Exploring mycorrhizal diversity in sympatric mycoheterotrophic plants: a comparative study of Monotropastrum humile var. humile and M. humile var. glaberrimum.

Mycoheterotrophic plants (MHPs) rely on their mycorrhizal fungus for carbon and nutrient supply, thus a shift in mycobionts may play a crucial role in speciation. This study aims to explore the mycorrhizal diversity of two closely related and sympatric fully MHPs, Monotropastrum humile var. humile (Mhh) and M. humile var. glaberrimum (Mhg), and determine their mycorrhizal associations. A total of 1,108,710 and 1,119,071 ectomycorrhizal fungal reads were obtained from 31 Mhh and 31 Mhg, and these were finally assigned to 227 and 202 operational taxonomic units, respectively. Results show that sympatric Mhh and Mhg are predominantly associated with different fungal genera in Russulaceae. Mhh is consistently associated with members of Russula, whereas Mhg is associated with members of Lactarius. Associating with different mycobionts and limited sharing of fungal partners might reduce the competition and contribute to their coexistence. The ectomycorrhizal fungal communities are significantly different among the five forests in both Mhh and Mhg. The distinct mycorrhizal specificity between Mhh and Mhg suggests the possibility of different mycobionts triggered ecological speciation between sympatric species.

Bacteria inhabiting spider webs enhance host silk extensibility.

Spider silk is a promising material with great potential in biomedical applications due to its incredible mechanical properties and resistance to degradation of commercially available bacterial strains. However, little is known about the bacterial communities that may inhabit spider webs and how these microorganisms interact with spider silk. In this study, we exposed two exopolysaccharide-secreting bacteria, isolated from webs of an orb spider, to major ampullate (MA) silk from host spiders. The naturally occurring lipid and glycoprotein surface layers of MA silk were experimentally removed to further probe the interaction between bacteria and silk. Extensibility of major ampullate silk produced by Triconephila clavata that was exposed to either Microbacterium sp. or Novosphigobium sp. was significantly higher than that of silk that was not exposed to bacteria (differed by 58.7%). This strain-enhancing effect was not observed when the lipid and glycoprotein surface layers of MA silks were removed. The presence of exopolysaccharides was detected through NMR from MA silks exposed to these two bacteria but not from those without exposure. Here we report for the first time that exopolysaccharide-secreting bacteria inhabiting spider webs can enhance extensibility of host MA silks and silk surface layers play a vital role in mediating such effects.

Nitrogen inaccessibility protects spider silk from bacterial growth.

Spider silks are protein-based fibers that are incorporated into webs with the unique combination of high mechanical toughness and resistance to microbial degradation. While spiders are undoubtedly exposed to saprophytic microorganisms in their native habitats, such as the forest understory and bush, their silks have rarely been observed to decompose in either field or laboratory studies. We performed cross-streaking assays using silk from three spider species and four bacterial strains and found no inhibition zones, indicating the absence of antibacterial properties. We also cultured all bacteria directly upon silk in Luria-Bertani (LB) broth (full nutrients), phosphate-buffered saline (PBS; no nutrients) and nitrogen-free glucose broth (NFG; full nutrients, no nitrogen), and found that bacteria grew readily on silk in LB broth but not in PBS or NFG buffer. Our results indicate that spider silk's resistance to bacterial degradation is likely due to bacteriostatic rather than antibacterial mechanisms when nitrogen is inaccessible.

Does Spore Count Matter in Fungal Allergy?: The Role of Allergenic Fungal Species.

PURPOSE: Fungi have been known to be important aeroallergens for hundreds of years. Most studies have focused on total fungal concentration; however, the concentration of specific allergenic fungi may be more important on an individual basis. METHODS: Ten fungal allergic patients and 2 non-fungal allergic patients were enrolled. The patients with a decrease in physician or patient global assessment by more than 50% of their personal best were considered to have an exacerbation of allergic symptoms and to be in the active stage. Those who maintained their physician and patient global assessment scores at their personal best for more than 3 months were considered to be in the inactive stage. The concentrations of dominant fungi in the patients' houses and outdoors were measured by direct and viable counts at active and inactive stages. RESULTS: The exacerbation of allergic symptoms was not correlated with total fungal spore concentration or the indoor/outdoor ratio (I/O). Specific fungi, such as Cladosporium oxysporum (C. oxyspurum), C. cladosporioides, and Aspergillus niger (A. niger), were found to be significantly higher concentrations in the active stage than in the inactive stage. Presumed allergenic spore concentration threshold levels were 100 CFU/m³ for C. oxysporum, and 10 CFU/m³ for A. niger, Penicillium brevicompactum and Penicillium oxalicum. CONCLUSIONS: The major factor causing exacerbation of allergic symptoms in established fungal allergic patients may be the spore concentration of specific allergenic fungi rather than the total fungal concentration. These results may be useful in making recommendations as regards environmental control for fungal allergic patients.

Responses of Soil Fungal Populations and Communities to the Thinning of Cryptomeria Japonica Forests.

