Biology subjects

Nirody, J. A.

Publications and source records attributed to Nirody, J. A..

6 recordsLinked to original sources

bioRxiv2026

Takeoff dynamics are stereotyped across jumping spiders

Jumping is a challenging locomotive mode, requiring rapid force generation and precise coordination of multiple limbs. Many animals meet this challenge using elastic mechanisms that store and rapidly release energy. Jumping spiders (Salticidae), however, rely on a semi-hydraulic system that constrains how their legs can generate propulsion. Much about how these spiders reliably generate jumps within these mechanical constraints remains unknown. Here, we analyze 46 individuals spanning 14 genera and significant morphological diversity and show that this physically constrained system is coupled to a remarkably stereotyped coordination strategy. Whole-body kinematics and novel graph-based analyses of inter-limb coordination reveal a stereotyped two-stage takeoff sequence: a "swing" driven by extension of the fourth legs, followed by a rapid "fling" by the third legs that generates propulsion for takeoff. We further demonstrate that this pattern is preserved beyond Amazonian species, persisting in salticids from North America and Australia. Our results suggest that physical and biomechanical constraints may canalize locomotor evolution toward a common dynamical solution.

animal behavior and cognition↗

bioRxiv2024

Bacterial motility patterns adapt smoothly in response to spatial confinement and disorder

In unconfined environments, bacterial motility patterns are an explicit expression of the internal states of the cell. Bacteria operating a run-and-tumble behavioral program swim forward when in a run state, and are stalled in place when in a reorienting tumble state. However, in natural environments, motility dynamics often represent a convolution of bacterial behavior and environmental constraints. Recent investigations showed that Escherichia coli swimming through highly confined porous media exhibit extended periods of trapping punctuated by forward hops, a seemingly drastic restructuring of run-and-tumble behavior. We introduce a microfluidic device to systematically explore bacterial movement in a range of spatially structured environments, bridging the extremes of unconfined and highly confined conditions. We observe that trajectories reflecting unconstrained expression of run-and-tumble behavior and those reflecting hop-and-trap dynamics coexist in all structured environments considered, with ensemble dynamics transitioning smoothly between these two extremes. We present a unifying swim-and-stall framework to characterize this continuum of observed motility patterns and demonstrate that bacteria employing a consistent set of behavioral rules can present motility patterns that smoothly transition between the two extremes. Our results indicate that the control program underlying run-and-tumble motility is robust to changes in the environment, allowing flagellated bacteria to navigate and adapt to a diverse range of complex, dynamic habitats using the same set of behavioral rules.

biophysics↗

bioRxiv2023

Cell arrangement impacts metabolic activity and antibiotic tolerance in Pseudomonas aeruginosa biofilms

Cells must access resources to survive, and the anatomy of multicellular structures influences this access. In diverse multicellular eukaryotes, resources are provided by internal conduits that allow substances to travel more readily through tissue than they would via diffusion. Microbes growing in multicellular structures, called biofilms, are also affected by differential access to resources and we hypothesized that this is influenced by the physical arrangement of the cells. In this study, we examined the microanatomy of biofilms formed by the pathogenic bacterium Pseudomonas aeruginosa and discovered that clonal cells form striations that are packed lengthwise across most of a mature biofilms depth. We identified mutants, including those defective in pilus function and in O-antigen attachment, that show alterations to this lengthwise packing phenotype. Consistent with the notion that cellular arrangement affects access to resources within the biofilm, we found that while the wild type shows even distribution of tested substrates across depth, the mutants show accumulation of substrates at the biofilm boundaries. Furthermore, we found that altered cellular arrangement within biofilms affects the localization of metabolic activity, the survival of resident cells, and the susceptibility of subpopulations to antibiotic treatment. Our observations provide insight into cellular features that determine biofilm microanatomy, with consequences for physiological differentiation and drug sensitivity.

microbiology↗

bioRxiv2023

Fungal zoospores show contrasting swimming patterns specific to phylum and cytology

