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The pathogenicity of the fungus, Metarhizium anisopliae, commonly referred to as the green muscardine fungus, has been demonstrated against numerous insect species inhabiting various habitats. Laboratory experiments were carried out to investigate the impact of naturally derived adjuvants on the growth and spore characteristics of M. anisopliae. The natural polysaccharide (guar gum, gum acacia and carboxymethyl cellulose), vegetable oil (groundnut and cottonseed oil) and a synthetic adjuvant were used in the study at three distinct concentrations: 0.05%, 0.1%, and 0.2% v/v or w/v. Among the various adjuvants tested, both gum acacia and guar gum at concentrations of 0.1% and 0.2% were observed to have a positive impact on the growth of the fungus, resulting in enhanced radial mycelial growth, conidiospore production, surface area coverage, and conidiospore germination. Conversely, this fundamental study highlights the detrimental effects of synthetic adjuvants on the growth and spore characteristics of M. anisopliae. [ABSTRACT FROM AUTHOR]

Plant volatile organic compounds are an abundant resource that can be used to explore natural gaseous fungicides. Recently, we found that (E)-2-heptenal, a green leaf volatile, could effectively inhibit the growth of Aspergillus flavus, showing promise for application as a biofumigant to prevent grain spoilage by A. flavus. In this study, the inhibitory effects of (E)-2-heptenal on A. flavus spore germination and mechanisms underlying these effects were investigated through morphological, biochemical, and transcriptomic analyses. The minimum inhibitory concentration and minimum fungicidal concentration of (E)-2-heptenal for spore germination of A. flavus were 4.0 and 6.0 µL/mL, respectively. (E)-2-heptenal treatment resulted in irregularly deformed, collapsed, and ruptured surface morphology of A. flavus spores, as well as destroyed cell wall integrity and reduced ergosterol content in A. flavus spores. Transcriptomic analysis revealed 4,312 differentially expressed genes in A. flavus spores exposed to (E)-2-heptenal, including 1,913 upregulated and 2,399 downregulated genes; these genes were mainly involved in ribosome biogenesis, cell cycle, linoleic acid metabolism, MAPK signaling, nucleoplasmic transport, meiosis, lipoic acid metabolism, DNA replication, and pyruvate metabolism pathways. (E)-2-heptenal can induce reactive oxygen species accumulation and mitochondrial dysfunction in A. flavus spores in a dose-dependent manner. Besides, DNA damage and autophagy was observed in (E)-2-heptenal-treated A. flavus spores with 4′,6-diamidino-2-phenylindole and monodansylcadaverine fluorescence staining. The findings of the present study provide insights into the underlying inhibitory mechanisms of (E)-2-heptenal on A. flavus spore germination. [ABSTRACT FROM AUTHOR]

This work addresses the problem of having no existent protocol that closely simulates the harsh concrete environment, namely, high pH (about 13) and temperature (up to above 50 ℃ during cement hydration), for selecting microorganisms to use in microbe-effected self-healing concrete (MESHC). This problem critically impedes the progress of MESHC development, which has tremendous significance because concrete cracking reduces service life while making new concrete consumes substantial energy and emits a large amount of CO2. The objective of this work was to develop an effective and innovative screening protocol that mimics not only the concrete-relevant pH and temperature but also the essential process/scenario of MESHC, that is, microbial spores remain dormant through the harsh conditions during concrete mixing and curing and germinate later at the less harsh condition (pH 9-11, ambient temperature) in concrete cracks. The protocol includes 4 steps with increasing complexity to reduce strains for time-consuming steps. The first 2 steps screen for strains capable of vegetative growth on agar and liquid media with initial pH = 10. Step 3 evaluates the spore germinability in medium with pH gradually decreasing from 12. In Step 4, spores were subjected to both high pH (12, 12.9) and temperature (45, 55 ℃) for 2 h before being stored in the high-pH medium at room temperature for up to 21 days. Spores were finally collected and resuspended in pH 9.5 medium to observe germinability. 18 alkalotolerant strains were screened. Scopulariopsis brevicaulis (S. brevicaulis) is identified as the best candidate. Results also indicate the importance of incorporating designs to locally lower pH near spores, at least slightly (from 12.9 to 12), and to limit temperature to below 53 ℃. Survivability of S. brevicaulis spores in contact with mortar undergoing cement hydration was also monitored. The work identifies promising fungi and indicates critical directions for developing spore-protection technologies for MESHC. [ABSTRACT FROM AUTHOR]

The flea beetle Nisotra uniformis Jacoby is a widespread pest of malvaceous crops for which synthetic chemical insecticides remain the principal control tool, particularly in sub-Saharan Africa. With the ultimate aim of developing a microbial alternative for N. uniformis control, we conducted laboratory experiments (25 ± 1°C; 70 - 80% RH) to evaluate the biological attributes of three Cameroonian isolates of the entomopathogenic fungi Beauveria bassiana (Balsamo-Crivelli) Vuillemin and Metarhizium anisopliae sensu lato (Metchnikoff) Sorokin. Spore germination rates of the isolates varied from 0.5% after 4 hrs to 100% after 24 hrs on PDA medium, with MIITAC11.3.4 spores germinating fastest. Pathogenicity tests consisted of dipping adult beetles in conidial suspensions. All isolates were pathogenic to N. uniformis, with corrected mortalities varying between 23.3 - 86.7%. BIITAC-O-2 had the lowest LC50 at 5.17 × 106 conidia/ml, while MIITAC11.3.4 and BIITAC6.2.2 had LC50 at 4.11 × 107 conidia/ml, and 2.00 × 108 conidia/ml, respectively. BIITAC6.2.2 produced the shortest time to the highest mortality rate (1.17 days) and the shortest LT50 of 1.64 days but only at the highest concentration, followed by the two highest concentrations of MIITAC11.3.4 (LT50 at 3.43 and 5.70 days). The c parameter in the Weibull model showed that BIITAC-O-2 caused the highest rate of increase in mortality (2.42) at the highest concentration, followed by MIITAC11.3.4 (1.09) and BIITAC6.2.2 (0.50). The results of our study provide the basis for including N. uniformis in the ongoing development of BIITAC6.2.2 and MIITAC11.3.4 into biopesticide while continuing with further laboratory studies on BIITAC-O-2.

Bacillus thuringiensis (Bt) and Lysinibacillus sphaericus (Ls) are the most widely used microbial insecticides. Both encounter unfavorable environmental factors and pesticides in the field. Here, the responses of Bt and Ls spores to glutaraldehyde were characterized using Raman spectroscopy and differential interference contrast imaging at the single-cell level. Bt spores were more sensitive to glutaraldehyde than Ls spores under prolonged exposure: <1.0% of Bt spores were viable after 10 min of 0.5% (v/v) glutaraldehyde treatment, compared to ~ 20% of Ls spores. The Raman spectra of glutaraldehyde-treated Bt and Ls spores were almost identical to those of untreated spores; however, the germination process of individual spores was significantly altered. The time to onset of germination, the period of rapid Ca2+–2,6-pyridinedicarboxylic acid (CaDPA) release, and the period of cortex hydrolysis of treated Bt spores were significantly longer than those of untreated spores, with dodecylamine germination being particularly affected. Similarly, the germination of treated Ls spores was significantly prolonged, although the prolongation was less than that of Bt spores. Although the interiors of Bt and Ls spores were undamaged and CaDPA did not leak, proteins and structures involved in spore germination could be severely damaged, resulting in slower and significantly prolonged germination. This study provides insights into the impact of glutaraldehyde on bacterial spores at the single cell level and the variability in spore response to glutaraldehyde across species and populations. [ABSTRACT FROM AUTHOR]

