Biology subjects

Goudenege, D.

Publications and source records attributed to Goudenege, D..

4 recordsLinked to original sources

bioRxiv2024

Generalists in a Specialist World: Vibrio-Phages with Broad Host Range

The host range of a bacteriophage--the diversity of hosts it can infect--is central to understanding phage ecology and applications. While most well-characterized phages have narrow host ranges, broad-host-range phages represent an intriguing component of marine ecosystems. The genetic and evolutionary mechanisms driving their generalism remain poorly understood. In this study, we analyzed Schizotequatroviruses and their Vibrio crassostreae hosts, collected from an oyster farm. Schizotequatroviruses exhibit broad host ranges, large genomes (~252 kbp) encoding 26 tRNAs, and conserved genomic organization interspersed with recombination hotspots. These recombination events, particularly in regions encoding receptor-binding proteins and antidefense systems, highlight their adaptability to host resistance. Notably, some lineages demonstrated receptor-switching between OmpK and LamB, showcasing their evolutionary flexibility. Despite their broad host range, Schizotequatroviruses were rare in the environment. Their scarcity could not be attributed to burst size, which was comparable to other phages in vitro, but may result from ecological constraints or fitness trade-offs, such as their preference for targeting generalist vibrios in seawater rather than the patho-phylotypes selected in oyster farms. Our findings clarify the genetic and ecological trade-offs shaping Schizotequatrovirus generalism and provide a foundation for future phage applications in aquaculture and beyond.

microbiology↗

bioRxiv2024

Vibrio are a potential source of novel colistin-resistance genes in European coastal environments

Colistin is a widespread last resort antibiotic for treatment of multidrug-resistant bacteria. The recent worldwide emergence of colistin resistance (Col-R) conferred by mcr-1 in human pathogens has raised concern, but the putative sources and reservoirs of novel mcr genes in the marine environment remain underexplored. We observed a high prevalence of Col-R, particularly in Vibrio isolated from European coastal waters by using a unique stock of specific-pathogen-free (SPF) oysters as a bioaccumulator. The high sequence diversity found in the mcr/eptA gene family was geographically structured, particularly for three novel eptA gene variants, which were restricted to the Mediterranean (France, Spain) and occurred as a dgkA-eptA operon controlled by the RstA/RstB two component system. By analyzing 29427 Vibrionaceae genome assemblies, we showed that this mechanism of intrinsic resistance is prevalent and specific to the Harveyi clade, which includes strains of Vibrio parahaemolyticus and Vibrio alginolyticus causing infections in humans. The operon conferred colistin-resistance when transferred to sensitive non-Vibrio strains. While mcr-and arn-based Col-R mechanisms were also identified, the widespread presence of eptA gene variants in Vibrio suggests they play a key role in intrinsic resistance to colistin. Beyond these ancient eptA gene copies having evolved with the Vibrio lineage, we also identified mobile eptA paralogues that have been recently transferred between and within Vibrio clades. This highlights Vibrio as a potential source of Col-R mechanisms, emphasizing the need for enhanced surveillance to prevent colistin-resistant infections in coastal areas.

microbiology↗

bioRxiv2024

A human mitochondrial isoform of TRPV1 regulates intracellular Ca2+ simultaneously with mitochondrial thermolysis

Mitochondria are the cornerstones of cellular and body thermogenesis, with an inner temperature possibly reaching 50{degrees}C. Here, we report the identification of a human Transient Receptor Potential Vanilloid 1 alternative isoform located in mitochondria. This isoform, which we have termed mitoTRPV1, acts as a thermostat to restrict the mitochondrial temperature. The mitoTRPV1 open reading frame overlaps TRPV1 exons 1 and 2 and intron 2 in a +1 frame, encoding for a predicted 150 amino-acid N-terminal mitochondrial targeting sequence (MTS) conserved amongst mammalian species, followed by the 687 amino acids of TRPV1 C-terminal. This ORF is ubiquitously expressed in most human organs, underscoring its broad relevance. The deduced MTS, conserved among mammalian species, effectively addresses this TRPV1 isoform to the mitochondrial inner membrane. Our experiments, using heterologous wild-type and mutated mitoTRPV1 expression, combined with Ca2+ imaging, mitochondrial temperature and oxygraphy measurements, disclosed that mitoTRPV1 activation induces Ca2+ efflux and mitochondrial cooling, without modification of mitochondrial respiration and ATP production. Notably, the loss of function mitoTRPV1-G684V isoform, responsible for exertional heat stroke predisposition in humans, abolished mitochondrial Ca2+ efflux and cooling. These findings reveal a new thermolysis function for TRPV1 in preventing mitochondrial overwarming while not affecting the OXPHOS efficiency. They also highlight the potential implications of mitoTRPV1 in human diseases related to temperature dysregulation.

cell biology↗

bioRxiv2023

Phage inducible chromosomal minimalist island (PICMI), a family of satellites of marine virulent phages

Phage satellites are genetic elements that hijack the phage machinery for their own dissemination. However, only few phage satellites have been characterized, and mechanisms by which they influence microbial evolution in nature are unclear. Here we identify a new family of satellites, the Phage Inducible Chromosomal Minimalist Island (PICMI), which is broadly distributed in the marine bacteria Vibrionaceae. PICMI is characterized by reduced gene content, does not encode genes for capsid remodeling and packages its DNA as a concatemer. PICMI is integrated in the bacterial host genome at the end of the fis regulator and encodes three core proteins necessary for excision and replication. PICMI is dependent on virulent phage particles to spread to other bacteria and confers host protection from other competitive phages, without interfering with its helper phage. The discovery of PICMI strongly suggests that phages, including virulent ones, play important roles for mobility of phage defense elements.

microbiology↗