Fungal Traits Important for Soil Aggregation

Soil structure, the complex arrangement of soil into aggregates and pore spaces, is a key feature of soils and soil biota. Among them, filamentous saprobic fungi have well-documented effects on soil aggregation. However, it is unclear what properties, or traits, determine the overall positive effect of fungi on soil aggregation. To achieve progress, it would be helpful to systematically investigate a broad suite of fungal species for their trait expression and the relation of these traits to soil aggregation. Here, we apply a trait-based approach to a set of 15 traits measured under standardized conditions on 31 fungal strains including Ascomycota, Basidiomycota, and Mucoromycota, all isolated from the same soil. We find large differences among these fungi in their ability to aggregate soil, including neutral to positive effects, and we document large differences in trait expression among strains. We identify biomass density, i.e., the density with which a mycelium grows (positive effects), leucine aminopeptidase activity (negative effects) and phylogeny as important factors explaining differences in soil aggregate formation (SAF) among fungal strains; importantly, growth rate was not among the important traits. Our results point to a typical suite of traits characterizing fungi that are good soil aggregators, and our findings illustrate the power of employing a trait-based approach to unravel biological mechanisms underpinning soil aggregation. Such an approach could now be extended also to other soil biota groups. In an applied context of restoration and agriculture, such trait information can inform management, for example to prioritize practices that favor the expression of more desirable fungal traits

Growth rate trades off with enzymatic investment in soil filamentous fungi

Saprobic soil fungi drive many important ecosystem processes, including decomposition, and many of their effects are related to growth rate and enzymatic ability. In mycology, there has long been the implicit assumption of a trade-off between growth and enzymatic investment, which we test here using a set of filamentous fungi from the same soil. For these fungi we measured growth rate (as colony radial extension) and enzymatic repertoire (activities of four enzymes: laccase, cellobiohydrolase, leucine aminopeptidase and acid phosphatase), and explored the interaction between the traits based on phylogenetically corrected methods. Our results support the existence of a trade-off, however only for the enzymes presumably representing a larger metabolic cost (laccase and cellobiohydrolase). Our study offers new insights into potential functional complementarity within the soil fungal community in ecosystem processes, and experimentally supports an enzymatic investment/growth rate trade-off underpinning phenomena including substrate succession

Tradeoffs in hyphal traits determine mycelium architecture in saprobic fungi

The fungal mycelium represents the essence of the fungal lifestyle, and understanding how a mycelium is constructed is of fundamental importance in fungal biology and ecology. Previous studies have examined initial developmental patterns or focused on a few strains, often mutants of model species, and frequently grown under non-harmonized growth conditions; these factors currently collectively hamper systematic insights into rules of mycelium architecture. To address this, we here use a broader suite of fungi (31 species including members of the Ascomycota, Basidiomycota and Mucoromycota), all isolated from the same soil, and tested for ten architectural traits under standardized laboratory conditions. We find great variability in traits among the saprobic fungal species, and detect several clear tradeoffs in mycelial architecture, for example between internodal length and hyphal diameter. Within the constraints so identified, we document otherwise great versatility in mycelium architecture in this set of fungi, and there was no evidence of trait ‘syndromes’ as might be expected. Our results point to an important dimension of fungal properties with likely consequences for coexistence within local communities, as well as for functional complementarity (e.g. decomposition, soil aggregation)

