Biology subjects

Mueller, T. G.

Publications and source records attributed to Mueller, T. G..

6 recordsLinked to original sources

bioRxiv2026

Atta Leafcutter Ants are Fine-Scale Bioindicators of Geographic and Seasonal Climate Changes Across the Americas

AimWe develop Atta leafcutter-ants as bioindicators that respond at fine scales to geographic and seasonal climate changes in the Americas, thereby addressing the paucity of versatile insect bioindicator systems capable of monitoring climate in both Southern and Northern Hemispheres. LocationAmerican tropics and sub-tropics from latitudes S33.6{degrees} to N33.2{degrees}, with case studies from Colombia, Mexico, and southern USA. Time Period2012-2024. Taxon StudiedAtta leafcutter-ants. MethodsWe elucidate biogeographic patterns of mating-flight phenology of Atta leafcutter-ants across the entire Atta range from Uruguay/Argentina to the USA, using 2335 records of Atta reproductives from the community database iNaturalist, then ground-truth these patterns by comparison with (i) mating-flight records (n=806) from the Atta literature; and (ii) mating-flight observations (n=836) accumulated by a consortium of experts who have researched Atta for a combined 1000+ work-years. Onset of mating flights can be timed with great precision in Atta populations because mass-mating flights are synchronized and triggered by the first major rainfall of a rainy season. ResultsBiogeographic patterns in climate-dependent mating-flight phenologies recorded at iNaturalist are corroborated by observations accumulated in the literature and by Atta experts. Analyses reveal so-far unknown gradients in mating-flight phenology (e.g., Colombia to USA) that are correlated to geographic climate gradients, and season switches of mating flights from early to late in the year between proximate Atta populations (e.g., 200 kilometers apart), for example in the climatically complex Andean regions of Colombia. Regional differences in Atta mating-flight phenology correspond to temporal differences in rainfall between ecoregions of Colombia. Main ConclusionsAtta ants are tractable insect bioindicators to monitor climate impacts with detailed spatial and temporal resolution across a 9200-kilometer trans-equatorial transect in the Americas. We outline future research directions to explore climate-dependent biology using the continuously growing, and now ground-truthed, information at iNaturalist on Atta mating behavior.

ecology↗

bioRxiv2025

Lenacapavir-induced capsid damage exposes HIV-1 genomes from nuclear speckles.

Following cell entry, HIV-1 capsids enter the nucleus by passage through nuclear pores and reach nuclear speckles, where uncoating of the reverse-transcribed genome and integration occur. Here, we characterized the ultrastructure of HIV-1 subviral complexes in nuclei of primary monocyte-derived macrophages and cell lines using live-cell imaging, super-resolution microscopy and correlative light and electron tomography in the absence and presence of capsid-targeting inhibitors Lenacapavir and PF74. Capsid-like structures containing viral DNA as well as broken capsids clustered in nuclear speckles and were displaced from speckles by drug treatment. This was accompanied by alteration of the nuclear capsid structure, with electron-dense protrusions emanating from the narrow end of capsid cones and exposure of complete, or almost complete, genomic HIV-1 DNA. Our data indicate that synthesis of genomic dsDNA can be completed inside the closed HIV-1 capsid, and speckle-associated factors appear to be required to promote genome uncoating. This may ensure that genome uncoating occurs at optimal sites for integration into transcriptionally active chromatin. The results also shed further light on the mechanism of action of Lenacapavir.

microbiology↗

bioRxiv2025

UAV-based Remote Sensing of Bee Nesting Aggregations with Computer Vision for Object Detection

O_LIPollinating insects are in decline globally, threatening pollination services and driving a growing interest in pollinator monitoring and conservation. However, the implementation of conservation programs for these insects is often hindered by labor-intensive monitoring methods and in turn insufficient data to assess population trends. C_LIO_LIWe detail a method for surveying and censusing ground nesting bee aggregations, pairing automated UAV image capture with a custom trained computer vision-based object detection workflow using the YOLOv5m architecture. To highlight the ease of application and accuracy of the workflow, we surveyed a roughly 65m2 portion of a large Colletes inaequalis nesting aggregation. We compared the efficiency and performance of our model to manual counts of a technician. C_LIO_LIOur model detected the location of 1,094 nests, representing 88% of the nests present in our test dataset, and a true positive rate of 97%. Adjusting for error, our model estimated a total of 1,250 nests across the study site, comparable to the total estimated from a manual count of 1,259 nests. Our model detected nests 20 times faster than the manual counts while mapping the aggregation with millimeter accuracy. Spatial analyses show that bee nest density was heterogenous, with dense spatially clustered regions comprised of upwards of 60 nests per m2. C_LIO_LISynthesis and applications: Our novel application of UAV imagery and object detection models for mapping and censusing a ground nesting bee aggregation represents a rapid, cost-effective solution for overcoming limitations in traditional manual methods. Our workflow generates essential data with the high throughput required to help inform the conservation decisions needed to stem global bee declines. C_LI

ecology↗

bioRxiv2023

Dispersal overwhelms variation in host quality to shape nectar microbiome assembly.

