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1.
Sci Total Environ ; 901: 166028, 2023 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-37549700

RESUMO

To investigate the effect of wastewater (WW) treatment on soil bacterial communities, water of different quality was used to irrigate eight lettuces per tank: raw municipal wastewater (RWW), WW treated with an aerated constructed wetland (CWW) and WW treated with a membrane bioreactor (MBW), and tap water (TW). The physicochemical and microbiological characteristics (quality indicators) of these water types were characterized, and the water and soil bacterial communities were monitored by quantitative PCR (qPCR) and 16S rRNA gene sequencing. Despite marked differences in microbial load and diversity of waters, soil communities remained remarkably stable after irrigation. Microbial biomass was increased only in soils irrigated with RWW. At the end of the irrigation period (day 84), soil and water shared a large fraction of their bacterial communities, from 43 % to 70 %, depending on the water quality, indicating a transfer of bacterial communities from water to soil. Overall, the relative abundance of Proteobacteria and Acidobacteria was increased and that of Actinobacteria was decreased in soils irrigated with MBW, CWW and even more with RWW. Multivariate ordination clearly separated soils in three groups: soils irrigated with the cleanest water (TW), with treated WW (MBW and CWW), and with untreated WW (RWW). Nitrifying, denitrifying, and nitrogen-fixing bacteria were quantified by qPCR targeting amoA, narG, and nifH, respectively. Nitrifying bacteria were the most affected by the water quality, as indicated by amoA copy number increase in RWW-irrigated soil and decrease in CWW-irrigated soil. Overall, the abundance of all three genes was positively influenced by RWW treatment. In conclusion, the 84 days of irrigation influenced the soil microbial communities, and the impact depended on the quality of the used water.

2.
Sci Rep ; 13(1): 3809, 2023 03 07.
Artigo em Inglês | MEDLINE | ID: mdl-36882458

RESUMO

We study the dynamics of interactions between a traditional medium, the New York Times journal, and its followers in Twitter, using a massive dataset. It consists of the metadata of the articles published by the journal during the first year of the COVID-19 pandemic, and the posts published in Twitter by a large set of followers of the @nytimes account along with those published by a set of followers of several other media of different kind. The dynamics of discussions held in Twitter by exclusive followers of a medium show a strong dependence on the medium they follow: the followers of @FoxNews show the highest similarity to each other and a strong differentiation of interests with the general group. Our results also reveal the difference in the attention payed to U.S. presidential elections by the journal and by its followers, and show that the topic related to the "Black Lives Matter" movement started in Twitter, and was addressed later by the journal.


Assuntos
Comunicação , Jornais como Assunto , Mídias Sociais , Humanos , Metadados
3.
Rev Mal Respir ; 34(1): 61-65, 2017 Jan.
Artigo em Francês | MEDLINE | ID: mdl-27282326

RESUMO

INTRODUCTION: The breast is a rare site for metastases from lung cancers. Their occurrence in patients with adenocarcinoma which has the EGFR mutation is exceptional. In this context, it is sometimes difficult to differentiate a second primary breast cancer from a breast metastasis. OBSERVATIONS: We report the cases of two patients who developed breast metastases from lung adenocarcinoma that was TTF1 positive with a deletion of exon 19 of the EGFR gene. A non-smoking woman of Asian origin, presented with a solitary breast metastasis 29 months after being established on first-line chemotherapy. The second case was a Caucasian patient who was an active smoker presented with tumor progression with multiple metastases including involvement of both breasts 10 months after the start of treatment with a tyrosine kinase inhibitor. In both, tumor cells from the breast showed positive immunostaining for TTF1 and genotyping detected the presence of the deletion of exon 19 of the EGFR gene. CONCLUSION: In patients with lung adenocarcinoma and EGFR mutation, immunohistochemical examination, including TTF1 and genotyping of synchronous breast tumour, is needed to confirm its metastatic nature and to guide treatment.


