Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 23
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Food Funct ; 12(20): 9680-9692, 2021 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-34664589

RESUMO

Cocoa is a highly consumed food with beneficial effects on human health. Cocoa roasting has an important influence on its sensory and nutritional characteristics; therefore, roasting could also play a role in cocoa bioactivity. Thus, the aim of this paper is to unravel the effect of cocoa roasting conditions on its antioxidant capacity and modifications of gut microbiota after in vitro digestion-fermentation. HMF and furfural, chemical markers of non-enzymatic browning, were analyzed in unroasted and roasted cocoa powder at different temperatures, as well as different chocolates. The antioxidant capacity decreased with roasting, most probably due to the loss of phenolic compounds during heating. In the case of the evaluated chocolates, the antioxidant capacity was 2-3 times higher in the fermented fraction. On the other hand, HMF and furfural content increased during roasting due to increasing temperatures. Moreover, unroasted and roasted cocoa powder have different effects on gut microbial communities. Roasted cocoa favored butyrate production, whereas unroasted cocoa favored acetate and propionate production in a significant manner. In addition, unroasted and roasted cocoa produced significantly different gut microbial communities in terms of composition. Although many bacteria were affected, Veillonella and Faecalibacterium were some of the most discriminant ones; whereas the former is a propionate producer, the latter is a butyrate producer that has also been linked to positive effects on the inflammatory health of the gut and the immune system. Therefore, unroasted and roasted cocoa (regardless of the roasting temperature) promote different bacteria and a different SCFA production.

2.
Front Immunol ; 12: 683028, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34025683

RESUMO

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease with no therapeutic consensus. Oxidation and inflammation are hallmarks in the progression of this complex disease, which also involves interactions between the genetic background and the environment. Mastiha is a natural nutritional supplement known to possess antioxidant and anti-inflammatory properties. This study investigated how a 6-month Mastiha supplementation (2.1 g/day) could impact the antioxidant and inflammatory status of patients with NAFLD, and whether genetic variants significantly mediate these effects. We recruited 98 patients with obesity (BMI ≥ 30 kg/m2) and NAFLD and randomly allocated them to either the Mastiha or the placebo group for 6 months. The anti-oxidative and inflammatory status was assessed at baseline and post-treatment. Genome-wide genetic data was also obtained from all participants, to investigate gene-by-Mastiha interactions. NAFLD patients with severe obesity (BMI > 35kg/m2) taking the Mastiha had significantly higher total antioxidant status (TAS) compared to the corresponding placebo group (P value=0.008). We did not observe any other significant change in the investigated biomarkers as a result of Mastiha supplementation alone. We identified several novel gene-by-Mastiha interaction associations with levels of cytokines and antioxidant biomarkers. Some of the identified genetic loci are implicated in the pathological pathways of NAFLD, including the lanosterol synthase gene (LSS) associated with glutathione peroxidase activity (Gpx) levels, the mitochondrial pyruvate carrier-1 gene (MPC1) and the sphingolipid transporter-1 gene (SPNS1) associated with hemoglobin levels, the transforming growth factor-beta-induced gene (TGFBI) and the micro-RNA 129-1 (MIR129-1) associated with IL-6 and the granzyme B gene (GZMB) associated with IL-10 levels. Within the MAST4HEALTH randomized clinical trial (NCT03135873, www.clinicaltrials.gov) Mastiha supplementation improved the TAS levels among NAFLD patients with severe obesity. We identified several novel genome-wide significant nutrigenetic interactions, influencing the antioxidant and inflammatory status in NAFLD. Clinical Trial Registration: ClinicalTrials.gov, identifier NCT03135873.


