Spore Morphology Research Articles

Inactivation Mechanism of Aspergillus flavus Conidia by High Hydrostatic Pressure.

This study investigated the inactivation mechanism of Aspergillus flavus conidia by high hydrostatic pressure (HHP). Activity counts, scanning electron microscopic (SEM) analysis, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) were used to study the effects of the HHP treatment on the morphology and protein composition of A. flavus spores. The results showed that that a 3-min-lasting 600 MPa treatment could completely abolish 107 colony-forming units/mL of live fungi. Furthermore, we also observed that lower spore viability corresponded to a higher Propidium Iodide absorption rate. The SEM images revealed that HHP disrupted the spore morphology and resulted in pore formation that led to the release of intracellular molecules, such as nucleic acids and proteins. The nucleic acid and protein concentration in the spore suspension increased in parallel with the increasing treatment pressure. The SDS-PAGE analysis showed that there were differences in the protein bands between the HHP-treated and untreated A. flavus spores, as the HHP treatment caused partial protein degradation and extracellular release. Therefore, the results of this study proved that high pressure could induce a morphological disruption in the internal and external cellular structures and degrade intracellular and extracellular proteins leading to an inactive state in A. flavus.

Description of myxosporeans (Cnidaria: Myxozoa) infecting the popular food fish Notopterus notopterus (Pisces: Notopteridae) in Malaysia and India

This study was a co-operative investigation of myxosporean infections of Notopterus notopterus, the bronze featherback, which is a popular food fish in the South Asian region. We examined fish from Lake Kenyir, Malaysia and the River Ganga, Hastinapur, Uttar Pradesh, India, and observed infections with two myxosporeans: Myxidium cf. notopterum (Myxidiidae) and Henneguya ganapatiae (Myxobolidae), respectively. These species were identified by myxospore morphology, morphometry and host tissue affinity, and the original descriptions supplemented with small-subunit ribosomal DNA sequences and phylogenetic analysis. Free myxospores of M. cf. notopterum were found in the gallbladder, and measured 14.7 ± 0.6 μm long and 6.3 ± 0.6 μm wide; host, tissue and myxospore dimensions overlapped with the type, but differed in morphological details (spore shape, valve cell ridges) and locality (Malaysia versus India). Plasmodia and spores of H. ganapatiae were observed in gills, and myxospores had a spore body 9.7 ± 0.4 μm long, 4.5 ± 0.5 μm wide; sample locality, host, tissue, spore morphology and morphometry matched the original description. Small-subunit ribosomal DNA sequences were deposited in GenBank (M. cf. notopterum MT365527, H. ganapatiae MT365528) and both differed by >7% from congeneric species. Although the pathogenicity and clinical manifestation of myxozoan in humans are poorly understood, consumption of raw fish meat with myxozoan infection was reported to be associated with diarrhea. Identification of current parasite fauna from N. notopterus is an essential first step in assessing pathogen risks to stocks of this important food fish.

Identification and characterization of fungi associated with blister blight lesions of tea (Camellia sinensis L. Kuntze) isolated from Meghalaya, India

Diseases in plants are mostly caused by fungi. Fungal interactions with the host can be either biotrophic, necrotrophic or hemibiotrophic. Synergistic polymicrobial interactions have been recently recognized that can also attribute to the occurrence of complex plant diseases. Tea is one of the most widely consumed beverages worldwide, although tea plants are affected by many different diseases causing a significant reduction in global tea production. Blister blight is one such serious and damaging leaf disease of tea. An assessment of blister blight disease was carried out at the tea development center in Umsning, Meghalaya. A considerable number of tea varieties showed characteristic blister blight symptoms that ranged from preliminary yellow spots in the upper leaf surface, matured white sporulating blisters in the lower leaf surface, and delayed brown necrotic lesions throughout the surfaces of the leaves. A total of 42 isolates, 15 from initial, 15 from mature, and 12 from necrotic stages were isolated from the symptomatic leaf samples. Pestalotiopsis and Nigrospora were the two fungi incessantly isolated from the diseased leaves. Colony characteristics that included colony, hyphal, and spore morphologies were examined and mycelial accumulation, sporulation, and sporal germination were determined for all the isolates of Pestalotiopsis and Nigrospora. Molecular analysis based on ITS-RFLP was performed for identification and genetic variability. In vitro pathogenicity assay revealed that Pestalotiopsis spp. and Nigrospora sp. developed distinct characteristics symptoms on greenhouse acclimated TV17 tea clones. To our knowledge, this is the first report of the prevalence of tea blister blight disease in Meghalaya and it is an initial attempt to identify fungal pathogens during different stages of blister blight disease.

