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ABSTRACT Potent antimicrobial metabolites are produced by filamentous fungi in pure culture, but their ecological functions in nature are often unknown. Using an antibacterial Penicillium isolate and a cheese rind microbial community, we demonstrate that a fungal specialized metabolite can regulate the diversity of bacterial communities. Inactivation of the global regulator, LaeA, resulted in the loss of antibacterial activity in the Penicillium isolate. Cheese rind bacterial communities assembled with the laeA deletion strain had significantly higher bacterial abundances than the wild-type strain. RNA-sequencing and metabolite profiling demonstrated a striking reduction in the expression and production of the natural product pseurotin in the laeA deletion strain. Inactivation of a core gene in the pseurotin biosynthetic cluster restored bacterial community composition, confirming the role of pseurotins in mediating bacterial community assembly. Our discovery demonstrates how global regulators of fungal transcription can control the assembly of bacterial communities and highlights an ecological role for a widespread class of fungal specialized metabolites. IMPORTANCE Cheese rinds are economically important microbial communities where fungi can impact food quality and aesthetics. The specific mechanisms by which fungi can regulate bacterial community assembly in cheeses, other fermented foods, and microbiomes in general are largely unknown. Our study highlights how specialized metabolites secreted by a Penicillium species can mediate cheese rind development via differential inhibition of bacterial community members. Because LaeA regulates specialized metabolites and other ecologically relevant traits in a wide range of filamentous fungi, this global regulator may have similar impacts in other fungus-dominated microbiomes. 

Face individuation involves sensitivity to physical characteristics that provide information about identity. We examined whether Black and White American faces differ in terms of individuating information, and whether Black and White perceivers differentially weight information when judging same-race and cross-race faces. Study 1 analyzed 20 structural metrics (e.g., eye width, nose length) of 158 Black and White faces to determine which differentiate faces within each group. High-utility metrics (e.g., nose length, eye height, chin length) differentiated faces of both groups, low-utility metrics (e.g., face width, eye width, face length) offered less individuating information. Study 2 ( N = 4,510) explored Black and White participants’ sensitivity to variation on structural metrics using similarity ratings. High-utility metrics affected perceived dissimilarity more than low-utility metrics. This relationship was non-significantly stronger for same-race faces rather than cross-race faces. Perceivers also relied more on features that were racially stereotypic of the faces they were rating.

 

Helium atom scattering and density-functional theory (DFT) are used to characterize the phonon band structure of the (3 × 1)-O surface reconstruction of Nb(100). Innovative DFT calculations comparing surface phonons of bare Nb(100) to those of the oxide surface show increased resonances for the oxide, especially at higher energies. Calculated dispersion curves align well with experimental results and yield atomic displacements to characterize polarizations. Inelastic helium time-of-flight measurements show phonons with mixed longitudinal and shear-vertical displacements along both the ⟨[Formula: see text]⟩, [Formula: see text] and ⟨[Formula: see text]⟩, [Formula: see text] symmetry axes over the entire first surface Brillouin zone. Force constants calculated for bulk Nb, Nb(100), and the (3 × 1)-O Nb(100) reconstruction indicate much stronger responses from the oxide surface, particularly for the top few layers of niobium and oxygen atoms. Many of the strengthened bonds at the surface create the characteristic ladder structure, which passivates and stabilizes the surface. These results represent, to our knowledge, the first phonon dispersion data for the oxide surface and the first ab initio calculation of the oxide’s surface phonons. This study supplies critical information for the further development of advanced materials for superconducting radiofrequency cavities.

 

Pathogens and other parasites can have profound effects on biological communities and ecosystems. Here we explore how two strains of a plant virus – Barley Yellow Dwarf Virus, BYDV – influence the foraging performance and fecundity of two aphid species:Rhopalosiphum maidisandR.padi. We found that pre-inhabitation byR.padion plants facilitates the subsequent foraging of conspecifics andR.maidis. Without the virus, the occurrence of facilitation is asymmetric because it depends on the order of species arrival. However, with virus we found facilitation irrespective of the order of species arrival. Furthermore, the virus also boosted the fecundity of both aphids. Analyses of nutrient content of virus-free and virus-infected plants show significant increases of essential amino acids, sterols, and carbohydrates. Such nutrient increases appear to underlie the facilitative interactions and fecundity of aphids on virus-infected plants. Our experiments demonstrate that the virus dramatically increases the food consumption and fecundity of aphids through intra and interspecific trophic facilitation, resulting in processes that could affect community organization.