Assuntos
Anti-Inflamatórios/uso terapêutico , Antioxidantes/uso terapêutico , Suplementos Nutricionais , Resina Mástique/química , Hepatopatia Gordurosa não Alcoólica/tratamento farmacológico , Hepatopatia Gordurosa não Alcoólica/metabolismo , Nutrigenômica , Adulto , Idoso , Anti-Inflamatórios/administração & dosagem , Antioxidantes/administração & dosagem , Biomarcadores , Gerenciamento Clínico , Suscetibilidade a Doenças , Feminino , Predisposição Genética para Doença , Humanos , Masculino , Pessoa de Meia-Idade , Hepatopatia Gordurosa não Alcoólica/diagnóstico , Hepatopatia Gordurosa não Alcoólica/etiologia , Nutrigenômica/métodos , Estresse Oxidativo/efeitos dos fármacos , Adulto Jovem
3.
Front Microbiol ; 12: 625782, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33796085

RESUMO

Food and food bioactive components are major drivers of modulation of the human gut microbiota. Tannin extracts consist of a mix of bioactive compounds, which are already exploited in the food industry for their chemical and sensorial properties. The aim of our study was to explore the viability of associations between tannin wood extracts of different origin and food as gut microbiota modulators. 16S rRNA amplicon next-generation sequencing (NGS) was used to test the effects on the gut microbiota of tannin extracts from quebracho, chestnut, and tara associated with commercial food products with different composition in macronutrients. The different tannin-enriched and non-enriched foods were submitted to in vitro digestion and fermentation by the gut microbiota of healthy subjects. The profile of the short chain fatty acids (SCFAs) produced by the microbiota was also investigated. The presence of tannin extracts in food promoted an increase of the relative abundance of the genus Akkermansia, recognized as a marker of a healthy gut, and of various members of the Lachnospiraceae and Ruminococcaceae families, involved in SCFA production. The enrichment of foods with tannin extracts had a booster effect on the production of SCFAs, without altering the profile given by the foods alone. These preliminary results suggest a positive modulation of the gut microbiota with potential benefits for human health through the enrichment of foods with tannin extracts.

4.
Mol Nutr Food Res ; 65(10): e2001178, 2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-33629536

RESUMO

SCOPE: Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease with poor therapeutic strategies. Mastiha possesses antioxidant/anti-inflammatory and lipid-lowering properties. The authors investigate the effectiveness of Mastiha as a nonpharmacological intervention in NAFLD. METHODS AND RESULTS: Ninety-eight patients with NAFLD in three countries (Greece, Italy, Serbia) are randomly allocated to either Mastiha or Placebo for 6 months, as part of a multicenter, randomized, double-blind, placebo-controlled, parallel-group clinical trial. The authors assess NAFLD severity via magnetic resonance imaging (MRI) scanning and LiverMultiScan technique and evaluate the effectiveness of Mastiha through medical, anthropometric, biochemical, metabolomic, and microbiota assessment. Mastiha is not superior to Placebo on changes in iron-corrected T1 (cT1) and Liver Inflammation Fibrosis score (LIF) in entire patient population; however, after BMI stratification (BMI ≤ 35 kg m-2 and BMI > 35 kg m-2 ), severely obese patients show an improvement in cT1 and LIF in Mastiha versus Placebo. Mastiha increases dissimilarity of gut microbiota, as shown by the Bray-Curtis index, downregulates Flavonifractor, a known inflammatory taxon and decreases Lysophosphatidylcholines-(LysoPC) 18:1, Lysophosphatidylethanolamines-(LysoPE) 18:1, and cholic acid compared to Placebo. CONCLUSION: Mastiha supplementation improves microbiota dysbiosis and lipid metabolite levels in patients with NAFLD, although it reduces parameters of liver inflammation/fibrosis only in severely obese patients.


Assuntos
Resina Mástique/administração & dosagem , Hepatopatia Gordurosa não Alcoólica/tratamento farmacológico , Adulto , Idoso , Índice de Massa Corporal , Suplementos Nutricionais , Método Duplo-Cego , Disbiose/tratamento farmacológico , Feminino , Microbioma Gastrointestinal/efeitos dos fármacos , Grécia , Humanos , Itália , Fígado/patologia , Masculino , Pessoa de Meia-Idade , Hepatopatia Gordurosa não Alcoólica/microbiologia , Hepatopatia Gordurosa não Alcoólica/fisiopatologia , Obesidade/complicações , Placebos , Sérvia
6.
Mol Nutr Food Res ; 63(24): e1900927, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31599067

