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Fish biologists have long assumed a link between intestinal length and diet, and relative gut length or Zihler's index are often used to classify species into trophic groups. This has been done for specific fish taxa or specific ecosystems, but not for a global fish dataset. Here, we assess these relationships across a dataset of 468 fish species (254 marine, 191 freshwater, and 23 that occupy both habitats) in relation to body mass and fish length. Herbivores had significantly relatively stouter bodies and longer intestines than omni- and faunivores. Among faunivores, corallivores had longer intestines than invertivores, with piscivores having the shortest. There were no detectable differences between herbivore groups, possibly due to insufficient understanding of herbivorous fish diets. We propose that reasons for long intestines in fish include (i) difficult-to-digest items that require a symbiotic microbiome, and (ii) the dilution of easily digestible compounds with indigestible material (e.g., sand, wood, exoskeleton). Intestinal indices differed significantly between dietary groups, but there was substantial group overlap. Counter-intuitively, in the largest dataset, marine species had significantly shorter intestines than freshwater fish. These results put fish together with mammals as vertebrate taxa with clear convergence in intestine length in association with trophic level, in contrast to reptiles and birds, even if the peculiar feeding ecology of herbivorous fish is probably more varied than that of mammalian herbivores. Supplementary Information: The online version contains supplementary material available at 10.1007/s11160-024-09853-3.
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The gut microbiota of the marine herbivorous fish Kyphosus sydneyanus are thought to play an important role in host nutrition by supplying short-chain fatty acids (SCFAs) through fermentation of dietary red and brown macroalgae. Here, using 645 metagenome-assembled genomes (MAGs) from wild fish, we determined the capacity of different bacterial taxa to degrade seaweed carbohydrates along the gut. Most bacteria (99%) were unclassified at the species level. Gut communities and CAZyme-related transcriptional activity were dominated by Bacteroidia and Clostridia. Both classes possess genes CAZymes acting on internal polysaccharide bonds, suggesting their role initiating glycan depolymerization, followed by rarer Gammaproteobacteria and Verrucomicrobiae. Results indicate that Bacteroidia utilize substrates in both brown and red algae, whereas other taxa, namely, Clostridia, Bacilli, and Verrucomicrobiae, utilize mainly brown algae. Bacteroidia had the highest CAZyme gene densities overall, and Alistipes were especially enriched in CAZyme gene clusters (n = 73 versus just 62 distributed across all other taxa), pointing to an enhanced capacity for macroalgal polysaccharide utilization (e.g., alginate, laminarin, and sulfated polysaccharides). Pairwise correlations of MAG relative abundances and encoded CAZyme compositions provide evidence of potential inter-species collaborations. Co-abundant MAGs exhibited complementary degradative capacities for specific substrates, and flexibility in their capacity to source carbon (e.g., glucose- or galactose-rich glycans), possibly facilitating coexistence via niche partitioning. Results indicate the potential for collaborative microbial carbohydrate metabolism in the K. sydneyanus gut, that a greater variety of taxa contribute to the breakdown of brown versus red dietary algae, and that Bacteroidia encompass specialized macroalgae degraders.
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Due to their widespread production and known environmental contamination, the need for the detection and remediation of per- and polyfluoroalkyl substances (PFAS) has grown quickly. While destructive thermal treatment of PFAS at low temperatures (e.g., 200-500 °C) is of interest due to lower energy and infrastructure requirements, the range of possible degradation products remains underexplored. To better understand the low temperature decomposition of PFAS species, we have coupled gas-phase infrared spectroscopy with a multivariate curve resolution (MCR) analysis and a database of high-resolution PFAS infrared reference spectra to characterize and quantify a complex mixture resulting from potassium perfluorooctanesulfonate (PFOS-K) decomposition. Beginning at 375 °C, nine prevalent decomposition products (namely smaller perfluorocarbon species) are identified and quantified.
