiotics.

The cell-end protein Tea4 spatially regulates hyphal branch initiation and appressorium remodeling in the blast fungus Magnaporthe oryzae.

The differentiation of specialized infection cells, called appressoria, from polarized germ tubes of the blast fungus Magnaporthe oryzae, requires remarkable remodeling of cell polarity and architecture, yet our understanding of this process remains incomplete. Here we investigate the behavior and role of cell-end marker proteins in appressorium remodeling and hyphal branch emergence. We show that the SH3 domain-containing protein Tea4 is required for the normal formation of an F-actin ring at Tea1-GFP-labeled polarity nodes, which contributes to the remodeling of septin structures and repolarization of the appressorium. Further, we show that Tea1 localizes to a cortical structure during hyphal septation which, unlike contractile septin rings, persists after septum formation, and, in combination with other polarity determinants, likely spatially regulates branch emergence. Genetic loss of Tea4 leads to mislocalization of Tea1 at the hyphal apex and with it, impaired growth directionality. In contrast, Tea1 is largely depleted from septation events in Δtea4 mutants and branching and septation are significantly reduced. Together, our data provide new insight into polarity remodeling during infection-related and vegetative growth by the blast fungus.

Synthesis and evaluation of imidazo[1,2-a]quinoxaline derivatives as potential antifungal agents against phytopathogenic fungi.

To discover novel and effective potential agricultural antifungal agents, various kinds of imidazo[1,2-a]quinoxaline derivatives were designed, and synthesized from available and inexpensive reagents. Their antifungal activities were first evaluated against ten typical phytopathogenic fungi. The in vitro antifungal activity showed that some compounds exhibited more obvious broad-spectrum fungicidal activity than the two commercially-available fungicides chlorothalonil and hymexazol. Valsa mali and Botrytis cinerea strains exhibited the highest susceptibility with EC50 values of 1.4-27.0μg/mL to more than ten compounds. Compounds 5c and 5f showed the most promising inhibitory effects against Valsa mali (EC50 = 5.6μg/mL) and Fusarium solani (EC50 = 5.1μg/mL), respectively. Preliminary studies on the mechanism of action indicated that the imidazo[1,2-a]quinoxaline skeleton likely exerted its antifungal effects by disrupting hyphal differentiation, spore germination, and germ tube growth. Moreover, the cell experiment results indicated that these target compounds possessed good safety to BV2 cells. Overall, compounds 5c and 5f can be considered candidate compounds against specific fungi for further detailed research. This study can provide a theoretical basis for the application of imidazo[1,2-a]quinoxaline scaffolds as novel fungicides in agriculture.

The occurrence of fungi from burn wound patients and antifungal susceptibility patterns: a cross-sectional study in Lusaka, Zambia.

Fungal opportunistic infections in burn wound patients are among the leading cause of morbidity and mortality. Attention remains focused on preventing bacterial infection at the expense of increasing fungal infection in burn wound patients. To determine the occurrence of common fungi in admitted burn wound patients and their environment: and their antifungal susceptibility patterns at the University Teaching Hospitals, Lusaka, Zambia. This laboratory-based cross-sectional study enrolled a total 101 participants whose pus swab specimens were collected from their burn wounds as well as 50 environmental swabs collected from strategic points. Wet mount, gram stain, culture on Sabouraud dextrose agar, Corn meal agar and Germ tube were used to identify possible fungal isolates. Agar based disc susceptibility test was carried out using fluconazole. Data was analysed using Excel and STAT version 14. Median age was 3 years and median burn % of TBSA was 18 in participants' who had burn wound fungal infection and consisted of 3 males and 6 females. Organisms isolated included Candida albicans from 8(7.9%) participants and 2(4%) from 50 environmental swabs. 1(1%) Candida spp was isolated from pus swabs. Out of the total 11 Candida isolates, 4 (36.4%) were susceptible to fluconazole and 7 (63.6%) were resistant. The isolation of Candida albicans and Candida spp from burn wound patients and the hospital ward environment suggests presence of fungi in burn wound patients and hospital ward environments. Candida isolated showed varying susceptibility patterns to fluconazole.