Study on the spore morphology of Ceratopteris Brongn.

Based on the significance of palynology in plant taxonomic identification, the purpose of this paper is to provide palynology basis for taxonomy, interspecific identification and resource protection of Ceratopteris Brongn. plant system. The spores of C. thalictroides and C. pteridoides of domestic Ceratopteris Brongn. were observed and compared by scanning electron microscope. The two types of spores of Ceratopteris Brongn. are radially symmetrical, tetrahedral, trilete suture, spherosome in polar view and equatorial view, and have common morphological characteristics such as perispore and ridge-like bulge of perispore, but there are obvious differences such as density of ridge-like bulge and ornamentation among bulges between two types of spores. The spore morphology is of great significance in the interspecific taxonomy of Ceratopteris Brongn.. It does not only provide the palynology scientific basis for the taxonomy and identification of Ceratopteris Brongn., but also provides a series of feasible measures for the exploitation and the resource conservation of Ceratopteris Brongn..

Spore morphology and leaf epidermal anatomy as a taxonomic source in the identification of Asplenium species from Malakand division Pakistan.

Several studies have demonstrated the usefulness of leaf epidermal, and spore morphological characters in the taxonomy of genus Asplenium. However, works on the Pakistani species of Asplenium are not existent. With the objective to verify the efficacy of leaf epidermal and spore morphological traits, the leaf epidermis and spore morphology in nine Asplenium species occurring in Malakand division was studied. The spores were studied under light microscope (LM) and scanning electron microscope (SEM), whereas for leaf epidermal anatomy, the LM was used. The spores are monolete, ellipsoidal in shape, the equatorial and polar diameter ranges between 28.3 and 50.2 × 27.6 and 45.8 μm. The exospore thickness varied from 0.5 to 3.8 μm. The perispore is 0.8-3.5 μm thick, ornamented, and morphologically variable. The spores characters specifically the perispore ornamentation are useful in distinguishing species within the genus. The irregular spore shape and unusual development of perispore wall surface characterize aborted spores in the species of Asplenium × alternifolium. The most informative quantitative characters appeared to be length and width of epidermal cells, and length and width of stomata were useful to distinguish species. The most significant qualitative characters to distinguish species were the anticlinal wall pattern. Our study has shown that considerable variations exist in the leaf epidermis of Asplenium species, at least some of which has taxonomic significance. We confirmed the prevalent taxonomic value of stomatal and epidermal cells traits. The leaf epidermal anatomy and spore morphological features showed to be a good source of information for taxonomy of the genus Asplenium.

Chitosan–citric acid edible coating to control Colletotrichum gloeosporioides and maintain quality parameters of fresh-cut guava

This study aimed to verify the action of edible chitosan–citric acid (CHI–CA) coating to control Colletotrichum gloeosporioides and maintain quality parameters of fresh-cut guava. Chitosan was obtained from Litopenaeus vannamei shells using high temperature and short exposure times. The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of CHI–CA against C. gloeosporioides were determined by macrodilutions at 28 °C/120 h in the absence/presence of CHI–CA (0–10 mg/mL). Scanning electron microscopy was used to evaluate morphological changes in the fungus. Guava slices were coated with CHI–CA (MIC) or 5 mg/mL glycerol (control). Rot incidence and physicochemical, physical, and microbiological factors were determined at 0, 3, 7, and 14 days at 24 °C and 4 °C. Chitosan presented typical structural characterization, 64% deacetylation, and a molecular weight of 1.6 × 104 g/mol. CHI–CA exhibited MIC and MFC values of 5 mg/mL and 10 mg/mL, respectively, and promoted changes in the morphology and cell surface of fungal spores. The fresh-cut guava coated with CHI–CA maintained quality parameters during storage and preserved their sensorial characteristics. Therefore, the use of CHI–CA as a coating is a promising strategy for improving postharvest quality of fresh-cut fruits.