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Recuperação e Remediação Ambiental , Fluorocarbonos , Espectrofotometria Infravermelho , Fluorocarbonos/química , Fluorocarbonos/análise , Recuperação e Remediação Ambiental/métodos , Ácidos Alcanossulfônicos/química , Ácidos Alcanossulfônicos/análise , Poluentes Ambientais/química , Poluentes Ambientais/análise , TemperaturaRESUMO
Alzheimer's disease (AD) is a severe neurodegenerative disorder and the most common form of dementia in elderly individuals, characterized by memory deficits, cognitive decline, and neuropathology. The identification of preclinical markers for AD remains elusive. We employed an ultrasound-evoked spatial memory assay to investigate path integration (PI) in wild type C57BL/6â¯J and 5xFAD mice. We observed significant recruitment of the mammillary bodies (MB) and subiculum (Sub) - core regions of the Papez circuit during PI, as indicated by increased expression of the immediate early gene c-Fos in C57BL/6â¯J mice. In 5xFAD mice, amyloid-beta (Aß) vulnerability in the MB and Sub was evident at 3-months of age, preceding widespread pathology at 5-months of age. In parallel, we detected significant behavioral deficits in PI in the 5XFAD mice at 5- but not 3-months of age. Sex based analysis revealed a more profound deficit in males compared to females at 5-months of age. Our data suggest PI may be as an early indicator of AD, potentially associated with dysfunction within the Papez circuit.
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Doença de Alzheimer , Encéfalo , Humanos , Masculino , Feminino , Camundongos , Animais , Idoso , Lactente , Camundongos Transgênicos , Encéfalo/metabolismo , Camundongos Endogâmicos C57BL , Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/metabolismo , Modelos Animais de DoençasRESUMO
Due to a legacy originating in the limited capability of early computers, the spectroscopic resolution used in Fourier transform infrared spectroscopy and other systems has largely been implemented using only powers of two for more than 50 years. In this study, we investigate debunking the spectroscopic lore of, e.g., using only 2, 4, 8, or 16â cm-1 resolution and determine the optimal resolution in terms of both (i) a desired signal-to-noise ratio and (ii) efficient use of acquisition time. The study is facilitated by the availability of solids and liquids reference spectral data recorded at 2.0â cm-1 resolution and is based on an examination in the 4000-400â cm-1 range of 61 liquids and 70 solids spectra, with a total analysis of 4237 peaks, each of which was also examined for being singlet/multiplet in nature. Of the 1765 liquid bands examined, only 27 had widths <5â cm-1. Of the 2472 solid bands examined, only 39 peaks have widths <5â cm-1. For both the liquid and solid bands, a skewed distribution of peak widths was observed: For liquids, the mean peak width was 24.7â cm-1 but the median peak width was 13.7â cm-1, and, similarly, for solids, the mean peak width was 22.2â cm-1 but the median peak width was 11.2â cm-1. While recognizing other studies may differ in scope and limiting the analysis to only room temperature data, we have found that a resolution to resolve 95% of all bands is 5.7â cm-1 for liquids and 5.3â cm-1 for solids; such a resolution would capture the native linewidth (not accounting for instrumental broadening) for 95% of all the solids and liquid bands, respectively. After decades of measuring liquids and solids at 4, 8, or 16â cm-1 resolution, we suggest that, when accounting only for intrinsic linewidths, an optimized resolution of 6.0â cm-1 will capture 91% of all condensed-phase bands, i.e., broadening of only 9% of the narrowest of bands, but yielding a large gain in signal-to-noise with minimal loss of specificity.
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A Gram-stain-negative, non-spore-forming, rod-shaped, obligately anaerobic bacterium, designated strain BP5GT, was isolated from the hindgut of a silver drummer (Kyphosus sydneyanus) fish collected from the Hauraki Gulf, New Zealand. Phylogenetic analysis based on the 16S rRNA gene sequence indicated that the isolate belonged to the family Lachnospiraceae in the phylum Bacillota and was most closely related to Anaerotignum propionicum with 94.06â% sequence identity. Isolate BP5GT grew on agar medium containing mannitol and fish gut fluid as carbon sources. Clear colonies of approximately 1 mm diameter of the isolate grew within a week at 20-28â°C (optimum, 28â°C) and pH 7.6-8.5 (optimum, pH 8.5). Strain BP5GT was very sensitive to NaCl and the optimal concentration for growth was 0.045â% (w/v). Acetate and propionate were the major fermentation products. The major cellular fatty acids were C12â:â0, C14â:â0, C15â:â0 and C16â:â0. The genome sequence of the isolate was determined. Its G+C content was 38.41âmol% and the 71.41â% average nucleotide identity of the BP5GT genome to its closest neighbour with a sequenced genome (A. propionicum DSM 1682T) indicated low genomic relatedness. Based on the phenotypic and taxonomic characteristics observed in this study, a novel genus and species named Chakrabartyella piscis gen. nov., sp. nov. is proposed for isolate BP5GT (=ICMP 24687T=JCM 35769T).
