Biology subjects

Lefevre, C. T.

Publications and source records attributed to Lefevre, C. T..

3 recordsLinked to original sources

bioRxiv2025

Intracellular amorphous calcium carbonate biomineralization in methanotrophic gammaproteobacteria was acquired by horizontal gene transfer from cyanobacteria

Some bacteria genetically control the biomineralization of intracellular amorphous calcium carbonates (iACC) with potential implications for microbial physiology, evolution, bioremediation and biogeochemical cycling. Until now, this capacity has been documented in Cyanobacteria, the giant gammaproteobacterium Achromatium and a few magnetotactic Pseudomonadota and Nitrospirota. Here, we report the discovery of iACC biomineralization in members of the Methylococcaceae, a family of aerobic methanotrophic Gammaproteobacteria. A homolog of the ccyA gene, previously considered a diagnostic marker for iACC formation in Cyanobacteria, was identified in several Methylococcaceae genomes, based on a search of the conserved C-terminal (GlyZip)3 domain of the encoded calcyanin protein, with a sequence coverage higher than 60% and an E-value lower than 1e-20. Moreover, two cultivated strains, Methylococcus geothermalis and Methylococcus mesophilus, whose genomes contained the ccyA gene, were consistently shown to form iACC granules. The ccyA genes of Methylococcaceae and Microcystis share higher sequence similarity (47%) than with other Cyanobacteria (around 30%) within their common (GlyZip)3 domain, suggesting horizontal gene transfer (HGT) from an ancestral Microcystis-like cyanobacterium to Methylococcaceae. This finding extends the known taxonomic distribution of ccyA and suggests that the capability to biomineralize iACC was acquired by HGT, possibly in environments such as those close to the oxyclines of lakes, where Cyanobacteria and Methylococcaceae commonly co-exist. The discovery of iACC in methane-oxidizing Methylococcaceae highlights a previously unrecognized coupling between calcium carbonate biomineralization and methane cycling in aquatic environments, suggesting that iACC formation may play an overlooked role in microbial carbon storage and local geochemical regulation.

microbiology↗

bioRxiv2022

McaA and McaB control the dynamic positioning of a bacterial magnetic organelle

Magnetotactic bacteria (MTB) are a diverse group of microorganisms that use intracellular chains of ferrimagnetic nanocrystals, produced within their magnetosome organelles, to align and navigate along the geomagnetic field. The cell biological and biochemical properties of magnetosomes make them a powerful model for studying the molecular mechanisms of biomineralization and compartmentalization in bacteria. While several conserved magnetosome formation genes have been described, the evolutionary strategies for their species-specific diversification remain unknown. Here, we demonstrate that the fragmented nature of magnetosome chains in Magnetospirillum magneticum AMB-1 is controlled by two genes named mcaA and mcaB. McaA recognizes the positive curvature of the inner cell membrane while McaB localises to magnetosomes. Along with the MamK actin-like cytoskeleton, they create space for addition of new magnetosomes in between pre-existing magnetosomes. Phylogenetic analyses suggest that McaAB homologs are widespread and may represent an ancient strategy for organelle positioning in MTB.

microbiology↗

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↗