Hyphal Mass Research Articles

Effects of zinc oxide nanocomposites on microorganism growth and protection of physicochemical quality during maize storage

Maize moldy and spoilage due to microbial growth is a significant challenge in grain storage. This study aimed to evaluate the effectiveness of a zinc oxide nanocomposite, ZnO@mSiO2, prepared in our previous research, in inhibiting mold growth and preserving maize cell quality. The results demonstrated that ZnO@mSiO2 could effectively inhibit the growth of dominant microorganism, Aspergillus flavus, Talaromyces variabilis, Penicillium citrinum and Fusarium graminearum, in maize storage. Aspergillus flavus was selected as the model fungus, ZnO@mSiO2 effectively disrupted fungal hyphae structure, leading to reduced hyphal mass and inhibited spore germination. The inhibitory effect of ZnO@mSiO2 on mold growth was concentration-dependent. However, the ZnO@mSiO2 at an appropriate concentration (not exceeding 3.0 g/kg) preserved the integrity of maize cell membranes and enhancing the antioxidant activity within maize cells. The findings highlight the potential of ZnO@mSiO2 as an effective protectant to inhibit mold growth and preserve maize quality during storage.

Coat protein of partitiviruses isolated from mycorrhizal fungi functions as an RNA silencing suppressor in plants and fungi

Orchid seeds depend on colonization by orchid mycorrhizal (OM) fungi for their germination; therefore, the orchids and OM fungi have long maintained a close relationship (e.g., formation of the hyphal mass structure, peloton) during their evolution. In the present study, we isolated new partitiviruses from OM fungi; partitivirus were separately found in different subcultures from the same fungi. Partitiviruses have been believed to lack an RNA silencing suppressor (RSS), which is generally associated with viral pathogenicity, because most partitiviruses isolated so far are latent in both plants and fungi. However, we found that the coat protein (CP) of our partitiviruses indeed had RSS activity, which differed among the virus isolates from OM fungi; one CP showed RSS activity in both plants and fungi, while another CP showed no activity. The family Partitiviridae include viruses isolated from plants and fungi, and it has been suggested that these viruses may occasionally be transmitted between plant and fungal hosts. Given that there are several reports showing that viruses can adapt to nonhost using strong RSS, we here discussed the idea that partitiviruses may be better able to migrate between the orchid and fungus probably through the pelotons formed in the orchid cells, if host RNA silencing is suppressed by partitivirus RSS.

Oxidation states of iron and manganese in lignocellulose altered by the brown rot fungus Gloeophyllum trabeum measured in-situ using X-ray absorption near edge spectroscopy (XANES)

Brown rot fungi utilize iron as part of a chelator-mediated Fenton (CMF) reaction during wood biodegradation. Research suggests these fungi reduce Fe3+ to promote oxygen radical generation resulting in depolymerization of the wood cell wall. High levels of Mn are also found in wood decayed by brown rot fungi. However, little is known about the oxidation states of Fe and Mn during the decay process. X-ray absorption near edge spectroscopy (XANES) can be used to examine metal oxidation states and coordination chemistry. XANES experiments were conducted on wood decayed by Gloeophyllum trabeum over 2–8 weeks with results showing that Mn2+ and Fe3+ predominated for metal oxidation states. However, Fe2+ was present at sites of greater fungal growth In certain cases, the μXANES measurements showed that the fraction of Fe2+ in the wood samples was as high as 50%. Localized areas of reduced iron corresponded with areas of greater fungal hyphal mass which is in agreement with how brown rot fungi decay wood via the CMF reaction. The limited change in oxidation state of Mn observed in wood with active fungal activity suggests that the role of manganese in CMF biodegradation chemistry should be further explored.