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Ácidos Graxos , Perciformes , Animais , Ácidos Graxos/química , Filogenia , Composição de Bases , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Técnicas de Tipagem Bacteriana , DNA Bacteriano/genética , PeixesRESUMO
This article reviews the legal frameworks of diminished criminal responsibility in eighteen civil law jurisdictions across the globe-Brazil, Chile, China, the Czech Republic, Finland, France, Germany, Greece, Italy, Japan, Luxembourg, Poland, Portugal, Russia, Spain, Switzerland, Taiwan, and Turkey. Specifically, it reports the legal standards and main features of partial responsibility, associated penalty reductions, and potential dispositions following a partial responsibility finding. It also surveys empirical data on the prevalence of diminished responsibility as compared to criminal nonresponsibility. This article, which reflects contemporary penal codes and draws from both English and non-English sources, is the only known existing source to compile these partial responsibility standards or to delineate their precise sentencing consequences. It is also the only known source in English to describe Portugal's and Chile's treatment of diminished responsibility. Providing a comparative overview of graduated responsibility in nearly twenty countries invites global discussion on whether and how society should recognize partial responsibility, as well as the punitive and therapeutic consequences that should attend this finding.
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Criminosos , Humanos , França , Alemanha , Itália , EspanhaRESUMO
BACKGROUND: Gut microbiota play a key role in the nutrition of many marine herbivorous fishes through hindgut fermentation of seaweed. Gut microbiota composition in the herbivorous fish Kyphosus sydneyanus (family Kyphosidae) varies between individuals and gut sections, raising two questions: (i) is community composition stable over time, especially given seasonal shifts in storage metabolites of dietary brown algae, and (ii) what processes influence community assembly in the hindgut? RESULTS: We examined variation in community composition in gut lumen and mucosa samples from three hindgut sections of K. sydneyanus collected at various time points in 2020 and 2021 from reefs near Great Barrier Island, New Zealand. 16S rRNA gene analysis was used to characterize microbial community composition, diversity and estimated density. Differences in community composition between gut sections remained relatively stable over time, with little evidence of temporal variation. Clostridia dominated the proximal hindgut sections and Bacteroidia the most distal section. Differences were detected in microbial composition between lumen and mucosa, especially at genus level. CONCLUSIONS: High variation in community composition and estimated bacterial density among individual fish combined with low variation in community composition temporally suggests that initial community assembly involved environmental selection and random sampling/neutral effects. Community stability following colonisation could also be influenced by historical contingency, where early colonizing members of the community may have a selective advantage. The impact of temporal changes in the algae may be limited by the dynamics of substrate depletion along the gut following feeding, i.e. the depletion of storage metabolites in the proximal hindgut. Estimated bacterial density, showed that Bacteroidota has the highest density (copies/mL) in distal-most lumen section V, where SCFA concentrations are highest. Bacteroidota genera Alistipes and Rikenella may play important roles in the breakdown of seaweed into useful compounds for the fish host.