Zoosporic fungi, also called chytrids, produce motile spores with flagellar swimming tails (zoospores)1,2. These fungi are key components of aquatic food webs, acting as pathogens, saprotrophs and prey3-8. Little is known about the swimming behaviour of fungal zoospores, a crucial factor governing dispersal, biogeographical range, ecological function and infection dynamics6,9. Here, we track the swimming patterns of zoospores from 12 evolutionary divergent species of zoosporic fungi across seven orders of the Chytridiomycota and the Blastocladiomycota phyla. We report two major swimming patterns which correlate with the cytoskeletal ultrastructure of these zoospores. Specifically, we show that species without major cytoplasmic tubulin components swim in a circular fashion, while species that harbour prominent cytoplasmic tubulin structures swim in a pattern akin to a random walk (move-stop-redirect-move). We confirm cytoskeleton architecture by performing fluorescence confocal microscopy of the zoospores across all 12 species. We then treat representative species with variant swimming behaviours and cytoplasmic-cytoskeletal arrangements with tubulin stabilizing (Taxol) and depolymerizing (Nocodazole) pharmacological-compounds. We observed that when treating the random-walk species with Nocodazole their swimming behaviour changes to a circular swimming pattern. Confocal imaging of the nocodazole-treated zoospores demonstrates these cells maintain flagellum tubulin structures but lack their characteristic cytoplasmatic tubulin arrangement. These data confirm that the capability of zoospores to perform complex movements as a random walk is linked to the presence of prominent cytoplasmatic tubulin structures. We discuss the link between cytology, sensation, and swimming behaviour manifest in zoosporic fungi.

evolutionary biology↗

bioRxiv2021

Tardigrades exhibit robust inter-limb coordination across walking speeds

Tardigrades must negotiate heterogeneous, fluctuating environments, and accordingly utilize locomotive strategies capable of dealing with variable terrain. We analyze the kinematics and inter-leg coordination of freely walking tardigrades (species: Hypsibius dujardini). We find that tardigrade walking replicates several key features of walking in insects despite disparities in size, skeleton, and habitat. To test the effect of environmental changes on tardigrade locomotor control circuits, we measure kinematics and inter-leg coordination during walking on two substrates of different stiffnesses. We find that the phase offset between contralateral leg pairs is flexible, while ipsilateral coordination is preserved across environmental conditions. This mirrors similar results in insects and crustaceans. We propose that these functional similarities in walking co-ordination between tardigrades and arthropods is either due to a generalized locomotor control circuit common to panarthropods, or to independent convergence onto an optimal strategy for robust multi-legged control in small animals with simple circuitry. Our results highlight the value of tardigrades as a comparative system towards understanding the mechanisms - neural and/or mechanical - underlying coordination in panarthropod locomotion.

animal behavior and cognition↗

bioRxiv2017

A catch-bond drives stator mechanosensitivity in the Bacterial Flagellar Motor

The bacterial flagellar motor (BFM) is the rotary motor which powers the swimming and swarming of many motile bacteria. The torque is provided by stator units, ion motive force powered ion channels known to assemble and disassemble dynamically in the BFM. This turnover is mechano-sensitive, with the number of engaged units dependent upon the viscous load experienced by the motor through the flagellum. However, the molecular mechanism driving BFM mechano-sensitivity is unknown. Here we directly measure the kinetics of arrival and departure of the stator units in individual wild-type motors via analysis of high-resolution recordings of motor speed, while dynamically varying the load on the motor via external magnetic torque. Obtaining the real-time stator stoichiometry before and after periods of forced motor stall, we measure both the number of active stator units at steady-state as a function of the load and the kinetic association and dissociation rates, by fitting the data to a reversible random sequential adsorption model. Our measurements indicate that BFM mechano-sensing relies on the dissociation rate of the stator units, which decreases with increasing load, while their association rate remains constant. This implies that the lifetime of an active stator unit assembled within the BFM increases when a higher force is applied to its anchoring point in the cell wall, providing strong evidence that a catch-bond mechanism can explain the mechano-sensitivity of the BFM.

biophysics↗