Biology subjects

Sanfilippo, J.

Publications and source records attributed to Sanfilippo, J..

6 recordsLinked to original sources

bioRxiv2023

Type-IV pili tune an adhesion-migration trade-off during surface colonization of Pseudomonas aeruginosa

Bacterial pathogenicity relies on both firm surface adhesion and cell dissemination. How twitching bacteria resolve the fundamental contradiction between adhesion and migration is unknown. To address this question, we employ live-cell imaging of type-IV pili (T4P) and therewith construct a comprehensive mathematical model of Pseudomonas aeruginosa migration. The data show that only 10% to 50% of T4P bind to substrates and contribute to migration through random extension and retraction. Individual T4P do not display a measurable sensory response to surfaces, but their number increases on cellular surface contact. Attachment to surfaces is mediated, besides T4P, by passive adhesive forces acting on the cell body. Passive adhesions slow down cell migration and result in local random motion on short time scales, which is followed by directionally persistent, superdiffusive motion on longer time scales. Moreover, passive adhesions strongly enhance surface attachment under shear flow. {Delta}pilA mutants, which produce no T4P, robustly stick to surfaces under shear flow. In contrast, rapidly migrating {Delta}pilH cells, which produce an excessive number of T4P, are easily detached by shear. Wild-type cells sacrifice migration speed for robust surface attachment by maintaining a low number of active pili. The different cell strains pertain to disjunct regimes in a generic adhesion-migration trait space. Depending on the nature of the adhesion structures, adhesion and migration are either compatible or a trade-off is required for efficient bacterial surface colonization under different conditions.

biophysics↗

bioRxiv2022

Corner flows induced by surfactant-producing bacteria Bacillus subtilis and Pseudomonas fluorescens

Mechanistic understanding of bacterial spreading in soil is critical to control pathogenic contamination of groundwater and soil as well as design bioremediation projects. However, our understanding is currently limited by the lack of direct bacterial imaging in soil conditions. Here, we overcome this limitation by directly observing the spread of bacterial solution in a transparent chamber with varying corner angles designed to replicate soil-like conditions. We show that two common soil bacteria, Bacillus subtilis and Pseudomonas fluorescens, generate flows along sharp corners (< 60{degrees}) by producing surfactants that turn nonwetting solid surfaces into wetting surfaces. We further show that a surfactant-deficient mutant of B. subtilis cannot generate corner flows along sharp corners, confirming that the bacteria-generated corner flows require the production of bacterial surfactants. The speed of biosurfactant-induced corner flow at the sharp corner is about several millimeters per hour, similar to that of bacterial swarming, the fastest mode of known bacterial surface translocation. We further demonstrate that the bacteria-generated corner flow only occurs when the corner angle is less than a critical value, which can be predicted from the contact angle of the bacterial solution. Furthermore, we show that the corner flow has a maximum height due to the roundness or cutoff of corners. The mechanistic understanding and mathematical theories of bacterial spreading presented in this study will help improve predictions of bacterial spreading in soil, where corners are ubiquitous, and facilitate future designs of soil contamination mitigation and other bioremediation projects. ImportanceThe spread of bacterial cells in soil regulates soil biogeochemical cycles, increases the possibility of soil and groundwater contamination, and controls the efficiency of many bacteria-based bioremediation projects. However, mechanistic understanding of bacterial spreading in soil remains incomplete due to a lack of direct or in-situ observations. Here, we simulate confined spaces of soil using a transparent material with similar hydrophobicity as hydrocarbon-covered soil and directly visualize the spread of two common soil bacteria, Bacillus subtilis and Pseudomonas fluorescens. We show that both bacteria can generate vertical flows along sharp corners of the transparent chamber. The velocity of the bacterial corner flow is several millimeters per hour. We further demonstrate that the corner flow was generated by bacteria-produced bio-surfactants, which are soap-like chemicals and turn nonwetting solid surfaces into wetting surfaces. Our results will help improve predictions of bacterial spreading in soil and facilitate designs of soil-related bioremediation projects.

microbiology↗

bioRxiv2021

Home literacy environment mediates the relationship between socioeconomic status and white matter structure in infants