Curcumin, a natural bioactive compound derived from Curcuma longa , has been widely recognized for its antifungal properties. In this study, we investigated the effects of curcumin on the phytopathogenic fungus Alternaria alternata and its pathogenicity in cherry tomato fruit. The results demonstrated that curcumin treatment significantly inhibited mycelial growth and spore germination of A. alternata in a dose-dependent manner. Scanning electron microscopy revealed alterations in the morphology of A. alternata mycelia treated with curcumin. Furthermore, curcumin treatment led to an increase in malondialdehyde and hydrogen peroxide contents, indicating cell membrane damage in A. alternata. Moreover, curcumin exhibited a remarkable inhibitory effect on the incidence and lesion diameters of black rot caused by A. alternata in cherry tomato fruit. Gene expression analysis revealed upregulation of defense-related genes (POD , SOD , and CAT) in tomato fruit treated with curcumin. Additionally, curcumin treatment resulted in decreased activity of exocellular pathogenic enzymes (polygalacturonase, pectin lyase, and endo-1,4-β- d -glucanase) in A. alternata. Overall, our findings highlight the potential of curcumin as an effective antifungal agent against A. alternata , providing insights into its inhibitory mechanisms on mycelial growth, spore germination, and pathogenicity in cherry tomato fruit. [ABSTRACT FROM AUTHOR]

SUMMARY: The establishment of moss spores is considered a milestone in plant evolution. They harbor protein networks underpinning desiccation tolerance and accumulation of storage compounds that can be found already in algae and that are also utilized in seeds and pollen. Furthermore, germinating spores must produce proteins that drive the transition through heterotrophic growth to the autotrophic plant. To get insight into the plasticity of this proteome, we investigated it at five timepoints of moss (Physcomitrium patens) spore germination and in protonemata and gametophores. The comparison to previously published Arabidopsis proteome data of seedling establishment showed that not only the proteomes of spores and seeds are functionally related, but also the proteomes of germinating spores and young seedlings. We observed similarities with regard to desiccation tolerance, lipid droplet proteome composition, control of dormancy, and β‐oxidation and the glyoxylate cycle. However, there were also striking differences. For example, spores lacked any obvious storage proteins. Furthermore, we did not detect homologs to the main triacylglycerol lipase in Arabidopsis seeds, SUGAR DEPENDENT1. Instead, we discovered a triacylglycerol lipase of the oil body lipase family and a lipoxygenase as being the overall most abundant proteins in spores. This finding indicates an alternative pathway for triacylglycerol degradation via oxylipin intermediates in the moss. The comparison of spores to Nicotiana tabacum pollen indicated similarities for example in regards to resistance to desiccation and hypoxia, but the overall developmental pattern did not align as in the case of seedling establishment and spore germination. [ABSTRACT FROM AUTHOR]

In this study, we investigated the spore germination phenotype of Clostridium perfringens strains isolated from diarrheic animals (animal strains). The transcripts of germination-specific genes and their protein products were also measured. Our study found the following results: (i) animal strains spores germinated at a slower rate with AK (mixture of L-asparagine and KCl), L-cysteine, or L-lysine, but the extent of germination varied based on strains and germinants used; (ii) none of the amino acids (excluding L-cysteine and L-lysine) were identified as a universal germinant for spores of animal strains; (iii) animal strain spores germinated better at a pH range of 6.0–7.0; (iv) all tested germination-specific genes were expressed in animal strains; the levels of expression of major germinant receptor gene (gerKC) were higher and the cortex hydrolysis machinery genes (cspB and sleC) were lower in animal strains, compared to the food poisoning strain SM101; and (v) the levels of CspB and SleC were significantly lower in spores of animal strains compared to strain SM101, suggesting that these animal strains lack an efficient spore cortex hydrolysis machinery. In summary, our findings suggest that the poor or slow spore germination in C. perfringens animal strains might be due to incomplete spore cortex hydrolysis. [ABSTRACT FROM AUTHOR]

SUMMARY: DELAY OF GERMINATION 1 is a key regulator of dormancy in flowering plants before seed germination. Bryophytes develop haploid spores with an analogous function to seeds. Here, we investigate whether DOG1 function during germination is conserved between bryophytes and flowering plants and analyse the underlying mechanism of DOG1 action in the moss Physcomitrium patens. Phylogenetic and in silico expression analyses were performed to identify and characterise DOG1 domain‐containing genes in P. patens. Germination assays were performed to characterise a Ppdog1‐like1 mutant, and replacement with AtDOG1 was carried out. Yeast two‐hybrid assays were used to test the interaction of the PpDOG1‐like protein with DELLA proteins from P. patens and A. thaliana. P. patens possesses nine DOG1 domain‐containing genes. The DOG1‐like protein PpDOG1‐L1 (Pp3c3_9650) interacts with PpDELLAa and PpDELLAb and the A. thaliana DELLA protein AtRGA in yeast. Protein truncations revealed the DOG1 domain as necessary and sufficient for interaction with PpDELLA proteins. Spores of Ppdog1‐l1 mutant germinate faster than wild type, but replacement with AtDOG1 reverses this effect. Our data demonstrate a role for the PpDOG1‐LIKE1 protein in moss spore germination, possibly alongside PpDELLAs. This suggests a conserved DOG1 domain function in germination, albeit with differential adaptation of regulatory networks in seed and spore germination. Significance Statement: Seed and spore germination are considered analogous because they occur in the sporophyte (seed plants) and gametophyte (bryophytes). Here we show that an ortholog of Arabidopsis DELAY OF GERMINATION 1 (DOG1) controls spore germination in the moss P. patens, suggesting deep evolutionary conservation of germination control of reproductive diaspores. [ABSTRACT FROM AUTHOR]

Introduction. The study of the ability of Bacillus anthracis strains with different phenotypic properties to spore germination, reproduction and sporulation on a medium based on an aqueous soil extract can help assess the significance of these processes in the formation and maintenance of soil anthrax foci. Aim. The analysis of individual characteristics of the development of a vegetative culture of anthrax pathogen strains with different phenotypes in a soil medium model. Materials and methods. On a group of anthrax microbe strains with different plasmid composition and virulence, the possibility of spore germination, reproduction of bacilli and, at least in some of them, productive spore formation on the soil medium was studied. Results. Three variants of culture development of B. anthracis strains were identified: 1 spores remain intact, not germinating; 2 after germination of spores, bacilli are formed, which multiply with different intensity, passing into involutional forms without spore formation; 3 the passage of a complete physiological cycle "sporebacillusspore". The presence of 2% blood in the soil environment contributed to the germination of spores and reproduction of the culture, but inhibited the process of sporulation during the observation period of 3 days. No correlation was found between a certain phenotype of the studied strains of B. anthracis and the ability to germinate and vegetate on soil media. Conclusion. The data obtained that only 17% of CFU gives rise to the formation of colonies on the soil medium suggest the heterogeneity of the properties of the population of the studied strains. Isolation of such cultures and their further detailed study will make it possible to identify the most significant complexes of biological properties for the realization of a complete physiological cycle under soil-simulating conditions.

