Multilocus Genotyping and Intergenic Spacer Single Nucleotide Polymorphisms of Amylostereum areolatum (Russulales: Amylostereacea) Symbionts of Native and Non-Native Sirex Species

Sirex noctilio along with its mutualistic fungal symbiont, Amylostereum areolatum (a white rot fungus), is an invasive pest that causes excessive damage to Pinus plantations in Northeast China. In 2015, S. noctilio were found to attack Pinus sylvestris var. mongolica, and often share larval habitat with the native woodwasp, S. nitobei. The objective of this study was to determine the possible origin(s) of the introduced pest complex in China and analyse the genetic diversity between A. areolatum isolated from invasive S. noctilio, native S. nitobei and other woodwasps collected from Europe (native range) and other countries. Phylogenetic analyses were performed using the intergenic spacer (IGS) dataset and the combined 4-locus dataset (the internal transcribed spacer region (ITS), translation elongation factor alpha 1 (tef1), DNA-directed ribosomal polymerase II (RPB2), and mitochondrial small subunit (mtSSU)) of three Amylostereum taxa. The multilocus genotyping of nuclear ribosomal regions and protein coding genes revealed at least three distinct multilocus genotypes (MLGs) of the fungus associated with invasive S. noctilio populations in Northeast China, which may have come from North America or Europe. The IGS region of A. areolatum carried by S. noctilio from China was designated type B1D2. Our results showed a lack of fidelity (the paradigm of obligate fidelity to a single fungus per wasp species) between woodwasp hosts and A. areolatum. We found that the native S. nitobei predominantly carried A. areolatum IGS-D2, but a low percentage of females instead carried A. areolatum IGS-B1D2 (MLG A13), which was presumably due to horizontal transmission from S. noctilio, during the sequential use of the same wood for larval development. The precise identification of the A. areolatum genotypes provides valuable insight into co-evolution between Siricidae and their symbionts, as well as understanding of the geographical origin and history of both Sirex species and their associated fungi.

Mechanical characteristics of bacterial cellulose-reinforced mycelium composite materials

Background While mycelium is considered a promising alternative for fossil-based resins in lignocellulosic materials, the mechanical properties of mycelium composite materials remain suboptimal, among other reasons due to the weak internal bonds between the hyphae and the natural fibres. A solution could be provided by the hybridisation of mycelium materials with organic additives. More specifically, bacterial cellulose seems to be a promising additive that could result in reinforcing mycelium composites; however, this strategy is underreported in scientific literature. Results In this study, we set out to investigate the mechanical properties of mycelium composites, produced with the white-rot fungus Trametes versicolor, and supplemented with bacterial cellulose as an organic additive. A methodological framework is developed for the facile production of bacterial cellulose and subsequent fabrication of mycelium composite particle boards based on a hybrid substrate consisting of bacterial cellulose and hemp in combination with a heat-pressing approach. We found that, upon adding bacterial cellulose, the internal bond of the composite particle boards significantly improved. Conclusions The addition of bacterial cellulose to mycelium composite materials not only results in a strengthening of internal bonding of mycelium material, but also renders tuneable mechanical properties to the material. As such, this study contributes to the ongoing development of fully biological hybrid materials with performant mechanical characteristics.

Influence of sucrosis on the degradation of pesticide by white rot fungus

The influence of sucrose on the removal of Paraquat (PQT) in synthetic aqueous medium was evaluated by Phanerochaete chrysosporium. Initially, a toxicity test was performed on plates containing paraquat at concentrations of 1, 5, 10, 20 and 30 mg.L-1. Then, they were carried out in batches - agitated batch (RBA) and sequential batch (RBS). Four reactors were submitted, containing medium with 30 mg.L-1 of paraquat, under a reaction time of 144 h, the reactors being RBA-2 and RBS-2 with the addition of 2 gL-1 of sucrose, and without the adding sucrose to the RBA-0 and RBS-0 reactors. In all reactors, paraquat was removed, but in RBS-0, the best mean removal efficiency was obtained (41.1 ± 0.89%). The best values ​​of apparent speed of degradation (k) were found in reactors with sucrose RBA-2 and RBS-2, 0.015 ± 0.002 h-1 and 0.018 ± 0.002 h-1, respectively, indicating that the addition of sucrose influenced the speed removal of paraquat. It was also verified that the pollutant was not completely removed by adsorption to fungal biomass, which microorganisms predominated in the medium at the end of the treatment, demonstrating their role in the paraquat bioremediation process. Therefore, the addition of sucrose influenced the removal speed of the PQT and COD, but not the removal efficiency.

