Biology subjects

Bertaux, L.

Publications and source records attributed to Bertaux, L..

3 recordsLinked to original sources

bioRxiv2023

Fatty Acid Metabolism and The Oxidative Stress Response Support Bacterial Predation

Despite growing awareness of their importance in soil ecology, the genetic and physiological traits of bacterial predators are still relatively poorly understood. In the course of a Myxococcus xanthus predator evolution experiment, we discovered a class of genotypes leading to enhanced predation against diverse species. RNA-seq analysis demonstrated that this phenotype is linked to the constitutive activation of a predation-specific program. Functional analysis of the mutations accumulated across the evolutionary time in a two- component system and Acyl-CoA-manipulating enzymes revealed the critical roles of fatty acid metabolism and antioxidant gene induction. The former likely adapts the predator to metabolites derived from the prey while the latter protects predatory cells from reactive oxygen species (ROS) generated by prey cells under stress and released upon lysis during predation. These findings reveal interesting parallels between bacterial predator-prey dynamics and pathogen-host cell interactions. Significance StatementThis study illuminates the largely unexplored genetic and metabolic strategies used by bacterial predators in soil ecosystems. Through experimental evolution in Myxococcus xanthus, we discovered that more efficient predators accumulate mutations that activate a genetic program for predation. This program simultaneously triggers a metabolic shift favoring fatty acid degradation for energy production and upregulates antioxidant gene expression, enhancing protection against reactive oxygen species generated during prey cell lysis. This adaptive mechanism proves advantageous across a wide range of prey species, suggesting that metabolic adaptation plays a crucial role in the evolutionary trajectory of bacterial predators within their natural ecological niche.

microbiology↗

bioRxiv2019

Commensalism in the Mimiviridae giant virus family

Acanthamoeba-infecting Mimiviridae belong to three clades: Mimiviruses (A), Moumouviruses (B) and Megaviruses (C). The uniquely complex mobilome of these giant viruses includes virophages and linear 7 kb-DNA molecules called \"transpovirons\". We recently isolated a virophage (Zamilon vitis) and two transpovirons (maBtv and mvCtv) respectively associated to B-clade and C-clade mimiviruses. We used the capacity of the Zamilon virophage to replicate both on B-clade and C-clade host viruses to investigate the three partite interaction network governing the propagation of transpovirons. We found that the virophage could transfer both types of transpovirons to B-clade and C-clade host viruses provided they were devoid of a resident transpoviron (permissive effect). If not, only the resident transpoviron was replicated and propagated within the virophage progeny (dominance effect). Although B- and C-clade viruses devoid of transpoviron could replicate both maBtv and mvCtv, they did it with a lower efficiency across clades, suggesting an ongoing process of adaptive co-evolution. We performed proteomic comparisons of host viruses and virophage particles carrying or cleared of transpovirons in search of proteins involved in this adaptation process. These experiments revealed that transpoviron-encoded proteins are synthetized during the combined mimiviruses/virophage/transpoviron replication process and some of them are specifically incorporated into the virophage and giant virus particles together with the cognate transpoviron DNA. This study also highlights a unique example of intricate commensalism in the viral world, where the transpoviron uses the virophage to propagate from one host virus to another and where the Zamilon virophage and the transpoviron depend on their host giant virus to replicate, this without affecting the giant virus infectious cycle, at least in laboratory conditions.\n\nAuthor SummaryThe Mimiviridae are giant viruses with dsDNA genome up to 1.5 Mb. They build huge viral factories in the host cytoplasm in which the nuclear-like virus-encoded functions (transcription and replication) take place. They are themselves the target of infections by 20 kb-dsDNA virophages, replicating in the giant virus factories. They can also be found associated with 7kb-DNA episomes, dubbed transpovirons. We investigated the relationship between these three players by combining competition experiments involving the newly isolated Zamilon vitis virophage as a vehicle for transpovirons of different origins with proteomics analyses of virophage and giant virus particles. Our results suggest that relationship of the virophage, the transpoviron, and their host giant virus, extend the concept of commensalism to the viral world.

microbiology↗

bioRxiv2017

Diversity and evolution of the emerging Pandoraviridae family

With DNA genomes up to 2.5 Mb packed in particles of bacterium-like shape and dimension, the first two Acanthamoeba-infecting Pandoraviruses remained the most spectacular viruses since their description in 2013. Our isolation of three new strains from distant locations and environments allowed us to perform the first comparative genomics analysis of the emerging worldwide-distributed Pandoraviridae family. Thorough annotation of the genomes combining transcriptomic, proteomic, and bioinformatic analyses, led to the discovery of many non-coding transcripts while significantly reducing the former set of predicted protein-coding genes. We found that the Pandoraviridae exhibit an open pan genome, the enormous size of which is not adequately explained by gene duplications or horizontal transfers. As most of the strain specific genes have no extant homolog and exhibit statistical features comparable to intergenic regions, we suggests that de novo gene creation is a strong component in the evolution of the giant Pandoravirus genomes.

microbiology↗