In this study, the effect of citronellal on the synthesis of ergosterol in the spores of imazalil-sensitive (Pds01) and imazalil-resistant (Pdw03) strains of Penicillium digitatum was investigated. The results showed that citronellal significantly inhibited the spore germination of Pds01 and Pdw03 with half maximal inhibitory concentration (IC50) of 0.8 and 3.2 µL/mL, respectively. Citronellal at its IC50 significantly decreased and increased the contents of ergosterol and lanosterol in Pds01 and Pdw03 spores, respectively. The expression of key genes involved in ergosterol synthesis was significantly affected. The up-regulated expression of the ERG9 gene in Pds01 peaked earlier than that in Pdw03, and the expression level of ERG3 was significantly down-regulated in both strains. This study showed that citronellal reduced ergosterol synthesis in Pds01 and Pdw03 spores by inhibiting ERG3 expression, thereby affecting spore germination, which could provide a theoretical basis for the development of green preservatives for postharvest citrus diseases.

Background Interactions between moss species in their earliest growth stages have received little attention. To what extent interspecific competition or priority effects influence spore germination, protonemal development and gametophore emergence is unknown. We evaluated such effects in pairwise interaction between six common bryophyte species: Atrichum undulatum, Bryum argenteum, Ceratodon purpureus, Funaria hygrometrica, Hypnum cupressiforme, Leptobryum pyriforme Methods Interspecific interactions were assessed in vitro. Spores were sterilized and sown on agar plates in three treatments: 1) as single species cultures (controls), 2) as pairwise species cultures inoculated simultaneously, and 3) with a time lag of 20 days between species. Data on time needed for spore germination, germination rate, the time needed for gametophore differentiation, number of gametophores per germinated spore and average diameter of colonies were collected. We also performed spore germination tests in single-species cultures at the start and end of the study, as well as tests for density-dependency at spore germination and gametophore formation. Results We observed strong pairwise interactive effects when sowing spores of different species simultaneously or with a delay of 20 days. The results indicate that spore germination is often inhibited by interspecific competition. The first species has an advantage as compared to the later colonizing species, i.e., an apparent priority effect. Interspecific interactions were also evident during gametophore development and included both inhibition and facilitation. Conclusion We found pronounced differences in the relative performance of species in interaction with other species during spore germination and gametophore formation. Allelopathic effects are the most probable explanation for these observations. Our results under sterile lab conditions are likely to reflect processes that occur in the wild, governing biotic filtering and bryophyte community assembly during primary and secondary colonization.

Abstract Pteris congesta an endemic and endangered species was investigated to identify morphological differences between its sterile and fertile leaves. Our findings have unveiled, leaf dimorphism in both morphology and growth patterns between fertile and sterile leaves. The sterile leaves petioles exhibited equivalent growth to the laminae, achieving complete leaf expansion within a month. In contrast, the petioles of fertile leaves elongated more than twice the size of the leaf blades that remain closed for the initial 30 days. Spore germination was carried out in both sterile and non-sterile soils, and juvenile sporophytes were cultivated to allow for morphological comparisons with those collected from the wild. One month after sowing the spores germinated in both soils resulting in a uniseriate germ filament Vittaria-type, and differentiated into laminar gametophytes, forming a Ceratopteris-type prothallus. The first leaf of the sporophyte emerged two months after sowing, and its development was completed one month later. Based on our studies, we propose that seedlings cultivated from spores germinated in soil can be used for the reintroduction of endangered fern species.

The quaternary structure with specific stoichiometry is pivotal to the specific function of protein complexes. However, determining the structure of many protein complexes experimentally remains a major bottleneck. Structural bioinformatics approaches, such as the deep learning algorithm Alphafold2‐multimer (AF2‐multimer), leverage the co‐evolution of amino acids and sequence‐structure relationships for accurate de novo structure and contact prediction. Pseudo‐likelihood maximization direct coupling analysis (plmDCA) has been used to detect co‐evolving residue pairs by statistical modeling. Here, we provide evidence that combining both methods can be used for de novo prediction of the quaternary structure and stoichiometry of a protein complex. We achieve this by augmenting the existing AF2‐multimer confidence metrics with an interpretable score to identify the complex with an optimal fraction of native contacts of co‐evolving residue pairs at intermolecular interfaces. We use this strategy to predict the quaternary structure and non‐trivial stoichiometries of Bacillus subtilis spore germination protein complexes with unknown structures. Co‐evolution at intermolecular interfaces may therefore synergize with AI‐based de novo quaternary structure prediction of structurally uncharacterized bacterial protein complexes. [ABSTRACT FROM AUTHOR]

In plants, the ability to produce hydrophobic substances that would provide protection from dehydration was required for the transition to land. This genome-wide investigation outlines the evolution of GDSL-type esterase/lipase (GELP) proteins in the moss Physcomitrium patens and suggests possible functions of some genes. GELP proteins play roles in the formation of hydrophobic polymers such as cutin and suberin that protect against dehydration and pathogen attack. GELP proteins are also implicated in processes such as pollen development and seed metabolism and germination. The P. patens GELP gene family comprises 48 genes and 14 pseudogenes. Phylogenetic analysis of all P. patens GELP sequences along with vascular plant GELP proteins with reported functions revealed that the P. patens genes clustered within previously identified A, B and C clades. A duplication model predicting the expansion of the GELP gene family within the P. patens lineage was constructed. Expression analysis combined with phylogenetic analysis suggested candidate genes for functions such as defence against pathogens, cutin metabolism, spore development and spore germination. The presence of relatively fewer GELP genes in P. patens may reduce the occurrence of functional redundancy that complicates the characterization of vascular plant GELP genes. Knockout lines of GELP31, which is highly expressed in sporophytes, were constructed. Gelp31 spores contained amorphous oil bodies and germinated late, suggesting (a) role(s) of GELP31 in lipid metabolism in spore development or germination. Future knockout studies of other candidate GELP genes will further elucidate the relationship between expansion of the family and the ability to withstand the harsh land environment. [ABSTRACT FROM AUTHOR]

The bacterial strain Collimonas fungivorans Ter331 (CfTer331) inhibits mycelial growth and spore germination in Aspergillus niger N402 (AnN402). The mechanisms underlying this antagonistic bacterial-fungal interaction have been extensively studied, but knowledge on the long-term outcome of this interaction is currently lacking. Here, we used experimental evolution to explore the dynamics of fungal adaptation to recurrent exposure to CfTer331. Specifically, five single-spore isolates (SSIs) of AnN402 were evolved under three selection scenarios in liquid culture, i.e., (i) in the presence of CfTer331 for 80 growth cycles, (ii) in the absence of the bacterium for 80 cycles, and (iii) in the presence of CfTer331 for 40 cycles and then in its absence for 40 cycles. The evolved SSI lineages were then evaluated for phenotypic changes from the founder fungal strain, such as germinability with or without CfTer331. The analysis showed that recurrent exposure to CfTer331 selected for fungal lineages with reduced germinability and slower germination, even in the absence of CfTer331. In contrast, when AnN402 evolved in the absence of the bacteria, lineages with increased germinability and faster germination were favored. SSIs that were first evolved in the presence of CfTer331 and then in its absence showed intermediate phenotypes but overall were more similar to SSIs that evolved in the absence of CfTer331 for 80 cycles. This suggests that traits acquired from exposure to CfTer331 were reversible upon removal of the selection pressure. Overall, our study provides insights into the effects on fungi from the long-term coculture with bacteria. IMPORTANCE The use of antagonistic bacteria for managing fungal diseases is becoming increasingly popular, and thus there is a need to understand the implications of their long-term use against fungi. Most efforts have so far focused on characterizing the antifungal properties and mode of action of the bacterial antagonists, but the possible outcomes of the persisting interaction between antagonistic bacteria and fungi are not well understood. In this study, we used experimental evolution in order to explore the evolutionary aspects of an antagonistic bacterial-fungal interaction, using the antifungal bacterium Collimonas fungivorans and the fungus Aspergillus niger as a model system. We show that evolution in the presence or absence of the bacteria selects for fungal lineages with opposing and conditionally beneficial traits, such as slow and fast spore germination, respectively. Overall, our studies reveal that fungal responses to biotic factors related to antagonism could be to some extent predictable and reversible.