Assuntos
Adenocarcinoma/genética , Adenocarcinoma/patologia , Neoplasias da Mama/secundário , Receptores ErbB/genética , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/patologia , Mutação , Adenocarcinoma de Pulmão , Idoso , Neoplasias da Mama/genética , Feminino , Humanos , Pessoa de Meia-Idade
4.
Water Res ; 110: 161-169, 2017 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-28006706

RESUMO

A quantitative structure activity relationship (QSAR) between relative abundance values and digester methane production rate was developed. For this, 50 triplicate anaerobic digester sets (150 total digesters) were each seeded with different methanogenic biomass samples obtained from full-scale, engineered methanogenic systems. Although all digesters were operated identically for at least 5 solids retention times (SRTs), their quasi steady-state function varied significantly, with average daily methane production rates ranging from 0.09 ± 0.004 to 1 ± 0.05 L-CH4/LR-day (LR = Liter of reactor volume) (average ± standard deviation). Digester microbial community structure was analyzed using more than 4.1 million partial 16S rRNA gene sequences of Archaea and Bacteria. At the genus level, 1300 operational taxonomic units (OTUs) were observed across all digesters, whereas each digester contained 158 ± 27 OTUs. Digester function did not correlate with typical biomass descriptors such as volatile suspended solids (VSS) concentration, microbial richness, diversity or evenness indices. However, methane production rate did correlate notably with relative abundances of one Archaeal and nine Bacterial OTUs. These relative abundances were used as descriptors to develop a multiple linear regression (MLR) QSAR equation to predict methane production rates solely based on microbial community data. The model explained over 66% of the variance in the experimental data set based on 149 anaerobic digesters with a standard error of 0.12 L-CH4/LR-day. This study provides a framework to relate engineered process function and microbial community composition which can be further expanded to include different feed stocks and digester operating conditions in order to develop a more robust QSAR model.


Assuntos
Reatores Biológicos/microbiologia , Águas Residuárias , Anaerobiose , Metano/biossíntese , Microbiota , RNA Ribossômico 16S
5.
J R Soc Interface ; 13(125)2016 12.
Artigo em Inglês | MEDLINE | ID: mdl-27974571

RESUMO

The uneven distribution of wealth and individual economic capacities are among the main forces, which shape modern societies and arguably bias the emerging social structures. However, the study of correlations between the social network and economic status of individuals is difficult due to the lack of large-scale multimodal data disclosing both the social ties and economic indicators of the same population. Here, we close this gap through the analysis of coupled datasets recording the mobile phone communications and bank transaction history of one million anonymized individuals living in a Latin American country. We show that wealth and debt are unevenly distributed among people in agreement with the Pareto principle; the observed social structure is strongly stratified, with people being better connected to others of their own socioeconomic class rather than to others of different classes; the social network appears to have assortative socioeconomic correlations and tightly connected 'rich clubs'; and that individuals from the same class live closer to each other but commute further if they are wealthier. These results are based on a representative, society-large population, and empirically demonstrate some long-lasting hypotheses on socioeconomic correlations, which potentially lay behind social segregation, and induce differences in human mobility.


Assuntos
Telefone Celular , Modelos Teóricos , Dinâmica Populacional , Apoio Social , Feminino , Humanos , América Latina , Masculino , Fatores Socioeconômicos
6.
Water Res ; 104: 128-136, 2016 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-27522023

RESUMO

Nine anaerobic digesters, each seeded with biomass from a different source, were operated identically and their quasi steady state function was compared. Subsequently, digesters were bioaugmented with a methanogenic culture previously shown to increase specific methanogenic activity. Before bioaugmentation, different seed biomass resulted in different quasi steady state function, with digesters clustering into three groups distinguished by methane (CH4) production. Digesters with similar functional performance contained similar archaeal communities based on clustering of Illumina sequence data of the V4V5 region of the 16S rRNA gene. High CH4 production correlated with neutral pH and high Methanosarcina abundance, whereas low CH4 production correlated to low pH as well as high Methanobacterium and DHVEG 6 family abundance. After bioaugmentation, CH4 production from the high CH4 producing digesters transiently increased by 11 ± 3% relative to non-bioaugmented controls (p < 0.05, n = 3), whereas no functional changes were observed for medium and low CH4 producing digesters that all had pH higher than 6.7. The CH4 production increase after bioaugmentation was correlated to increased relative abundance of Methanosaeta and Methaospirillum originating from the bioaugment culture. In conclusion, different anaerobic digester seed biomass can result in different quasi steady state CH4 production, SCOD removal, pH and effluent VFA concentration in the timeframe studied. The bioaugmentation employed can result in a period of increased methane production. Future research should address extending the period of increased CH4 production by employing pH and VFA control concomitant with bioaugmentation, developing improved bioaugments, or employing a membrane bioreactor to retain the bioaugment.