 

Pioneer trees with fleshy fruits are typically planted in restoration projects to attract frugivores as a mean to increase dispersal and accelerate forest regeneration. However, differences in fruit traits of pioneer trees can potentially influence dispersal and their restoration outcomes.

Here we investigated the effects of bird and plant traits, and distance to forest fragments, on the seed rain using a tree‐planting experiment replicated in 12 deforested sites in Brazil. Factors were fruit traits of pioneer trees (wind‐dispersed, bird‐dispersed with lipids or with carbohydrates and controls) and distance (10, 50, 300 m) from forest fragments.

We found that density and richness of birds and seeds decreased exponentially with distance from fragments, yet these effects were minor compared to the effects of fruit traits on the structure of the seed rain.

Overall, plots with fleshy fruited pioneers attracted much greater bird activity and seed dispersal than plots with wind‐dispersal pioneers and the controls. For instance, plots with carbohydrate‐rich fruits received more than twice the average species richness and density of birds and seeds of plots with lipid‐rich pioneer trees, surpassing wind‐dispersed pioneers by more than 80%, and controls by over 90%. Furthermore, the fruit trait treatments resulted in morphological shifts in the average traits of visiting birds. Significant differences in bill gape and flight capacities (wing‐loading) were associated with the differences in the seed rain associated with each treatment.

Synthesis and applications. Understanding how trait‐matching processes mediating mutualistic seed dispersal by frugivores interact with distance‐dependent dispersal limitation on deforested tropical landscapes is critical for improving forest restoration efforts. This is especially relevant in the context of applied nucleation. As shown here, avian seed dispersal can thus be manipulated in restoration projects in order to increase connectivity and speed up forest recovery and the provision of the multiple ecosystem services that follow forest succession.

 

Global atmospheric methane growth rates have wildly fluctuated over the past three decades, which may be driven by the proportion of tropical land surface saturated by water. The El Niño/Southern Oscillation Event (ENSO) cycle drives large‐scale climatic trends globally, with El Niño events typically bringing drier weather than La Niña. In a lowland tropical wet forest in Costa Rica, we measured methane flux bimonthly from March 2016 to June 2017 and using an automated chamber system. We observed a strong drying trend for several weeks during the El Niño in 2016, reducing soil moisture below normal levels. In contrast, soil conditions had high water content prior to the drought and during the moderate La Niña that followed. Soil moisture varied across the period studied and significantly impacted methane flux. Methane consumption was greater during the driest part of the El Niño period, while during La Niña and other time periods, soils had lower methane consumption. The mean methane flux observed was −0.022 mg CH₄‐C m⁻²hr⁻¹, and methane was consumed at all timepoints, with lower consumption in saturated soils. Our data show that month studied, and the correlation between soil type and month significantly drove methane flux trends. Our data indicate that ENSO cycles may impact biogenic methane fluxes, mediated by soil moisture conditions. Climate projections for Central America show dryer conditions and increased El Niño frequency, further exacerbating predicted drought. These trends may lead to negative climate feedbacks, with drier conditions increasing soil methane consumption from the atmosphere.

 

Leaf‐cutter ants are dominant herbivores that disturb the soil and create biogeochemical hot spots. We studied how leaf‐cutter antAtta cephalotesimpacts soil CO₂dynamics in a wet Neotropical forest. We measured soil CO₂concentration monthly over 2.5 years at multiple depths in nonnest and nest soils (some of which were abandoned during the study) and assessed CO₂production. We also measured nest and nonnest soil efflux, nest vent efflux, and vent concentration. Nest soils exhibited lower CO₂accumulation than nonnest soils for the same precipitation amounts. During wet periods, soil CO₂concentrations increased across all depths, but were significantly less in nest than in nonnest soils. Differences were nonsignificant during drier periods. Surface efflux was equal across nest and nonnest plots (5 μmol CO₂m⁻²s⁻¹), while vent efflux was substantially (10³to 10⁵times) greater, a finding attributed to free convection and sporadic forced convection. Vent CO₂concentrations were less than in soil, suggesting CO₂efflux from the soil matrix into the nest. Legacy effects in abandoned nests were still observable after more than two years. These findings indicate that leaf‐cutter ant nests provide alternative transport pathways to soil CO₂that increase total emissions and decrease soil CO₂concentrations, and have a lasting impact. Estimated total nest‐soil CO₂emissions were 15 to 60% more than in nonnest soils, contributing 0.2 to 0.7% to ecosystem‐scale soil emissions. The observed CO₂dynamics illuminate the significant carbon footprint of ecosystem engineerAtta cephalotesand have biogeochemical implications for rainforest ecosystems.