The home literacy environment (HLE) in infancy has been associated with subsequent pre-literacy skill development and HLE at pre-school age has been shown to correlate with white matter organization in tracts that subserve prereading and reading skills. Furthermore, childhood socioeconomic status (SES) has been linked with both HLE and white matter organization. It is also important to understand whether the relationships between environmental factors such as HLE and SES and white matter organization can be detected as early as infancy, as this period is characterized by rapid brain development that may make white matter pathways particularly susceptible to these early experiences. Here, we hypothesized (1) an association between HLE and white matter organization in pre-reading and reading-related tracts in infants, and (2) that this association mediates a link between SES and white matter organization. To test these hypotheses, infants (mean age: 9.2 {+/-} 2.5 months, N = 18) underwent diffusion-weighted imaging MRI during natural sleep. Fractional anisotropy (FA) was estimated from the left superior longitudinal fasciculus (SLF) and left arcuate fasciculus using the automated fiber-tract quantification method. HLE was measured with the Reading subscale of the StimQ and SES was measured with years of maternal education. Self-reported maternal reading ability was also quantified and applied to all statistical models to control for confounding genetic effects. The Reading subscale of the StimQ positively related to FA in left SLF and mediated the association between maternal education and FA in the left SLF. Taken together, these findings underscore the importance of considering HLE from the start of life and may inform novel prevention and intervention strategies targeted at low-SES families to support developing infants during a period of heightened brain plasticity.

neuroscience↗

bioRxiv2021

Depth of sedation with dexmedetomidine modulates cortical excitability non-linearly

BackgroundCortical excitability changes across conscious states, being higher in unconsciousness compared to normal wakefulness. Anaesthesia offers controlled manipulation to investigate conscious processes and underlying brain dynamics. Among commonly used anaesthetic agents, dexmedetomidine (DEX) effects are not completely known. In this study, we investigated cortical excitability as a function of DEX sedation depth. MethodsTranscranial magnetic stimulation coupled with electroencephalography was recorded in 20 healthy subjects undergoing DEX sedation in four conditions (baseline, light sedation, deep sedation, recovery). Frontal and parietal cortices were stimulated using a neuronavigation system. Cortical excitability was inferred by slope, amplitude, positive and negative peak latencies of the first component (0-30 ms) of the TMS-evoked potential. Four Generalized Linear Mixed Models (GLMM) were used to test the effect of condition and brain region over cortical excitability. ResultsDexmedetomidine modulated amplitude (P<0.001), slope (P=0.0001) and positive peak (P=0.042), while the targeted brain region affected amplitude (P<0.001), slope (P<0.001), and negative peak (P=0.001). The interaction between dexmedetomidine and region had an effect over amplitude (P=0.004), and slope (P=0.009) such that cortical excitability was higher during all conditions where DEX was present as compared to the baseline. ConclusionsCortical excitability changes non-linearly as a function of the depth of DEX sedation, with a paradoxical non dose-dependent increase. The effect is region-specific, being present in the frontal but not in the parietal region. Future research should extend the current results with other anaesthetics to better understand the link between cortical excitability and depth of sedation.

neuroscience↗

bioRxiv2020

Infant functional connectivity fingerprints predict long-term language and pre-literacy outcomes

Functional brain networks undergo extensive development within the first few years of life. Previous studies have linked infant functional connectivity to cognitive abilities in toddlerhood. However, little is known regarding the long-term relevance of functional connections established in infancy for the protracted development of higher-order abilities of language and literacy. Employing a five-year longitudinal imaging project starting in infancy, this study utilizes resting-state functional MRI to demonstrate prospective associations between infant functional connectivity fingerprints and subsequent language and foundational literacy skills at a mean age of 6.5. These longitudinal associations are preserved when key environmental influences are controlled for and are independent of emergent language abilities in infancy, suggesting early development of functional network characteristics in supporting the acquisition of high-order language and pre-literacy skills. Altogether, the current results highlight the importance of functional organization established in infancy as a neural scaffold underlying the learning process of complex cognitive functions.

neuroscience↗

bioRxiv2019

White matter in infancy is prospectively associated with language outcome in kindergarten

Language acquisition is of central importance to a childs development. Although the trajectory of acquisition is shaped by input and experience postnatally, the neural basis for language emerges prenatally. Thus a fundamental question remains unexamined: to what extent may the structural foundations for language established in infancy predict long-term language abilities? In this longitudinal neuroimaging investigation of children from infancy to kindergarten, we find that white matter organization in infancy is prospectively associated with subsequent language abilities, specifically between: (i) the left arcuate fasciculus in infancy and subsequent phonological awareness and vocabulary knowledge, and (ii) the left corticospinal tract in infancy and phonological awareness and phonological memory in kindergarten. Results are independent of age and home literacy environment. These findings directly link white matter organization in infancy with language abilities after school entry, and suggest that structural organization in infancy sets an important foundation for subsequent language development.

neuroscience↗