Assuntos
Archaea/genética , RNA Ribossômico 16S/genética , Anaerobiose , Reatores Biológicos , Metano
7.
Appl Microbiol Biotechnol ; 99(19): 8295-308, 2015 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-26254785

RESUMO

Hydrogen is a promising alternative as an energetic carrier and its production by dark fermentation from wastewater has been recently proposed, with special attention to crude glycerol as potential substrate. In this study, two different feeding strategies were evaluated for replacing the glucose substrate by glycerol substrate: a one-step strategy (glucose was replaced abruptly by glycerol) and a step-by-step strategy (progressive decrease of glucose concentration and increase of glycerol concentration from 0 to 5 g L(-1)), in a continuous stirred tank reactor (12 h of hydraulic retention time (HRT), pH 5.5, 35 °C). While the one-step strategy led to biomass washout and unsuccessful H2 production, the step-by-step strategy was efficient for biomass adaptation, reaching acceptable hydrogen yields (0.4 ± 0.1 molH2 mol(-1) glycerol consumed) around 33 % of the theoretical yield independently of the glycerol concentration. Microbial community structure was investigated by single-strand conformation polymorphism (SSCP) and denaturing gradient gel electrophoresis (DGGE) fingerprinting techniques, targeting either the total community (16S ribosomal RNA (rRNA) gene) or the functional Clostridium population involved in H2 production (hydA gene), as well as by 454 pyrosequencing of the total community. Multivariate analysis of fingerprinting and pyrosequencing results revealed the influence of the feeding strategy on the bacterial community structure and suggested the progressive structural adaptation of the community to increasing glycerol concentrations, through the emergence and selection of specific species, highly correlated to environmental parameters. Particularly, this work highlighted an interesting shift of dominant community members (putatively responsible of hydrogen production in the continuous stirred tank reactor (CSTR)) according to the gradient of glycerol proportion in the feed, from the family Veillonellaceae to the genera Prevotella and Clostridium sp., putatively responsible of hydrogen production in the CSTR.


Assuntos
Bactérias/metabolismo , Glicerol/metabolismo , Hidrogênio/metabolismo , Esgotos/microbiologia , Ácidos/metabolismo , Bactérias/classificação , Bactérias/genética , Bactérias/isolamento & purificação , Reatores Biológicos/microbiologia , Fermentação , Glicerol/análise , Dados de Sequência Molecular , Filogenia , Esgotos/química
8.
Target Oncol ; 10(3): 415-21, 2015 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-25420993

RESUMO

Recent data showed that metastatic colorectal (mCRC) tumors exhibiting extended RAS-BRAF mutations were resistant to anti-epidermal growth factor receptor (EGFR) monoclonal antibodies, making these drugs suitable for the so-called "super" wild-type (WT) patients only. This study aimed to compare the extended RAS-BRAF mutation frequency and characteristics according to location of tumor sampling. All consecutive mCRC specimens (N = 1659) referred to our institution from January 2008 till June 2014 were included in the analysis. Tumor genotyping (first for KRAS exon 2, then for BRAF exon 15, and later for KRAS exons 2, 3, and 4 and NRAS exons 2, 3, and 4) was performed with high-resolution melting analysis or allelic discrimination. The factors predicting for the presence of mutation were explored using multivariate binary logistic regression. Overall, the prevalence of KRAS exon 2 was 36.8%, and it was lower in liver metastases (N = 138/490; 28.2%) in comparison with primary tumors (N = 442/1086; 40.7%), lung metastases (16/32; 50%), or other metastatic sites (15/51; 29.4%; P < 0.0001). Similarly, in the 1428 samples analyzed, BRAF mutations were less often found in liver metastases (N = 9/396; 2.3%) as compared to primary tumors (N = 79/959; 8.2%), lung metastases (N = 2/29; 6.9%), or other metastatic locations (N = 2/44; 4.5%; P < 0.0002). Overall occurrence of extended RAS mutation was 51.7%. Of the 503 samples tested, the prevalence of extended RAS-BRAF mutations was twice as low in liver metastases (N = 53/151; 34.2 %) as compared to primary tumors (N = 191/322; 59.3%, P < 0.0001). Univariate analysis identified age ≤65 years, male gender, and liver localization as predictors of super WT status. At multivariate analysis, only liver metastases were retained (RR 2.85 [95% CI 1.91-4.30]). Colorectal liver metastases are twice as likely to exhibit a super WT genotype as compared to other tumor locations independently from other factors. This molecular feature has the potential to influence therapeutic strategy in mCRC patients.