Stabilität des Bodens und fadenförmige Pilze

The main goal of this dissertation was to explore the connection between soil aggregation and soil water repellency trough soil fungi under the umbrella of the trait-based approach. In the study two types of soil fungi, ectomycorrhizal (EcM) fungi and saprotrophic fungi, were included. In Chapter 2 we show that: (1) ectomycorrhiza establishment in Pinus sylvestris L. plants inoculated with different isolates of EcM fungi produced an increase in water- stable aggregates (WSA), compared to initial values – in contrast with non- mycorrhizal plants, which did not produce any change but increased the mean weight diameter (MWD) ; (2) soil water repellency (SWR), which measured as water drop penetration time (WDPT) was induced by three EcM fungal isolates which also exhibited mycelium hydrophobicity; (3) root development was only weakly positively correlated with both WSA and WDPT; (4) different EcM fungal isolates affected stability of soil aggregates and repellency of soil differently. This suggests that EcM fungi play a role in both soil aggregation and soil water repellency and using a trait-based approach for the observation of fungal effects on soil structure will be fruitful. In Chapter 3 we performed a quantitative data synthesis (meta-analysis), in which we tested whether AS and SWR are two interrelated soil processes, as well as whether the edaphic factors (SOC, soil pH, and soil sand content) and experimental factors (experimental setting, duration, sampling depth, sample drying temperature, measuring methods and burning temperature when treated with fire) affect SWR. We found (1) correlations among SWR, AS and SOC indicating SWR and AS were joint processes connected by SOC; (2) soil pH and sand content both positively related to SWR in the reported ranges; (3) the methods used to quantify SWR did not bias the results; (4) when soil was treated with fire, SWR increases more strongly with increasing AS; and at higher temperature SWR disappeared whereas at lower temperature SWR showed up. The included studied covered less frequently microbial treatments and did not report some crucial abiotic factors like soil water content. SWR can associate with SOC and AS in multiple ways and influenced by abiotic conditions. Our study emphasizes the importance of integrating AS and SWR in the study of soil stability, and of controlling or recording specific conditions to reveal different aspects of mechanisms. In Chapter 4, we experimentally tested fungal traits of 31 saprotrophic fungi; the traits examined are related to soil aggregation and stability. The chosen traits are growth features (colony extension rate (Kr) and biomass density), enzyme activities (acid phosphatase, cellobiohydrolase, leucine aminopeptidase and laccase) and water-related features (mycelial water content and hydrophobicity of fungal surface (HFS). We showed that fungal traits were affected by cellophane membrane morphologically and physiologically. The colonies had higher enzyme activities at younger age. But the shifts of enzyme activities were not lead to changes in phylogenetic signal. We showed that mycelial water content was an intrinsic trait that should be included in future studies. For the first time we found that HFS, the activity of leucine aminopeptidase and biomass density had phylogenetic signals. We found the chosen traits were phylogenetically convergent, which means the grouping of the strains based on trait information were similar to their phylogenetic groups. In trade-offs among the traits, Kr and biomass density were potentially negatively related to each when three extreme data points were removed. At the same time the relationship between cellobiohydrolase and laccase activities was strongly influenced by the suspicious extreme points. Here, the extreme data points arise from divergent traits of the phylogenetically close strains, which suggests divergent evolution. In all, our results suggest that HFS and mycelial water content are two crucial fungal traits, that using cellophane membrane to facilitate collecting fungal traits needs to be employed with care, and that plasticity of fungal traits is a concern when building trait databases.Die Hauptzielsetzung dieser Dissertation war es, den Zusammenhang zwischen Aggregation (BA) und dem Wasserabweisungsvermögen des Bodens (BWV) mittels Boden-assoziierter Pilze unter Anwendung des Merkmal-basierten Ansatzes („trait-based approach“) zu ergründen. Im Rahmen dieser Studie wurden zwei Pilztypen in Experimente einbezogen – Ektomykorrhizapilze (EkM) und saprobische Pilze (SP). In Kapitel 2 zeigten wir, dass (1) die Etablierung von Ektomykorrhiza in Pinus sylvestris L. Pflanzen mittels verschiedener