Biology subjects

Peccia, J.

Publications and source records attributed to Peccia, J..

4 recordsLinked to original sources

bioRxiv2025

Tree microbiomes and methane emissions in upland forests

RationaleUpland forest trees emit CH , but whether emissions derive from internal microbial production or soil-derived transport remains debated. Methanogens have been detected in heartwood of several species, yet the prevalence of wood-associated methanogenesis, its metabolic basis, and its relationship to co-occurring methanotrophy are poorly understood. MethodsWe measured 1,148 stem fluxes and 276 soil fluxes, sampled internal stem gases including {delta}{superscript 1}3CH , quantified methanogens and methanotrophs via ddPCR in 564 samples, characterized communities via 16S rRNA sequencing, and upscaled fluxes. Key resultsMethanogens were detected in 97% of heartwood samples (up to 10 copies g {superscript 1}) at concentrations exceeding soil by [~]2 orders of magnitude; methane consumers were likewise near-ubiquitous across forest compartments. Wood harbored distinct microbial communities dominated by hydrogenotrophic Methanobacteriaceae, corroborated by depleted {delta}{superscript 1}3CH . Vertical flux profiles indicated soil transport only in wet microsites, with uniform emissions across height consistent with internal production across most upland species. Species-level methanogen:methanotroph ratios predicted emissions (R{superscript 2} = 0.51), indicating net flux reflects the balance between production and oxidation. Main conclusionMethane-cycling microbes are widespread in upland trees, and net methane flux reflects the species-level balance between production and consumption. Internal methanogenesis contributes widely to upland tree emissions; resolving ecosystem-scale magnitude requires improved quantification of woody surface area and vertical flux variability.

ecology↗

bioRxiv2025

The Susceptibility of Airborne SARS-CoV-2 to Far-UVC Irradiation

Far-ultraviolet-C (far-UVC) irradiation has emerged as a breakthrough disinfection technology for the treatment of indoor air. Far-UVC wavelengths (222 nm) from filtered krypton-chloride excimer lamps are effective at inactivating airborne viruses and safe for human exposure, thus enabling the continuous treatment of bulk air in occupied settings. This study quantifies the susceptibility of airborne SARS-CoV-2, aerosolized in human saliva, to far-UVC radiation. We measured fluence rate-based Z value susceptibility constants ({+/-} std. err.) of 4.4 {+/-} 0.6 and 6.8 {+/-} 0.7 cm2 mJ-1 for airborne SARS-CoV-2 under 40% and 65% relative humidity (RH) levels, respectively. At modeled far-UVC irradiation levels corresponding to 25% of the maximum safe human exposure limit, the resulting far-UVC equivalent air changes per hour (eACH) exceeded 62 hr {superscript 1} at 65% RH and were significantly greater than the corresponding airborne SARS-CoV-2 natural decay rate (( std. err.) of 5.4 {+/-} 1.1 hr {superscript 1}, measured in the absence of far-UVC. These results define first-order loss rates for airborne SARS-CoV-2 under far-UVC exposure and support quantitative risk assessments and rational disinfection system implementation. Synopsis StatementQuantified the ability of far-UVC to facilitate airborne SARS-CoV-2 inactivation, guiding the implementation of far-UVC to promote transmission risk reduction in occupied spaces.

microbiology↗

bioRxiv2024

A diverse and distinct microbiome inside living trees

Despite significant advances in microbiome research across various environments1, the microbiome of Earths largest biomass reservoir- the wood of living trees2- remains largely unexplored. This oversight neglects a critical aspect of global biodiversity and potentially key players in tree health and forest ecosystem functions. Here we illuminate the microbiome inhabiting and adapted to wood, and further specialized to individual host species. We demonstrate that a single tree can host approximately a trillion microbes in its aboveground internal tissues, with microbial communities partitioned between heartwood and sapwood, each maintaining a distinct microbiome with minimal similarity to other plant tissues or nearby ecosystem components. Notably, the heartwood microbiome emerges as a unique ecological niche, distinguished in part by endemic archaea and anaerobic bacteria that drive consequential biogeochemical processes. Our research supports the emerging idea of a plant as a "holobiont"3,4--a single ecological unit comprising host and associated microorganisms--and parallels human microbiome research in its implications for host health, disease, and functionality5. By mapping the structure, composition, and potential sources and functions of the tree internal microbiome, our findings pave the way for novel insights into tree physiology and forest ecology, and establish a new frontier in environmental microbiology.

ecology↗

bioRxiv2023

A Method for Sampling the Living Wood Microbiome

Efforts to characterize microbial life across diverse environments have progressed tremendously, yet the microbiome of Earths largest biomass reservoir--the wood of living trees--has been largely unexplored. Current understanding of the tree microbiome is largely confined to roots and leaves, with little attention given to the endophytic microbiome of wood, even though emergent studies have indicated this zone as a niche for unique taxa, of consequence for ecosystem health and global biogeochemical cycles. The lack of investigation derives partly from the physical recalcitrance of wood, which presents challenges during sampling, homogenization, and the extraction of nucleic acids. In response to these issues, we present an optimized method for processing wood for use in microbial analyses, from sampling through to downstream analyses. Using methane-cycling taxa as model endophytes, we assess losses in recovery during our method, and determine a limit-of-detection of approximately 500 cells per 100 mg of (dry) wood. For all six species evaluated--which represented several diverse taxa of hardwoods and softwoods--PCR inhibition proved minimal, and we expect this method to be applicable for a majority of tree species. The methods presented herein can facilitate future investigation into the wood microbiome and global microbial ecology of methane cycling.

ecology↗