Biology subjects

Adiba, S.

Publications and source records attributed to Adiba, S..

4 recordsLinked to original sources

bioRxiv2022

Single-cell phenotypic plasticity modulates social behaviour in Dictyostelium discoideum.

In Dictyostelium chimeras, strains social behaviour is defined based on their relative representation in the spores - the reproductive cells resulting from development - referred to as spore bias. Some strains, called cheaters, display systematically positive spore bias in chimeras and are considered a threat to the evolutionary stability of multicellular organization. The selective advantage gained by cheaters is indeed predicted to undermine collective functions whenever social behaviours are genetically determined. However, genotypes are not the only determinant of spore bias, and the relative role of genetic and plastic phenotypic differences in strains evolutionary success is unclear. Here, we control phenotypic heterogeneity by harvesting cells in different growth phases, and study the effects of plastic variation on spore bias in chimeras composed of isogenic or genetically different populations. Spore bias is shown to depend both on growth phase and on population composition, and to be negatively correlated to the fraction of loners, i.e. cells that do not join aggregates. We examined several single-cell mechanical properties that are expected to affect aggregation efficiency, and found that variations in the fraction of slowly moving cells with growth phase may explain why earlier cultures appear to be underrepresented in the spores. The involvement of a go-or-grow mechanism during cell aggregation is also consistent with known variations of cell-cycle phase distribution during population growth. We confirm the expected ubiquity of growth-phase induced spore bias variation by showing that it is not negligible in genetic chimeras, and can even reverse the classification of a strains social behaviour. These results suggest that aggregation can provide an efficient lottery system to harness the evolutionary spread of cheaters.

evolutionary biology↗

bioRxiv2022

A Plastidial Glycolytic-Gluconeogenic Switch of Mitochondrial Origin Enables Diatom Adaptations to High Latitudes

Organic carbon fixed in chloroplasts through the Calvin Cycle can be diverted towards different metabolic fates, including cytoplasmic and mitochondrial respiration; gluconeogenesis; and synthesis of diverse plastid metabolites via the pyruvate hub. In plants, pyruvate is principally produced via cytoplasmic glycolysis, although a plastid-targeted lower glycolytic pathway is known in non-photosynthetic tissue. Here, we characterize a lower plastid glycolytic-gluconeogenesis pathway in diatoms, ecologically important marine algae distantly related to plants. We show that two reversible enzymes required to complete diatom plastid glycolysis-gluconeogenesis, Enolase and PGAM (bis- phospho-glycerate mutase), originated through duplications of mitochondria-targeted respiratory isoforms. Through CRISPR-Cas9 mutagenesis, integrative omic analyses, and measured kinetics of expressed enzymes in the diatom Phaeodactylum tricornutum, we present evidence that this pathway diverts plastid glyceraldehyde-3-phosphate into the pyruvate hub, and may also function in the gluconeogenic direction. Considering experimental data, we show that this pathway has different roles dependent in particular on day length and environmental temperature, and show that it is expressed at elevated levels in high latitude oceans where diatoms are abundant. Our data provide evolutionary, meta-genomic and functional insights into a poorly understood yet evolutionarily recurrent plastid metabolic pathway.

plant biology↗

bioRxiv2022

Variable effects on virulence of bacteriophage resistance mechanisms in extraintestinal pathogenic Escherichia coli

AO_SCPLOWBSTRACTC_SCPLOWBacteria exposed to killing agents such as antibiotics or viruses develop resistance. While phage therapy, the use of bacteriophages (phages) for treating bacterial infections, is proposed to answer the antibiotic resistance crisis, bacterial resistance to phages remains poorly characterized during phage treatment. We studied a large population of phage-resistant extra-intestinal pathogenic Escherichia coli 536 clones emerging from both in vitro (non-limited liquid medium) and in vivo (murine pneumonia) conditions. Genome sequencing revealed a mutational convergence of phage resistance mechanisms towards the modification of two cell-wall components, the K15 capsule and the LPS, whatever the condition, showing that their identification could be predicted from the in vitro conditions. The fitness cost of all phage resistant clones was broad in terms of growth rate and resistance to grazing by amoeba and could not discriminate K15 capsule to LPS mutants. By contrast, the virulence of the clones tested in mice showed that K15 capsule mutants were as virulent as the wildtype strain while LPS mutants were strongly attenuated. We also found that resistance to one phage led to the sensitization to other phages. In clinics, to control phage-resistant clones that remains virulent phage cocktail should include phages infecting both phage susceptible and future phage resistant clones. ImportanceEscherichia coli is a leading cause of life-threatening infections, including pneumonia acquired during ventilatory assistance for patients hospitalized in Intensive Care Unit, and a major multidrug resistant pathogen. A century-old concept, phage therapy (i.e. using specific anti-bacterial viruses), is being clinically re-evaluated supported with hundreds of successful compassionate phage treatments. However, along billions of years of coevolution bacteria have developed many ways to resist to phages. Phage resistance occurring during phage therapy remains often overlooked despite its critical role for a successful outcome. During this work we characterized phage resistant mutants in a virulent extra-intestinal pathogenic E coli strain and found that (1) phage resistance taking place during a phage treatment in vivo could be predicted from an in vitro assay; (2) phage resistance has, often but not always, a major fitness cost in terms of virulence; and (3) could be countered by appropriate cocktails of phages.

microbiology↗

bioRxiv2021

Evolving social behaviour through selection of single-cell adhesion in Dictyostelium discoideum

The social amoeba Dictyostelium discoideum commonly forms chimeric fruiting bodies. Genetic variants that produce a higher proportion of spores are predicted to undercut multicellular organization unless cooperators assort positively. Cell adhesion is considered a primary factor driving such assortment, but evolution of adhesion has not been experimentally connected to changes in social performance. We modified by experimental evolution the efficiency of individual cells in attaching to a surface. Surprisingly, evolution appears to have produced social cooperators irrespective of whether stronger or weaker adhesion was selected. Quantification of reproductive success, cell-cell adhesion and developmental patterns, however, revealed two distinct social behaviours, as captured when the classical metric for social success is generalized by considering clonal spore production. Our work shows that cell mechanical interactions can constrain evolution of development and sociality in chimeras, and that elucidation of proximate mechanisms is necessary in order to understand the ultimate emergence of multicellular organization.

evolutionary biology↗