Effects of wood resource size and decomposition on hyphal outgrowth of a cord-forming basidiomycete, Phanerochaete velutina

To assess the relationship between resource use and hyphal growth in a cord-forming basidiomycete, Phanerochaete velutina, soil microcosm experiments were conducted using wood blocks of three different sizes in three different soil quantities, thereby simulating the different amounts of available nutrients. The highest percentage weight loss was observed in the smallest wood blocks after a 27-d incubation period in soil microcosms, although the percentage weight loss over the 2-month pure culture colonization prior to inoculation was not significantly different among various block sizes. The greatest hyphal outgrowth was also observed in the smallest wood blocks and was positively associated with wood decay. The slopes of the regression lines between hyphal coverage and percentage wood mass loss were identical among different wood sizes, but the slopes between hyphal coverage and absolute wood mass loss were steeper in the smaller wood blocks than that in largest one. These results suggest that the level of intensity of mycelial foraging for new resources in the soil depends on the percentage of the amount of wood resource utilized, and not on the absolute amount of carbon obtained from the wood.

Pseudocercospora exilis Causing Leaf Spot Disease on Brassica rapa subsp. parachinensis in China

Chinese flowering cabbage (Brassica rapa L. subsp. parachinensis) is an important vegetable crop of China and widely cultivated in the southern provinces. During February of 2017 to 2019, a severe leaf spot disease was seen on Chinese flowering cabbage plants in different agricultural fields around Lianzhou and Guangzhou cities of Guangdong province, China. Disease incidence reached up to 70% in severely infested fields. Early disease symptoms observed were small circular or irregular spots of brown color, 3 to 11 mm in diameter and often coalesced. Ten symptomatic leaves were cut into small pieces (5 × 5 mm), surface sterilized with 1% NaOCl, plated onto potato dextrose agar (PDA) medium, and incubated at room temperature for 7 days under continuous fluorescent light. A total of 11 pathogen isolates were purified by successively subculturing on new PDA medium plates using the single-spore technique. A cercosporoid fungus was consistently isolated from diseased leaves. The colonies were raised and greenish black in color. Conidiophores were brown, subcylindrical, multiseptate, straight or slightly curved, unbranched, and smooth. Conidiogenous cells were pale brown, smooth, and arranged terminally. Conidia were pale brown, smooth, obclavate or fusoid, straight to slightly curved, with obtuse apex, one- to seven-septate, and 44.3 to 69.12 × 4.8 to 6.2 μm (n = 20). The morphological and cultural characteristics of all isolates were consistent with Pseudocercospora exilis Hern.-Gut. & Dianese (Hernandez-Gutierrez and Dianese 2009; Silva et al. 2016). One monosporic isolate (PE-1) was obtained by plating individual spores on V8 agar medium. To further confirm the species, genomic DNA was extracted from the hyphal mass of the isolate PE-1 using the DZup fungal DNA extraction kit (Sangon Biotech, Shanghai, China). The internal transcribed spacer (ITS) and translational elongation factor (EF-1α) regions of the isolate PE-1 were amplified with primers ITS1/ITS4 (White et al. 1990) and EF1-728F/EF1-986R (Carbone and Kohn 1999) and sequenced by Sangon Biotech. The obtained DNA sequences were deposited in GenBank (accessions MN971630 for the ITS sequence and MN991198 for the EF-1α). BLAST analysis showed that the ITS and EF-1α sequences shared 99% nucleotide identity with the previously submitted P. exilis sequences (GenBank accessions NR147302 and KT290193 for ITS and EF-1α, respectively). Pathogenicity testing was performed by spraying conidial suspension (1 × 10⁶ conidia/ml) of isolate PE-1 on the leaves of 40-day-old Chinese flowering cabbage plants. Five plants were used for inoculation. Another five plants were sprayed with distilled sterilized water to serve as a control. Plants were kept in transparent boxes for 2 days to retain moisture and subsequently incubated in a growth room at 28 ± 2°C with a 12-h photoperiod. Similar leaf spots were observed on the leaves of all inoculated plants after 1 week of inoculation. No symptoms were seen on control plants. The same pathogen was reisolated consistently from inoculated leaves. The species identity was confirmed by both morphological and molecular characteristics, thus fulfilling Koch’s postulates. Previously, P. exilis has been reported to cause leaf spot disease on Chamaecrista orbiculata in Brazil (Hernandez-Gutierrez and Dianese 2009). To our knowledge, this is the first report of leaf spot on Chinese flowering cabbage caused by P. exilis. This disease can cause severe economic losses, because Chinese flowering cabbage is mainly sold in the market and used in salads or cooked dishes. Timely measures must be taken to manage this disease.