The effect of low-intensity fixed-frequency continuous ultrasound (LIFFCU) on the growth of Bacillus licheniformis YYC4 was investigated. The changes in morphology and activity of the organism, contributing to the growth were also explored. Compared with the control, a significant increase (48.95%) in the biomass of B. licheniformis YYC4 (at the logarithmic metaphase) was observed following the LIFFCU (28 kHz, 1.5 h and 120 W (equivalent to power density of 40 W/L)) treatment. SEM images showed that ultrasonication caused sonoporation, resulting in increased membrane permeability, evidenced by increase in cellular membrane potential, electrical conductivity of the culture, extracellular protein and nucleic acid, and intracellular Ca2+ content. Furthermore, LIFFCU action remarkably increased the extracellular protease activity, volatile components of the culture medium, microbial metabolic activity, and spore germination of the strain. Therefore, LIFFCU could be used to efficiently promote the growth of targeted microorganisms.

ABSTRACT Bacterial spores are metabolically dormant, resistant to microbicides, and vectors of food spoilage and diseases, while germinated spores are easy to kill. Consequently, understanding germination mechanisms may facilitate the development of “germinate-to-eradicate” strategies. Spores germinate in response to many compounds (called germinants). They can also retain the memory of a germinant exposure, such that a second exposure triggers more efficient germination, but how is not clear. A recent high-profile paper [Science (2022) 378:43] suggested that increasing spore electrochemical potential is how memory is “stored” based on measurements of Bacillus subtilis spores’ accumulation of the dye thioflavin-T after germinant exposure. Indeed, we found that wild-type spores of three Bacillus and one Clostridioides species all exhibited this early thioflavin-T accumulation during nutrient pulses. However, our data indicate that inferring spores’ electrochemical potential from thioflavin-T accumulation is problematic. We found that B. subtilis spores lacking their proteinaceous coat exhibited memory but did not accumulate thioflavin-T prior to germinant addition or during nutrient pulses. Furthermore, wild-type Bacillus spores germinating with dodecylamine, which also elicits memory, showed no thioflavin-T accumulation. Finally, we found that thioflavin-T accumulation by a germinating spore is outside the spore core at early stages but inside the spore core as germination proceeds. These findings suggest that thioflavin-T accumulation during the early stages of germination is due to its binding to one or more protein in the spore coat rather than to changes in spores’ electrochemical potential; thus, thioflavin-T is not a potentiometric dye for the study of spore memory of germinant pulses. IMPORTANCE Bacillus and Clostridium spores cause food spoilage and disease because of spores’ dormancy and resistance to microbicides. However, when spores “come back to life” in germination, their resistance properties are lost. Thus, understanding the mechanisms of spore germination could facilitate the development of “germinate to eradicate” strategies. One germination feature is the memory of a pulsed germinant stimulus leading to greater germination following a second pulse. Recent observations of increases in spore binding of the potentiometric dye thioflavin-T early in their germination of spores led to the suggestion that increasing electrochemical potential is how spores “remember” germinant pulses. However, new work finds no increased thioflavin-T binding in the physiological germination of Coatless spores or of intact spores germinating with dodecylamine, even though spore memory is seen in both cases. Thus, using thioflavin-T uptake by germinating spores to assess the involvement of electrochemical potential in memory of germinant exposure, as suggested recently, is questionable.

Many fungal pathogens are associated with grapevine trunk diseases (GTDs), which cause important yield and economic losses in grape production. There are no effective control methods against GTDs once plants are infected, so research is aimed at preventive measures to avoid infections in nurseries and vineyards. Inhibitory activities of the phenolic compounds eugenol, epigallocatechin–3–O–gallate (EGCG) and thymol against the GTD fungi Diplodia seriata, Eutypa lata, Fomitiporia mediterranea and Neofusicoccum parvum were assessed in vitro, and in planta as grapevine pruning wound treatments. Greatest inhibition of pathogen mycelium growth was observed with eugenol (fungistatic at 1,500 µg mL–1, fungicidal at 2,500 µg mL–1). No inhibitory activity against GTD fungi was observed with EGCG. Minimum concentrations with in vitro inhibitory effects on D. seriata and N. parvum spore germination were 360 µg mL–1 for thymol and 750 µg mL–1 for eugenol. In the grapevine wound protection tests, thymol was effective against N. parvum at 360 µg mL–1, but eugenol was not. [ABSTRACT FROM AUTHOR]

Daylily (Hemerocallis spp) rust caused by Puccinia hemerocallidis is a common disease that has become a global problem. This study identified and characterized the causal agent of daylily rust in east China. Based on the internal transcribed spacer (ITS) sequences, a phylogenetic tree of the P. hemerocallidis from China and other geographical regions was constructed, and the result showed that P. hemerocallidis from daylilies in east China grouped with other P. hemerocallidis isolates collected from North-, Central-American and Europe. In addition, the effects of incubation condition, temperature, and light on urediniospores germination were investigated in vitro. The results showed that the P. hemerocallidis urediniospores could germinate at 10–40 ℃ under light intensity of 10–100 Klux, but they hardly germinated at 5 ℃. W-WA medium (water agar medium covered with sterile water) was the most suitable in vitro germination substrate, combined with the temperature of 20–30 ℃ and light intensity of 40–70 Klux. The results of this study provided a basis for understanding the biology of the causal agent of daylily rust disease. [ABSTRACT FROM AUTHOR]

The pathogen Verticillium dahliae causes Verticillium wilt in a number of crops, including cotton Verticillium wilt. Chaetoviridin A, a secondary metabolite of Chaetomium globosum, significantly inhibits the growth of V. dahliae. Spore germination is a major part of the disease cycle. However, the molecular mechanism of chaetoviridin A inhibiting spore germination of V. dahliae is unknown. In this work, we found that chaetoviridin A significantly inhibited spore germination of V. dahliae. Transcriptome analysis showed that DEGs were enriched in linolenic acid metabolism, alpha-Linolenic acid metabolism, Arachidonic acid metabolism and Purine metabolism pathways at 1 h, which were related to cell membrane. At 3 h, DEGs were enriched in the pathways of galactose metabolism, diterpenoid biosynthesis, cysteine and methionine metabolism, and starch and sucrose metabolism, which were mainly related to amino acid metabolism and sugar metabolism. Several genes related to glucose metabolism were identified, mainly including Glucagon endo-1,3-alpha-glucosidase agn1, glucoamylase, maltose O-acetyltransferase, and beta-galactosidase. Stress resistance gene PAL, detoxification gene P450 2C31 and ABA receptor were also down- regulated. These genes may be related to spore germination. These results provide a theoretical basis for chaetoviridin A to control fungal diseases. [ABSTRACT FROM AUTHOR]