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Microbioma Gastrointestinal , Perciformes , Animais , RNA Ribossômico 16S/genética , Peixes/microbiologia , Sistema Digestório , Bactérias/genética , Bacteroidetes/genéticaRESUMO
Using the context of an intimate partner homicide trial, the study explored the effects of defendant gender and age on mock-jurors' verdicts, sentences, and culpability ratings-and whether defendant credibility and juror anger mediate these effects. The study used a 2 (Defendant Gender: male vs. female) × 3 (Defendant Age: 25, 45, or 65 years) between-subjects design. Participants (N = 513 community members) completed the experiment online. Participants were randomly assigned to one of the six Defendant Gender × Age Conditions. Participants read the trial transcripts that included the age and gender manipulations, provided verdicts and sentences, and completed the following measures: culpability, anger, credibility, and manipulation checks. Consistent with our hypotheses mock-jurors were more likely to find the male defendant guilty and give him longer sentences than the female defendant. Additionally, when the defendant was male (vs. female) mock-jurors provided higher anger ratings and rated the defendant as more culpable in the victim's death. Also consistent with our hypotheses, mock-jurors were more likely to find the youngest defendant guilty and view him as more culpable and less credible than the oldest defendant. The mechanisms responsible for jurors' biased decisions varied as a function of the extra-legal variable (defendant gender vs. age). The defendant age effect was mediated by defendant credibility and the gender effect by juror anger. A defendant's right to a fair trial is dependent on a court's ability to limit extra-legal variables from influencing jurors' decisions. Understanding the mechanism responsible for such bias is required before the courts can effectively remedy bias.
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Culpa , Homicídio , Feminino , Humanos , Masculino , Ira , Direito Penal , Tomada de Decisões , Julgamento , Função Jurisdicional , Adulto , Pessoa de Meia-Idade , IdosoRESUMO
Metacognition is the process by which we know what we know. Knowing has both declarative and sensed components. Differences exist in the information that moves to our conscious awareness and how it is synthesised with existing knowledge. The current study measured metacognition by extending a visual change detection paradigm that promoted explicit or implicit detection by either a local or global manipulation of a scene. A within-subjects design was used to investigate how 91 participants detected change and made metacognitive judgements. Cognitive modelling, based on confidence judgements, estimated the relative contributions of discrete and continuous cognitive processes to change detection, and to metacognition. Metacognition was sensitive to both the discrete and continuous processes underlying change detection, but was more sensitive to the discrete process. These results demonstrate that metacognition attunes confidence differentially to explicit and implicit processes, and support direct-access theories for discrete processing and meta-representation theories for continuous processing.
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Metacognição , Humanos , JulgamentoRESUMO
During the COVID-19 pandemic, healthcare workers (HCW) were categorized as "essential" and "non-essential", creating a division where some were "locked-in" a system with little ability to prepare for or control the oncoming crisis. Others were "locked-out" regardless of whether their skills might be useful. The purpose of this study was to systematically gather data over the course of the COVID-19 pandemic from HCW through an interprofessional lens to examine experiences of locked-out HCW. This convergent parallel mixed-methods study captured perspectives representing nearly two dozen professions through a survey, administered via social media, and video blogs. Analysis included logistic regression models of differences in outcome measures by professional category and Rapid Identification of Themes from Audio recordings (RITA) of video blogs. We collected 1299 baseline responses from 15 April 2020 to 16 March 2021. Of those responses, 12.1% reported no signs of burnout, while 21.9% reported four or more signs. Qualitative analysis identified four themes: (1) professional identity, (2) intrinsic stressors, (3) extrinsic factors, and (4) coping strategies. There are some differences in the experiences of locked-in and locked-out HCW. This did not always lead to differing reports of moral distress and burnout, and both groups struggled to cope with the realities of the pandemic.
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Esgotamento Profissional , COVID-19 , Humanos , COVID-19/epidemiologia , Pandemias , Adaptação Psicológica , Blogging , Pessoal de SaúdeRESUMO
A spectral analysis tool has been developed to interactively identify and quantify individual gas-phase species from complex infrared absorbance spectra obtained from laboratory or field data. The SpecQuant program has an intuitive graphical interface that accommodates both reference and experimental data with varying resolution and instrumental lineshape, as well as algorithms to readily align the wavenumber axis of a sample spectrum with the raster of a reference spectrum. Using a classical least squares model in conjunction with reference spectra such as those from the Pacific Northwest National Laboratory (PNNL) gas-phase infrared database or simulated spectra derived from the HITRAN line-by-line database, the mixing ratio of each identified species is determined along with its associated estimation error. After correcting the wavelength and intensity of the field data, SpecQuant displays the calculated mixing ratio versus the experimental data for each analyte along with the residual spectrum with any or all analyte fits subtracted for visual inspection of the fit and residuals. The software performance for multianalyte quantification was demonstrated using moderate resolution (0.5â cm-1) infrared spectra that were collected during the time-resolved infrared photolysis of methyl iodide.