EkM- Isolate die Wasserstabilität von Bodenaggregaten (WSA) sowie die Größenklassenverteilung („mean weight diameter“, MWD) signifikant erhöht im Verhältnis zum Ausgangsboden und den unmykorrhizierten Kontrollpflanzen; (2) Das Wasserabweisungsvermögen des Bodens (BWV), welches als Wassertropfeneindringungszeit („water drop penetration time“, WDPT) gemessen wurde, wurde durch drei der getestete Isolate verstärkt, die ebenfalls nachweisbar ein hydrophobes Myzel aufwiesen; (3) Die Wurzelentwicklung (Wurzelbiomasse und –länge) korrelierte nur geringfügig positiv mit WSA und WDPT; (4) Der Einfluss der verschiedenen EkM-Isolate auf die Faktoren WSA und BWV variierte zwischen den einzelnen Pilzgenotypen. Diese Fakten legen nahe, dass EkM-Pilze eine entscheidende Rolle in der Bodenaggregation sowie dem Wasserabweisungsvermögen von Boden spielen. Diese sollte unter Anwendung des Merkmal-basierten Ansatzes weiter ergründet werden. In Kapitel 3 wurde eine quantitative Datensynthese (Meta-Analyse) durchgeführt, mit der wir die Fragen klären wollten, (1) ob BA und BWV zwei Bodenprozesse sind, die in gegenseitiger Wechselwirkung stehen und (2) ob edaphische Faktoren (organischer Bodenkohlenstoff, Boden-pH und Sandgehalt) und experimentelle Faktoren (experimentelle Umgebung, Experimentdauer, Beprobungstiefe, Probentrocknungstemperatur, Messmethode sowie Temperatur von Feuerbehandlungen) BWV beeinflussen. Wir fanden (1) Korrelationen zwischen BWV, BA und organischem Bodenkohlenstoff, was darauf schließen lässt, dass der organische Kohlenstoff im Boden ein verbindender Prozess zwischen BWV und BA ist; (2) Boden-pH und Sandgehalt korrelieren positiv mit BWV; (3) Die Messmethode zur Bestimmung des BWV hatte keinen verzerrenden Einfluss auf die Analysen; (4) Wenn die Testböden mit Feuer behandelt wurden, konnte eine stärkere Korrelation zwischen BWV und BA festgestellt werden. Dies lag unter anderem daran, dass bei hohen Feuertemperaturen BWV nicht nachweisbar war im Gegensatz zu niedrigen Feuertemperaturen. Die Studien, die in diese Meta- Analyse einbezogen wurden, untersuchten und dokumentierten selten mikrobielle Behandlungsgruppen und Informationen über abiotische Faktoren wie z.B. Bodenwassergehalt. Diese Informationen sind jedoch wichtig, da BWV, BA und organsicher Bodenkohlenstoff auf vielfältige Weisen miteinander interagieren können. Unsere Studie erbringt einen wichtigen Beweis für die Bedeutsamkeit von BA und BWV für die Bodenstabilität. In Kapitel 4 untersuchten wir experimentell Charakteristika von 31 saprobischen Pilzen, die wir als bedeutsam für die Bodenaggregation und –stabilität einstuften. Die ausgewählten Merkmale waren Wachstumseigenschaften der Pilzkolonien (Kolonieausdehnungsrate (Kr) und Biomassendichte), Enzymaktivitäten der sauren Phosphatase, Cellobiohydrolase, Leucin-Aminopeptidase und Laccase sowie Wasser-bezogene Merkmale (Myzelwassergehalt und Hydrophobizität der Pilzoberfläche (HPO)). Die Experimente wurden auf Nährmedien mit und ohne Cellophan durchgeführt und wir konnten nachweisen, dass Cellophan die getesteten Pilze physiologisch und morphologisch beeinflussen kann. Des Weiteren war das Koloniealter ein entscheidender Faktor: Die Pilzkolonien hatten eine höhere Enzymaktivität im jüngeren Außenbereich als im älteren Zentrum. Diese Aktivitätsverschiebung war jedoch nicht phylogenetisch manifestiert. Ebenfalls konnten wir zeigen, dass der Myzelwassergehalt ein intrinsisches Merkmal war, welches in zukünftigen Studien Berücksichtigung finden muss. Mit unserer Studie konnte nun zum ersten Mal nachgewiesen werden, dass HPO, die Aktivität der Leucin-Aminopeptidase und die Biomassendichte phylogenetisch konserviert sind. Darüber hinaus fanden wir, dass die untersuchten Pilzmerkmale phylogenetisch konserviert waren; dies bedeutet, dass die Gruppierung der Pilzisolate basierend auf ihrer Merkmalsinformation mit der phylogenetischen Gruppierung übereinstimmte. Korrelationen innerhalb dieser Merkmale zeigte, dass Kr und die Myzelbiomassendichte negative zusammenhängen, wenn drei Extremwerte aus der Analyse ausgeschlossen wurden. Die Beziehung zwischen Cellobiohydrolase- und Laccaseaktivität wurde stark durch eben diese drei Extremwerte beeinflusst. Diese Werte beruhten auf divergenten Merkmalen phylogenetisch sehr naher Pilzisolate; dies weist auf eine potentielle divergente Evolution hin. Zusammengefasst zeigen unsere Ergebnisse auf, dass HPO und der Myzelwassergehalt zwei wesentliche Pilzcharacteristika sind, und dass der Einsatz von Cellophanmembranen in Experimenten zur Merkmalserhebung mit Vorsicht durchzuführen ist. Des Weiteren zeitg sich deutlich, dass die Plastizität der Merkmalsausprägungen von Pilzen bei der Etablierung von Datenbank berücksichtigt werden muss