Assuntos
Neoplasias Colorretais/genética , Neoplasias Colorretais/patologia , Neoplasias Hepáticas/genética , Neoplasias Hepáticas/secundário , Mutação , Idoso , Análise Mutacional de DNA , Éxons , Feminino , GTP Fosfo-Hidrolases/genética , Genótipo , Humanos , Masculino , Proteínas de Membrana/genética , Pessoa de Meia-Idade , Análise Multivariada , Metástase Neoplásica , Prevalência , Proteínas Proto-Oncogênicas B-raf/genética , Proteínas Proto-Oncogênicas p21(ras)/genética , Análise de Regressão , Transdução de Sinais
9.
Bioresour Technol ; 173: 185-192, 2014 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-25305647

RESUMO

The effect of milling pretreatment on performances of Solid-State Anaerobic Digestion (SS-AD) of raw lignocellulosic residue is still controverted. Three batch reactors treating different straw particle sizes (milled 0.25 mm, 1 mm and 10 mm) were followed during 62 days (6 sampling dates). Although a fine milling improves substrate accessibility and conversion rate (up to 30% compared to coarse milling), it also increases the risk of media acidification because of rapid and high acids production during fermentation of the substrate soluble fraction. Meanwhile, a gradual adaptation of microbial communities, were observed according to both reaction progress and methanogenic performances. The study concluded that particle size reduction affected strongly the performances of the reaction due to an increase of substrate bioaccessibility. An optimization of SS-AD processes thanks to particle size reduction could therefore be applied at farm or industrial scale only if a specific management of the soluble compounds is established.


Assuntos
Anaerobiose
10.
Water Sci Technol ; 69(5): 960-5, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24622543

RESUMO

The potential for total nitrogen removal from municipal wastewater has been evaluated in an autotrophic membrane bioreactor running with a low chemical oxygen demand (COD)/N ratio to simulate its combination with an upstream physicochemical process that retains a large proportion of organic matter. The tests were conducted in a laboratory scale submerged membrane bioreactor loaded with a synthetic influent. Nitrogen loading rate was 0.16 kgN-NH4+.m(-3).d(-1) and sodium acetate was added as a carbon source. Results have shown that nitrogen elimination can reach 85% for a COD/N ratio of 5, with COD removal exceeding 97%. However, a COD/N ratio of 3.5 was found to be the limiting factor for successfully reaching the overall target value of 10 mgN.L(-1) in the effluent. Nevertheless, low COD/N ratios make it possible to work with low total suspended solid concentrations in the bioreactor, which greatly facilitates membrane fouling control by a simple aeration and backwashing strategy.


Assuntos
Análise da Demanda Biológica de Oxigênio , Reatores Biológicos , Nitrogênio/isolamento & purificação , Purificação da Água , Processos Autotróficos , Reatores Biológicos/microbiologia , Desnitrificação , Membranas Artificiais , Modelos Teóricos , Nitrificação
11.
Cell Death Differ ; 21(5): 685-95, 2014 May.
Artigo em Inglês | MEDLINE | ID: mdl-24464223

RESUMO

Intrinsic and acquired chemoresistance are frequent causes of cancer eradication failure. Thus, long-term cis-diaminedichloroplatine(II) (CDDP) or cisplatin treatment is known to promote tumor cell resistance to apoptosis induction via multiple mechanisms involving gene expression modulation of oncogenes, tumor suppressors and blockade of pro-apoptotic mitochondrial membrane permeabilization. Here, we demonstrate that CDDP-resistant non-small lung cancer cells undergo profound remodeling of their endoplasmic reticulum (ER) proteome (>80 proteins identified by proteomics) and exhibit a dramatic overexpression of two protein disulfide isomerases, PDIA4 and PDIA6, without any alteration in ER-cytosol Ca(2+) fluxes. Using pharmacological and genetic inhibition, we show that inactivation of both proteins directly stimulates CDDP-induced cell death by different cellular signaling pathways. PDIA4 inactivation restores a classical mitochondrial apoptosis pathway, while knockdown of PDIA6 favors a non-canonical cell death pathway sharing some necroptosis features. Overexpression of both proteins has also been found in lung adenocarcinoma patients, suggesting a clinical importance of these proteins in chemoresistance.