Visualising confirmation of the endophytic relationship of Metarhizium anisopliae with maize roots using molecular tools and fluorescent labelling

ABSTRACTMetarhizium anisopliae, an entomopathogenic fungus, is found to contribute to plant nutrient uptake and condidered as a plant endophyte. However, there is very little visual evidence that demonstratrates the endophytic relationship. Since the incidence of Metarhizium within host plants may be ephemeral or of limited distribution within host tissue, visualisation is reliant on both presence and the ability to detect the fungus even when present at low levels. We inoculated maize seeds with an egfp-labelled isolate of M. anisopliae, and then detected the egfp fragment by qualitative and quantitative PCR, and examined fluorescence of mycelia in the inoculated roots by laser scanning confocal microscopy (LSCM). The optimised PCR qualitatively identified the presence of egfp-labelled M. anisopliae at a 1:3000 M. anisopliae-maize DNA ratio. Root samplings of inoculated plants at intervals over 24 days were discovered egfp-labelled fragments with 14-d roots having the highest proportion with amplification. The egfp-label concentrations ranged very low in 2.976 × 10−7.42∼−7.02 ng/μL, with a rise process in 4–11 days after M. anisopliae treatment. Under LSCM, fluorescent mycelia in roots were identified, and the clear images were captured to show hyphal development extending along a longitudinal line of root cells and even forming a hyphal mass in the intercellular space. There were many hyphae at the branch junctions of the lateral roots. The methodology used to detect the fungus will be important for exploring the multi-trophic function of M. anisopliae and co-evolution in plants.

Infection pathways and penetration modes of Fusarium langsethiae

Fusarium langsethiae is one of the common Fusarium species infecting small grain cereals in the Nordic region and the UK. It is usually described as a weak pathogen, and with a strong preference for oats, although no studies have yet addressed the explanations for this at the microscopic level. Using microscope techniques we have studied the early steps of colonization of oat and wheat grain by F. langsethiae particularly addressing the role of pollen in the infection process and the fungal ability to penetrate plant cell wall. The aim was to better understand its non-aggressive colonization picture and why oat is preferred over wheat as a host. Spray inoculated oat and wheat plants were scored for fungal progression at 3, 6, 10 and 14 days post inoculation (dpi) using light microscopy and scanning electron microscopy (SEM). Fungal hyphae entered the grain at the apex, or along the sides in the overlapping zone between palea wings and lemma, then spread basipetally and laterally, with a clear directional growth towards the caryopsis. Hyphal growth was clearly aided by the presence of pollen. On oat proliferating hyphae developed a variety of penetration structures on all internal surfaces. F. langsethiae infection on wheat progressed along the same routes, however slower and overall with less hyphal mass. Interestingly, hyphae closely associated to the wheat caryopsis seemed to undergo degradation, and profuse conidiation was observed at 14 dpi. Explanations for the differences in F. langsethiae colonization of oat versus wheat are suggested in light of the results.

Ascarosides Promote the Prevalence of Ophiostomatoid Fungi and an Invasive Pathogenic Nematode, Bursaphelenchus xylophilus.

Understanding the coevolution of pathogens and their associated mycoflora depend upon a proper elucidation of the basis of their chemical communication. In the case of pine wilt disease, the mutual interactions between cerambycid beetles, invasive pathogenic nematodes, (Bursaphelenchus xylophilus) and their symbiotic ophiostomatoid fungi provide a unique opportunity to understand the role of small molecules in mediating their chemical communication. Nematodes produce ascarosides, a highly conserved family of small molecules that serve essential functions in nematode biology and ecology. Here we demonstrated that the associated fungi, one of the key natural food resources of pine wood nematodes, can detect and respond to these ascarosides. We found that ascarosides significantly increase the growth of L. pini-densiflorae and Sporothrix sp. 1, which are native fungal species in China that form a symbiotic relationship with pinewood nematodes. Hyphal mass of L. pini-densiflorae increased when treated with asc-C5 compared to other ophiostomatoid species. Field results demonstrated that in forests where higher numbers of PWN were isolated from beetle galleries, L. pini-densiflorae had been prevalent; the same results were confirmed in laboratory studies. Furthermore, when treated with asc-C5, L. pini-densiflorae responded by increasing its production of spores, which leads to a higher likelihood of dispersal by insect vectors, hence explaining the dominance of L. pini-densiflorae over S. sp. 1 in the Tianwang and Nanlu Mountains within the Northern Forestry Centre of China. These findings provide an emphatic representation of coevolution of pine wood nematode and its associated fungi. Our results lay a broader foundation for a better understanding of inter-kingdom mutualisms and the chemical signals that mediate their establishment.