RESUMO

SCOPE: As a result of the obesity epidemic, the prevalence of non-alcoholic steatohepatitis (NASH) is increasing. No drug is approved for the treatment of NASH. In this study, the effect of a nutritional supplement, Mastiha or Chios mastic gum, on metabolic and histological parameters and on the gut microbiome in mice with NASH and fibrosis was investigated. METHODS AND RESULTS: Advanced NASH was induced by feeding C57BL/6J mice a diet rich in fat, sucrose, and cholesterol for 41 weeks. After randomization, animals received the NASH-inducing diet with or without 0.2% (w/w) Mastiha for a further 8 weeks. Disease activity was assessed by liver histology and determination of plasma transaminase activities. Fecal microbiota DNA extraction and 16S rRNA amplicon sequencing were used to determine the composition of the gut microbiome. Mastiha supplementation led to a significant reduction in circulating alanine aminotransferase (ALT) activity, improvement in hepatic steatosis and collagen content, and a reduction in NAFLD activity score. Furthermore, it resulted in a partial but significant recovery of gut microbiota diversity and changes in identity and abundance of specific taxa. CONCLUSION: This is the first study demonstrating an improvement in disease activity in mice with advanced NASH with fibrosis by a diet containing Mastiha.


Assuntos
Microbioma Gastrointestinal , Cirrose Hepática/dietoterapia , Hepatopatia Gordurosa não Alcoólica/dietoterapia , Pistacia , Animais , Biópsia , Composição Corporal , Dieta Hiperlipídica , Modelos Animais de Doenças , Ingestão de Alimentos , Fezes/microbiologia , Regulação da Expressão Gênica/efeitos dos fármacos , Cirrose Hepática/patologia , Masculino , Camundongos Endogâmicos C57BL , Hepatopatia Gordurosa não Alcoólica/microbiologia , Hepatopatia Gordurosa não Alcoólica/patologia
7.
Front Microbiol ; 10: 848, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31105659

RESUMO

Predicting the metabolic behavior of the human gut microbiota in different contexts is one of the most promising areas of constraint-based modeling. Recently, we presented a supra-organismal approach to build context-specific metabolic networks of bacterial communities using functional and taxonomic assignments of meta-omics data. In this work, this algorithm is applied to elucidate the metabolic changes induced over the first year after birth in the gut microbiota of a cohort of Spanish infants. We used metagenomics data of fecal samples and nutritional data of 13 infants at five time points. The resulting networks for each time point were analyzed, finding significant alterations once solid food is introduced in the diet. Our work shows that solid food leads to a different pattern of output metabolites that can be potentially released from the gut microbiota to the host. Experimental validation is presented for ferulate, a neuroprotective metabolite involved in the gut-brain axis.

8.
J Agric Food Chem ; 67(9): 2500-2509, 2019 Mar 06.
Artigo em Inglês | MEDLINE | ID: mdl-30724071

RESUMO

Coffee is one of the most consumed beverages around the world, and as a consequence, spent coffee grounds are a massively produced residue that is causing environmental problems. Reusing them is a major focus of interest presently. We extracted mannooligosaccharides (MOS) from spent coffee grounds and submitted them to an in vitro fermentation with human feces. Results obtained suggest that MOS are able to exert a prebiotic effect on gut microbiota by stimulating the growth of some beneficial genera, such as Barnesiella, Odoribacter, Coprococcus, Butyricicoccus, Intestinimonas, Pseudoflavonifractor, and Veillonella. Moreover, short-chain fatty acids (SCFA) production also increased in a dose-dependent manner. However, we observed that 5-(hydroxymethyl)furfural, furfural, and polyphenols (which are either produced or released from the spent coffee grounds matrix during hydrolysis) could have an inhibitory effect on other beneficial genera, such as Faecalibacterium, Ruminococcus, Blautia, Butyricimonas, Dialister, Collinsella, and Anaerostipes, which could negatively affect the prebiotic activity of MOS.