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Algoritmos , Software , Espectroscopia de Infravermelho com Transformada de FourierRESUMO
In degraded coral reef ecosystems, allelopathic macroalgae have received increasing attention from marine ecologists because their secondary metabolites (also known as allelochemicals) kill corals that grow adjacent to them and weaken the recovery of degraded reefs. One well-known coral-killing macroalga is the calcareous red seaweed Galaxaura. However, our knowledge of how coral reef fishes interact with allelopathic algae like Galaxaura is very limited. Here, we documented novel observations of feeding interactions of 17 species of coral reef fishes (herbivorous and carnivorous) with the filamentous Galaxaura divaricata on degraded lagoon patch reefs in Dongsha Atoll (South China Sea). Video analyses showed that territorial farming damselfishes (i.e., Dischistodus perspicillatus, D. prosopotaenia, Hemiglyphidodon plagiometopon, Pomacentrus grammorhynchus, P. adelus, and Neoglyphidodon nigroris) and juvenile parrotfishes (Scarus schlegeli, S. ghobban, S. rivulatus, and Chlorurus spilurus) likely used G. divaricata as a feeding substratum. Further, microscopic analyses revealed that the filamentous surface of G. divaricata harbored a wealth of epiphytic microalgae, such as filamentous cyanobacteria (i.e., Leptolyngbya, Lyngbya, Rivularia, Oscillatoria, and Stigonema), diatoms (i.e., Synedra, Nitzschia, Mastogloia, and Pleurosigma), and filamentous red algae (i.e., Heterosiphonia), suggesting that these fishes targeted the nutrient-rich microscopic epiphytes rather than the nutrient-poor host. Juvenile benthic carnivores (i.e., Labridae, Parupeneus multifasciatus, and Meiacanthus grammistes) form feeding assemblages with roving parrotfishes to feed on small invertebrates (i.e., amphipods, copepods, isopods, gastropods, and polychaetes) associated with G. divaricata. Given that coral reef fishes appear to target the epiphytes associated with Galaxaura rather than the alga itself, these observations thus substantiate the threat posed by the overgrowth of G. divaricata to coral recovery in degraded reef systems due to the lack of natural grazers.
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Symbiotic gut microbiota in the herbivorous marine fish Kyphosus sydneyanus play an important role in digestion by converting refractory algal carbohydrate into short-chain fatty acids. Here we characterised community composition using both 16S rRNA gene amplicon sequencing and shotgun-metagenome sequencing. Sequencing was carried out on lumen and mucosa samples (radial sections) from three axial sections taken from the hindgut of wild-caught fish. Both lumen and mucosa communities displayed distinct distributions along the hindgut, likely an effect of the differing selection pressures within these hindgut locations, as well as considerable variation among individual fish. In contrast, metagenomic sequences displayed a high level of functional similarity between individual fish and gut sections in the relative abundance of genes (based on sequencing depth) that encoded enzymes involved in algal-derived substrate degradation. These results suggest that the host gut environment selects for functional capacity in symbionts rather than taxonomic identity. Functional annotation of the enzymes encoded by the gut microbiota was carried out to infer the metabolic pathways used by the gut microbiota for the degradation of important dietary substrates: mannitol, alginate, laminarin, fucoidan and galactan (e.g. agar and carrageenan). This work provides the first evidence of the genomic potential of K. sydneyanus hindgut microbiota to convert highly refractory algal carbohydrates into metabolically useful short-chain fatty acids.