Bacillus anthracis Ser/Thr protein kinase PrkC is necessary for phenotypic memory and spore germination, and the loss of PrkC-dependent phosphorylation events affect the spore development. During sporulation, Bacillus sp. can store 3-Phosphoglycerate (3-PGA) that will be required at the onset of germination when ATP will be necessary. The Phosphoglycerate mutase (Pgm) catalyzes the isomerization of 2-PGA and 3-PGA and is important for spore germination as a key metabolic enzyme that maintains 3-PGA pool at later events. Therefore, regulation of Pgm is important for an efficient spore germination process and metabolic switching. While the increased expression of Pgm in B. anthracis decreases spore germination efficiency, it remains unexplored if PrkC could directly influence Pgm activity. Here, we report the phosphorylation and regulation of Pgm by PrkC and its impact on Pgm stability and catalytic activity. Mass spectrometry revealed Pgm phosphorylation on seven threonine residues. In silico mutational analysis highlighted the role of Thr459 residue towards metal and substrate binding. Altogether, we demonstrated that PrkC-mediated Pgm phosphorylation negatively regulates its activity that is essential to maintain Pgm in its apo-like isoform before germination. This study advances the role of Pgm regulation that represents an important switch for B. anthracis resumption of metabolism and spore germination. • Ser/Thr protein phosphorylation regulates glycolysis in B. anthracis. • Phosphorylation of glycolytic enzyme phosphoglycerate mutase (Pgm) is important in morphogenesis. • During the spore formation and germination, Pgm activity is regulated. • Unphosphorylated Pgm represents the active form, suggesting that phosphorylation has a negative effect on its function. • PrkC-dependent regulation of Pgm indicates the complexity of bacterial signaling and control of metabolism. [ABSTRACT FROM AUTHOR]

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Sodium silicate (Na2SiO3) and ethylenediaminetetraacetic acid disodium salt (EDTA-Na2) are inorganic salts classified as 'Generally Recognized as Safe' (GRAS) compounds with great advantages in controlling various pathogens of postharvest fruits and vegetables. Here, we determined the median effective concentration (EC50) of Na2SiO3 (0.06%, 0.05%, 0.07% and 0.08%) and EDTA-Na2 (0.11%, 0.08%, 0.5%, and 0.07%) against common pathogens affecting postharvest citrus fruit, including Penicillium digitatum, Penicillium italicum, Geotrichum citri-aurantii, and Colletotrichum gloeosporioides. Na2SiO3 and EDTA-Na2 treatments at the EC50 decreased the spore germination rate, visibly disrupted the spore cell membrane integrity, and significantly increased the lipid droplets (LDs) of the four postharvest pathogens. Moreover, both treatments at EC50 significantly reduced the disease incidence of P. italicum (by 60% and 93.335, respectively) and G. citri-aurantii (by 50% and 76.67%, respectively) relative to the control. Furthermore, Na2SiO3 and EDTA-Na2 treatment resulted in dramatically lower disease severity of the four pathogens, while also demonstrating no significant change in citrus fruit quality compared with the control. Therefore, Na2SiO3 and EDTA-Na2 present a promising approach to control the postharvest diseases of citrus fruit. [ABSTRACT FROM AUTHOR]

Rice blast is a destructive rice disease that is rapidly spread by the drift of Magnaporthe oryzae spores. Conidial attachment to the rice leaf surface is the most crucial step in the rapid spread of rice blast. Therefore, blocking the chance of contact between spores and the rice leaf surface is extremely vital for controlling rice blast. In this study, based on the strong affinity between the lectin protein-ConA and M. oryzae spores, we successfully constructed ConA-loaded PEGylated graphene oxide (GO-PEG-ConA) as targeted nanopesticide carriers to load epoxiconazole (EPX) against M. oryzae. The ConA loading capacity of the GO-PEG-EPX-ConA nanocarrier was 14.7% by the sodium dodecyl sulfate–polyacrylamide gel electrophoresis assay. The GO-PEG-ConA nanocarrier could obviously inhibit the germination of M. oryzae spores by 41.7% and showed 2.4-fold higher inhibitory activity than the inhibition ratio (17.4%) of GO-PEG nanocarriers, which was mainly due to the higher affinity between the GO-PEG-ConA nanocarrier and M. oryzae spores. Moreover, the greenhouse experiment indicated that the GO-PEG-EPX-ConA nanopesticide could significantly reduce rice blast lesions in rice seedlings, fundamentally settling the transmission of rice blast. Therefore, GO-PEG-ConA could be a targeted nanopesticide carrier to realize precise release of pesticides, which would offer an important reference value for improving pesticide utilization efficiency. [ABSTRACT FROM AUTHOR]

Phomopsis vexans is a phytopathogenic fungus that causes Phomopsis blight of eggplant. Because spore germination is required for infection, preventing it may be a viable approach to disease management. The proteome during the conversion of spores to mycelium was analyzed in the current study to gain more insight into this process. A total of 3337 proteins were discovered and functionally classified. There were 929 proteins with significant fold changes (P value ≤ 0.05, Fold change > 2) among them. which were grouped into 6 clusters based on their relative expression similarities. Sphingolipid metabolism, Glycosylphosphatidylinositol (GPI)-anchor biosynthesis, Riboflavin metabolism, and Glutathione metabolism were found to be significantly upregulated during the germ tube emerging stage, according to Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment. Proteins in these pathways may be important in spore germination and may be antifungal targets. In addition, eight potential effectors were discovered. This is the first report on proteomic analysis of Phomopsis vexans spore germination. It can aid in understanding the mechanisms of host invasion and shed light on Phomopsis vexans control. [ABSTRACT FROM AUTHOR]

Anthracnose is a fungal disease that seriously threatens grape production and quality. Multiple Colletotrichum species are detected in anthracnose grapes in vineyards. In this study, diseased grapes were collected in four counties in Zhejiang, and 43 Colletotrichum isolates were obtained. Multi-genes (ITS, TUB2, ACT, CHS-I, and GAPDH) and morphological characteristic analyses showed that C. fructicola (40 isolates, 93%), C. aenigma (two isolates, 4.7%), and C. pseudoacutatum (one isolate, 2.3%) were the cause of grape anthracnose in Zhejiang. Among the three Colletotrichum species, C. fructicola was the prevalent and dominant species in all sampled counties; C. pseudoacutatum was first identified as the pathogen responsible for grape anthracnose. There were significant differences in the sporulation among the three Colletotrichum species, as well as in the spore germination. Pathogenicity testing showed that all species can infect grapes, resulting in anthracnose. On the other hand, the virulence of species was varied and may be associated with their spore germination. This is the first study to characterize the Colletotrichum species causing grape anthracnose in Zhejiang Province and reveal that C. fructicola is the dominant species. The determination of Colletotrichum species associated with grape anthracnose may contribute to the study of epidemiology and development of an efficient strategy for controlling anthracnose in the vineyards. [ABSTRACT FROM AUTHOR]