Arbuscular mycorrhizal fungi associated with Phoenix dactylifera L. grown in Tunisian Sahara oases of different salinity levels

Soil salinity continuously threatens the sustainability of several economically strategic crop production systems in Tunisia, especially in the arid and Saharan areas. In addition, it also affects microbial populations associated with the roots of crop plants, which are known to contribute efficiently to crop’s productivity and adaptation to environmental stresses. In this respect, the effect of soil salinity on arbuscular mycorrhizal fungi (AMF) associated with date palm (Phoenix dactylifera L.), the flagship crop of Tunisian oases, is still rarely studied. The present work is the first investigation of the colonization of date palm roots by AMF and the production of easily-extractable glomalin related soil protein (EE-GRSP) in different date palm plantations where soils present high salinity rates up to 7.6 dS m−1. The results revealed a negative correlation between soil salinity and the intensity of mycorrhization on one hand but a positive correlation between soil salinity and EE-GRSP and spore density on the other hand. This suggests that the production of EE-GRSP might be involved in the tolerance of AMF to elevated salinity in the soil. In addition, four AMF species, identified based on spore morphology and molecular phylogenetic analyses, have been recovered in single spore derived cultures, namely Albahypha drummondii, Dominikia disticha, Funneliformis coronatus and Rhizoglomus irregulare. The investigation of the current mycorrhizal status of date palm roots and rhizosphere soil EE-GRSP concentrations along a salinity gradient on one side and isolation and identification of AMF strains native to Tunisian oases ecosystems one the other represent first steps towards the development of sustainable agricultural practices in this region where salinity is the main production-limiting factor.

Inhibitory Effects of Eurotium cristatum on Growth and Aflatoxin B1 Biosynthesis in Aspergillus flavus.

Probiotic strain Eurotium cristatum was isolated from Chinese Fuzhuan brick-tea and tested for its in vitro activity against aflatoxigenic Aspergillus flavus. Results indicated that E. cristatum can inhibit the radial growth of A. flavus. Furthermore, this inhibition might be caused by E. cristatum secondary metabolites. The ability of culture filtrate of strain E. cristatum against growth and aflatoxin B1 production by toxigenic A. flavus was evaluated in vitro. Meanwhile, the influence of filtrate on spore morphology of A. flavus was analyzed by scanning electron microscopy (SEM). Results demonstrated that both radial growth of A. flavus and aflatoxin B1 production were significantly weakened following increases in the E. cristatum culture filtrate concentration. In addition, SEM showed that the culture filtrate seriously damaged hyphae morphology. Gas chromatography mass spectrometry (GC/MS) analysis of the E. cristatum culture supernatant revealed the presence of multiple antifungal compounds. Real-time quantitative polymerase chain reaction (RT-qPCR) analysis showed that the expression of aflatoxin biosynthesis-related genes (aflD, aflQ, and aflS) were down-regulated. Importantly, this latter occurrence resulted in a reduction of the AflS/AflR ratio. Interestingly, cell-free supernatants of E. cristatum facilitated the effective degradation of aflatoxin B1. In addition, two degradation products of aflatoxin B1 lacking the toxic and carcinogenic lactone ring were identified. A toxicity study on the HepG2 cells showed that the degradation compounds were less toxic when compared with AFB1.

