Biology subjects

Sime-Ngando, T.

Publications and source records attributed to Sime-Ngando, T..

4 recordsLinked to original sources

bioRxiv2025

Pera virus mimics bacteria to infect Pedopumella sp. a freshwater heterotrophic Chrysophyceae

Heterotrophic Chrysophyceae play a key role in the functioning of many aquatic food webs as primary predators of prokaryotes, but their top-down regulatory factors are poorly understood. To date, no virus isolates from heterotrophic Chrysophyceae have been described in the literature. Here we describe Pera virus, a giant virus infecting the heterotrophic Chrysophyceae Pedospumella sp.. Pera virus have an icosahedral capsid-vesicle morphology, a feature unprecedented in viruses. We hypothesize that this vesicle mimics the shape of bacteria so that the virus is recognized as such by its bacteriophage protist host. This constitutes a morphological evolution of viruses that promotes infection of their heterotrophic host. The capside measures 414 nm in diameter. The vesicle has a variable diameter ranging from 231 to 587 nm. The virion as a whole can reach 1008 nm in length. We searched for this new type of virus under environmental conditions during time series studies in hyper-eutrophic freshwater lakes. Surprisingly, we report the existence of Pera virus-like particles (PVLs) of various shapes and size that can reach 5 {micro}m illustrating the hidden diversity of this undescribed virus types. The dynamics of PVLs, which can reach 2.4 x 105 PVL.mL-1, are closely associated with those of unicellular heterotrophic eukaryotes, acting as major regulatory agents of protozoan bacterivory in freshwater. This pair provides a new model for understanding the evolution of giant viruses and their ecological role.

ecology↗

bioRxiv2024

Unexpected diversity and ecological significance of uncultivable large virus-like particles in aquatic environments

The discovery of Jumbo phages and giant viruses of microeukaryotes has transformed our perception of the virosphere. Metagenomic and metatranscriptomic data further highlight their diversity and ecological impact. Nevertheless, sequence-based approaches fail to take into account the morphological diversity of non-cultivated viruses, resulting in our fragmented understanding of their nature and role in the environment. Here, we combined flow cytometry and electron microscopy to uncover both previously unsuspected morphological diversity as well as significant abundances of large viruses in aquatic environments. We discovered four new viral morphotypes, all of which were associated with microeukaryotes. We also obtained insights into the multi-year dynamics of the abundances of both giant microeukaryotic viruses and Jumbo phages. This work deepens our understanding of large viruses and reveals their key role as regulators of microbial communities.

ecology↗

bioRxiv2021

Long-term incubation of lake water enables genomic sampling of consortia involving Planctomycetes and Candidate Phyla Radiation bacteria

Microbial communities in lakes can profoundly impact biogeochemical processes through their individual activities and collective interactions. However, the complexity of these communities poses challenges, particularly for studying rare members. Laboratory enrichments can select for subsystems of interacting organisms and enable genome recovery for enriched populations. Here, a reactor inoculated with water from Lake Fargette, France, and maintained under dark conditions at 4{degrees}C for 31 months enriched for diverse Planctomycetes and Candidate Phyla Radiation (CPR) bacteria. We reconstructed draft genomes and predicted metabolic traits for 12 diverse Planctomycetes and 9 CPR bacteria, some of which are likely representatives of undescribed families or genera. One CPR genome representing the little-studied lineage Peribacter (1.239 Mbp) was curated to completion, and unexpectedly, encodes the full gluconeogenesis pathway. Metatranscriptomic data indicate that some Planctomycetes and CPR bacteria were active under the culture conditions. We also reconstructed genomes and obtained transmission electron microscope images for numerous phages, including one with a >300 kbp genome and several predicted to infect Planctomycetes. Together, our analyses suggest that freshwater Planctomycetes may act as hubs for interaction networks that include symbiotic CPR bacteria and phages.

microbiology↗

bioRxiv2018

Hygroregulation, a key ability for eusocial insects: Native Western European bees as a case study

Sociality has brought many advantages to various hymenoptera species, including their ability of regulating physical factors in their nest (e.g., temperature). Although less studied, humidity is known to be important for egg, larval and pupal development. Two subspecies of Apis mellifera of the M branch, also called black bees, were used as models to test the \"hygroregulation hypothesis\", by means of monitoring hygrometry in hives during one year in four conservation centers: two in France (A. m. mellifera) and two in Portugal (A. m. iberiensis). We investigated the ability of both subspecies to regulate the hygrometry daily, but also during the seasons and one complete year. Our data and statistical analysis probed the capacity of the bees to regulate humidity in their hive, regardless of the day, season or subspecies. Furthermore, the study showed that humidity in beehives is very stable even during winter, when brood is absent, and when temperature is known to be less stable in the beehives. These results would support that hygrometry could prevail over temperature in maintaining nest homeostasis, maybe because of a bigger importance of hygrometry for all the population during a year, or because of the imprint of the evolutionary history of this hymenopteran lineage.

ecology↗