Characterization, phylogeny and pathogenicity of Fusarium solani causing quinoa basal stem rot in Shanxi Province, China

AbstractA new emerging disease of quinoa, quinoa basal stem rot (QBSR), has been recorded in Shanxi Province, China. Observed during the inflorescence emergence stage, the pathogen causes wilting, foliar chlorosis, leaf abscission and eventual death of quinoa. In this study, isolates were identified as Fusarium solani using morphology, molecular and phylogenetic analysis (using sequences of calmodulin, rDNA internal transcribed spacer region, RNA polymerase II B‐subunits RPB1 RPB1 and RPB2 RPB2, and translation elongation factor 1‐α), and pathogenicity analysis. Twenty‐seven isolates were classified into two different groups according to their morphological characteristics, and the mycelial growth rate of Group 2 was higher than that of Group 1 on six different media. The optimum growth temperature for both groups was 30°C and the highest mycelial growth rates were 9.2 and 10.0 mm/day, for Groups 1 and 2, respectively. The sporodochial conidia (SC) and aerial conidia (AC) germinated normally at 15–25°C and 10–40°C, respectively, and the width of SC and AC germ tubes were 1.4 and 2.2 μm. The lethal temperature for AC was 51°C for 20 min, and SC stopped germinating at 45°C. Pathogenicity tests of representative isolates showed that mycelia or conidia caused typical symptoms of QBSR on wounded basal stems of Chenopodium quinoa at 6 days postinoculation. The optimum temperature for the onset of QBSR was 30°C for both groups of isolates, and lesion lengths ranged from 5.4 to 5.9 cm. Knowledge of this pathogen will provide useful information for effective disease management to prevent its spread.

Distinct dynamics of the nucleolus in response to nutrient availability and during development in the rice blast fungus.

The nucleolus is a dynamic subnuclear structure that is involved in many fundamental processes of the nucleus. In higher eukaryotic cells, the size and shape of nucleoli correlate with nucleolar activities. For fungi, knowledge of the nucleolus and its functions is primarily gleaned from budding yeast. Whether such correlation is conserved and how nucleolar functions are regulated in filamentous fungi including important human and crop pathogens are largely unknown. Our observations reveal that the dynamics of nucleolus in a model plant pathogenic fungus, Magnaporthe oryzae, is distinct from those of animal and yeast nucleoli under low nutrient availability and during pathogenic development. Our data not only provide new insight into the nucleoli in filamentous fungi but also highlight the need for investigating how nucleolar dynamics is regulated in comparison to other eukaryotes.

Study of Ecological Relationship of Yeast Species with Candida albicans in the Context of Vulvovaginal Infections.

The role of the fungal community, the mycobiota, in the health of the vagina is currently an important area of research. The emergence of new sequencing technologies and advances in bioinformatics made possible the discovery of novel fungi inhabiting this niche. Candida spp. constitutes the most important group of opportunistic pathogenic fungi, being the most prevalent fungal species in vulvovaginal infections. However, fungi such as Rhodotorula spp., Naganishia spp. and Malassezia spp. have emerged as potential pathogens in this niche, and therefore it is clinically relevant to understand their ecological interaction with Candida spp. The main aim of this study was to evaluate the impact of yeasts on Candida albicans' pathogenicity, focusing on in-vitro growth, and biofilm formation at different times of co-culture and germ tube formation. The assays were performed with isolated species or with co-cultures of C. albicans (ATCC10231) with one other yeast species: Rhodotorula mucilaginosa (DSM13621), Malassezia furfur (DSM6170) or Naganishia albida (DSM70215). The results showed that M. furfur creates a symbiotic relationship with C. albicans, enhancing the growth rate of the co-culture (149.69%), and of germ tube formation of C. albicans (119.8%) and inducing a higher amount of biofilm biomass of the co-culture, both when mixed (154.1%) and preformed (166.8%). As for the yeasts R. mucilaginosa and N. albida, the relationship is antagonistic (with a significant decrease in all assays), thus possibly repressing the mixture's pathogenicity. These results shed light on the complex interactions between yeasts in the vaginal mycobiome.

Efficacy of Wickerhamomyces anomalus in the biocontrol of black spot decay in tomatoes and investigation of the mechanisms involved

Black spot caused by Alternaria alternata is a common postharvest disease of tomato. In the current study, Wickerhamomyces anomalus was used to control the disease. The experimental results showed that W. anomalus had the effect of controlling black spot disease, and 108 cells/mL of W. anomalus was the most suitable concentration for controlling the disease. W. anomalus has the ability to reduce the spore germination and inhibit germ tubes growth of A. alternata, and its volatile substances also have inhibitory effects on pathogenic fungi. W. anomalus can reduce the natural decay rate of tomato, retain postharvet quality of tomato, and increase the contents of ascorbic acid and lycopene. In addition, W. anomalus can significantly reduce the H2O2, O2– production rate, and MDA contents of tomato. It increased the enzymatic activities of catalase (CAT), glutathione reductase (GR), glutathione peroxidase (GPX), glutathione S-transferase (GST), and increased the content of glutathione (GSH). Furthermore, the yeast improved the ability of tomato to resist oxidative stress, thereby better resisting the pathogen infection. Generally, this study will significantly contribute to use antagonistic yeasts or their products to control postharvest diseases of horticultural produces.

