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1. Draft Genome Sequence of Mortierella alpina Strain LL118, Isolated from an Aspen (Populus tremuloides) Leaf Litter Sample

   https://doi.org/10.1128/MRA.00864-21  

   Yang, Shu; Vinatzer, Boris A. (November 2021, Microbiology Resource Announcements)

   Bruno, Vincent (Ed.)

   ABSTRACT Mortierella alpina is a filamentous fungus commonly associated with soil and is one of very few fungal species known to include strains with ice nucleation activity. Here, we report the draft genome sequence of the ice nucleation-active M. alpina strain LL118, isolated from aspen leaf litter collected in Alberta, Canada. 

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2. A biogenic secondary organic aerosol source of cirrus ice nucleating particles

   https://doi.org/10.1038/s41467-020-18424-6  

   Wolf, Martin J.; Zhang, Yue; Zawadowicz, Maria A.; Goodell, Megan; Froyd, Karl; Freney, Evelyn; Sellegri, Karine; Rösch, Michael; Cui, Tianqu; Winter, Margaux; et al (December 2020, Nature Communications)

   null (Ed.)

   Abstract Atmospheric ice nucleating particles (INPs) influence global climate by altering cloud formation, lifetime, and precipitation efficiency. The role of secondary organic aerosol (SOA) material as a source of INPs in the ambient atmosphere has not been well defined. Here, we demonstrate the potential for biogenic SOA to activate as depositional INPs in the upper troposphere by combining field measurements with laboratory experiments. Ambient INPs were measured in a remote mountaintop location at –46 °C and an ice supersaturation of 30% with concentrations ranging from 0.1 to 70 L –1 . Concentrations of depositional INPs were positively correlated with the mass fractions and loadings of isoprene-derived secondary organic aerosols. Compositional analysis of ice residuals showed that ambient particles with isoprene-derived SOA material can act as depositional ice nuclei. Laboratory experiments further demonstrated the ability of isoprene-derived SOA to nucleate ice under a range of atmospheric conditions. We further show that ambient concentrations of isoprene-derived SOA can be competitive with other INP sources. This demonstrates that isoprene and potentially other biogenically-derived SOA materials could influence cirrus formation and properties. 

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3. Evaluating the roles of microbial functional breadth and home‐field advantage in leaf litter decomposition

   https://doi.org/10.1111/1365-2435.14026  

   Osburn, Ernest_D; Hoch, Peter_J; Lucas, Jane_M; McBride, Steven_G; Strickland, Michael_S (March 2022, Functional Ecology)

   Abstract Soil biota are increasingly recognized as a primary control on litter decomposition at both local and regional scales, but the precise mechanisms by which biota influence litter decomposition have yet to be identified.There are multiple hypothesized mechanisms by which biotic communities may influence litter decomposition—for example, decomposer communities may be specially adapted to local litter inputs and therefore decompose litter from their home ecosystem at elevated rates. This mechanism is known as the home‐field advantage (HFA) hypothesis. Alternatively, litter decomposition rates may simply depend upon the range of metabolic functions present within a decomposer community. This mechanism is known as the functional breadth (FB) hypothesis. However, the relative importance of HFA and FB in litter decomposition is unknown, as are the microbial community drivers of HFA and FB. Potential relationships/trade‐offs between microbial HFA and FB are also unknown.To investigate the roles of HFA and FB in litter decomposition, we collected litter and soil from six different ecosystems across the continental US and conducted a full factorial litter × soil inoculum experiment. We measured litter decomposition (i.e. cumulative CO₂‐C respired) over 150 days and used an analytical model to calculate the HFA and FB of each microbial decomposer community.Our results indicated clear functional differences among decomposer communities, that is, litter sources were decomposed differently by different decomposer communities. These differences were primarily due to differences in FB between different communities, while HFA effects were less evident.We observed a positive relationship between HFA and the disturbance‐sensitive bacterial phylum Verruomicrobia, suggesting that HFA may be an important mechanism in undisturbed environments. We also observed a negative relationship between bacterial r versus K strategists and FB, suggesting an important link between microbial life‐history strategies and litter decomposition functions.Microbial FB and HFA exhibited a strong unimodal relationship, where high HFA was observed at intermediate FB values, while low HFA was associated with both low and high FB. This suggests that adaptation of decomposers to local plant inputs (i.e. high HFA) constrains FB, which requires broad rather than specialized functionality. Furthermore, this relationship suggests that HFA effects will not be apparent when communities exhibit high FB and therefore decompose all litters well and also when FB is low and communities decompose all litters poorly. Overall, our study provides new insights into the mechanisms by which microbial communities influence the decomposition of leaf litter. Read the freePlain Language Summaryfor this article on the Journal blog. 

