DNA barcoding survey of Trichoderma diversity in soil and litter of the Colombian lowland Amazonian rainforest reveals Trichoderma strigosellum sp. nov. and other species

The diversity of Trichoderma (Hypocreales, Ascomycota) colonizing leaf litter as well as the rhizosphere of Garcinia macrophylla (Clusiaceae) was investigated in primary and secondary rain forests in Colombian Amazonia. DNA barcoding of 107 strains based on the internal transcribed spacers 1 and 2 (ITS1 and 2) of the ribosomal RNA gene cluster and the partial sequence of the translation elongation factor 1 alpha (tef1) gene revealed that the diversity of Trichoderma was dominated (71 %) by three common cosmopolitan species, namely Trichoderma harzianum sensu lato (41 %), Trichoderma spirale (17 %) and Trichoderma koningiopsis (13 %). Four ITS 1 and 2 phylotypes (13 strains) could not be identified with certainty. Multigene phylogenetic analysis and phenotype profiling of four strains with an ITS1 and 2 phylotype similar to Trichoderma strigosum revealed a new sister species of the latter that is described here as Trichoderma strigosellum sp. nov. Sequence similarity searches revealed that this species also occurs in soils of Malaysia and Cameroon, suggesting a pantropical distribution.     

Global genetic diversity,lineage distribution,and Wolbachia infection of the alfalfa weevil Hypera postica (Coleoptera: Curculionidae)

The alfalfa weevil (Hypera postica) is a well‐known example of a worldwide‐distributed pest with high genetic variation. Based on the mitochondrial genes, the alfalfa weevil clusters into two main mitochondrial lineages. However, there is no clear picture of the global diversity and distribution of these lineages; neither the drivers of its diversification are known. However, it appears likely that historic demographic events including founder effects played a role. In addition, Wolbachia, a widespread intracellular parasite/symbiont, likely played an important role in the evolution of the species. Wolbachia infection so far was only detected in the Western lineage of H. postica with no information on the infecting strain, its frequency, and its consequences on the genetic diversity of the host. We here used a combination of mitochondrial and nuclear sequences of the host and sequence information on Wolbachia to document the distribution of strains and the degree of infection. The Eastern lineage has a higher genetic diversity and is found in the Mediterranean, the Middle East, Eastern Europe, and eastern America, whereas the less diverse Western lineage is found in Central Europe and the western America. Both lineages are infected with the same common strain of Wolbachia belonging to Supergroup B. Based on neutrality tests, selection tests, and the current distribution and diversification of Wolbachia in H. postica, we suggested the Wolbachia infection did not shape genetic diversity of the host. The introduced populations in the United States are generally genetically less diverse, which is in line with founder effects.     

The VELVET A Orthologue VEL1 of Trichoderma reesei Regulates Fungal Development and Is Essential for Cellulase Gene Expression

Trichoderma reesei is the industrial producer of cellulases and hemicellulases for biorefinery processes. Their expression is obligatorily dependent on the function of the protein methyltransferase LAE1. The Aspergillus nidulans orthologue of LAE1 - LaeA - is part of the VELVET protein complex consisting of LaeA, VeA and VelB that regulates secondary metabolism and sexual as well as asexual reproduction. Here we have therefore investigated the function of VEL1, the T. reesei orthologue of A. nidulans VeA. Deletion of the T. reesei vel1 locus causes a complete and light-independent loss of conidiation, and impairs formation of perithecia. Deletion of vel1 also alters hyphal morphology towards hyperbranching and formation of thicker filaments, and with consequently reduced growth rates. Growth on lactose as a sole carbon source, however, is even more strongly reduced and growth on cellulose as a sole carbon source eliminated. Consistent with these findings, deletion of vel1 completely impaired the expression of cellulases, xylanases and the cellulase regulator XYR1 on lactose as a cellulase inducing carbon source, but also in resting mycelia with sophorose as inducer. Our data show that in T. reesei VEL1 controls sexual and asexual development, and this effect is independent of light. VEL1 is also essential for cellulase gene expression, which is consistent with the assumption that their regulation by LAE1 occurs by the VELVET complex.     