Assuntos
Coffea , Microbioma Gastrointestinal/efeitos dos fármacos , Manose/farmacologia , Oligossacarídeos/farmacologia , Extratos Vegetais/farmacologia , Sementes/química , Bactérias/efeitos dos fármacos , Bactérias/crescimento & desenvolvimento , Café/química , Relação Dose-Resposta a Droga , Ácidos Graxos Voláteis/biossíntese , Fezes/microbiologia , Fermentação , Humanos , Extratos Vegetais/química , Prebióticos/administração & dosagem
9.
EBioMedicine ; 39: 497-509, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30415891

RESUMO

BACKGROUND: The relationship between the gut microbiome and the human host is dynamic and we may expect adjustments in microbiome function if host physiology changes. Metatranscriptomic approaches should be key in unraveling how such adjustments occur. METHODS: We employ metatranscriptomic sequencing analyses to study gene expression in the gut microbiota of infants through their first year of life, and of their mothers days before delivery and one year afterwards. FINDINGS: In infants, hallmarks of aerobic metabolism disappear from the microbial metatranscriptome as development proceeds, while the expression of functions related to carbohydrate transport and metabolism increases and diversifies, approaching that observed in non-pregnant women. Butyrate synthesis enzymes are overexpressed at three months of age, even though most butyrate-producing organisms are still rare. In late pregnancy, the microbiota readjusts the expression of carbohydrate-related functions in a manner consistent with a high availability of glucose. INTERPRETATION: Our findings suggest that butyrate production may be ensured in the gut of young infants before the typical butyrate synthesizers of the adult gut become abundant. The late pregnancy gut microbiota may be able to access the high levels of blood glucose characteristic of this period. Moreover, late pregnancy gut bacteria may reach stationary phase, which may affect their likelihood of translocating across the intestinal epithelium. FUNDS: This work was supported by grants CSD2009-00006 (CONSOLIDER Program) and SAF2009-13032-C02-02 from MICINN (Ministry of Science and Innovation, Spain), and by grant SAF2012-31187 from MINECO (Ministry of Economics and Competitiveness, Spain).


Assuntos
Bactérias/genética , Proteínas de Bactérias/genética , Butiratos/metabolismo , Fezes/microbiologia , Perfilação da Expressão Gênica/métodos , Adulto , Bactérias/classificação , Bactérias/metabolismo , Feminino , Microbioma Gastrointestinal , Regulação Bacteriana da Expressão Gênica , Humanos , Lactente , Recém-Nascido , Metabolismo dos Lipídeos , Masculino , Idade Materna , Gravidez , Terceiro Trimestre da Gravidez , Análise de Sequência de RNA/métodos
10.
J Agric Food Chem ; 66(43): 11500-11509, 2018 Oct 31.
Artigo em Inglês | MEDLINE | ID: mdl-30346155

RESUMO

Cooking modifies food composition due to chemical reactions. Additionally, food composition shapes the human gut microbiota. Thus, the objective of this research was to unravel the effect of different food cooking methods on the structure and functionality of the gut microbiota. Common culinary techniques were applied to five foods, which were submitted to in vitro digestion-fermentation. Furosine, 5-(hydroxymethyl)furfural, and furfural were used as Maillard reaction indicators to control the heat treatment. Short-chain fatty acids production was quantified as indicator of healthy metabolic output. Gut microbial community structure was analyzed through 16S rRNA. Both food composition and cooking methods modified the microbiota composition and released short-chain fatty acids. In general, intense cooking technologies (roasting and grilling) increased the abundance of beneficial bacteria like Ruminococcus spp. or Bifidobacterium spp. compared to milder treatments (boiling). However, for some foods (banana or bread), intense cooking decreased the levels of healthy bacteria.


Assuntos
Culinária , Microbioma Gastrointestinal , Temperatura Alta , Bactérias/classificação , Grão Comestível , Fabaceae , Ácidos Graxos Voláteis/análise , Fermentação , Frutas , Furaldeído/análogos & derivados , Furaldeído/análise , Humanos , Lisina/análogos & derivados , Lisina/análise , Reação de Maillard , Carne , RNA Ribossômico 16S/genética , Verduras
11.
Curr Environ Health Rep ; 5(4): 512-521, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30269309

RESUMO

PURPOSE OF REVIEW: We review how an altered microbiome in early life impacts on immune, metabolic, and neurological development, focusing on some of the most widespread diseases related to each of these processes, namely atopic disease, obesity, and autism. RECENT FINDINGS: The early development of the microbial communities that inhabit the human body is currently challenged by factors that range from reduced exposure to microbes, antibiotic use, and poor dietary choices to widespread environmental pollution. Recent work has highlighted some of the long-term consequences that early alterations in the establishment of these microbiotas can have for different aspects of human development and health. The long-term consequences of early microbiome alterations for human development and health are only beginning to be understood and will require in-depth investigation in the years to come. A solid understanding of how present day environmental conditions alter microbiome development, and of how an altered microbiome in early life impacts on life-long health, should inform both public health policies and the development of dietary and medical strategies to counteract early microbiota imbalances.