Assuntos
Adenocarcinoma/tratamento farmacológico , Adenocarcinoma/enzimologia , Antineoplásicos/farmacologia , Cisplatino/farmacologia , Neoplasias Pulmonares/tratamento farmacológico , Neoplasias Pulmonares/enzimologia , Isomerases de Dissulfetos de Proteínas/metabolismo , Adenocarcinoma/patologia , Adenocarcinoma de Pulmão , Apoptose/efeitos dos fármacos , Linhagem Celular Tumoral , Resistencia a Medicamentos Antineoplásicos , Humanos , Neoplasias Pulmonares/patologia
12.
Sci Rep ; 3: 2517, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23982757

RESUMO

We uncover the global organization of clustering in real complex networks. To this end, we ask whether triangles in real networks organize as in maximally random graphs with given degree and clustering distributions, or as in maximally ordered graph models where triangles are forced into modules. The answer comes by way of exploring m-core landscapes, where the m-core is defined, akin to the k-core, as the maximal subgraph with edges participating in at least m triangles. This property defines a set of nested subgraphs that, contrarily to k-cores, is able to distinguish between hierarchical and modular architectures. We find that the clustering organization in real networks is neither completely random nor ordered although, surprisingly, it is more random than modular. This supports the idea that the structure of real networks may in fact be the outcome of self-organized processes based on local optimization rules, in contrast to global optimization principles.


Assuntos
Análise por Conglomerados , Modelos Estatísticos , Simulação por Computador
13.
J Biotechnol ; 165(2): 85-92, 2013 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-23524058

RESUMO

A heterotrophic biofilm (B1) and a mixed autotrophic-heterotrophic biofilm (B2) were developed in an annular reactor and submitted to an erosion test in order to selectively detach top layers from the bottom layers. Densities of the basal layers were 5-fold higher and 3-fold higher than the densities of the entire biofilms B1 and B2, respectively. After extraction, EPS content in B1 biofilm was found higher in the basal layer (95 mg g⁻¹ VSS) compared to the top layer (30 mg g⁻¹ VSS), while B2 biofilm had a higher EPS content in the top layer (303 mg g⁻¹ VSS) compared to the basal layer (135 mg g⁻¹ VSS). Hydrophobic Interaction Chromatography (HIC) indicates that hydrophobic EPS (HEPS) in both biofilms reached 21% of EPS in basal cohesive layers, and remained slightly lower or identical (16-19%) in top detached biofilm layers. Strong interacting HEPS were found in a higher proportion in the mixed autotrophic-heterotrophic B2 which was also more diversified in terms of bacterial populations than the B1 heterotrophic biofilm. These results show that HEPS content correlates better with cohesive properties of the biofilm layers than global EPS content and that strong hydrophobic adhesion forces may be related to microbial populations such as the presence of nitrifiers.


Assuntos
Biofilmes/crescimento & desenvolvimento , Polímeros/metabolismo , Aderência Bacteriana/fisiologia , Interações Hidrofóbicas e Hidrofílicas
14.
J Intellect Disabil Res ; 56(11): 1110-21, 2012 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-23106754

RESUMO

BACKGROUND: People with intellectual disabilities (ID) have unequal access to health care. While systemic efforts are addressing health inequalities, there remains a need to demonstrate that persons with ID can increase their health self-advocacy skills. METHOD: A randomised control design with up to 6-month follow-up was used to evaluate the 3Rs (Rights, Respect and Responsibility) health self-advocacy training program for persons with ID (n = 31). Training involved teaching participants to recognise and redress health rights violations in the context of respect and responsibility. Training materials included PowerPoint slides and interactive video scenarios illustrating health rights, respect and responsibility problem and non-problems. Two-hour training sessions were conducted twice a week in a group format where participants played a game and answered questions. RESULTS: The health rights training group made significantly more correct responses on post training and follow-up tests than the control group. Training effects generalised to untrained scenarios and in situ health interviews. CONCLUSIONS: The results of this study suggest that persons with ID can learn complex skills related to health self-advocacy. More research is needed to improve in situ generalisation.