O_LIEpiphytic microbes frequently impact plant phenotype and fitness, but effects depend on microbe community composition. Deterministic filtering by plant traits and dispersal-mediated processes can affect microbiome assembly yet their relative contribution is poorly understood. C_LIO_LIWe tested the impact of host-plant filtering and dispersal limitation on nectar microbiome abundance and composition. We inoculated bacteria and yeast into 30 plants across 4 phenotypically distinct cultivars of Epilobium canum. We compared the growth of inoculated communities to openly visited flowers from a subset of the same plants. C_LIO_LIThe abundance and composition of microbial communities differed among plant individuals and cultivars in both inoculated and open flowers. However, plants hosting the highest microbial abundance when inoculated did not have the highest abundances when openly visited. Rather microbial density among open flowers was correlated with pollen receipt, a proxy for animal visitation, suggesting a primary role of deterministic dispersal in floral microbiome assembly despite variation in host-quality. C_LIO_LIWhile host-quality can affect microbiome assembly, variation in dispersal was more important here. Host quality could drive microbial community assembly in plant tissues where species pools are large and dispersal is consistent, but dispersal may be more important when microbial dispersal is limited, or arrival order is important. C_LI

ecology↗

bioRxiv2022

Nectar compounds impact bacterial and fungal growth and shift community dynamics in a nectar analog

Floral nectar is frequently colonized by fungi and bacteria. However, within individual flowers, nectar microbial communities are typically species-poor and dominated by few cosmopolitan genera. One hypothesis is that nectar constituents may act as a strong environmental filter. Non-sugar constituents in nectar could affect species composition via broad antimicrobial activity or differential effects on nectar microbial species. Here, we tested how five non-sugar nectar compounds as well as elevated sugar impacted the growth of 12 fungal and bacterial species isolated from flowers, pollinators, and the environment. We hypothesized that microbes isolated from nectar would be better able to grow in the presence of these compounds. Additionally, to test if nectar compounds could affect the outcome of competition among microbial taxa, we grew a subset of microbes in co-culture assays across a subset of treatments. We found that some compounds such as H2O2 broadly suppressed microbial growth across many but not all microbes tested. Other tested compounds were more specialized in the microbes they impacted. As hypothesized, the nectar specialist Metschnikowia reukaufii was unaffected by most nectar compounds assayed. However, many non-nectar specialist microbes remained unaffected by compounds thought to reduce microbial growth in nectar. Our results show that nectar chemistry can influence nectar microbial communities but that microbe-specific responses to nectar compounds are common. Nectar chemistry also affected the outcome of species interactions among microbial taxa, suggesting that non-sugar compounds in nectar can affect microbial community assembly and abundance in flowers.

microbiology↗

bioRxiv2021

Direct capsid labeling of infectious HIV-1 by genetic code expansion allows detection of largely complete nuclear capsids and suggests nuclear entry of HIV-1 complexes via common routes

The cone-shaped mature HIV-1 capsid is the main orchestrator of early viral replication. After cytosolic entry, it transports the viral replication complex along microtubules towards the nucleus. While it was initially believed that the reverse transcribed genome is released from the capsid in the cytosol, recent observations indicate that a high amount of capsid protein (CA) remains associated with subviral complexes during import through the nuclear pore complex (NPC). Observation of post-entry events via microscopic detection of HIV-1 CA is challenging, since epitope shielding limits immunodetection and the genetic fragility of CA hampers direct labeling approaches. Here, we present a minimally invasive strategy based on genetic code expansion and click chemistry that allows for site-directed fluorescent labeling of HIV-1 CA, while retaining virus morphology and infectivity. Thereby, we could directly visualize virions and subviral complexes using advanced microscopy, including nanoscopy and correlative imaging. Quantification of signal intensities of subviral complexes revealed an amount of CA associated with nuclear complexes in HeLa-derived cells and primary T cells consistent with a complete capsid and showed that treatment with the small molecule inhibitor PF74 did not result in capsid dissociation from nuclear complexes. Cone-shaped objects detected in the nucleus by electron tomography were clearly identified as capsid-derived structures by correlative microscopy. High-resolution imaging revealed dose-dependent clustering of nuclear capsids, suggesting that incoming particles may follow common entry routes.

microbiology↗