Assuntos
Microbioma Gastrointestinal/fisiologia , Sistema Imunitário/microbiologia , Microbiota , Efeitos Tardios da Exposição Pré-Natal/metabolismo , Poluição do Ar/efeitos adversos , Feminino , Trato Gastrointestinal/microbiologia , Humanos , Intestinos/microbiologia , Doenças Metabólicas/metabolismo , Gravidez
12.
Ann Nutr Metab ; 73 Suppl 3: 12-16, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30041189

RESUMO

BACKGROUND: The process of early gut colonization is extremely variable among individuals and is influenced by numerous factors. Among these, the mode of birth will strongly shape the early microbial exposure and immune environment of the neonate. SUMMARY: Here, I review how the concomitant processes of microbiota and immune system development are altered by C-section delivery and the effects of such alterations on long-term health. Key messages: C-section delivery impinges on microbiota and immune system development through various means: (i) if labor is lacking, intrauterine immune responses dependent on this process will not occur, affecting the immune environment of the neonate; (ii) the lack of exposure to the vaginal and fecal microbes of the mother will alter the type and diversity of the microbes that colonize the gut at birth; (iii) the different starting points in terms of microbial exposure and immune environment will mark the course of microbiota and immune system development during the first months of life, generating multiple feedbacks between these 2 processes. Given that the first months of life represent a crucial time window in the ontogenesis of the immune system and the establishment of tolerance, C-section delivery will impact on the lifelong risk of developing immune disease.


Assuntos
Cesárea , Microbioma Gastrointestinal , Sistema Imunitário/microbiologia , Parto Obstétrico , Fezes/microbiologia , Feminino , Humanos , Recém-Nascido , Gravidez , Vagina/microbiologia
14.
Pathogens ; 3(3): 769-90, 2014 Sep 24.
Artigo em Inglês | MEDLINE | ID: mdl-25438024

RESUMO

In recent years, the increase in human microbiome research brought about by the rapidly evolving "omic" technologies has established that the balance among the microbial groups present in the human gut, and their multipronged interactions with the host, are crucial for health. On the other hand, epidemiological and experimental support has also grown for the 'early programming hypothesis', according to which factors that act in utero and early in life program the risks for adverse health outcomes later on. The microbiota of the gut develops during infancy, in close interaction with immune development, and with extensive variability across individuals. It follows that the specific process of gut colonization and the microbe-host interactions established in an individual during this period have the potential to represent main determinants of life-long propensity to immune disease. Although much remains to be learnt on the progression of events by which the gut microbiota becomes established and initiates its intimate relationships with the host, and on the long-term repercussions of this process, recent works have advanced significatively in this direction.

15.
PLoS Genet ; 10(6): e1004406, 2014 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-24901968

RESUMO

In spite of its major impact on life-long health, the process of microbial succession in the gut of infants remains poorly understood. Here, we analyze the patterns of taxonomic and functional change in the gut microbiota during the first year of life for a birth cohort of 13 infants. We detect that individual instances of gut colonization vary in the temporal dynamics of microbiota richness, diversity, and composition at both functional and taxonomic levels. Nevertheless, trends discernible in a majority of infants indicate that gut colonization occurs in two distinct phases of succession, separated by the introduction of solid foods to the diet. This change in resource availability causes a sharp decrease in the taxonomic richness of the microbiota due to the loss of rare taxa (p = 2.06e-9), although the number of core genera shared by all infants increases substantially. Moreover, although the gut microbial succession is not strictly deterministic, we detect an overarching directionality of change through time towards the taxonomic and functional composition of the maternal microbiota. Succession is however not complete by the one year mark, as significant differences remain between one-year-olds and their mothers in terms of taxonomic (p = 0.009) and functional (p = 0.004) microbiota composition, and in taxonomic richness (p = 2.76e-37) and diversity (p = 0.016). Our results also indicate that the taxonomic composition of the microbiota shapes its functional capacities. Therefore, the observed inter-individual variability in taxonomic composition during succession is not fully compensated by functional equivalence among bacterial genera and may have important physiological consequences. Finally, network analyses suggest that positive interactions among core genera during community assembly contribute to ensure their permanence within the gut, and highlight an expansion of complexity in the interactions network as the core of taxa shared by all infants grows following the introduction of solid foods.