The current investigation addressed the green synthesis of silver nanoparticles (AgNPs) using newly isolated silver-resistant rare actinomycetes, Glutamicibacter nicotianae SNPRA1 and Leucobacter aridicollis SNPRA2, and investigated their impact on the mycotoxigenic fungi Aspergillus flavus ATCC 11498 and Aspergillus ochraceus ATCC 60532. The formation of AgNPs was evidenced by the reaction's color change to brownish and the appearance of the characteristic surface plasmon resonance. The transmission electron microscopy of biogenic AgNPs produced by G. nicotianae SNPRA1 and L. aridicollis SNPRA2 (designated Gn-AgNPs and La-AgNPs, respectively) revealed the generation of monodispersed spherical nanoparticles with average sizes of 8.48 ± 1.72 nm and 9.67 ± 2.64 nm, respectively. Furthermore, the XRD patterns reflected their crystallinity and the FTIR spectra demonstrated the presence of proteins as capping agents. Both bioinspired AgNPs exhibited a remarkable inhibitory effect on the conidial germination of the investigated mycotoxigenic fungi. The bioinspired AgNPs caused an increase in DNA and protein leakage, suggesting the disruption of membrane permeability and integrity. Interestingly, the biogenic AgNPs completely inhibited the production of total aflatoxins and ochratoxin A at concentrations less than 8 μg/mL. At the same time, cytotoxicity investigations revealed the low toxicity of the biogenic AgNPs against the human skin fibroblast (HSF) cell line. Both biogenic AgNPs exhibited feasible biocompatibility with HSF cells at concentrations up to 10 μg/mL and their IC50 values were 31.78 and 25.83 μg/mL for Gn-AgNPs and La-AgNPs, respectively. The present work sheds light on the antifungal prospect of the biogenic AgNPs produced by rare actinomycetes against mycotoxigenic fungi as promising candidates to combat mycotoxin formation in food chains at nontoxic doses. [ABSTRACT FROM AUTHOR]

Rust fungi (Pucciniales) are a diverse group of plant pathogens in natural and agricultural systems. They pose ongoing threats to the diversity of native flora and cause annual crop yield losses. Agricultural rusts are predominantly managed with fungicides and breeding for resistance, but new control strategies are needed on non‐agricultural plants and in fragile ecosystems. RNA interference (RNAi) induced by exogenous double‐stranded RNA (dsRNA) has promise as a sustainable approach for managing plant‐pathogenic fungi, including rust fungi. We investigated the mechanisms and impact of exogenous dsRNA on rust fungi through in vitro and whole‐plant assays using two species as models, Austropuccinia psidii (the cause of myrtle rust) and Coleosporium plumeriae (the cause of frangipani rust). In vitro, dsRNA either associates externally or is internalized by urediniospores during the early stages of germination. The impact of dsRNA on rust infection architecture was examined on artificial leaf surfaces. dsRNA targeting predicted essential genes significantly reduced germination and inhibited development of infection structures, namely appressoria and penetration pegs. Exogenous dsRNA sprayed onto 1‐year‐old trees significantly reduced myrtle rust symptoms. Furthermore, we used comparative genomics to assess the wide‐scale amenability of dsRNA to control rust fungi. We sequenced genomes of six species of rust fungi, including three new families (Araucariomyceaceae, Phragmidiaceae, and Skierkaceae) and identified key genes of the RNAi pathway across 15 species in eight families of Pucciniales. Together, these findings indicate that dsRNA targeting essential genes has potential for broad‐use management of rust fungi across natural and agricultural systems. [ABSTRACT FROM AUTHOR]

The flea beetle Nisotra uniformis Jacoby is a widespread pest of malvaceous crops for which synthetic chemical insecticides remain the principal control tool, particularly in sub-Saharan Africa. With the ultimate aim of developing a microbial alternative for N. uniformis control, we conducted laboratory experiments (25 ± 1°C; 70 - 80% RH) to evaluate the biological attributes of three Cameroonian isolates of the entomopathogenic fungi Beauveria bassiana (Balsamo-Crivelli) Vuillemin and Metarhizium anisopliae sensu lato (Metchnikoff) Sorokin. Spore germination rates of the isolates varied from 0.5% after 4 hrs to 100% after 24 hrs on PDA medium, with MIITAC11.3.4 spores germinating fastest. Pathogenicity tests consisted of dipping adult beetles in conidial suspensions. All isolates were pathogenic to N. uniformis, with corrected mortalities varying between 23.3 - 86.7%. BIITAC-O-2 had the lowest LC50 at 5.17 × 106 conidia/ml, while MIITAC11.3.4 and BIITAC6.2.2 had LC50 at 4.11 × 107 conidia/ml, and 2.00 × 108 conidia/ml, respectively. BIITAC6.2.2 produced the shortest time to the highest mortality rate (1.17 days) and the shortest LT50 of 1.64 days but only at the highest concentration, followed by the two highest concentrations of MIITAC11.3.4 (LT50 at 3.43 and 5.70 days). The c parameter in the Weibull model showed that BIITAC-O-2 caused the highest rate of increase in mortality (2.42) at the highest concentration, followed by MIITAC11.3.4 (1.09) and BIITAC6.2.2 (0.50). The results of our study provide the basis for including N. uniformis in the ongoing development of BIITAC6.2.2 and MIITAC11.3.4 into biopesticide while continuing with further laboratory studies on BIITAC-O-2. [ABSTRACT FROM AUTHOR]

ABSTRACT Clostridioides difficile infections begin when its metabolically dormant spores germinate in response to sensing bile acid germinants alongside amino acid and divalent cation co-germinants in the small intestine. While bile acid germinants are essential for C. difficile spore germination, it is currently unclear whether both co-germinant signals are required. One model proposes that divalent cations, particularly Ca2+, are essential for inducing germination, while another proposes that either co-germinant class can induce germination. The former model is based on the finding that spores defective in releasing large stores of internal Ca2+ in the form of calcium dipicolinic acid (CaDPA) cannot germinate when germination is induced with bile acid germinant and amino acid co-germinant alone. However, since the reduced optical density of CaDPA-less spores makes it difficult to accurately measure their germination, we developed a novel automated, time-lapse microscopy-based germination assay to analyze CaDPA mutant germination at the single-spore level. Using this assay, we found that CaDPA mutant spores germinate in the presence of amino acid co-germinant and bile acid germinant. Higher levels of amino acid co-germinants are nevertheless required to induce CaDPA mutant spores to germinate relative to WT spores because CaDPA released by WT spores during germination can function in a feedforward loop to potentiate the germination of other spores within the population. Collectively, these data indicate that Ca2+ is not essential for inducing C. difficile spore germination because amino acid and Ca2+ co-germinant signals are sensed by parallel signaling pathways. IMPORTANCE Clostridioides difficile spore germination is essential for this major nosocomial pathogen to initiate infection. C. difficile spores germinate in response to sensing bile acid germinant signals alongside co-germinant signals. There are two classes of co-germinant signals: Ca2+ and amino acids. Prior work suggested that Ca2+ is essential for C. difficile spore germination based on bulk population analyses of germinating CaDPA mutant spores. Since these assays rely on optical density to measure spore germination and the optical density of CaDPA mutant spores is reduced relative to WT spores, this bulk assay is limited in its capacity to analyze germination. To overcome this limitation, we developed an automated image analysis pipeline to monitor C. difficile spore germination using time-lapse microscopy. With this analysis pipeline, we demonstrate that, although Ca2+ is dispensable for inducing C. difficile spore germination, CaDPA can function in a feedforward loop to potentiate the germination of neighboring spores.