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Microbioma Gastrointestinal , Microbiota , Perciformes , Animais , Ácidos Graxos Voláteis/farmacologia , Peixes/genética , Perciformes/genética , RNA Ribossômico 16S/genéticaRESUMO
A Gram-stain-positive, non-spore-forming, rod-shaped, obligately anaerobic bacterium, designated strain BP52GT, was isolated from the hindgut of a Silver Drummer (Kyphosus sydneyanus) fish collected from the Hauraki Gulf, New Zealand. Phylogenetic analysis based on 16S rRNA gene sequencing indicated that the isolate belonged to the family Erysipelotrichaceae in the phylum Firmicutes and was most closely related to Clostridium saccharogumia with 93.3â% sequence identity. Isolate BP52GT grew on agar medium containing mannitol as the sole carbon source. White, opaque and shiny colonies of the isolate measuring approximately 1 mm diameter grew within a week at 20-28 °C (optimum, 24 °C) and pH 6.9-8.5 (optimum, pH 7.8). BP52GT tolerated the addition of up to 1â% NaCl to the medium. Formate and acetate were the major fermentation products. The major cellular fatty acids were C16â:â0, C16:1n-7t and C18:1n-7t. The genome sequence of the isolate was determined. Its G+C content was 30.7 mol%, and the 72.65â% average nucleotide identity of the BP52GT genome to its closest neighbour with a completely sequenced genome (Erysipelatoclostridium ramosum JCM 1298T) indicated low genomic relatedness. Based on the phenotypic and taxonomic characteristics observed in this study, a novel genus and species Tannockella kyphosi gen. nov., sp. nov. is proposed for isolate BP52GT (=NZRM 4757T=JCM 34692T).
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Cifose , Tenericutes , Animais , Técnicas de Tipagem Bacteriana , Composição de Bases , DNA Bacteriano/genética , Ácidos Graxos/química , Firmicutes , Bacilos Gram-Positivos/genética , Filogenia , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Tenericutes/genéticaRESUMO
Abalone around the world are subject to increasing frequency of marine heatwaves, yet we have a limited understanding of how acute high temperature events impact the physiology of these commercially and ecologically important species. This study examines the impact of a 5 °C temperature increase over ambient conditions for six weeks on the metabolic rates, digestive enzyme activities in the digestive gland, and digestive efficiency of Red Abalone (Haliotis rufescens) and Paua (H. iris) on their natural diets. We test the hypothesis that abalone digestive function can keep pace with this increased metabolic demand in two separate experiments, one for each species. H. iris had higher food intake in the heat treatment. Both species had higher metabolic rates in the heat treatment with Q10 = 1.73 and Q10 = 2.46 for H. rufescens and H. iris, respectively. Apparent organic matter digestibility, protein digestibility, and carbohydrate digestibility did not differ between the heat treatment and the ambient (control) treatment in either experiment. H. rufescens exhibited higher maltase, alanine-aminopeptidase, and leucine-aminopeptidase activities in the heat treatment. Amylase, ß-glucosidase, trypsin, and alkaline phosphatase activities in the digestive gland tissue did not differ between temperature treatments. H. iris exhibited lower amylase and ß-glucosidase activities in the heat treatment, while maltase, trypsin, leucine-aminopeptidase, and alkaline phosphatase activities did not differ between treatments. We conclude that over six weeks of moderate heat stress both abalone species were able to maintain digestive function, but achieved this maintenance in species-specific ways.
