Sebastien Wielgoss

Last Name

Wielgoss

First Name

Sebastien

ORCID

0000-0002-0127-3380

Organisational unit

03939 - Velicer, Gregory J. / Velicer, Gregory J.

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Publications 1 - 10 of 19

Local Variation in Myxococcus xanthus Fruiting Body Development
Yuen, Lok Man; La Fortezza, Marco; Wielgoss, Sebastien; et al. (2025)
Though developmental biology has mostly focused on obligately multicellular organisms, some unicellular organisms are capable of aggregating into a multicellular structures during their life cycle. During this process, cells diﬀerentiate into multiple cell types unique to multicellular development. Myxobacteria are gram-negative bacteria capable of developing multicellular fruiting bodies upon starvation. The shape and size of fruiting bodies varies greatly between myxobacteria, both between and within species, but how this morphological diversity has evolved is poorly understood. An early study showed that morphology correlates with 16S rRNA phylogeny broadly across myxobacterial species, with more closely related species produce more similar fruiting bodies. How fruiting body morphologies might correlate with genome-based phylogenies at the intra-specific scale – the scale at which evolution plays out – has not been investigated, but may provide insights into the rate, patterns and genomic basis of morphological evolution. Here, we investigate relationships between phylogeny and fruiting body morphology in closely related isolates of the model species Myxococcus xanthus, quantifying developmental features not only of mature fruiting bodies, but as they emerge over time with time-lapse microscopy. Most strains are morphologically similar, but one monophyletic clade displays a vastly diﬀerent morphologies, with larger and fewer fruiting bodies than most isolates. While most strains have similar developmental timing, the morphologically distinct clade exhibits slower aggregation and darkening of fruiting bodies. Study of distinguishing genomic features of this clade may lead to genetic-level understanding of fine-scale, natural morphological evolution in this model species for the study of aggregative multicellularity.
Mutation Rate and Effective Population Size of the Model Cooperative Bacterium Myxococcus xanthus
Wielgoss, Sebastien; Van Dyken, James David; Velicer, Gregory J. (2024)
Genome Biology and Evolution
Intrinsic rates of genetic mutation have diverged greatly across taxa and exhibit statistical associations with several other parameters and features. These include effective population size (Nₑ), genome size, and gametic multicellularity, with the latter being associated with both increased mutation rates and decreased effective population sizes. However, data sufficient to test for possible relationships between microbial multicellularity and mutation rate (µ) are lacking. Here, we report estimates of two key population-genetic parameters, Nₑ and µ, for Myxococcus xanthus, a bacterial model organism for the study of aggregative multicellular development, predation, and social swarming. To estimate µ, we conducted an ∼400-day mutation accumulation experiment with 46 lineages subjected to regular single colony bottlenecks prior to clonal regrowth. Upon conclusion, we sequenced one clonal-isolate genome per lineage. Given collective evolution for 85,323 generations across all lines, we calculate a per base-pair mutation rate of ∼5.5 × 10⁻¹⁰ per site per generation, one of the highest mutation rates among free-living eubacteria. Given our estimate of µ, we derived Nₑ at ∼10⁷ from neutral diversity at four-fold degenerate sites across two dozen M. xanthus natural isolates. This estimate is below average for eubacteria and strengthens an already clear negative correlation between µ and Nₑ in prokaryotes. The higher and lower than average mutation rate and Nₑ for M. xanthus, respectively, amplify the question of whether any features of its multicellular life cycle—such as group-size reduction during fruiting-body development—or its highly structured spatial distribution have significantly influenced how these parameters have evolved.
A barrier to homologous recombination between sympatric strains of the cooperative soil bacterium Myxococcus xanthus
Didelot, Xavier; Chaudhuri, Roy R.; Liu, Xuan; et al. (2016)
The ISME Journal
The bacterium Myxococcus xanthus glides through soil in search of prey microbes, but when food sources run out, cells cooperatively construct and sporulate within multicellular fruiting bodies. M. xanthus strains isolated from a 16 × 16-cm-scale patch of soil were previously shown to have diversified into many distinct compatibility types that are distinguished by the failure of swarming colonies to merge upon encounter. We sequenced the genomes of 22 isolates from this population belonging to the two most frequently occurring multilocus sequence type (MLST) clades to trace patterns of incipient genomic divergence, specifically related to social divergence. Although homologous recombination occurs frequently within the two MLST clades, we find an almost complete absence of recombination events between them. As the two clades are very closely related and live in sympatry, either ecological or genetic barriers must reduce genetic exchange between them. We find that the rate of change in the accessory genome is greater than the rate of amino-acid substitution in the core genome. We identify a large genomic tract that consistently differs between isolates that do not freely merge and therefore is a candidate region for harbouring gene(s) responsible for self/non-self discrimination.
L'évolution en action: Rêve ou réalité?
Hindré, Thomas; Gac, Mickaël Le; Plucain, Jessica; et al. (2010)
Biofutur
When maths meets phytoplankton ecology
Wielgoss, Sebastien (2022)
Nature Ecology & Evolution
Kin discrimination and outer membrane exchange in Myxococcus xanthus
Wielgoss, Sebastien; Fiegna, Francesca; Rendueles, Olaya; et al. (2018)
Molecular Ecology
Complete Genome Sequence of Myxococcus Phage Mx4