Background: Interactions between moss species in their earliest growth stages have received little attention. To what extent interspecific competition or priority effects influence spore germination, protonemal development and gametophore emergence is unknown. We evaluated such effects in pairwise interaction between six common bryophyte species: Atrichum undulatum, Bryum argenteum, Ceratodon purpureus, Funaria hygrometrica, Hypnum cupressiforme, Leptobryum pyriforme Methods: Interspecific interactions were assessed in vitro. Spores were sterilized and sown on agar plates in three treatments: 1) as single species cultures (controls), 2) as pairwise species cultures inoculated simultaneously, and 3) with a time lag of 20 days between species. Data on the time needed for spore germination, germination rate, the time needed for gametophore differentiation, number of gametophores per germinated spore and average diameter of colonies were collected. We also performed spore germination tests in single-species cultures at the start and end of the study, as well as tests for density-dependency at spore germination and gametophore formation. Results: We observed strong pairwise interactive effects when sowing spores of different species simultaneously or with a delay of 20 days. The results indicate that spore germination is often inhibited by interspecific competition. The first species has an advantage as compared to the later colonizing species, i.e., an apparent priority effect. Interspecific interactions were also evident during gametophore development and included both inhibition and facilitation. Conclusion: We found pronounced differences in the relative performance of species in interaction with other species during spore germination and gametophore formation. Allelopathic effects are the most probable explanation for these observations. Our results under sterile lab conditions are likely to reflect processes that occur in the wild, governing biotic filtering and bryophyte community assembly during primary and secondary colonization.

In this study, we investigated the spore germination phenotype of Clostridium perfringens strains isolated from diarrheic animals (animal strains). The transcripts of germination-specific genes and their protein products were also measured. Our study found the following results: (i) animal strains spores germinated at a slower rate with AK (mixture of L-asparagine and KCl), L-cysteine, or L-lysine, but the extent of germination varied based on strains and germinants used; (ii) none of the amino acids (excluding L-cysteine and L-lysine) were identified as a universal germinant for spores of animal strains; (iii) animal strain spores germinated better at a pH range of 6.0–7.0; (iv) all tested germination-specific genes were expressed in animal strains; the levels of expression of major germinant receptor gene (gerKC) were higher and the cortex hydrolysis machinery genes (cspB and sleC) were lower in animal strains, compared to the food poisoning strain SM101; and (v) the levels of CspB and SleC were significantly lower in spores of animal strains compared to strain SM101, suggesting that these animal strains lack an efficient spore cortex hydrolysis machinery. In summary, our findings suggest that the poor or slow spore germination in C. perfringens animal strains might be due to incomplete spore cortex hydrolysis.

Fungal infections cause losses amounting to between 20 and 25% of the fruit industry's total outcome, with an escalating impact on agriculture in the last decades. As seaweeds have long demonstrated relevant antimicrobial properties against a wide variety of microorganisms, extracts from Asparagopsis armata, Codium sp., Fucus vesiculosus, and Sargassum muticum were used to find sustainable, ecofriendly, and safe solutions against Rocha pear postharvest fungal infections. Alternaria alternata, Botrytis cinerea, Fusarium oxysporum, and Penicillium expansum mycelial growth and spore germination inhibition activities were tested in vitro with five different extracts of each seaweed (n-hexane, ethyl acetate, aqueous, ethanolic, and hydroethanolic). An in vivo assay was then performed using the aqueous extracts against B. cinerea and F. oxysporum in Rocha pear. The n-hexane, ethyl acetate, and ethanolic extracts from A. armata showed the best in vitro inhibitory activity against B. cinerea, F. oxysporum, and P. expansum, and promising in vivo results against B. cinerea using S. muticum aqueous extract were also found. The present work highlights the contribution of seaweeds to tackle agricultural problems, namely postharvest phytopathogenic fungal diseases, contributing to a greener and more sustainable bioeconomy from the sea to the farm. [ABSTRACT FROM AUTHOR]

Ustilago maydis expresses a number of proteases during its pathogenic lifecycle. Some of the proteases including both intracellular and extracellular ones have previously been shown to influence the virulence of the pathogen. However, any role of secreted proteases in the sporulation process of U. maydis have not been explored earlier. In this study we have investigated the biological function of one such secreted protease, Ger1 belonging to aspartic protease A1 family. An assessment of the real time expression of ger1 revealed an infection specific expression of the protein especially during late phases of infection. We also evaluated any contribution of the protein in the pathogenicity of the fungus. Our data revealed an involvement of Ger1 in the sporulation and spore germination processes of U. maydis. Ger1 also showed positive influence on the pathogenicity of the fungus and accordingly the ger1 deletion mutant exhibited reduced pathogenicity. The study also demonstrated the protease activity associated with Ger1 to be essential for its biological function. Fluorescence microscopy of maize plants infected with U. maydis cells expressing Ger1‐mcherry‐HA also revealed that Ger1 is efficiently secreted within maize apoplast. Take‐away: A secreted aspartic acid protease (Ger1) is found to be involved in pathogenesis of Ustilago maydis. Ger1 deletion mutants of U. maydis exhibit reduced efficiency of spore germination. Ger1 regulates sporulation in U. maydis through its protease activity. [ABSTRACT FROM AUTHOR]

Desiccation tolerance (DT) is the ability of an organism or structure to dry completely and subsequently survive in that air-dry state. Hornworts are excellent plant models to study desiccation effects as they have contrasting life histories which are likely associated with DT. We tested whether (1) epiphytic species had more efficient DT responses to drying and postrehydration than non-epiphytic species and whether (2) "green" spores were more sensitive than non-green spores to extreme drying. Hornwort species were collected from the Atlantic Forest of Rio de Janeiro, Brazil. We studied five species (gametophytes and spores: Dendroceros crispus, D. crispatus, Nothoceros vincentianus, Phaeoceros carolinianus; and only spores of Anthoceros lamellatus), using different relative humidity values, drying durations, and postrehydration conditions. All DT treatments affected the chlorophyll fluorescence (Fv/Fm) of gametophytes, with species-specific responses. D. crispatus and D. crispus (epiphytes) performed better than P. carolinianus and N. vincentianus, with fast recovery of Fv/Fm values postrehydration. The ability of non-green spores of P. carolinianus and A. lamellatus and green spores of D. crispus to support desiccation led us to reject our second hypothesis. The DT strategies of hornworts highlighted the trade-offs that are important in spore dispersal and plant establishment, such as fast colonization in Dendroceros spp. and potential spore soil banks in Phaeoceros and Anthoceros species. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Food Safety & Quality is the property of Journal of Food Safety & Quality Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Pteris congesta an endemic and endangered species was investigated to identify morphological differences between its sterile and fertile leaves. Our findings have unveiled, leaf dimorphism in both morphology and growth patterns between fertile and sterile leaves. The sterile leaves petioles exhibited equivalent growth to the laminae, achieving complete leaf expansion within a month. In contrast, the petioles of fertile leaves elongated more than twice the size of the leaf blades that remain closed for the initial 30 days. Spore germination was carried out in both sterile and non-sterile soils, and juvenile sporophytes were cultivated to allow for morphological comparisons with those collected from the wild. One month after sowing the spores germinated in both soils resulting in a uniseriate germ filament Vittaria-type, and differentiated into laminar gametophytes, forming a Ceratopteris-type prothallus. The first leaf of the sporophyte emerged two months after sowing, and its development was completed one month later. Based on our studies, we propose that seedlings cultivated from spores germinated in soil can be used for the reintroduction of endangered fern species. [ABSTRACT FROM AUTHOR]

