Biology subjects

Oger, P. M.

Publications and source records attributed to Oger, P. M..

4 recordsLinked to original sources

bioRxiv2022

Unravelling the mechanisms of adaptation to high pressure in proteins

Life is thought to have appeared in the depth of the sea, under high hydrostatic pressure. Nowadays, it is known that the deep biosphere hosts a myriad of life forms thriving under high pressure conditions. However, the evolutionary mechanisms leading to their adaptation are still not known. Here we show the molecular bases of these mechanisms through a neutron scattering study of two orthologous proteins. We observed that pressure adaptation involves the decoupling of protein-water dynamics and the elimination of cavities in the protein core. This is achieved by an enrichment of acidic residues on the protein surface and by the use of bulkier hydrophobic residues in the core. These findings will be the starting point in the search of a complete genomic model explaining high pressure adaptation.

biophysics↗

bioRxiv2022

High temperature molecular motions within a model protomembrane architecture

Modern phospholipid membranes are known to be in a functional, physiological state, corresponding to the liquid crystalline phase, only under very precise external conditions. The phase is characterised by specific lipid motions, which seem mandatory to permit sufficient flexibility and stability for the membrane. It can be assumed that similar principles hold for proto-membranes at the origin of life although they were likely composed of simpler, single chain fatty acids and alcohols. In the present study we investigated molecular motions of four types of model membranes to shed light on the variations of dynamics and structure as a function of temperature as protocells might have existed close to hot vents. We find a clear hierarchy among the flexibilities of the samples, where some structural parameters seem to depend on the lipids used while others do not.

biophysics↗

bioRxiv2021

The exploration of Thermococcus barophilus lipidome reveals the widest variety of phosphoglycolipids in Thermococcales.

One of the most distinctive characteristics of Archaea is their unique lipids. While the general nature of archaeal lipids has been linked to their tolerance to extreme conditions, little is known about the diversity of lipidic structures Archaea are able to synthesize, which hinders the elucidation of the physicochemical properties of their cell membrane. In an effort to widen the known lipid repertoire of the piezophilic and hyperthermophilic model archaeon Thermococcus barophilus, we comprehensively characterized its intact polar lipid (IPL), core lipid (CL), and polar head group compositions using a combination of cutting-edge liquid chromatography and mass spectrometric ionization systems. We tentatively identified 82 different IPLs based on five distinct CLs and 10 polar head group derivatives of phosphatidylhexoses, including compounds reported here for the first time, e.g., di-N-acetylhexosamine phosphatidylhexose-bearing lipids. Despite having extended the knowledge on the lipidome, our results also indicate that the majority of T. barophilus lipids remain inaccessible to current analytical procedures and that improvements in lipid extraction and analysis are still required. This expanded yet incomplete lipidome nonetheless opens new avenues for understanding the physiology, physicochemical properties, and organization of the membrane in this archaeon as well as other Archaea.

microbiology↗

bioRxiv2021

Membrane adaptation in the hyperthermophilic archaeon Pyrococcus furiosus relies upon a novel strategy involving glycerol monoalkyl glycerol tetraether lipids

Microbes preserve membrane functionality under fluctuating environmental conditions by modulating their membrane lipid composition. Although several studies have documented membrane adaptations in Archaea, the influence of most biotic and abiotic factors on archaeal lipid compositions remains underexplored. Here, we studied the influence of temperature, pH, salinity, the presence/absence of elemental sulfur, the carbon source, and the genetic background on the core lipid composition of the hyperthermophilic neutrophilic marine archaeon Pyrococcus furiosus. Every growth parameter tested affected the core lipid composition to some extent, the carbon source and the genetic background having the greatest influence. Surprisingly, P. furiosus appeared to only marginally rely on the two major responses implemented by Archaea, i.e., the regulation of the ratio of diether to tetraether lipids and that of the number of cyclopentane rings in tetraethers. Instead, this species increased the ratio of glycerol monoalkyl glycerol tetraethers (GMGT, aka. H-shaped tetraethers) to glycerol dialkyl glycerol tetrathers (GDGT) in response to decreasing temperature and pH and increasing salinity, thus providing for the first time evidence of adaptive functions for GMGT. Besides P. furiosus, numerous other species synthesize significant proportions of GMGT, which suggests that this unprecedented adaptive strategy might be common in Archaea. Significance statementWe describe here the membrane adaptive strategies the hyperthermophilic, neutrophilic, and marine model archaeon Pyrococcus furiosus implements in response to one of the largest sets of environmental stressors tested to date, including temperature, pH, salinity, presence/absence of elemental sulfur, carbon source, and genetic background. In contrast to the other archaea investigated so far, which response mainly involves the modulation of their diether/tetraether ratio and/or of their average number of cyclopentane rings, P. furiosus regulates its monoalkyl (so called H-shaped) to dialkyl tetraether ratio. Our study thus provides for the first time evidence of adaptive functions of archaeal monoalkyl tetraethers towards low temperature and pH and high salinity.

microbiology↗