Biodegradation of Crude-oil by Fungi Isolated from Cow Dungcontaminated soils

This study assayed oil-degrading potential of fungi isolated from cow dung-contaminated soils. The samples were collected aseptically from four different cow dung dumping sites with no history of crude-oil pollution in Akure metropolis. These samples were analyzed for fungal loads and oil-degrading fungi using potato dextrose agar and mineral salt medium respectively. The biodegradation of crude oil was observed spectrophotometrically using the broth culture of the fungal isolates for a period of 15 days on mineral salt medium. The fungi were identified based on the microscopic and macroscopic features of the hyphal mass, nature of the fruiting bodies and the morphology of cells and spores. The sixteen (16) fungi identified from the contaminated soils include; Bdellospora helicoides, Aspergillus fumigatus, Gonadobotricum apiculata, Aspergillus niger, Trichoderma viridae, Pleurothecium recurvatum, Streptothrix atra, Thysarophora longispora, Candida albicans, Aspergillus flavus, Helminthosporium velutinum, Botrytis cinerea, Zoophage nitospora, Varicosporium elodeae, Articulospora inflata and Neurospora crassa . All fungi showed degradation of the crude oil, with Trichoderma viridae, Aspergillus flavus and Varicosporium elodeae demonstrating best degradation ability. Trichoderma viridae exhibited highest degradation (66.2%) while Varicosporium elodeae exhibited least degradation (40%). The measurement of the rate of biodegradation of crude oil by the three fungi was further confirmed using Gas Chromatography and Mass Spectrophotometer (GC-MS). The GC-MS analysis showed that the fungi degraded the hydrocarbon compounds when compared to that of the control. The result obtained revealed that oil-degrading fungi can be isolated from cow dung dumping sites and they are competent mycoflora for the biodegradation of crude oil polluted soils. They can be used as a better approach to restoring oil contaminated environments through bioremediation process. Keywords : Biodegradation, Mycoflora, Crude-oil, Gas chromatography and Mass spectrophotometer (GCMS).

Hyphal growth in ingrowth mesh bags in Fagus sylvatica, Quercus petraea and Pinus pinaster stands in France

Our objective was to quantify the production of ectomycorrhizal (ECM) hyphae throughout the growing season. For this purpose, we used ingrowth mesh bags (30 μm mesh filled with 40 g sand) in top soils of Fagus sylvatica, Quercus petraea and Pinus pinaster forests in France. Installations were done at three or four different growth phases at each site and mesh bags were retrieved after one to three months. Ingrowing ECM hyphae measured 250–2257 mm bag−1 on average after one to three months. Specific hyphal length was 14.6–42.9 km g−1 of hyphal mass and differed among sites. Hyphal colonization was generally greater after three months than after one month regardless of season or species. Ingrowth was lower in autumn relative to the growth in summer (Fagus) or in spring and summer (Quercus). In Pinus, growth in winter was lower than in other seasons. These differences in ingrowth may relate to differences in seasonal carbon allocation, but may also result from differences between soils and/or climate such as the prolonged summer drought, affecting in particular the Pinus site.

Novel insights into the early stages of infection by oval conidia of Colletotrichum sublineolum

Anthracnose, caused by Colletotrichum sublineolum Henn. ex Sacc. & Trotter, is one of the most important sorghum [Sorghum bicolor (L.) Moench] diseases in Brazil. This fungus exhibits conidial dimorphism, producing either falcate or oval conidia on solid and liquid media, respectively. We compared patterns of the initial infection events by these two types of conidia on sorghum leaves using light microscopy and scanning electron microscopy. The infection events during the first 24 h were similar for both oval and falcate conidia. Globose and melanized apressoria were formed at 24 h after inoculation (hai) regardless of the conidia type. Dense mycelium and oval conidia developed from germinated falcate conidia at 32 hai. Hyphal mass displaying acervuli filled with falcate conidia and surrounded by setae, developed from germinated oval conidia at 48 hai. Oval conidia were as capable as falcate conidia of infecting sorghum leaves. The inherent ability to grow faster and the easeness with which oval conidia can be produced in vitro as compared to falcate, make the former a preferred choice for studies on the C. sublineolum-sorghum interaction. It would be instructive to further investigate the potential role of the oval conidia in epidemics.