Passive control on deep cavity noise at subsonic speeds by leading-edge grooves

Control effects of leading-edge grooves on deep cavity noise are investigated numerically. The length-to-depth ratio of the grooves are 0.5, 1, and 4, respectively. The freestream Mach number is equal to 0.16, corresponding to the Re based on the cavity length of 7.7 x 10(5). The Detached Eddy Simulations (DES) combined with Ffowcs Williams-Hawkings (FW-H) acoustic analogy are adopted to simulate the characteristic information of the flow field and the acoustic field. The analysis results show that all grooves investigated in this paper have a certain noise control effect, and the groove with the most obvious noise reduction effect is the groove with a length-to-depth ratio of 0.5, namely, the deep groove. Narrowband noise generated by the flow-acoustic feedback (100-700 Hz) and the acoustic resonance mechanism (above 300 Hz) and broadband noise caused by the turbulent disturbance in the shear layer of the cavity mouth significantly reduce when the deep groove is used for the noise control. The reason for the noise reduction is that the leading-edge grooves can effectively change the flow characteristics near the mouth of the downstream cavity. When the flow passes the grooves, the groove flow reduces the energy in the fluid, resulting in the significant decrease of flow velocity of the boundary layer of the incoming flow of the cavity. In addition, the use of the deep groove also promotes the vortex concentration position to move towards the bottom of the cavity, pushes the energy in the shear layer of the downstream cavity towards the front-edge as well as the bottom of the cavity, and stabilizes the development of the shear layer near the cavity mouth

Multifunctional, Robust, and Porous PHBV—GO/MXene Composite Membranes with Good Hydrophilicity, Antibacterial Activity, and Platelet Adsorption Performance

The limitations of hydrophilicity, strength, antibacterial activity adsorption performance of the biobased and biocompatible polymer materials, such as polyhydroxyalkanoates (PHAs), significantly restrict their wider applications especially in medical areas. In this paper, a novel composite membrane with high antibacterial activity and platelet adsorption performance was prepared based on graphene oxide (GO), MXene and 3-hydroxybutyrate-co-hydroxyvalerate (PHBV), which are medium-chain-length-copolymers of PHA. The GO/MXene nanosheets can uniformly inset on the surface of PHBV fibre and give the PHBV—GO/MXene composite membranes superior hydrophilicity due to the presence of hydroxyl groups and terminal oxygen on the surface of nanosheets, which further provides the functional site for the free radical polymerization of ester bonds between GO/MXene and PHBV. As a result, the tensile strength, platelet adsorption, and blood coagulation time of the PHBV—GO/MXene composite membranes were remarkably increased compared with those of the pure PHBV membranes. The antibacterial rate of the PHBV—GO/MXene composite membranes against gram-positive and gram-negative bacteria can reach 97% due to the antibacterial nature of MXene. The improved strength, hydrophilicity, antibacterial activity and platelet adsorption performance suggest that PHBV—GO/MXene composite membranes might be ideal candidates for multifunctional materials for haemostatic applications