Isolation and identification of endophytic fungi in walnut

In this paper, endophytic fungi in four tissues (roots, branches, leaves, fruits) of walnuts were isolated by tissue isolation technic. Based on morphology, the isolated endophytic fungi were preliminarily identified. The results showed that 64 strains of endophytic fungi were isolated from walnut tissues. The number of endophytic fungi isolated from walnut branch tissues is the largest, followed by leaf, fruit, and root tissues. Observing the morphological and mycelial changes during fungal growth and the characteristics of spore morphology under the microscope, 64 strains of endophytic fungi belonged to 17 genera, of which Alternaria sp. was the dominant microflora. For the first time, Talaromyces sp., Curvularia sp. and Eurotium sp. were isolated from walnut plants.

Hydrophobicity of abiotic surfaces governs droplets deposition and evaporation patterns

Surface contamination with droplets containing bacteria is of concern in the food industry and other environments where hygiene control is essential. Deposition patterns after the drying of contaminated droplets is affected by numerous parameters. The present study evaluated the rate of evaporation and the shape of deposition patterns after the drying of water droplets on a panel of materials with different surface properties (topography, hydrophobicity). The influence of the particle properties (in this study 1 μm-microspheres and two bacterial spores) was also investigated. Polystyrene microspheres were hydrophobic, while Bacillus spores were hydrophilic or hydrophobic, and surrounded by different surface features. In contrast to material topography, hydrophobicity was shown to deeply affect droplet evaporation, with the formation of small, thick deposits with microspheres or hydrophilic spores. Among the particle properties, the spore morphology (size and round/ovoid shape) did not clearly affect the deposition pattern. Conversely, hydrophobic spores aggregated to form clusters, which quickly settled on the materials and either failed to migrate, or only migrated to a slight extent on the surface, resulting in a steady distribution of spores or spore clusters over the whole contaminated area.Adherent bacteria or spores are known to be highly resistant to many stressful environmental conditions. In view of all the quite different patterns obtained following drying of spore-containing droplets, it seems likely that some of these would entail enhanced resistance to hygienic processes.

<p><strong>Comprehensive analysis of <em>Actiniopteris</em> Link and <em>Onychium</em> Kaulf. (Pteridophyta) relationships according to their phylogeography, phylogeny and spore morphology</strong></p>

This research is the first comprehensive analysis of the intrageneric relationships of Actiniopteris and Onychium based on original data including spore morphology, phylogeny and phylogeography. Actiniopteris and Onychium are members of the large subfamily Pteridoideae of the family Pteridaceae. The Pteridaceae family is considered one of the most taxonomically confusing families due to its representatives high level of polymorphism. We used an interdisciplinary approach to study the “Onychium clade”: 13 taxa were studied using scanning electron microscopy (SEM) to characterize the morphology and morphometry of spores; 14 taxa were studied from a phylogenetic perspective, including character evolution and ancestral character state reconstructions; 15 taxa of “Onychium clade” were studied using herbarium data (B, P, PE, LE, VLA, TI, KYO, ALTB and TK) according to global botanical and geographical zones. As a result of this integrated analysis, we established a deep divergence of the taxa O. tenuifrons and O. siliculosum from the main composition of the genus Onychium and the division the genus Actiniopteris into two clades: A. radiata–A. semiflabellata and A. australis–A. dimorpha. We found that representatives of Actiniopteris and Onychium had originated in a common African-Indo-Malesian area. The “Onychium clade” center of diversity is the Indian Region, which is experiencing high levels of human impact, leading to disjunctions among the studied taxa.

Mycorrhiza: a natural resource assists plant growth under varied soil conditions.

In this overview, the authors have discussed the potential advantages of the association between mycorrhizae and plants, their mutual accelerated growth under favorable conditions and their role in nutrient supply. In addition, methods for isolating mycorrhizae are described and spore morphologies and their adaptation to various conditions are outlined. Further, the significant participation of controlled greenhouses and other supported physiological environments in propagating mycorrhizae is detailed. The reviewed information supports the lack of host- and niche-specificity by arbuscular mycorrhizae, indicating that these fungi are suitable for use in a wide range of ecological conditions and with propagules for direct reintroduction. Regarding their prospective uses, the extensive growth of endomycorrhizal fungi suggests it is suited for poor-quality and low-fertility soils.