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Celulases , Gastrópodes , Fosfatase Alcalina/metabolismo , Aminopeptidases/metabolismo , Amilases/metabolismo , Animais , Celulases/metabolismo , Gastrópodes/metabolismo , Resposta ao Choque Térmico , Leucina/metabolismo , Tripsina/metabolismo , alfa-Glucosidases/metabolismoRESUMO
We combine high field polarization, magneto-infrared spectroscopy, and lattice dynamics calculations with prior magnetization to explore the properties of (NH4)2[FeCl5·(H2O)]âa type II molecular multiferroic in which the mixing between charge, structure, and magnetism is controlled by intermolecular hydrogen and halogen bonds. Electric polarization is sensitive to the series of field-induced spin reorientations, increasing linearly with the field and reaching a maximum before collapsing to zero across the quasi-collinear to collinear-sinusoidal reorientation due to the restoration of inversion symmetry. Magnetoelectric coupling is on the order of 1.2 ps/m for the Pâ¥c, Hâ¥c configuration between 5 and 25 T at 1.5 K. In this range, the coupling takes place via an orbital hybridization mechanism. Other forms of mixing are active in (NH4)2[FeCl5·(H2O)] as well. Magneto-infrared spectroscopy reveals that all of the vibrational modes below 600 cm-1 are sensitive to the field-induced transition to the fully saturated magnetic state at 30 T. We analyze these local lattice distortions and use frequency shifts to extract spin-phonon coupling constants for the Fe-O stretch, Fe-OH2 rock, and NH4+ libration. Inspection also reveals subtle symmetry breaking of the ammonium counterions across the ferroelectric transition. The coexistence of such varied mixing processes in a platform with intermolecular hydrogen- and halogen-bonding opens the door to greater understanding of multiferroics and magnetoelectrics governed by through-space interactions.
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Many marine herbivorous fishes harbour diverse microbial communities in the hindgut that can play important roles in host health and nutrition. Kyphosus sydneyanus is a temperate marine herbivorous fish that feeds predominantly on brown seaweeds. We employed 16S rRNA gene amplicon sequencing and gas chromatography to characterize microbial communities and their metabolites in different hindgut regions of six K. sydneyanus. Measurements were confined to three distal sections of the intestine, labelled III, IV and V from anterior to posterior. A total of 625 operational taxonomic units from 20 phyla and 123 genera were obtained. Bacteroidota, Firmicutes and Proteobacteria were the major phyla in mean relative abundance, which varied along the gut. Firmicutes (76%) was the most dominant group in section III, whereas Bacteroidota (69.3%) dominated section V. Total short-chain fatty acid (SCFA) concentration was highest in sections IV and V, confirming active fermentation in these two most distal sections. The abundance of Bacteroidota correlated with propionate concentration in section V, while Firmicutes positively correlated with formate in sections III and IV. Acetate levels were highest in sections IV and V, which correlated with abundance of Bacteroidota. Despite differences in gut microbial community composition, SCFA profiles were consistent between individual fish in the different hindgut regions of K. sydneyanus, although proportions of SCFAs differed among gut sections. These findings demonstrate functional compartmentalization of the hindgut microbial community, highlighting the need for regional sampling when interpreting overall microbiome function. These results support previous work suggesting that hindgut microbiota in marine herbivorous fish are important to nutrition in some host species by converting dietary carbohydrates into metabolically useful SCFAs.
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Bactérias , Microbiota , Animais , Bacteroidetes/genética , Ácidos Graxos Voláteis/metabolismo , Fermentação , Firmicutes , Peixes/genética , Microbiota/genética , RNA Ribossômico 16S/genéticaRESUMO
The intestinal microbiota contributes to energy metabolism, but the molecular mechanisms involved remain less clear. Bacteria of the genus Bacillus regulate lipid metabolism in the host and are thus commonly used as beneficial probiotic supplements. In the present study, Bacillus licheniformis FA6 was selected to assess its role in modulating lipid metabolism of zebrafish (Danio rerio). Combining 16S rRNA high-throughput sequencing, micro-CT scan, metabolic parameters measurement, and gene expression analysis, we demonstrated that B. licheniformis FA6 changed the gut microbiota composition of zebrafish and increased both the Firmicutes/Bacteroidetes ratio and lipid accumulation. In terms of metabolites, B. licheniformis FA6 appeared to promote acetate production, which increased acetyl-CoA levels and promoted lipid synthesis in the liver. In contrast, addition of B. licheniformis lowered carnitine levels, which in turn reduced fatty acid oxidation in the liver. At a molecular level, B. licheniformis FA6 upregulated key genes regulating de novo fatty acid synthesis and downregulated genes encoding key rate-limiting enzymes of fatty acid ß-oxidation, thereby promoting lipid synthesis and reducing fatty acid oxidation. Generally, our results reveal that B. licheniformis FA6 promotes lipid accumulation in zebrafish through improving lipid synthesis and reducing ß-oxidation.