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4. Experimental assessment of tree canopy and leaf litter controls on the microbiome and nitrogen fixation rates of two boreal mosses

   https://doi.org/10.1111/nph.16611  

   Jean, Mélanie; Holland‐Moritz, Hannah; Melvin, April M.; Johnstone, Jill F.; Mack, Michelle C. (May 2020, New Phytologist)

   Summary Nitrogen (N₂)‐fixing moss microbial communities play key roles in nitrogen cycling of boreal forests. Forest type and leaf litter inputs regulate moss abundance, but how they control moss microbiomes and N₂‐fixation remains understudied. We examined the impacts of forest type and broadleaf litter on microbial community composition and N₂‐fixation rates ofHylocomium splendensandPleurozium schreberi.We conducted a moss transplant and leaf litter manipulation experiment at three sites with paired paper birch (Betula neoalaskana) and black spruce (Picea mariana) stands in Alaska. We characterized bacterial communities using marker gene sequencing, determined N₂‐fixation rates using stable isotopes (¹⁵N₂) and measured environmental covariates.Mosses native to and transplanted into spruce stands supported generally higher N₂‐fixation and distinct microbial communities compared to similar treatments in birch stands. High leaf litter inputs shifted microbial community composition for both moss species and reduced N₂‐fixation rates forH. splendens, which had the highest rates. N₂‐fixation was positively associated with several bacterial taxa, including cyanobacteria.The moss microbiome and environmental conditions controlled N₂‐fixation at the stand and transplant scales. Predicted shifts from spruce‐ to deciduous‐dominated stands will interact with the relative abundances of mosses supporting different microbiomes and N₂‐fixation rates, which could affect stand‐level N inputs. 

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5. Numerical Representations of Marine Ice‐Nucleating Particles in Remote Marine Environments Evaluated Against Observations

   https://doi.org/10.1029/2018GL081861  

   McCluskey, C. S.; DeMott, P. J.; Ma, P. ‐L.; Burrows, S. M. (July 2019, Geophysical Research Letters)

   Abstract The abundance and sources of ice‐nucleating particles, particles required for heterogeneous ice nucleation, are long‐standing sources of uncertainty in quantifying aerosol‐cloud interactions. In this study, we demonstrate near closure between immersion freezing ice‐nucleating particle number concentration (n_INPs) observations andn_INPscalculated from simulated sea spray aerosol and dust. The Community Atmospheric Model with constrained meteorology was used to simulate aerosol concentrations at the Mace Head Research Station (North Atlantic) and over the Southern Ocean to the south of Tasmania (Clouds, Aerosols, Precipitation, Radiation, and atmospherIc Composition Over the southeRN ocean campaign). Model‐predictedn_INPswere within a factor of 10 ofn_INPsobserved with an off‐line ice spectrometer at Mace Head Research Station and Clouds, Aerosols, Precipitation, Radiation, and atmospherIc Composition Over the southeRN ocean campaign, for 93% and 69% of observations, respectively. Simulated vertical profiles ofn_INPsreveal that transported dust may be critical ton_INPsin remote regions and that sea spray aerosol may be the dominate contributor to primary ice nucleation in Southern Ocean low‐level mixed‐phase clouds. 

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