Palynology of Polypodiaceae from Shandong and its significance in classification

According to the new classification system of international Lycopods and Ferns in the Flora of China,Polypodiaceae includes more than 20 genus of Polypodiaceae in the Qinrenchang classification system,and also includes independent families such as Drynariaceae and Platyceriaceae.The new classification system of Polypodiaceae in the Flora of China with many issues needs further investigation and classification.Here we investigated the spore morphology and perispore ornamentation submicroscopic structure of Polypodiaceae from Shandong Province using scanning electron microscopy(SEM).This is the first palynological study based on the new classification system of Polypodiaceae.The results were as follows: Spores of Polypodiaceae were reniform,bilaterally symmetrical,possessing a perispore with stable ornamentation within species and clear distinctions between subfamily,genus and species.The palynological studies supported two of the subfamilies of Polypodiaceae-Drynaria and Platycerium delineated in the FOC.In addition,the perispore ornamentation combined with leaf morphological characteristics showed that Phymatopteris shandongensis J.X.Li et C.Y.Wang was a distinct species,and should be restored to a species level position rather than incorporated with P.hastata(Thunb.) Pic.Serm.,not regard as Phymatopteris but as a new combination Selliguea shandongensis(J.X.Li et C.Y.Wang) J.X.Li & X.J.Li,comb.nov.according to the International Code of Botanical Nomenclature and the classification system of Flora of China.Our study not only has accumulated new information for the palynology of Polypodiaceae,but also provides a palynological basis for its new classification system,which is consistent with molecular analysis,and confirms the rationality of the new classification system of Polypodiaceae and its subfamilies.

Common dace (Leuciscus leuciscus) - A new host of the myxozoan fish parasite, Myxobolus elegans (Cnidaria: Myxozoa) - Short communication.

This paper reports the detection of the myxozoan species Myxobolus elegans Kashkovsky 1966 in common dace (Leuciscus leuciscus) that has not been previously listed as its host. The problem of differentiation of phenotypically similar Myxobolus species is addressed. During parasitological survey of common dace from the desalinated part of the Gulf of Finland at the city of Sestroretsk, Russia, numerous oval-shaped plasmodia, 0.2-0.4 mm in size, filled with Myxobolus spores were found on the gills. Pear-shaped myxospores were 15.4 (14.8-16.0) × 10.2 (9.6-10.9) µm in size with a rib on each valve. On the basis of spore morphology, the species appeared to be similar to M. elegans and Myxobolus hungaricus Jaczó, 1940. In order to identify the species, molecular genetic analysis was performed, and the species was identified on the basis of morphological characteristics and 18S rDNA data. The results obtained indicate that the Myxobolus species observed on the gills of dace is M. elegans. Thus, common dace is another valid host of M. elegans besides the type host, ide (Leuciscus idus).

Arbuscular Mycorrhizal Fungi Mitigate Nitrogen Leaching under Poplar Seedlings

The leaching of soil nitrogen (N) has become one of the most concerning environmental threats to ecosystems. Arbuscular mycorrhizal (AM) fungi have important ecological functions, however, their influence on soil N leaching and the mechanism of action remain unclear. We conducted a two-factor (N application level × AM inoculation) experiment on poplar, and for the first time, comprehensively analyzed the mechanism by which AM fungi influence soil N leaching. The results showed that, under optimum (7.5 mM) and high (20 mM) N levels, the nitrate (NO3−) and ammonium (NH4+) concentrations of leachate in the AM inoculated treatment (+AM) were lower than in the non-inoculated treatment (−AM), with significant reductions of 20.0% and 67.5%, respectively, under high N level, indicating that AM inoculation can reduce soil N leaching and that it is more effective for NH4+. The arbuscular and total colonization rates gradually increased, and the morphology of spores and vesicles changed as the N level increased. Under optimum and high N levels, +AM treatment increased the root N concentration by 11.7% and 50.7%, respectively; the increase was significant (p < 0.05) at the high N level, which was associated with slightly increased transpiration and root activity despite reductions in root surface area and root length. Additionally, the +AM treatment increased soil cation exchange capacity (CEC), soil organic carbon (SOC), and significantly (p < 0.05) increased the proportions of macroaggregates (but without significant change in microaggregates), causing soil total nitrogen (TN) to increase by 7.2% and 4.7% under optimum and high N levels, respectively. As the N levels increased, the relative contributions of AM inoculation on N leaching increased, however, the contributions of plant physiological and soil variables decreased. Among all of the variables, SOC had important contributions to NH4+ and total N in the leachate, while root N concentration had a higher contribution to NO3−. In conclusion, AM fungi can mitigate soil N leaching and lower the risk of environmental pollution via enhancing N interception by the inoculated fungi, increasing N sequestration in plant roots, and by improving soil N retention.

