Biology subjects

Sagne, E.

Publications and source records attributed to Sagne, E..

3 recordsLinked to original sources

bioRxiv2025

Bacterial Conjugation in the Ruminant Pathogen Mycoplasma agalactiae is Influenced by Eukaryotic Host Factors

Bacterial conjugation plays a pivotal role in the evolution and adaptation of genome-reduced mycoplasmas. Despite their fast evolution rate, the conjugative properties of these organisms remain largely understudied, particularly in vivo. In the present study, the ruminant pathogen Mycoplasma agalactiae was used as a model organism to document the conjugative properties of mycoplasmas in environments of increasing complexity, from axenic to cell and organotypic culture conditions. Compared to axenic mating conditions, mycoplasma co-cultivation with goat epithelial cells or bovine precision-cut lung slices (PCLS) resulted in enhanced mating frequencies with high rates of M. agalactiae Integrative and Conjugative Element (ICEA) self-dissemination. These results were conditioned by the presence of eukaryotic cells in the culture and influenced by competition between mating partners but were not limited to M. agalactiae, as similar results were observed with Mycoplasma bovis. Mycoplasma conjugation ex vivo was further characterized by analyzing mycoplasma chromosomal transfer (MCT), a newly discovered mechanism of horizontal exchange of chromosomal DNA that generates mosaic genomes. Although closely associated with ICEA transfer, MCT was detected at low rates under cell and organotypic culture conditions suggesting a complex interplay between these two conjugative processes or a poor viability of the MCT progeny. Finally, mating experiments under nutrient-deprived conditions identified nucleotide stress as a potential factor influencing the modulation of mycoplasma conjugation by eukaryotic host cells. In conclusion, these results suggest that horizontal gene transfer in vivo is likely underestimated and provide valuable models to further studying mycoplasma conjugation ex vivo. IMPORTANCEConjugation is an evolutionary shortcut that bacteria use to exchange genetic information with their neighbors. Despite the fast evolution rate of the genome-reduced mycoplasmas, their conjugative properties remain largely understudied, particularly in vivo. Here we used the ruminant pathogen Mycoplasma agalactiae to study how mycoplasmas conjugate in co-culture with hosts-derived cells and tissues. Interestingly, conjugation was stimulated when mycoplasmas were co-cultured with eukaryotic cells. This was documented by monitoring the self-propagation of a mobile genetic element known as Integrative and Conjugative Element (ICE) and the exchange of chromosomal DNA leading to the formation of mosaic genomes. While ICE transfer was observed at high frequency, only a few mosaic genomes were detected in the presence of eukaryotic cells. Further data point towards nucleotide stress as a possible factor modulating mycoplasma conjugation in cellular environments. These results suggest that mycoplasma-host interactions may stimulate conjugation in vivo.

microbiology↗

bioRxiv2021

Impacts of Mycoplasma agalactiae restriction-modification systems on pan-epigenome dynamics and genome plasticity

DNA methylation plays an important role in the biology of bacteria. Often associated with restriction modification (RM) systems, they also provide a defence against foreign DNA. Little is known regarding the methylome of the mycoplasma genus, which encompasses several pathogenic species with small genomes. Here, single molecule real-time (SMRT) and bisulphite sequencing combined with whole-genome analysis identified 19 methylated motifs associated with three orphan methyltransferases (MTases) and eight RM systems in Mycoplasma agalactiae, a ruminant pathogen and a model organism. All systems had a homolog in at least one phylogenetically distinct Mycoplasma spp. Our study also revealed that several superimposed genetic events may participate in the M. agalactiae dynamic epigenome landscape. These included (i) DNA shuffling and frameshift mutations that affect the MTase and restriction endonuclease content of a clonal population and (ii) gene duplication, erosion, and horizontal transfer that modulate MTase and RM repertoires of the species. Some of these systems were experimentally shown to play a major role in mycoplasma conjugative, horizontal DNA transfer. While the versatility of DNA methylation may contribute to regulating essential biological functions at cell and population levels, RM systems may be key in mycoplasma genome evolution and adaptation by controlling horizontal gene transfers.

microbiology↗

bioRxiv2018

The Integrative Conjugative Element (ICE) of Mycoplasma agalactiae: key elements involved in horizontal dissemination and influence of co-resident ICEs

The discovery of integrative conjugative elements (ICEs) in wall-less mycoplasmas and the demonstration of their role in massive gene flows within and across species has shed new light on the evolution of these minimal bacteria. Of these, ICEA of the ruminant pathogen Mycoplasma agalactiae represents a prototype and belongs to a new clade of the Mutatorlike superfamily that has no preferential insertion site and often occurs as multiple chromosomal copies. Here, functional genomics and mating experiments were combined to address ICEA functions and define the minimal ICEA chassis conferring conjugative properties to M. agalactiae. Data further indicated a complex interaction among co-resident ICEAs, since the minimal ICEA structure was influenced by the occurrence of additional ICEA copies that can trans-complement conjugative-deficient ICEAs. However, this cooperative behavior was limited to the CDS14 surface lipoprotein, which is constitutively expressed by co-resident ICEAs, and did not extend to other ICEA proteins including the cis-acting DDE recombinase and components of the mating channel whose expression was only sporadically detected. Remarkably, conjugative-deficient mutants containing a single ICEA copy knocked-out in cdsl4 can be complemented by neighboring cells expressing CDS14. This result, together with the conservation of CDS14 functions in closely related species, may suggest a way for mycoplasma ICEs to extend their interaction outside of their chromosomal environment. Overall, this study provides a first model of conjugative transfer in mycoplasmas and offers valuable insights towards the understanding of horizontal gene transfer in this highly adaptive and diverse group of minimal bacteria.\n\nIMPRTANCEIntegrative conjugative elements (ICEs) are self-transmissible mobile genetic elements that are key mediators of horizontal gene flow in bacteria. Recently, a new category of ICEs has been identified that confer conjugative properties to mycoplasmas, a highly adaptive and diverse group of wall-less bacteria with reduced genomes. Unlike classical ICEs, these mobile elements have no preferential insertion specificity and multiple mycoplasma ICE copies can be found randomly integrated into the host chromosome. Here, the prototype ICE of Mycoplasma agalactiae was used to define the minimal conjugative machinery and propose the first model of ICE transfer in mycoplasmas. This model unveils the complex interactions taking place among co-resident ICEs and suggests a way for these elements to extend their influence outside of their chromosomal environment. These data pave the way for future studies aiming at deciphering chromosomal transfer, an unconventional mechanism of DNA swapping that has been recently associated with mycoplasma ICEs.

microbiology↗