Assuntos
Trato Gastrointestinal/microbiologia , Consórcios Microbianos/genética , Microbiota/genética , Adulto , Fatores Etários , Sequência de Bases , Biodiversidade , DNA Bacteriano/genética , Dieta , Fezes/microbiologia , Feminino , Humanos , Lactente , Recém-Nascido , Masculino , Análise de Sequência de DNA , Espanha
16.
Int J Evol Biol ; 2012: 394026, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22900231

RESUMO

Much of the observed variation among closely related bacterial genomes is attributable to gains and losses of genes that are acquired horizontally as well as to gene duplications and larger amplifications. The genomic flexibility that results from these mechanisms certainly contributes to the ability of bacteria to survive and adapt in varying environmental challenges. However, the duplicability and transferability of individual genes imply that natural selection should operate, not only at the organismal level, but also at the level of the gene. Genes can be considered semiautonomous entities that possess specific functional niches and evolutionary dynamics. The evolution of bacterial genes should respond both to selective pressures that favor competition, mostly among orthologs or paralogs that may occupy the same functional niches, and cooperation, with the majority of other genes coexisting in a given genome. The relative importance of either type of selection is likely to vary among different types of genes, based on the functional niches they cover and on the tightness of their association with specific organismal lineages. The frequent availability of new functional niches caused by environmental changes and biotic evolution should enable the constant diversification of gene families and the survival of new lineages of genes.

17.
PLoS One ; 6(6): e21644, 2011.
Artigo em Inglês | MEDLINE | ID: mdl-21738748

RESUMO

The microbiota in the human gastrointestinal tract (GIT) is highly exposed to antibiotics, and may be an important reservoir of resistant strains and transferable resistance genes. Maternal GIT strains can be transmitted to the offspring, and resistances could be acquired from birth. This is a case study using a metagenomic approach to determine the diversity of microorganisms conferring tetracycline resistance (Tc(r)) in the guts of a healthy mother-infant pair one month after childbirth, and to investigate the potential for horizontal transfer and maternal transmission of Tc(r) genes. Fecal fosmid libraries were functionally screened for Tc(r), and further PCR-screened for specific Tc(r) genes. Tc(r) fosmid inserts were sequenced at both ends to establish bacterial diversity. Mother and infant libraries contained Tc(r), although encoded by different genes and organisms. Tc(r) organisms in the mother consisted mainly of Firmicutes and Bacteroidetes, and the main gene detected was tet(O), although tet(W) and tet(X) were also found. Identical Tc(r) gene sequences were present in different bacterial families and even phyla, which may indicate horizontal transfer within the maternal GIT. In the infant library, Tc(r) was present exclusively in streptococci carrying tet(M), tet(L) and erm(T) within a novel composite transposon, Tn6079. This transposon belongs to a family of broad host range conjugative elements, implying a potential for the joint spread of tetracycline and erythromycin resistance within the infant's gut. In addition, although not found in the infant metagenomic library, tet(O) and tet(W) could be detected in the uncloned DNA purified from the infant fecal sample. This is the first study to reveal the diversity of Tc(r) bacteria in the human gut, to detect a likely transmission of antibiotic resistance from mother to infant GITs and to indicate the possible occurrence of gene transfers among distantly related bacteria coinhabiting the GIT of the same individual.


Assuntos
Trato Gastrointestinal/microbiologia , Resistência a Tetraciclina/fisiologia , Humanos , Lactente , Recém-Nascido , Mães , Reação em Cadeia da Polimerase , Resistência a Tetraciclina/genética
18.
Genome Biol Evol ; 2: 53-66, 2010 Jan 06.
Artigo em Inglês | MEDLINE | ID: mdl-20333224