Phenotypic characterization in natural population of Spot Blotch (Bipolaris sorokiniana) of Barley (Hordeum vulgare L.)

A study was undertaken on phenotypic characterization of different isolates of Bipolaris sorokiniana isolated from the different varietal trials and nurseries of barley at the agricultural research farm, Institute of Agricultural sciences, Banaras Hindu University. The isolation was performed by transfer of single spore of the pathogen from diseased leaf in Potato Dextrose Agar media (PDA) under aseptic condition. The experiment revealed five groups of isolates on the basis of colony colour, morphology and number of spores. It was found that (42.2%) of the isolates were black in colour with profuse sporulation and suppressed type growth, (35.71%) of the isolates were greyish in colour and (21.42%) of the isolates possessed whitish colony with full plate growth and lower sporulation. The size of conidia ranged from 24 × 13µm to 36 × 14µm in size, while the number of spores per mm2 of colony varied from 20.36 to 162.77.

A whole noeggerathialean plant Tingia unita Wang from the earliest Permian peat-forming flora, Wuda Coalfield, Inner Mongolia

The genus Tingia Halle is one of the most typical taxa of the Cathaysia Flora. However, its affinity, has long been uncertain. Tingia unita Wang 2006 was named based on the discovery of a crown of a tree that shows the organic connection of the simple compound leaves and the strobili with the stem. It is among the very few species of the Noeggerathiales of which both fertile and sterile parts are known. Since its discovery, a large collection of specimens of Tingia unita has been accumulated from the early Permian peat-forming flora in Wuda Coalfield of Inner Mongolia (Chinese vegetational Pompeii), including various parts of the whole plant. This paper presents a full documentation of this species on the basis of this material, which now, represents the best-known taxon in the genus Tingia and in the order Noeggerathiales. The gross morphology, heterospory and in situ spore morphology, homology of leaf and strobilus, anatomy of the frond and strobilus, and sporophyll arrangement are all known, and conform to a progymnospermous affinity. The plant was an understory tree in the peat swamp forest, approaching the height of tree ferns, whereas Sigillaria Brongniart and Cordaites Unger formed the upper storey. Tingia unita produced a considerable proportion of the biomass of the peat-forming swamp vegetation. This in-depth study contributes to a better understanding of the systematic position of the genus Tingia and the enigmatic group of the Noeggerathiales.

Vertical Divergence of Cultivable Microfungal Communities Through Biocrusted and Bare Soil Profiles at the Tabernas Desert, Spain

We examined the depth-wise distribution of microfungi through 0–30 cm soil profiles under different surface types—cyanobacterial crusts, three lichen-dominated crusts, and non-crusted bare surface located at the north-oriented slope and sun-exposed plain at the Tabernas Desert, Spain. A total of 116 species from 60 genera was isolated using the soil dilution plate method. High ultraviolet and solar radiation, high temperatures and desiccation caused the dominance of species with the protective dark pigmentation and partly with the protective many-celled spore morphology in the majority of uppermost communities. At the same time, deeper layers were mostly inhabited by light-colored fungi producing a high amount of small thin-walled spores—thermotolerant Aspergillus spp. (at the depth of 1–5 cm) and mesophilic Penicillium spp. (at the depth of 10–20-cm, with the increase much more pronounced in the north-oriented profiles). Limited water infiltration in the fine-grained Tabernas soil causing the deposition of spores of aspergilli and penicillii at the depth of 1–10 cm most likely led to the substantial increase of isolate densities at these depths. Among environmental aspects, soil depth most strongly governed the microfungal communities, highly significantly influencing all their characteristics; meanwhile, habitat position and surface type significantly affected only the communities’ composition.