Calcium oxalate crystals: an integral component of the Sclerotinia sclerotiorum/Brassica carinata pathosystem.

Oxalic acid is an important virulence factor for disease caused by the fungal necrotrophic pathogen Sclerotinia sclerotiorum, yet calcium oxalate (CaOx) crystals have not been widely reported. B. carinata stems were infected with S. sclerotiorum and observed using light microscopy. Six hours post inoculation (hpi), CaOx crystals were evident on 46% of stem sections and by 72 hpi on 100%, demonstrating that the secretion of oxalic acid by S. sclerotiorum commences before hyphal penetration. This is the first time CaOx crystals have been reported on B. carinata infected with S. sclerotiorum. The shape of crystals varied as infection progressed. Long tetragonal rods were dominant 12 hpi (68% of crystal-containing samples), but by 72 hpi, 50% of stems displayed bipyramidal crystals, and only 23% had long rods. Scanning electron microscopy from 24 hpi revealed CaOx crystals in all samples, ranging from tiny irregular crystals (< 0.5 μm) to large (up to 40 μm) highly organized arrangements. Crystal morphology encompassed various forms, including tetragonal prisms, oval plates, crystal sand, and druses. Large conglomerates of CaOx crystals were observed in the hyphal mass 72 hpi and these are proposed as a strategy of the fungus to hold and detoxify Ca2+ions. The range of crystal morphologies suggests that S. sclerotiorum growth and infection controls the form taken by CaOx crystals.

Toxic indole alkaloids avrainvillamide and stephacidin B produced by a biocide tolerant indoor mold Aspergillus westerdijkiae.

Toxic Aspergillus westerdijkiae were present in house dust and indoor air fall-out from a residence and a kindergarten where the occupants suffered from building related ill health. The A.westerdijkiae isolates produced indole alkaloids avrainvillamide (445Da) and its dimer stephacidin B (890Da). It grew and sporulated in presence of high concentrations of boron or polyguanidine (PHMB, PHMG) based antimicrobial biocides used to remediate mold infested buildings. The boar sperm cells were used as sensor cells to purify toxins from HPLC fractions of the fungal biomass. Submicromolar concentrations (EC50 0.3-0.4μM) blocked boar spermatozoan motility and killed porcine kidney tubular epithelial cells (PK-15). Plate grown hyphal mass of the A.westerdijkiae isolates contained 300-750ng of avrainvillamide and 30-300ng of stephacidin B per mg (wet weight). The toxins induced rapid (30min) loss of boar sperm motility, followed (24h) by loss of mitochondrial membrane potential (ΔΨm). Apoptotic cell death was observed in PK-15 cell monolayers, prior to cessation of glucose uptake or loss of ΔΨm. Avrainvillamide and stephacidin B were 100-fold more potent towards the porcine cells than the mycotoxins stephacidin A, ochratoxin A, sterigmatocystin and citrinin. The high toxicity of stephacidin B indicates a role of nitrone group in the mechanism of toxicity. Avrainvillamide and stephacidin B represent a new class of toxins with possible a threat to human health in buildings. Furthermore, the use of biocides highly enhanced the growth of toxigenic A. westerdijkiae.

