Biology subjects

Swafford, A.

Publications and source records attributed to Swafford, A..

5 recordsLinked to original sources

bioRxiv2025

The First of Us: Ophiocordyceps use a novel scramblase-binding peptide to manipulate zombie ants

Parasite-adaptive manipulation of behavior is a widespread natural phenomenon. While Ophiocordyceps zombie fungi are well-known for hijacking ant behavior to increase their fitness, functionally characterizing the biomolecules involved in behavior manipulation remains difficult in these non-model organisms. To circumvent this problem, we have adopted the powerful genetics toolbox of Caenorhabditis elegans to identify molecular targets and neurophysiological effects of candidate Ophiocordyceps effectors. With this approach, we discovered a novel cysteine-rich, small secreted fungal peptide that binds to well-conserved calcium-dependent scramblase channels in neurons, particularly those associated with sensory tissues. This binding suppressed nematode motor coordination and dampened ant olfactory systems vital for communication. Our findings are the first to directly connect an Ophiocordyceps effector with its extended phenotype, while demonstrating the neuroethological role of Scramblase-1.

molecular biology↗

bioRxiv2023

Genetic transformation of the frog-killing chytrid fungus Batrachochytrium dendrobatidis

Batrachochytrium dendrobatidis (Bd), a causative agent of chytridiomycosis, is decimating amphibian populations around the world. Bd belongs to the chytrid lineage, a group of early-diverging fungi that are widely used to study fungal evolution. Like all chytrids, Bd develops from a motile form into a sessile, growth form, a transition that involves drastic changes in its cytoskeletal architecture. Efforts to study Bd cell biology, development, and pathogenicity have been limited by the lack of genetic tools with which to test hypotheses about underlying molecular mechanisms. Here, we report the development of a transient genetic transformation system for Bd. We used electroporation to deliver exogenous DNA into Bd cells and detected transgene expression for up to three generations under both heterologous and native promoters. We also adapted the transformation protocol for selection using an antibiotic resistance marker. Finally, we used this system to express fluorescent protein fusions and, as a proof of concept, expressed a genetically encoded probe for the actin cytoskeleton. Using live-cell imaging, we visualized the distribution and dynamics of polymerized actin at each stage of the Bd life cycle, as well as during key developmental transitions. This transformation system allows, for the first time, direct testing of key hypotheses regarding mechanisms of Bd pathogenesis. This technology also paves the way for answering fundamental questions of chytrid cell, developmental, and evolutionary biology.

cell biology↗

bioRxiv2022

Bacterial metatranscriptomes in wastewater can differentiate virally infected human populations

Monitoring wastewater samples at building-level resolution screens large populations for SARS-CoV-2, prioritizing testing and isolation efforts. Here we perform untargeted metatranscriptomics on virally-enriched wastewater samples from 10 locations on the UC San Diego campus, demonstrating that resulting bacterial taxonomic and functional profiles discriminate SARS-CoV-2 status even without direct detection of viral transcripts. Our proof-of-principle reveals emergent threats through changes in the human microbiome, suggesting new approaches for untargeted wastewater-based epidemiology.

microbiology↗

bioRxiv2021

Naegleria's mitotic spindles are built from unique tubulins and highlight core spindle features

Naegleria gruberi is a unicellular eukaryote whose evolutionary distance from animals and fungi has made it useful for developing hypotheses about the last common eukaryotic ancestor. Naegleria amoebae lack a cytoplasmic microtubule cytoskeleton and assemble microtubules only during mitosis, and thus provides a unique system to study the evolution and functional specificity of mitotic tubulins and the resulting spindle. Previous studies showed that Naegleria amoebae express a divergent -tubulin during mitosis and we now show that Naegleria amoebae express a second mitotic - and two mitotic {beta}-tubulins. The mitotic tubulins are evolutionarily divergent relative to typical - and {beta}- tubulins, contain residues that suggest distinct microtubule properties, and may represent drug targets for the "brain-eating amoeba" Naegleria fowleri. Using quantitative light microscopy, we find that Naeglerias mitotic spindle is a distinctive barrel-like structure built from a ring of microtubule bundles. Similar to those of other species, Naeglerias spindle is twisted and its length increases during mitosis suggesting that these aspects of mitosis are ancestral features. Because bundle numbers change during metaphase, we hypothesize that the initial bundles represent kinetochore fibers, and secondary bundles function as bridging fibers.

cell biology↗

bioRxiv2017

Multimodal Sensorimotor System in Unicellular Zoospores of a Fungus

Complex sensory suites often underlie critical behaviors, including avoiding predators or locating prey, mates, and shelter. Multisensory systems that control motor behavior even appear in unicellular eukaryotes, such as Chlamydomonas, which are important laboratory models for sensory biology. However, we know of no unicellular opisthokont models that control motor behavior using a multimodal sensory suite. Therefore, existing single-celled models for multimodal sensorimotor integration are very distantly related to animals. Here, we describe a multisensory system that controls the motor function of unicellular, fungal zoospores. We find zoospores of Allomyces arbusculus exhibit both phototaxis and chemotaxis. While swimming, they move towards light and settle on cellulose membranes exuding combinations of amino acids. Furthermore, we report that closely related Allomyces species do not share this multisensory system. Instead, each possesses only one of the two modalities present in A. arbusculus. This diversity of sensory suites within Allomyces provides a rare example of a comparative framework that can be used to examine the evolution of sensory suites. The tractability of Allomyces and related fungi as laboratory organisms will allow detailed mechanistic investigations into how sensory systems may have functioned in early opisthokonts before multicellularity allowed for the evolution of specialized cell types.\n\nSummary StatementZoospores ability to detect light or chemical gradients varies within Allomyces. Here, we report a multimodal sensory system controlling behavior in a fungus, and previously unknown variation in zoospore sensory suites.

cell biology↗