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Auguet, J. C., Barberan, A., & Casamayor, E. O. (2010). Global ecological patterns in uncultured Archaea. Isme J, 4(2), 182–190.
Résumé: We have applied a global analytical approach to uncultured Archaea that for the first time reveals well-defined community patterns along broad environmental gradients and habitat types. Phylogenetic patterns and the environmental factors governing the creation and maintenance of these patterns were analyzed for c. 2000 archaeal 16S rRNA gene sequences from 67 globally distributed studies. The sequences were dereplicated at 97% identity, grouped into seven habitat types, and analyzed with both Unifrac (to explore shared phylogenetic history) and multivariate regression tree (that considers the relative abundance of the lineages or taxa) approaches. Both phylogenetic and taxon-based approaches showed salinity and not temperature as one of the principal driving forces at the global scale. Hydrothermal vents and planktonic freshwater habitats emerged as the largest reservoirs of archaeal diversity and consequently are promising environments for the discovery of new archaeal lineages. Conversely, soils were more phylogenetically clustered and archaeal diversity was the result of a high number of closely related phylotypes rather than different lineages. Applying the ecological concept of 'indicator species', we detected up to 13 indicator archaeal lineages for the seven habitats prospected. Some of these lineages (that is, hypersaline MSBL1, marine sediment FCG1 and freshwater plSA1), for which ecological importance has remained unseen to date, deserve further attention as they represent potential key archaeal groups in terms of distribution and ecological processes. Hydrothermal vents held the highest number of indicator lineages, suggesting it would be the earliest habitat colonized by Archaea. Overall, our approach provided ecological support for the often arbitrary nomenclature within uncultured Archaea, as well as phylogeographical clues on key ecological and evolutionary aspects of archaeal biology.
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Bettarel, Y., Combe, M., Adingra, A., Ndiaye, A., Bouvier, T., Panfili, J., et al. (2018). Hordes of Phages in the Gut of the Tilapia Sarotherodon melanotheron. Sci Rep, 8, 11311.
Résumé: Preliminary studies conducted on the human gastro-intestinal tract have revealed that enteric viral communities play a preponderant role in microbial homeostatis. However to date, such communities have never been investigated in the fish gut. Herein, we examined the main ecological traits of viruses in the digestive tract of a euryhaline fish, the tilapia Sarotherodon melanotheron. Individuals were collected at 8 different sites in Senegal covering a salinity gradient from 3 to 104 parts per thousand, and showing large disparities in their organic pollutant concentrations. Results showed that the gut of S. melanotheron is home to a highly abundant viral community (0.2-10.7 x 10(9) viruses ml(-1)), distinct from the surrounding water, and essentially composed of phages of which a substantial proportion is temperate (the fraction of lysogenized cells-FLC ranging from 8.1 to 33.0%). Also, a positive and significant correlation was detected between FLC and the concentrations of polycyclic aromatic hydrocarbon in sediment, while no clear relationships were found between salinity and any of the microbial parameters considered. Finally, our data suggest that virus-bacteria interactions within the fish intestine are likely sensitive to the presence of particular xenobiotics, which may compromise the balance in the gut microbiota, and subsequently affect the health of their host.
Mots-Clés: bacterial communities; diversity; fish gut; host; microbiome; physiology; virome; viruses; xenobiotics
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Damsgaard, C., Baliga, V. B., Bates, E., Burggren, W., McKenzie, D. J., Taylor, E., et al. (2019). Evolutionary and cardio-respiratory physiology of air-breathing and amphibious fishes. Acta Physiol., , Unsp-e13406.
Résumé: Air-breathing and amphibious fishes are essential study organisms to shed insight into the required physiological shifts that supported the full transition from aquatic water-breathing fishes to terrestrial air-breathing tetrapods. While the origin of air-breathing in the evolutionary history of the tetrapods has received considerable focus, much less is known about the evolutionary physiology of air-breathing among fishes. This review summarizes recent advances within the field with specific emphasis on the cardiorespiratory regulation associated with air-breathing and terrestrial excursions, and how respiratory physiology of these living transitional forms are affected by development and personality. Finally, we provide a detailed and re-evaluated model of the evolution of air-breathing among fishes that serves as a framework for addressing new questions on the cardiorespiratory changes associated with it. This review highlights the importance of combining detailed studies on piscine air-breathing model species with comparative multi-species studies, to add an additional dimension to our understanding of the evolutionary physiology of air-breathing in vertebrates.