Assuntos
Pessoas com Deficiência/psicologia , Educação de Pessoa com Deficiência Intelectual/métodos , Deficiência Intelectual/psicologia , Educação de Pacientes como Assunto/métodos , Autonomia Pessoal , Adulto , Pessoas com Deficiência/reabilitação , Feminino , Seguimentos , Direitos Humanos/psicologia , Humanos , Deficiência Intelectual/reabilitação , Masculino , Pessoa de Meia-Idade , Avaliação de Programas e Projetos de Saúde , Autocuidado/métodos , Autocuidado/psicologia , Inquéritos e Questionários
15.
Water Res ; 46(3): 601-10, 2012 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-22154106

RESUMO

Nonylphenols (NP) have estrogenic potential because of their phenolic ring, but the organisms involved in the degradation of this alkylated phenol remain unidentified. Using 16S ribosomal RNA (rRNA)-based stable isotope probing (SIP) and a new method based on pyrosequencing, we identified the bacteria involved in the degradation of the aromatic ring of [U-ring-(13)C] 4-n-NP in aerobic sludge. The first order degradation rate of 4-n-NP was 5.5d(-1). Single strand conformation polymorphism of density-separated labeled and unlabeled 16S rRNA showed significant differences and enabled selection of four representative fractions for pyrosequencing. Nineteen phylotypes showed a significant enrichment in the heavy fraction in the labeled pulse. The relative abundances of these phylotypes were combined with the RNA concentration of each fraction to yield a simple model of the distribution of each phylotype across the gradient. This model was used to estimate the percentage of labeling for each phylotype. The sequences showing the highest labeling (11%) were closely related to Afipia sp. but represented only 2 % of the RNA in the heavy fraction of the labeled pulse. The sequences representing the largest proportion of the RNA in the heavy fraction were related to Propionibacterium acnes and Frateuria aurantia, which are known to possess enzymes for phenol degradation. The model shows that despite Afipia having the highest (13)C enrichment, other species encoding phenol degradation pathways are responsible for more (13)C incorporation. Last, we showed that some species represent 12% of the total RNA but contain only 1% (13)C above natural abundance.


Assuntos
Bactérias/genética , Marcação por Isótopo/métodos , Fenóis/metabolismo , RNA Ribossômico 16S/genética , Análise de Sequência de RNA/métodos , Esgotos/microbiologia , Temperatura , Biodegradação Ambiental , Isótopos de Carbono , Eletroforese Capilar , Dados de Sequência Molecular , Filogenia
17.
J Appl Microbiol ; 107(5): 1642-50, 2009 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-19457023

RESUMO

AIMS: Improved knowledge of the bacterial community of the digestive tract is required to enhance the efficiency of digestion in herbivores. This work aimed to study spatial and temporal variations of the bacterial communities in the bovine digestive tract and their correlation with gut environmental parameters. METHODS AND RESULTS: Rumen content and faeces of five cows were sampled for 3 weeks. In addition, reticulum content was sampled during the third week. Bacterial communities were assessed by studying capillary electrophoresis single-stranded conformation polymorphism (CE-SSCP) profiles of 16S rRNA genes. The bacterial community structure differed between the forestomach and faecal contents. The abundance of several operational taxonomic units changed from week to week. Bacterial community structure of the rumen was correlated to propionic acid and NH(3)-N concentrations. CONCLUSIONS: The bacterial community of the bovine digestive tract varied in space and time. SIGNIFICANCE AND IMPACT OF THE STUDY: The study of the bacterial communities of the digestive tract in herbivores should be widened from the rumen to the large intestine. The amplitude and origin of the temporal variation of the ruminal bacterial community need to be better understood to improve the control of the fermentative activity in herbivores.


Assuntos
Bactérias/genética , Bactérias/isolamento & purificação , Bovinos/microbiologia , Trato Gastrointestinal/microbiologia , RNA Ribossômico 16S/análise , Animais , Derivados de Benzeno/análise , Biodiversidade , DNA Bacteriano/análise , Eletroforese Capilar , Fezes/microbiologia , Reação em Cadeia da Polimerase/métodos , Polimorfismo Conformacional de Fita Simples , Propionatos/análise , Retículo/microbiologia , Rúmen/química , Rúmen/microbiologia
18.
J Appl Microbiol ; 105(6): 2123-32, 2008 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-19120658

