Biology subjects

Faivre, D.

Publications and source records attributed to Faivre, D..

5 recordsLinked to original sources

bioRxiv2026

The metallome of Methanosarcina barkeri during electron uptake from acathode

Electromethanogenesis, the cathode-dependent reduction of CO2 to CH4 by methanogens, offers a sustainable route to methane fuel. Methanosarcina barkeri lacks surface-exposed multiheme cytochromes for extracellular electron transfer (EET). Instead, we recently showed that surface-bound G-quadruplex ribonucleic acids (G4-RNA) are required for EET, yet how electrons traverse this extracellular matrix remains unresolved. Here, we quantified metal accumulation during cathodic growth by inductively coupled plasma mass spectrometry in cells grown on cathodes poised at -430 mV versus the standard hydrogen electrode, using acetate-grown cells, open-circuit controls and abiotic cathodes for comparison. Cathode-grown M. barkeri showed CH4 buildup attributable to cathodic electrons (2.1 {+/-} 0.8% CH4), whereas open-circuit controls showed negligible increase (0.26 {+/-} 0.15% CH4). Cathode-bound cells exhibited [~]55-fold enrichment in Co, Ni and Mo, and 5- to 21-fold enrichment in Cu, Zn, and Fe relative to acetate-grown cells; neither acetate-grown cells nor abiotic cathodes accumulated metals. To resolve where metals reside, we mapped the elemental distribution in acetate-grown cells by scanning transmission electron microscopy-energy dispersive X-ray spectroscopy and high-resolution nano X-ray fluorescence. Fe co-localized with phosphorus in intracellular storage bodies, whereas Co and Zn localized within the extracellular capsule. Together, these data indicate selective metal sequestration during electromethanogenesis and raise the possibility that certain metals associate with G4-RNA and/or the methanochondroitin matrix to support charge transfer at the cell surface. This metalomic fingerprint provides a new proxy for dissecting archaeal EET strategies and may inform the design of more efficient bioelectrochemical systems.

microbiology↗

bioRxiv2025

Chemical coupling of biological magnetosomes with amine-functionalized therapeutic antibody conjugates

BackgroundImmunotherapy, particularly in cancer treatment, can be enhanced using antibody-drug or antibody-radionuclide conjugates. These conjugates disrupt cell signaling and induce cell death, requiring the targeted antigen to be highly expressed on tumor cells to avoid damage to healthy tissues. A promising strategy to improve delivery is the use of magnetosomes, biological magnetic nanoparticles, which can be guided to tumor sites using magnetic fields. However, most antibody-drug or antibody-radionuclide conjugates are functionalized using the antibody amine groups of the lysine residues on the heavy chains. Therefore, these amine groups are no longer available to bind the antibodies to the magnetosomes. ResultsHere, we explore an alternative approach to bind amine-functionalized antibodies to magnetosomes. Using SulfoSuccinimidyl-4-(N-Maleimidomethyl)Cyclohexane-1-Carboxylate (S-SMCC) as a crosslinker, the antibodies are chemically attached to the magnetosome membrane via thiol groups through antibody partial reduction. Our results demonstrate that this chemical process preserves the integrity and functionality of both magnetosomes and antibodies. Moreover, we prove that the produced magnetosome-antibody conjugates are stable under various in vivo-like conditions. ConclusionThis coupling method offers significant advantages, enabling the coupling of therapeutic molecules to antibodies combined with the magnetic properties of magnetosomes. This new strategy aims to improve cancer therapy through targeted delivery and rapid accumulation at tumor sites.

bioengineering↗

bioRxiv2023

Escape problem of magnetotactic bacteria - physiological magnetic field strength help magnetotactic bacteria navigate in simulated sediments

Bacterial motility is typically studied in bulk solution, while their natural habitats often are complex environments. Here, we produced microfluidic channels that contained sediment-mimicking obstacles to study swimming of magnetotactic bacteria in a near-realistic environment. Magnetotactic bacteria are microor-ganisms that form chains of nanomagnets and that orient in Earths magnetic field. The obstacles were produced based on micro-computer tomography reconstructions of bacteria-rich sediment samples. We characterized the swimming of the cells through these channels and found that swimming throughput was highest for physiological magnetic fields. This observation was confirmed by extensive computer simulations using an active Brownian particle model, which were parameterized based on experimental trajectories, in particular with the trajectories near the sediment-mimicking obstacles, from which the interactions of the swimming bacteria with the obstacles were determined. The simulations were used to quantify the swimming throughput in detail. They showed the behavior seen in experiments, but also exhibited considerable variability between different channel geometries. The simulations indicate that swimming at strong fields is impeded by the trapping of bacteria in "corners" that require transient swimming against the magnetic field for escape. At weak fields, the direction of swimming is almost random, making the process inefficient as well. We confirmed the trapping effect in our experiments and showed that lowering the field strength allows the bacteria to escape. We hypothesize that over the course of evolution, magnetotactic bacteria have thus evolved to produce magnetic properties that are adapted to the geomagnetic field in order to balance movement and orientation in such crowded environments.

biophysics↗

bioRxiv2021

Single-cell motion of magnetotactic bacteria in microfluidic confinement: interplay between surface interaction and magnetic torque

Swimming microorganisms often experience complex environments in their natural habitat. The same is true for microswimmers in envisioned biomedical applications. The simple aqueous conditions typically studied in the lab differ strongly from those found in these environments and often exclude the effects of small volume confinement or the influence that external fields have on their motion. In this work, we investigate magnetically steerable microswimmers, specifically magnetotactic bacteria, in strong spatial confinement and under the influence of an external magnetic field. We trap single cells in micrometer-sized microfluidic chambers and track and analyze their motion, which shows a variety of different trajectories, depending on the chamber size and the strength of the magnetic field. Combining these experimental observations with simulations using a variant of an active Brownian particle model, we explain the variety of trajectories by the interplay between the wall interactions and the magnetic torque. We also analyze the pronounced cell-to-cell heterogeneity, which makes single-cell tracking essential for an understanding of the motility patterns. In this way, our work establishes a basis for the analysis and prediction of microswimmer motility in more complex environments.

biophysics↗

bioRxiv2019

High-speed motility originates from cooperatively pushing and pulling flagella bundles in bilophotrichous bacteria

Bacteria propel and change direction by rotating long, helical filaments, called flagella. The number of flagella, their arrangement on the cell body and their sense of rotation hypothetically determine the locomotion characteristics of a species. The movement of the most rapid microorganisms has in particular remained unexplored because of additional experimental limitations. We show that magnetotactic cocci with two flagella bundles on one pole swim faster than 500 {micro}m*s-1 along a double helical path, making them one of the fastest natural microswimmers. We additionally reveal that the cells reorient in less than 5 ms, an order of magnitude faster than reported so far for any other bacteria. Using hydrodynamic modeling, we demonstrate that a mode where a pushing and a pulling bundle cooperate is the only possibility to enable both helical tracks and fast reorientations. The advantage of sheathed flagella bundles is the high rigidity, making high swimming speeds possible.

biophysics↗