The relationship between lignin peroxidase and manganese peroxidase production capacities and cultivation periods of mushrooms

Mushrooms are able to secrete lignin peroxidase (LiP) and manganese peroxidase (MnP), and able to use the cellulose as sources of carbon. This article focuses on the relation between peroxidase-secreting capacity and cultivation period of mushrooms with non-laccase activity. Methylene blue and methyl catechol qualitative assay and spectrophotometry quantitative assay show LiP secreting unvaryingly accompanies the MnP secreting in mushroom strains. The growth rates of hyphae are detected by detecting the dry hyphal mass. We link the peroxidase activities to growth rate of mushrooms and then probe into the relationship between them. The results show that there are close relationships between LiP- and/or MnP-secretory capacities and the cultivation periods of mushrooms. The strains with high LiP and MnP activities have short cultivation periods. However, those strains have long cultivation periods because of the low levels of secreted LiP and/or MnP, even no detectable LiP and/or MnP activity. This study provides the first evidence on the imitate relation between the level of secreted LiP and MnP activities and cultivation periods of mushrooms with non-laccase activity. Our study has significantly increased the understanding of the role of LiP and MnP in the growth and development of mushrooms with non-laccase activity.

Fungal infection as a complication of sinus bone grafting and implants: a case report

Sinus bone grafts have been used successfully to augment atrophic posterior maxilla for dental implant placement. Even though sinus bone grafting is generally considered to be a safe surgical procedure, postoperative maxillary sinus infections can occur and therefore need to be considered. Bacteria, as well as viruses and fungi, have been identified as causative agents. Because fungal infection of the maxillary sinus after sinus bone grafting is not well known, we report a case of a middle-aged male patient along with the clinical, radiographic, and histologic findings. The patient was referred from his private dentist because of failed sinus bone grafting and osseointegration of implants. The surgical approach to the sinus yielded a friable mass of brownish-red material from the sinus. Review of pathology slides revealed a noninvasive hyphal mass caused by Aspergillus and polypous mucosa. After surgical removal of the mycotic masses, sinus bone grafting, using allograft, was performed. Bone formation after the healing period was favorable and dental implants were placed. There was no recurrence of fungal sinusitis.

Cultural characteristics and extraction of the fungal pigment phleichrome from the phytopathogenic fungusCladosporium phlei

The cultural characteristics of the fungusCladosporium phlei were assessed in order to develop an improved method for the production of the fungal pigment, phleichrome, which is an intermediate in the production of a photodynamic therapeutic agent. The growth ofC. phlei, as measured by the hyphal growth rate and increase in biomass, varies significantly depending on the culture media utilized (V8 juice-based medium proved optimal for both growth rate and biomass increase). How-ever, even on a V8 juice plate, the growth ofC. phlei occurred slowly and in a limited fashion, in that the colony covered only 75% of the agar surface after more than 4 weeks of cultivation at 20°C. Supplementations of glucose, fructose, galactose, and sucrose increased both hyphal expansion and mass production, whereas supplementations of other carbon sources, including glycerol and sorbitol, exerted no detectable effects. The effect of inorganic nitrogen supplementation was negligible, whereas organic nitrogen evidenced significant effects, with enhanced growth with malt extract and growth inhibition with yeast extract and tryptone. Sporulation was enhanced under conditions of continuous light, and a minimum of 103 spores per mL of liquid media was found to be necessary for the optimal mass increase. A simple extraction procedure was established in order to isolate the deep red pigment which was subsequently identified as phleichrome via NMR analysis. WhenC. phlei was cultured on V8 medium containing 5% glucose and 2% malt extract, the quantity of mycelial mass was estimated as 20.6 g (dry weight) per liter of culture. The expected phleichrome yields from the mycelia and culture filtrates were estimated to be 43 and 2 mg/L, repectively.

Increasing endophyte alkaloid expression in tall fescue by selecting for increased endophyte hyphal density

Two AR542-endophyte infected tall fescue breeding pools were subjected to one cycle of selection for increased endophyte hyphal density. Hyphal density was assessed subjectively by microscopic examination of the leaf sheath. Levels of alkaloids produced by both the original and selected populations were subsequently measured during summer. Levels of lolines and peramine alkaloids increased significantly in one breeding pool (by 40% and 29%, respectively), with non-significant increases (by 24% and 2%) in the other breeding pool. The apparent correlation between observed hyphal density and levels of alkaloids supports the hypothesis that levels of lolines and peramine produced by fungal endophytes in their host grass are at least partly due to endophyte hyphal mass in the host sheath tissue. Measured lolines in one breeding pool were 21 times greater than the other, while sheath hyphal density was less. Possible explanations include contrasting patterns of hyphal colonisation beyond the sheath, and/or variation in the quantity of lolines produced per unit hyphal mass. Keywords: Neotyphodium coenophalium, endophyte, Festuca arundinacea, tall fescue, peramine, lolines, hyphal mass