Biological pretreatment of rice husks with the white-rot fungus pleurotus ostreatus: the role of laccase activity

The main objective of this study was to determine the influence of the composition of the culture medium and lignocellulosic compounds on the secretion of laccase enzymes by P. ostreatus in submerged cultures. These studies were done using a statistical and systematic approach that allowed the control of the culture media composition. The optimal nutritional conditions were found that simultaneously increased fungal growth and laccase activity in the absence and presence of copper sulfate, a recognized inducer of laccase. Under these conditions, the biochemical aspects of transcripts in P. ostreatus related to laccase secretion were evaluated , which revealed the participation of membrane transporters with high affinity for copper (CTRs) as intermediate candidates for the regulation of three laccase genes, lacc2, lacc6, and lacc10. Moreover, the evaluation of the results of the culture media composition suggests that the regulation of these transporters is closely linked to sufficient nutritional conditions in carbon and nitrogen, with central participation of the metabolism of organic nitrogen in this process. With these findings, it was possible to obtain more profound knowledge of the pretreatment of lignocellulosic biomass by P. ostreatus in a submerged culture that was oriented to determine the role of laccase activity in the biological pretreatment of rice husks.

Biodegradation and Micro- Scale Treatability Pattern of Loblolly Pine Heartwood Bioincised by Bacillus Subtilis and Physisporinus Vitreus

One strategy for improving the treatability of refractory wood species is biological incising, and its efficiency depends on how the microorganisms modify the porous structure of the wood. Evaluation of the bioincised wood treatability on a micro-scale can thus help to better understand the treatability enhancing mechanisms. In the present study, the biodegradation pattern and micro-scale treatability of Loblolly pine (Pinus taeda L.) heartwood were determined after bioincising with the white-rot fungus Physisporinus vitreus (Pers.: Fr.) P. Karsten isolate 136 and bacterium Bacillus subtilis UTB22. Oven-dried specimens with dimensions of 50 mm × 25 mm × 15 mm (L × T × R) were incubated with the microorganisms at (23±2) °C and (65±5) % relative humidity for six weeks. The control and exposed wood blocks were then pressure treated by 1 % fluorescent dye (fluorescein)-containing water to study the treatability pattern under a fluorescence microscope. The longitudinal and tangential air permeability and compression strength parallel to the grain of the specimens were also determined at the end of the incubation period. Scanning electron microscopic (SEM) studies showed that degradation by B. subtilis UTB22 was limited to the pit membranes, but the cell walls were also degraded to some extent by P. vitreus. The fungus caused a higher mass loss compared to the bacterium, whereas the permeability enhancing ability of the bacterium was more pronounced. The fluorescent dye tracer also showed that higher treatability with more uniformity was obtained by B. subtilis UTB22. The improvement in treatability by both microorganisms was mainly due to the degradation of the earlywood tracheids.

Cutlink Cleaning Head with a Spreading Feature for Biological Sprout Control

The ability of deciduous trees to sprout efficiently after cutting is problematic in young forests where the target is to cultivate coniferous trees for industry. Since the use of chemicals has been restricted, new alternatives are needed. One potential and environmentally friendly option is biological sprout control that is based on the use of a white-rot fungus, Chondrostereum purpureum (Pers. Ex Fr.) Pouzar. This method has been efficient in earlier investigations when performed manually, but efficient, fully mechanized devices which are able to cut and treat stumps with a fungus are still unavailable. Therefore, the efficacy of biological sprout control conducted with a Cutlink cleaning head equipped with a spreading feature was studied in two young Norway spruce (Picea abies (L.) H. Karst.) forests in central Finland.Sample plots for the control (cutting deciduous saplings only) and fungal treatment (cutting and spreading fungal inoculum on fresh stump surfaces) were established, and the ability of the Cutlink cleaning head in preventing sprouting of silver and downy birch (Betula pendula Roth and B. pubescens Ehrh., respectively) in the sample plots was investigated for two years.In the near vicinity of cultivated Norway spruce, the proportion of cut deciduous saplings varied from 50–60% after the Cutlink operation. The average mortality of silver and downy birch stumps in the fungal treatment plots was ca. 40%, while stump mortality in the control, i.e., cutting only, was only ca. 13%, after two years. Stump mortality increased up to 73% if the stumps did not include old branches, i.e., the stump was cut to a low enough height.These results confirmed that the Cutlink cleaning head is a potential tool in young stand management operation but further development will be needed in working methods in order to achieve lower stump heights (no branches on the stump) and also to increase the proportion of cut saplings.