Wielgoss, Sebastien (2021)
Microbiology Resource Announcements
Myxococcus xanthus is a bacterial model in microbial developmental biology and social evolution. Here, I present the 57.0-kb circular genomic sequence of the wild-type Myxococcus phage Mx4, with a GC content of 70.1%. Annotation predicted 97 protein-coding genes. Head-neck-tail protein classification assigns Mx4 to the tailed, Mu-like members of the family Myoviridae of group type 1 (cluster 8).
Regulation of sedimentation rate shapes the evolution of multicellularity in a close unicellular relative of animals
Dudin, Omaya; Wielgoss, Sebastien; New, Aaron M.; et al. (2022)
PLoS Biology
Significant increases in sedimentation rate accompany the evolution of multicellularity. These increases should lead to rapid changes in ecological distribution, thereby affecting the costs and benefits of multicellularity and its likelihood to evolve. However, how genetic and cellular traits control this process, their likelihood of emergence over evolutionary timescales, and the variation in these traits as multicellularity evolves are still poorly understood. Here, using isolates of the ichthyosporean genus Sphaeroforma-close unicellular relatives of animals with brief transient multicellular life stages-we demonstrate that sedimentation rate is a highly variable and evolvable trait affected by at least 2 distinct physical mechanisms. First, we find extensive (>300×) variation in sedimentation rates for different Sphaeroforma species, mainly driven by size and density during the unicellular-to-multicellular life cycle transition. Second, using experimental evolution with sedimentation rate as a focal trait, we readily obtained, for the first time, fast settling and multicellular Sphaeroforma arctica isolates. Quantitative microscopy showed that increased sedimentation rates most often arose by incomplete cellular separation after cell division, leading to clonal "clumping" multicellular variants with increased size and density. Strikingly, density increases also arose by an acceleration of the nuclear doubling time relative to cell size. Similar size- and density-affecting phenotypes were observed in 4 additional species from the Sphaeroforma genus, suggesting that variation in these traits might be widespread in the marine habitat. By resequencing evolved isolates to high genomic coverage, we identified mutations in regulators of cytokinesis, plasma membrane remodeling, and chromatin condensation that may contribute to both clump formation and the increase in the nuclear number-to-volume ratio. Taken together, this study illustrates how extensive cellular control of density and size drive sedimentation rate variation, likely shaping the onset and further evolution of multicellularity.
Adaptation to parasites and costs of parasite resistance in mutator and non-mutator bacteria
Wielgoss, Sebastien; Bergmiller, Tobias; Bischofberger, Anna M.; et al. (2016)
Molecular Biology and Evolution
Parasitism creates selection for resistance mechanisms in host populations and is hypothesized to promote increased host evolvability. However, the influence of these traits on host evolution when parasites are no longer present is unclear. We used experimental evolution and whole-genome sequencing of Escherichia coli to determine the effects of past and present exposure to parasitic viruses (phages) on the spread of mutator alleles, resistance, and bacterial competitive fitness. We found that mutator alleles spread rapidly during adaptation to any of four different phage species, and this pattern was even more pronounced with multiple phages present simultaneously. However, hypermutability did not detectably accelerate adaptation in the absence of phages and recovery of fitness costs associated with resistance. Several lineages evolved phage resistance through elevated mucoidy, and during subsequent evolution in phage-free conditions they rapidly reverted to nonmucoid, phage-susceptible phenotypes. Genome sequencing revealed that this phenotypic reversion was achieved by additional genetic changes rather than by genotypic reversion of the initial resistance mutations. Insertion sequence (IS) elements played a key role in both the acquisition of resistance and adaptation in the absence of parasites; unlike single nucleotide polymorphisms, IS insertions were not more frequent in mutator lineages. Our results provide a genetic explanation for rapid reversion of mucoidy, a phenotype observed in other bacterial species including human pathogens. Moreover, this demonstrates that the types of genetic change underlying adaptation to fitness costs, and consequently the impact of evolvability mechanisms such as increased point-mutation rates, depend critically on the mechanism of resistance.
Mutation Rate Inferred From Synonymous Substitutions in a Long-Term Evolution Experiment With Escherichia coli
Wielgoss, Sebastien; Barrick, Jeffrey E.; Tenaillon, Olivier; et al. (2011)
G3: Genes, Genomes, Genetics
The quantification of spontaneous mutation rates is crucial for a mechanistic understanding of the evolutionary process. In bacteria, traditional estimates using experimental or comparative genetic methods are prone to statistical uncertainty and consequently estimates vary by over one order of magnitude. With the advent of next-generation sequencing, more accurate estimates are now possible. We sequenced 19 Escherichia coli genomes from a 40,000-generation evolution experiment and directly inferred the point-mutation rate based on the accumulation of synonymous substitutions. The resulting estimate was 8.9 × 10−11 per base-pair per generation, and there was a significant bias toward increased AT-content. We also compared our results with published genome sequence datasets for other bacterial evolution experiments. Given the power of our approach, our estimate represents the most accurate measure of bacterial base-substitution rates available to date.

Publications 1 - 10 of 19

Sebastien Wielgoss

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