Function of Candida albicans Adhesin Hwp1 in Biofilm Formation

Hwp1 is a well-characterized Candida albicans cell surface protein, expressed only on hyphae, that mediates tight binding to oral epithelial cells. Prior studies indicate that HWP1 expression is dependent upon Bcr1, a key regulator of biofilm formation. Here we test the hypothesis that Hwp1 is required for biofilm formation. In an in vitro model, the hwp1/hwp1 mutant produces a thin biofilm that lacks much of the hyphal mass found in the hwp1/HWP1 reconstituted strain. In a biofilm cell retention assay, we find that the hwp1/hwp1 mutant is defective in retention of nonadherent bcr1/bcr1 mutant cells. In an in vivo rat venous catheter model, the hwp1/hwp1 mutant has a severe biofilm defect, yielding only yeast microcolonies in the catheter lumen. These properties of the hwp1/hwp1 mutant are consistent with its role as a hypha-specific adhesin and indicate that it is required for normal biofilm formation. Overexpression of HWP1 in a bcr1/bcr1 mutant background improves adherence in the in vivo catheter model. This finding provides additional support for the model that Hwp1 is critical for biofilm adhesion. Hwp1 is the first cell surface protein known to be required for C. albicans biofilm formation in vivo and is thus an excellent therapeutic target.

Reorganization of mycelial networks of Phanerochaete velutina in response to new woody resources and collembola ( Folsomia candida) grazing

Mycelial development of Phanerochaete velutina extending from wood inocula in 57 × 57 cm trays of non-sterile soil was characterized after adding: (1) collembola; (2) new wood resources; (3) both new wood resources and collembola; and (4) no new resources and no collembola. After 99 d, all systems had produced distinct mycelial cords, much of the diffuse mycelium and thinner cords that were produced early on having regressed. Systems to which new resources (but no collembola) had been added developed thick cords interconnecting inocula with new resources, and much of the non-connected mycelium regressed. Nonetheless, these systems had significantly greater hyphal coverage and mass fractal dimension than the other treatments, resulting from outgrowth from the new resources. Unexpectedly, morphology of grazed systems with no added resources was very similar to that of ungrazed systems with no added resources, apparently because the collembola grazed on senescing hyphae that would ultimately have regressed. Where new resources and collembola were added, there was proliferation of fine mycelium along connective cords and elsewhere, but this was not as extensive as in the new resource/no collembola systems, the fine mycelium apparently being grazed in patches. Fungus gnat (family Sciaridae) larvae contaminated eight (out of 14) trays with no added collembola, but none of the systems to which collembola had been added. They burrowed around the wood and caused cords to be severed.

Relationship between metabolism and biomass of medically important zygomycetes

Little is known about the relationships between metabolic activity and fungal biomass or time of incubation for medically important fungal pathogens. Understanding these relationships may be especially relevant for rapidly growing organisms, such as zygomycetes. A range of inocula of five clinical isolates of zygomycetes (one each of Rhizopus oryzae,Rhizopus microsporus, Cunninghamella bertholletiae, Mucor circinelloides and Absidia corymbifera) were incubated for 6, 8, 12, 24 and 48 h, after which hyphal mass was assessed spectrophotometrically and metabolic activity was measured using various concentrations of XTT and menadione. Both linear regression and the Boltzmann sigmoid model were used and compared for description of relationships between metabolic activity, biomass and time of incubation. Modeling was further applied to eleven additional zygomycete isolates. The relationships of biomass or metabolic activity as a function of time of incubation were well described with the Boltzmann sigmoid model. The latter was superior to linear regression in describing the relationship between metabolic activity and fungal biomass. For all isolates of zygomycetes, increases in metabolic activity preceded increases in biomass. Inter-species differences in growth patterns were observed, with Rhizopus microsporus and Mucor spp. reaching the plateau of growth earlier compared to other species. These findings on the temporal relationship and inter-species differences of hyphal growth and metabolic activity for zygomycetes may be useful in the design and interpretation of in vitro studies of these emerging pathogens.