The Impact of pH on Clostridioides difficile Sporulation and Physiology.

Clostridioides difficile is a pathogenic bacterium that infects the human colon to cause diarrheal disease. Growth of the bacterium is known to be dependent on certain bile acids, oxygen levels, and nutrient availability in the intestine, but how the environmental pH can influence C. difficile is mostly unknown. Previous studies indicated that C. difficile modulates the intestinal pH, and prospective cohort studies have found a strong association between a more alkaline fecal pH and C. difficile infection. Based on these data, we hypothesized that C. difficile physiology can be affected by various pH conditions. In this study, we investigated the impact of a range of pH conditions on C. difficile to assess potential effects on growth, sporulation, motility, and toxin production in the strains 630Δerm and R20291. We observed pH-dependent differences in sporulation rate, spore morphology, and viability. Sporulation frequency was lowest under acidic conditions, and differences in cell morphology were apparent at low pH. In alkaline environments, C. difficile sporulation was greater for strain 630Δerm, whereas R20291 produced relatively high levels of spores in a broad range of pH conditions. Rapid changes in pH during exponential growth impacted sporulation similarly among the strains. Furthermore, we observed an increase in C. difficile motility with increases in pH, and strain-dependent differences in toxin production under acidic conditions. The data demonstrate that pH is an important parameter that affects C. difficile physiology and may reveal relevant insights into the growth and dissemination of this pathogen.IMPORTANCEClostridioides difficile is an anaerobic bacterium that causes gastrointestinal disease. C. difficile forms dormant spores which can survive harsh environmental conditions, allowing their spread to new hosts. In this study, we determine how intestinally relevant pH conditions impact C. difficile physiology in the two divergent strains, 630Δerm and R20291. Our data demonstrate that low pH conditions reduce C. difficile growth, sporulation, and motility. However, toxin production and spore morphology were differentially impacted in the two strains at low pH. In addition, we observed that alkaline environments reduce C. difficile growth, but increase cell motility. When pH was adjusted rapidly during growth, we observed similar impacts on both strains. This study provides new insights into the phenotypic diversity of C. difficile grown under diverse pH conditions present in the intestinal tract, and demonstrates similarities and differences in the pH responses of different C. difficile isolates.

Investigation, analysis and identification of disease of Gastrodia elata f. glauca

Fungal disease is an important factor restricting the healthy development of Gastrodia elata industry. The control of fungal disease in G. elata is an important issue in production. This paper makes a detailed investigation on the current situation of G. elata disease in China through statistics on the failure rate, rotten pit rate and occurrence rate of G. elata disease in the main producing areas of China. It was found that G. elata disease was mainly infected from the top bud and junction, causing the occurrence rate of disease was 6%-17%, and the yield decreased by 10%-30%. The 23 dominant fungi were isolated from 18 typical G. elata disease samples. Through identification of colony morphology, mycelium morphology, spore morphology and genetic characteristics, they were finally identified as 13 species, belonging to 7 families and 7 genera. Trichoderma harzianum, Ilyonectria sp. and Ilyonectria destructans are the most frequently separated. Their isolation frequency were 22.22%,16.67%,16.67% respectively. Ilyonectria sp. and I. destructans were the first time isolated from G. elata disease samples. They may be the main pathogens causing soil-borne diseases of G. elata. T. harzianum has certain potential as Gastrodia biocontrol bacteria. This study can provide a theoretical basis for the research and development of control technology of Gastrodia fungi disease.