Forest management activities, such as tree thinning, alter forest ecology, including key components of forest ecosystems, including fungal communities. In the present study, we investigate the effects of forest thinning intensity on the populations and structures of fungal soil communities in the Cryptomeria japonica forests of central Taiwan as well as the dynamics of soil fungi communities in these forests after a thinning disturbance. Although the populations of soil fungi significantly increased in the first 6 months after thinning, these increases had subsided by 9 months. This pulse was attributed to a transient increase in the populations of rapid colonizers. A multiple regression analysis positively correlated fungal populations with organic matter content and cellulase activity. Thinning initially provided large amounts of fresh leaves and roots as nutrient-rich substrates for soil fungi. Denaturing gradient gel electrophoresis (DGGE) profiles indicated that soil fungal communities significantly differed among plots with 0% (control), 25%, and 50% tree thinning in the first 21 months post-thinning, with no significant differences being observed after 21 months. The fungal communities of these forest soils also changed with the seasons, and an interactive relationship was detected between seasons and treatments. Seasonal variations in fungal communities were the most pronounced after 50% tree thinning. The results of the present study demonstrate that the soil fungi of Taiwanese C. japonica forests are very sensitive to thinning disturbances, but recover stability after a relatively short period of time.

Biogeography of ectomycorrhizal fungi associated with alders (Alnus spp.) in relation to biotic and abiotic variables at the global scale.

· Much of the macroecological information about microorganisms is confounded by the lack of standardized methodology, paucity of metadata and sampling effect of a particular substrate or interacting host taxa. · This study aims to disentangle the relative effects of biological, geographical and edaphic variables on the distribution of Alnus-associated ectomycorrhizal (ECM) fungi at the global scale by using comparable sampling and analysis methods. · Ribosomal DNA sequence analysis revealed 146 taxa of ECM fungi from 22 Alnus species across 96 sites worldwide. Use of spatial and phylogenetic eigenvectors along with environmental variables in model selection indicated that phylogenetic relations among host plants and geographical links explained 43 and 10%, respectively,in ECM fungal community composition, whereas soil calcium concentration positively influenced taxonomic richness. · Intrageneric phylogenetic relations among host plants and regional processes largely account for the global biogeographic distribution of Alnus-associated ECM fungi. The biogeography of ECM fungi is consistent with ancient host migration patterns from Eurasia to North America and from southern Europe to northern Europe after the last glacial maximum, indicating codispersal of hosts and their mycobionts.

Yamadazyma siamensis sp. nov., Yamadazyma phyllophila sp. nov. and Yamadazyma paraphyllophila sp. nov., three novel yeast species isolated from phylloplane in Thailand and Taiwan.

Four strains representing three novel anamorphic yeast species were isolated from the external surface of sugarcane leaves (DMKU-RK254(T)), corn leaves (DMKU-RK548(T)), bean leaves (K129) in Thailand and hengchun pencilwood leaves (TrB1-1(T)) in Taiwan. On the basis of morphological, biochemical, physiological and chemotaxonomic characteristics, the sequence analysis of the D1/D2 region of the large subunit (LSU) rRNA gene, the internal transcribed spacer (ITS) region, the actin gene (ACT1) and the elongation factor 2 gene (EF2), the four strains were determined to represent novel Yamadazyma species although formation of ascospores was not observed. Strain DMKU-RK254(T) was determined to be related to Candida diddensiae, Candida naeodendra and Candida kanchanaburiensis but with 1.8, 1.8 and 2.0 % nucleotide substitutions in the D1/D2 region of the LSU rRNA gene, respectively. It was assigned to Yamadazyma siamensis sp. nov. (type strain DMKU-RK254(T) = BCC 50730(T) = NBRC 108901(T) = CBS 12573(T)). The sequences of the D1/D2 region of the LSU rRNA gene, the ITS region, ACT1 gene and EF2 gene of two strains (DMKU-RK548(T) and K129) were identical but differed from that of strain TrB1-1(T) by 0.6, 1.0, 3.3 and 5.9 % nucleotide substitutions, respectively. Therefore, the two strains (DMKU-RK548(T) and K129) and strain TrB1-1(T) were assigned to be two separate species. The closest species in terms of pairwise sequences similarity of the D1/D2 region to the two novel species was Yamadazyma philogaea but with 1.1-1.7 % nucleotide substitutions. The two strains (DMKU-RK548(T) and K129) were assigned to Yamadazyma phyllophila sp. nov. (type strain DMKU-RK548(T) = BCC 50736(T) = NBRC 108906(T) = CBS 12572(T)) and the strain TrB1-1(T) was named Yamadazyma paraphyllophila sp. nov. (type strain TrB1-1(T) = BCRC 23030(T) = CCTCC AY 204005(T) = CBS 9928(T)).

Farysizyma gen. nov., an anamorphic genus in the Ustilaginales to accommodate three novel epiphytic basidiomycetous yeast species from America, Europe and Asia.

Among many isolates that resulted from four independent surveys of yeasts associated with plants in Brazil, the USA, Portugal and Taiwan, we have characterized eighteen basidiomycetous strains, two of which were conspecific with the type strain of Rhodotorula acheniorum, whereas the remaining sixteen isolates appeared not to correspond to any previously described species. Microsatellite-PCR fingerprinting with primers M13 and (GTG)5 confirmed that the latter strains formed three genetically distinct groups. Each group was considered to represent a distinct species based on nucleotide sequences of the D1/D2 domains of the 26S rRNA gene and the internal transcribed spacer (ITS) region. Phylogenetic analyses of sequence data placed the putative novel species in a clade with R. acheniorum and the dimorphic smut fungus Farysia chardoniana. A novel anamorphic genus, Farysizyma, is created to accommodate the three undescribed species, which were named Farysizyma itapuensis, Farysizyma setubalensis and Farysizyma taiwaniana. A new combination, Farysizyma acheniorum, is proposed for R. acheniorum, which may represent the yeast-phase anamorph of Farysia thuemenii.