Identification and Morph-metric Characterization of Powdery Mildew Infecting Diverse Host Plants of Southern Gujarat, India

Identification and Morph-metric Characterization of Powdery Mildew Infecting Diverse Host Plants of Southern Gujarat, India

Synergy In Vitro of Nikkomycin Z with Azole Against the Invasive Form of Candida albicans.

In a previous study, therapeutic activity of nikkomycin Z (NZ) in a model of invasive candidiasis did not appear to correlate with lesser activity in vitro (using classical MIC methods) with planktonic organisms. However, NZ potency was much greater assaying activity in vitro against germ tubes, the initiator of the invasive mycelial form of the fungus, as occurs in infected tissues. Synergy has been demonstrated for NZ and other drugs, notably fluconazole (the most commonly used drug against candidiasis), in planktonic testing, which correlated with results in vivo. This raised the question whether activity shown by NZ alone against germ tubes would be reflected in drug combinations, and even whether synergy testing against germ tubes might be a better correlate of synergy in future in vivo studies. We show in this study significant NZ synergy with fluconazole against germ tubes, for several C. albicans isolates, with testing in many drug ratios. This observation opens the way for further explorations of this method of susceptibility testing for synergy, and correlation with combination therapy against candidiasis.

Antifungal effect of volatile organic compounds (VOCs) release from Antarctic bacteria under postharvest conditions

The generation of biological control agents for postharvest fungal control has prompted the search for different natural sources due to studies indicating adverse effects that may be related to the use of conventional fungicides (e.g., SO2). Some bacteria that have the ability to generate volatile organic compounds (VOCs) with antifungal activity stand out in this regard. Thus, the Antarctic bacterium Pseudomonas sp. AN3A02, which can grow in very cold environments with low nutrient availability, has shown a fungistatic effect on Botrytis cinerea in dual culture. In this study, in vitro assays were performed to evaluate its effect and activity on strains of B. cinerea isolated from blueberries using dual-plate assays. An antifungal assay (in vivo) was performed by artificial wounding on blueberries inoculated with B. cinerea (1 ×106 conidia/mL) and stored at 0 °C for 20 d plus 3 d at 20 °C. The results obtained showed that in the presence of the bacteria, the severity of gray mold on blueberries was reduced by 71.38 %. In addition, this bacterium released a diversity of VOCs, including alcohols (1-octanol, 10.3 %), aldehydes (paraldehyde, 2.1 %), esters (ethyl butyrate, 4 %; isoamyl acetate, 2 %), ketones (2-nonanone, 1.4 %), terpenes (linalool, 1.9 %; D-limonene, 0.7 %), phenolic derivatives (2,4-di-tert-butylphenol, 2.5 %) and other groups, which were identified by GC–MS. The release of VOCs affects and modifies the hyphae and germ tube of B. cinerea, influencing its growth. Therefore, a new and environmentally friendly alternative for postharvest pathogen control could be generated based on this Antarctic microorganism.

The Potential Association of Human ABO Blood Group in Candida albicans Germination

Candidiasis is an infection caused by Candida spp., mostly Candida albicans. Infection with Candida spp. in immunocompetent individuals is often limited to the mouth, genital area or skin. However, patients who are immunocompromised due to infections or medications including corticosteroids or anticancer drugs are more susceptible to systemic candidiasis and candidemia. Upon C. albicans infections, the pathogenic yeasts enter the bloodstream and disseminate to the remote organs, leading to the formation of germ tube. Dimorphic adaptation is one of contributing virulent factors in C. albicans, which is responsible for disease pathogenesis and severity. However, little is known about whether differences among human ABO blood groups facilitate the development of C. albicans germ tube. Therefore, this study investigated the germ tube formation of C. albicans that grown in human serums from different ABO blood groups. Human pool serums varying ABO blood groups from healthy individuals were tested for C. albicans germ tube induction. After incubation for 2 h at 37 °C, the rate of germ tube formation at 15-min intervals was determined. Serum from human blood group A exhibited the highest rate of germ tube formation. Humans with blood group A exhibited the unique serum biochemical structure that possibly helps facilitate germ tube formation during C. albicans infection. HIGHLIGHTS The association of blood groups of Thais to germination and invasion of Candida albicans were more common in Thai people. This research study focused on changes in Candida albicans germination related to the blood group. Human with blood group type A exhibited the highest rate of germ tube formation. GRAPHICAL ABSTRACT