Biology subjects

Cretin, P.

Publications and source records attributed to Cretin, P..

2 recordsLinked to original sources

bioRxiv2025

Prophage-marine diazotroph interplay shapes both biofilm structure and nitrogen release

Marine environments are frequently oligotrophic, characterized by low amount of bioassimilable Nitrogen sources. At the global scale, the microbial fixation of N2, or diazotrophy, represents the primary source of fixed nitrogen in pelagic marine ecosystems, playing a key role in supporting primary production and driving the export of organic matter to the deep ocean. However, given the high energetic cost of N2 fixation, the active release of fixed nitrogen by diazotrophs appears counterintuitive, suggesting the existence of alternative, passive release pathways, that remain understudied to date. Here, we show that the marine Non Cyanobacterial Diazotroph Vibrio diazotrophicus is endowed with a prophage belonging to the Myoviridae family, whose expression is induced under anoxic and biofilm-forming conditions. We demonstrate that this prophage can spontaneously excise from the genome of its host and that it forms intact and infective phage particles. Moreover, phage-mediated host cell lysis leads to increased biofilm production as compared to a prophage-free derivative mutant, and to increased release of Dissolved Organic Carbon and of ammonium. Altogether, we provide evidences that viruses may play a previously unrecognized role in oceanic ecosystem dynamics by structuring micro-habitats suitable for diazotrophy and by contributing to the recycling of (in-)organic matter. ImportanceDiazotrophs are key players in ocean functioning by providing fixed nitrogen to ecosystems and fueling primary production. However, from a physiological point-of-view, the active release of nitrogenous compounds by diazotrophs is paradoxical, since they would invest in an energy-intensive process and supply nutrient to non-sibling cells, with the risk of being outcompeted. Therefore, alternative ways leading to the release of fixed nitrogen must exist. Here, we show that the marine Non Cyanobacterial Diazotroph Vibrio diazotrophicus possesses one prophage, whose activation leads to cell death, to increased biofilm production and to the release of Dissolved Organic Compounds and of ammonium. Taken together, our results provide evidences that marine phage-diazotroph interplay leads to the creation of micro-habitats suitable for diazotrophy like biofilm and to nutrient cycling, and contribute to better understanding of the role of viruses in marine ecosystems.

microbiology↗

bioRxiv2023

Development and utilization of new O2-independent bioreporters

Fluorescent proteins have revolutionized science since their discovery in 1962. They have enabled imaging experiments to decipher the function of proteins, cells and organisms, as well as gene regulation. GFP and all its derivatives are now standard tools in cell biology, immunology, molecular biology and microbiology laboratories around the world. A common feature of these proteins is their O2-dependent maturation allowing fluorescence, which precludes their use in anoxic contexts. In this work, we report the development and in cellulo characterization of genetic circuits encoding the O2-independent KOFP-7 protein, a flavin-binding fluorescent protein. We have optimized the genetic circuit for high bacterial fluorescence at population and single-cell level, implemented this circuit in various plasmids differing in host range, and quantified their fluorescence under both aerobic and anaerobic conditions. Finally, we showed that KOFP-7 based constructions can be used to produce fluorescing cells of V. diazotrophicus, a facultative anaerobe, demonstrating the usefulness of the genetic circuits for various anaerobic bacteria. These genetic circuits can thus be modified at will, both to solve basic and applied research questions, opening a highway to shed light on the obscure anaerobic world. ImportanceFluorescent proteins are used since decades, and have allowed major discoveries in biology in a wide variety of fields, and are used in environmental as well as clinical contexts. GFP and all its derivatives share a common feature: they rely on the presence of O2 for protein maturation and fluorescence. This dependency precludes their use in anoxic environments. Here, we constructed a series of genetic circuits allowing production of KOFP-7, an O2-independant Flavin-Binding Fluorescent Protein. We demonstrated that Escherichia coli cells producing KOFP-7 are fluorescent, both at the population and single-cell levels. Importantly, we showed that, unlike cells producing GFP, cells producing KOFP-7 are fluorescent in anoxia. Finally, we demonstrated that Vibrio diazotrophicus NS1, a facultative anaerobe, is fluorescent in the absence of O2 when KOFP-7 is produced. Altogether, the development of new genetic circuits allowing O2-independent fluorescence will open new perspective to study anaerobic processes.

molecular biology↗