Plant pollens and fungal spores are massively produced in natural habitats and large‐scaled agricultural areas, and the airborne transported biomass can be accumulated on relatively large crop surfaces. A pollen grain contains a specific chemical composition in quantity and quality, highly varied among plant species. So, the accumulated pollens could provide a species‐specific nutrient supply for the initial fungal development in a pollen trap. Thus, this could increase the variation of the pathogen infection risk in certain plants due to selection mechanisms such as host–pathogen coevolution, crop breeding or pollination type. However, the role of the pollen‐stimulated spore germination and the species‐specific differences in the pollen‐spore interferences is still less understood. Therefore, we performed a multispecies experimental comparison (including 20 plant species) to test the role of the taxon‐specific attributes (i.e. host–pathogen compatibility, cultivation, pollination type and pollen size) in the dose and temporal response of the spore germination in Botrytis cinerea. We found a strong pollen‐stimulating effect on spore germination; however, the triggering effect highly varied among plant species and differed between specific functional categories across temporal and concentration gradients. Specifically, the B. cinerea hosts, the non‐cultivated plants and species with larger pollen size, increased the spore germination's stimulation effects, but not the pollination type. The systematic taxonomic and functional differences might reflect indirectly the diversity of the pollens' chemical profile (i.e. composition matrix or specific trigger molecules) which different selection mechanisms might shape. In the crop–pathogen interactions, the pollen‐stimulation effect could play an essential role in early fungal development. [ABSTRACT FROM AUTHOR]

Phenyllactic acid (PLA) has gained a lot of attention due to its broad antimicrobial activity, but the mechanism of its antifungal action has been barely reported until now. Herein, the inhibitory activity of PLA against Aspergillus flavus spore germination and its mechanism were preliminarily investigated. Results indicated that PLA had a strong antifungal activity against A. flavus with the minimal inhibitory concentration (MIC) and minimal fungicidal concentration (MFC) of 6 and 12 mg/ml, respectively. As observed by scanning electron microscopy (SEM), the A. flavus spores displayed wrinkled and shrunken appearance after treatment with PLA. In addition, the permeability and integrity of A. flavus cell membrane were changed obviously after PLA treatment as indicated by the propidium iodide (PI) staining results, which was further confirmed by a rise in electric conductivity and increased leakage of intracellular protein and nucleic acid. Furthermore, reduced activities of mitochondrial ATPase and dehydrogenases caused by PLA were also observed in A. flavus spores, with a result of remarkable decrease in ATP synthesis. Therefore, it could be concluded that PLA was effective in inhibiting spore germination of A. flavus mainly by disrupting cell membrane and interfering with mitochondrial energy metabolism. [ABSTRACT FROM AUTHOR]

In order to reveal the effect of main phenolic substances on the growth of black spot Alternaria alternata after fruit harvesting, and on the basis of the analysis of the content of Pingguoli pear peel phenolic substances during the development and storage period, this paper studied the effects of seven phenolic substances in the Pingguoli pear peel on the spore germination, mycelium growth, mycelium dry weight and melanin formation. The results showed that, in addition to arbutin, phenolic acids and flavonoids had a certain inhibitory effect on the germination of A. alternata, and there was a concentration dependence, and the inhibitory effect was phenolic acids> flavonoids> simple phenols, in turn. The inhibitory effect of ferulic acid was strong, and the spore germination, mycelial growth and dry weight of mycelium treated with 3 mg/mL ferulic acid were reduced by 98.5%, 29.4% and 22.2% respectively compared with the control (0 mg/mL). At the same time, the content of A. alternata melanin was increased in varying degrees after the treatment of seven phenolic substances. It can be seen that phenolic substances in Pingguoli pear peel have an important regulatory effect on the growth and pathogenicity of A. alternata.

The inhibitory effects of ClO2, clove essential oil and cinnamon essential oil on Fusarium graminearum were studied by observing the colony diameter, mycelial growth and spore germination. The results showed that ClO2, clove essential oil and cinnamon essential oil had significant inhibitory effect on Fusarium graminearum, among which, clove essential oil had lower inhibitory effect than cinnamon essential at low density (20~40 µL/L air), and its inhibitory effect was improved dramatically and better than cinnamon essential with the increase of density. Through the regression equation of inhibition rate, the IC50 of ClO2, clove essential oil and cinnamon essential oil were 27 mg/L, 58 µL/L air and 66 µL/L air respectively. By means of ergosterol content determination, scanning electron microscope observation and Fourier transform infrared analysis, we found that ClO2 and essential oil destroyed cell structure in different degrees, ClO2 destroyed cell membrane, leading to the exudation of contents. High density of clove essential oil destroyed cell structure, while cinnamon essential oil resulted in maldevelopment of mycelium.

Bacillus amyloliquefaciens (BAM) was identified as the predominant spoilage bacteria in instant wet noodles (IWNs). The utilization of industrial acid treatment as a long shelf-life strategy resulted in reduced consumer acceptance due to the acidic taste of the products. This study proposed a processing strategy that integrated spore germination (SG) and lactic acid (LA) treatment to effectively reduce the spore survival rate and extend the shelf life of IWNs. L-histidine, d -glucose, and sodium chloride were highly efficient and safe germinants for BAM spores. In IWNs, compound germinants (1.0 % L-histidine, 0.5 % d -glucose, and 1.0 % sodium chloride) boosted the SG rate by 3.61 times. With synergistic LA treatment, the spore lethality increased by 34.41 % -41.68 %. Under the SG and reduced acid-heat conditions of pH 2.30–2.50, the mortality of spores could reach 92.00 %–93.17 %, which was 14.11 %–15.28 % higher than the industrial acid-heat condition of pH 2.10. DPA, ATP, and membrane potential showed that germinants reduced the spore membrane permeability and promoted the occurrence of spore membrane damage under acid-heat conditions. Moreover, this strategy significantly extended the shelf-life of IWNs by 3.00–5.50 times and controlled the pH ≥ 5.50. Additionally, it improved color, texture, and overall sensory evaluation. Accordingly, this strategy solved the contradiction between the long shelf-life of IWNs and the unacceptable acidification in industrial production. [Display omitted] • L-histidine proved to be an effective germinant for Bacillus amyloliquefaciens spores. • The processing strategy combined spore germination (SG) and lactic acid (LA) treatment. • Compound germinants (1.0 % L-histidine, 0.5 % d -glucose, and 1.0 % sodium chloride) boosted the SG rate by 3.61 times. • This strategy extended the shelf-life of IWNs by 3.00–5.50 times with appropriate pH. [ABSTRACT FROM AUTHOR]

This study designed a new programmed temperature control (PTC) process for cooked chicken, aiming to increase the efficacy of Clostridium perfringens spore inactivation through inducing spore germination at different levels of dormancy. The results showed that the use of PTC treatment in the presence of germinant AGFK (a mixture of l -asparagine, D-glucose, D-fructose, and KCl) lead to a reduction of exceeding 6 lg CFU/mL spores in a model system after being subjected to 90 °C for 20 min. A significant up-regulation of gerKA , gerKC and gerAA relative expression suggested that the PTC treatment may induce more spore germination. Meanwhile, there was an observed rise in the release of pyridine-2,6-dicarboxylic acid, accompanied by a steady decline in refractivity. In the cooked chicken meat undergone a cooling process, the number of C. perfringens spores were reduced by approximately 5 lg CFU/g after the PTC treatment and heated at 90 °C for 20 min. In conclusion, the PTC treatment can effectively enhance the inactivation of C. perfringens spores by inducing more spore germination at different levels of dormancy during cooked meat preparation. • A new programmed temperature control (PTC) process was developed. • The PTC treatment was combined use with germinant AGFK. • The combined treatment induced germination of more Clostridium perfringens spores. • The spore count was reduced by approximately 5 lg CFU/g in cooked meat. • It provides a moderate heating method to inactivate C. perfringens spores. [ABSTRACT FROM AUTHOR]