RESUMO

Colonization of the gastrointestinal tract (GIT) of human infants with a suitable microbial community is essential for numerous aspects of health, but the progression of events by which this microbiota becomes established is poorly understood. Here, we investigate two previously unexplored areas of microbiota development in infants: the deployment of functional capabilities at the community level and the population genetics of its most abundant genera. To assess the progression of the infant microbiota toward an adult-like state and to evaluate the contribution of maternal GIT bacteria to the infant gut, we compare the infant's microbiota with that of the mother at 1 and 11 months after delivery. These comparisons reveal that the infant's microbiota rapidly acquires and maintains the range of gene functions present in the mother, without replicating the phylogenetic composition of her microbiota. Microdiversity analyses for Bacteroides and Bifidobacterium, two of the main microbiota constituents, reveal that by 11 months, the phylotypes detected in the infant are distinct from those in the mother, although the maternal Bacteroides phylotypes were transiently present at 1 month of age. The configuration of genetic variants within these genera reveals populations far from equilibrium and likely to be undergoing rapid growth, consistent with recent population turnovers. Such compositional turnovers and the associated loss of maternal phylotypes should limit the potential for long-term coadaptation between specific bacterial and host genotypes.

19.
Science ; 318(5855): 1449-52, 2007 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-17947550

RESUMO

Horizontal gene transfer, in which genetic material is transferred from the genome of one organism to that of another, has been investigated in microbial species mainly through computational sequence analyses. To address the lack of experimental data, we studied the attempted movement of 246,045 genes from 79 prokaryotic genomes into Escherichia coli and identified genes that consistently fail to transfer. We studied the mechanisms underlying transfer inhibition by placing coding regions from different species under the control of inducible promoters. Our data suggest that toxicity to the host inhibited transfer regardless of the species of origin and that increased gene dosage and associated increased expression may be a predominant cause for transfer failure. Although these experimental studies examined transfer solely into E. coli, a computational analysis of gene-transfer rates across available bacterial and archaeal genomes supports that the barriers observed in our study are general across the tree of life.


Assuntos
Escherichia coli/genética , Transferência Genética Horizontal , Genes Arqueais , Genes Bacterianos , Archaea/classificação , Archaea/genética , Bactérias/classificação , Bactérias/genética , Clonagem Molecular , Biologia Computacional , Dosagem de Genes , Especiação Genética , Genoma Arqueal , Genoma Bacteriano , Filogenia
20.
PLoS One ; 2(8): e745, 2007 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-17710145

RESUMO

Because binding of RNAP to misplaced sites could compromise the efficiency of transcription, natural selection for the optimization of gene expression should regulate the distribution of DNA motifs capable of RNAP-binding across the genome. Here we analyze the distribution of the -10 promoter motifs that bind the sigma(70) subunit of RNAP in 42 bacterial genomes. We show that selection on these motifs operates across the genome, maintaining an over-representation of -10 motifs in regulatory sequences while eliminating them from the nonfunctional and, in most cases, from the protein coding regions. In some genomes, however, -10 sites are over-represented in the coding sequences; these sites could induce pauses effecting regulatory roles throughout the length of a transcriptional unit. For nonfunctional sequences, the extent of motif under-representation varies across genomes in a manner that broadly correlates with the number of tRNA genes, a good indicator of translational speed and growth rate. This suggests that minimizing the time invested in gene transcription is an important selective pressure against spurious binding. However, selection against spurious binding is detectable in the reduced genomes of host-restricted bacteria that grow at slow rates, indicating that components of efficiency other than speed may also be important. Minimizing the number of RNAP molecules per cell required for transcription, and the corresponding energetic expense, may be most relevant in slow growers. These results indicate that genome-level properties affecting the efficiency of transcription and translation can respond in an integrated manner to optimize gene expression. The detection of selection against promoter motifs in nonfunctional regions also confirms previous results indicating that no sequence may evolve free of selective constraints, at least in the relatively small and unstructured genomes of bacteria.


Assuntos
Bactérias , Sequência de Bases , Regiões Promotoras Genéticas/genética , Biossíntese de Proteínas , Seleção Genética , Bactérias/classificação , Bactérias/genética , RNA Polimerases Dirigidas por DNA/genética , RNA Polimerases Dirigidas por DNA/metabolismo , Regulação Bacteriana da Expressão Gênica , Genoma Bacteriano , Dados de Sequência Molecular , Filogenia , RNA de Transferência/genética , Fator sigma/genética , Fator sigma/metabolismo
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...