Development of a chitosan nanofibrillar scaffold for skin repair and regeneration

The final goal of the present study was the development of a 3-D chitosan dressing that would shorten the healing time of skin wounds by stimulating migration, invasion, and proliferation of the relevant cutaneous resident cells. Three-dimensional chitosan nanofibrillar scaffolds produced by electrospinning were compared with evaporated films and freeze-dried sponges for their biological properties. The nanofibrillar structure strongly improved cell adhesion and proliferation in vitro. When implanted in mice, the nanofibrillar scaffold was colonized by mesenchymal cells and blood vessels. Accumulation of collagen fibrils was also observed. In contrast, sponges induced a foreign body granuloma. When used as a dressing covering full-thickness skin wounds in mice, chitosan nanofibrils induced a faster regeneration of both the epidermis and dermis compartments. Altogether our data illustrate the critical importance of the nanofibrillar structure of chitosan devices for their full biocompatibility and demonstrate the significant beneficial effect of chitosan as a wound-healing biomaterial.     

Evolution and Ecophysiology of the Industrial Producer Hypocrea jecorina (Anamorph Trichoderma reesei) and a New Sympatric Agamospecies Related to It

Background

Trichoderma reesei, a mitosporic green mould, was recognized during the WW II based on a single isolate from the Solomon Islands and since then used in industry for production of cellulases. It is believed to be an anamorph (asexual stage) of the common pantropical ascomycete Hypocrea jecorina.

Methodology/Principal Findings

We combined molecular evolutionary analysis and multiple methods of phenotype profiling in order to reveal the genetic relationship of T. reesei to H. jecorina. The resulting data show that the isolates which were previously identified as H. jecorina by means of morphophysiology and ITS1 and 2 (rRNA gene cluster) barcode in fact comprise several species: i) H. jecorina/T. reesei sensu stricto which contains most of the teleomorphs (sexual stages) found on dead wood and the wild-type strain of T. reesei QM 6a; ii) T. parareesei nom. prov., which contains all strains isolated as anamorphs from soil; iii) and two other hypothetical new species for which only one or two isolates are available. In silico tests for recombination and in vitro mating experiments revealed a history of sexual reproduction for H. jecorina and confirmed clonality for T. parareesei nom. prov. Isolates of both species were consistently found worldwide in pantropical climatic zone. Ecophysiological comparison of H. jecorina and T. parareesei nom. prov. revealed striking differences in carbon source utilization, conidiation intensity, photosensitivity and mycoparasitism, thus suggesting adaptation to different ecological niches with the high opportunistic potential for T. parareesei nom. prov.

Conclusions

Our data prove that T. reesei belongs to a holomorph H. jecorina and displays a history of worldwide gene flow. We also show that its nearest genetic neighbour - T. parareesei nom. prov., is a cryptic phylogenetic agamospecies which inhabits the same biogeographic zone. These two species thus provide a so far rare example of sympatric speciation within saprotrophic fungi, with divergent ecophysiological adaptations and reproductive strategies.     

Functional incorporation of the pore forming segment of AChR M2 into tethered bilayer lipid membranes

Tethered bilayer lipid membranes (tBLMs) are robust and flexible model platforms for the investigation of various membrane related processes. They are especially suited to study the incorporation and function of ion channel proteins, where a high background resistance of the membrane is essential. Synthetic M2 peptides, analogues of the transmembrane fragment of the acetylcholine receptor, could be incorporated into two different membrane architectures. The functional reconstitution and the formation of a conducting pore are shown by electrochemical impedance spectroscopy (EIS). The pore is selective for small monovalent cations, while bulky ions cannot pass. This is a significant step towards a novel biosensing approach. We envision a device, where a stable and insulating membrane would be attached to an electronic read-out unit and embedded proteins would serve as actual sensing units.     

Characterization of Erwinia amylovora strains from Bulgaria by pulsed-field gel electrophoresis

The aim of this study was to characterize genetically Bulgarian Erwinia amylovora strains using pulsed-field gel electrophoresis (PFGE) analysis. Fifty E. amylovora strains isolated from different hosts, locations, as well as in different years were analysed by PFGE after XbaI, SpeI, and XhoI digestion of the genomic DNA. The strains were distributed into four groups according to their XbaI-generated profile. About 82% of the strains displayed a PFGE profile identical to that of type Pt2. Three strains belonged to the Central Europe Pt1 type. Two new PFGE profiles, not reported so far, were established--one for a strain isolated from Malus domestica and another for all Fragaria spp. strains. The same grouping of the strains was obtained after analysis of the SpeI digestion patterns. On the basis of PFGE profiles, after XbaI and SpeI digestion, a genetic differentiation between the strains associated with subfamily Maloideae and subfamily Rosoideae was revealed. The presence of more than one PFGE profile in the population of E. amylovora in Bulgaria suggests a multiple source of inoculum.