Mots-Clés: acid-base; catfish clarias-gariepinus; development; developmental physiology; different strategies; evolution; kryptolebias-marmoratus; lungfish protopterus; metabolic-rate; phenotypic plasticity; risk-taking; terrestrial acclimation; terrestrialization; tinca-tinca l; water-to-air transition
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Duval, C., Thomazeau, S., Drelin, Y., Yepremian, C., Bouvy, M., Couloux, A., et al. (2018). Phylogeny and salt-tolerance of freshwater Nostocales strains: Contribution to their systematics and evolution. Harmful Algae, 73, 58–71.
Résumé: Phylogenetic relationships among heterocytous genera (the Nostocales order) have been profoundly modified since the use of polyphasic approaches that include molecular data. There is nonetheless still ample scope for improving phylogenetic delineations of genera with broad ecological distributions, particularly by integrating specimens from specific or up-to-now poorly sampled habitats. In this context, we studied 36 new isolates belonging to Chrysosporum, Dolichospermum, Anabaena, Anabaenopsis, and Cylindrospermopsis from freshwater ecosystems of Burkina-Faso, Senegal, and Mayotte Island. Studying strains from these habitats is of particular interest as we suspected different range of salt variations during underwent periods of drought in small ponds and lakes. Such salt variation may cause different adaptation to salinity. We then undertook a polyphasic approach, combining molecular phylogenies, morphological analyses, and physiological measurements of tolerance to salinity. Molecular phylogenies of 117 Nostocales sequences showed that the 36 studied strains were distributed in seven lineages: Dolichospermum, Chrysosporum, Cylindrospermopsis Raphidiopsis, Anabaenopsis, Anabaena sphaerica var tenuis/Sphaerospermopsis, and two independent Anabaena sphaerica lineages. Physiological data were congruent with molecular results supporting the separation into seven lineages. In an evolutionary context, salinity tolerance can be used as an integrative marker to reinforce the delineation of some cyanobacterial lineages. The history of this physiological trait contributes to a better understanding of processes leading to the divergence of cyanobacteria. In this study, most of the cyanobacterial strains isolated from freshwater environments were salt-tolerant, thus suggesting this trait constituted an ancestral trait of the heterocytous cyanobacteria and that it was probably lost two times secondarily and independently in the ancestor of Dolichospermum and of Cylindrospermopsis. (C) 2018 Elsevier B.V. All rights reserved.
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Ferrari, S., Rey, S., Hoglund, E., Overli, O., Chatain, B., MacKenzie, S., et al. (2020). Physiological responses during acute stress recovery depend on stress coping style in European sea bass, Dicentrarchus labrax. Physiol. Behav., 216, 112801.
Résumé: Individual stress coping style (reactive, intermediate and proactive) was determined in 3 groups of 120 pit tagged European seabass using the hypoxia avoidance test. The same three groups (no change in social composition) were then reared according to the standards recommended for this species. Then, 127 days later, individuals initially characterized as reactive, intermediate or proactive were submitted to an acute confinement stress for 30 min. Blood samples were taken to measure plasma cortisol levels 30 min (Stress30) or 150 min (Stress150) after the end of the confinement stress. Individuals were then sacrificed to sample the telencephalon in order to measure the main monoamines and their catabolites (at Stress30 only). Individuals from Stress150 were sampled for whole brain for a transcriptomic analysis. The main results showed that reactive individuals had a lower body mass than intermediate individuals which did not differ from proactive individuals. The physiological cortisol response did not differ between coping style at Stress30 but at Stress150 when intermediate and proactive individuals had recovered pre stress levels, reactive individuals showed a significant higher level illustrating a modulation of stress recovery by coping style. Serotonin turnover ratio was higher in proactive and reactive individuals compared to intermediate individuals and a significant positive correlation was observed with cortisol levels whatever the coping style. Further, the confinement stress led to a general increase in the serotonin turnover comparable between coping styles. Stress150 had a significant effect on target mRNA copy number (Gapdh mRNA copy number decreased while ifrd1 mRNA copy number increased) and such changes tended to depend upon coping style.
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