RESUMO

AIMS: To evaluate bacterial community structure and dynamics in triplicate vermicomposts made from the same start-up material, along with certain physico-chemical changes. METHODS AND RESULTS: The physico-chemical parameters (pH, temperature, carbon, nitrogen, soluble substances and cellulose) evolved similarly in the triplicate vermicomposts, indicating a steady function. The 16S bacterial gene abundance remained constant over time. To monitor changes in the bacterial community structure, fingerprinting based on capillary electrophoresis single-strand conformation polymorphism was employed. A rise in bacterial diversity occurred after precomposting and it remained stable during the maturation phase. However, a rapid shift in the structure of the bacterial community in the vermicompost replicates was noted at the beginning that stabilized with the process maturation. Multivariate analyses showed different patterns of bacterial community evolution in each vermicompost that did not correlate with the physico-chemical changes. CONCLUSIONS: The broad-scale functions remained similar in the triplicates, with stable bacterial abundance and diversity despite fluctuation in the community structure. SIGNIFICANCE AND IMPACT OF THE STUDY: This study has demonstrated that microbial fingerprinting with multivariate analysis can provide significant understanding of community structure and also clearly suggests that an ecosystem's efficacy could be the outcome of functional redundancy whereby a number of species carry out the same function.


Assuntos
Bactérias/genética , Ecossistema , RNA Ribossômico 16S/análise , Microbiologia do Solo , Solo/análise , Animais , DNA Bacteriano/análise , Eletroforese Capilar , Análise Multivariada , Reação em Cadeia da Polimerase/métodos , Polimorfismo Conformacional de Fita Simples
19.
Phys Rev E Stat Nonlin Soft Matter Phys ; 75(5 Pt 1): 051302, 2007 May.
Artigo em Inglês | MEDLINE | ID: mdl-17677049

RESUMO

We address the problem of recollisions in cooling granular gases. To this aim, we dynamically construct the interaction network in a granular gas, using the sequence of collisions collected in an event driven simulation of inelastic hard disks from time 0 until time t . The network is decomposed into its k -core structure: particles in a core of index k have collided at least k times with other particles in the same core. The difference between cores k+1 and k is the so-called k -shell, and the set of all shells is a complete and nonoverlapping decomposition of the system. Because of energy dissipation, the gas cools down: its initial spatially homogeneous dynamics, characterized by the Haff law, i.e., a t{-2} energy decay, is unstable toward a strongly inhomogeneous phase with clusters and vortices, where energy decays as t{-1} . The clear transition between those two phases appears in the evolution of the k -shells structure in the collision network. In the homogeneous state the k -shell structure evolves as in a growing network with a fixed number of vertices and randomly added links: the shell distribution is strongly peaked around the most populated shell, which has an index k{max} approximately 0.9(d) with (d) the average number of collisions experienced by a particle. During the final nonhomogeneous state a growing fraction of collisions is concentrated in small, almost closed, communities of particles: k{max} is no more linear in (d) and the distribution of shells becomes extremely large developing a power-law tail approximately k{-3} for high shell indexes. We conclude proposing a simple algorithm to build a correlated random network that reproduces, with few essential ingredients, the whole observed phenomenology, including the t{-1} energy decay. It consists of two kinds of collisions (links): single random collisions with any other particle and long chains of recollisions with only previously encountered particles. The algorithm disregards the exact spatial arrangement of clusters, suggesting that the observed stringlike structures are not essential to determine the statistics of recollisions and the energy decay.

20.
Microb Ecol ; 49(1): 63-72, 2005 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-15650915

RESUMO

A total of 1246 Pseudomonas strains were isolated from the rhizosphere of two perennial grasses (Lolium perenne and Molinia coerulea) with different nitrogen requirements. The plants were grown in their native soil under ambient and elevated atmospheric CO2 content (pCO2) at the Swiss FACE (Free Air CO2 Enrichment) facility. Root-, rhizosphere-, and non-rhizospheric soil-associated strains were characterized in terms of their ability to reduce nitrate during an in vitro assay and with respect to the genes encoding the membrane-bound (named NAR) and periplasmic (NAP) nitrate reductases so far described in the genus Pseudomonas. The diversity of corresponding genes was assessed by PCR-RFLP on narG and napA genes, which encode the catalytic subunit of nitrate reductases. The frequency of nitrate-dissimilating strains decreased with root proximity for both plants and was enhanced under elevated pCO2 in the rhizosphere of L. perenne. NAR (54% of strains) as well as NAP (49%) forms were present in nitrate-reducing strains, 15.5% of the 439 strains tested harbouring both genes. The relative proportions of narG and napA detected in Pseudomonas strains were different according to root proximity and for both pCO2 treatments: the NAR form was more abundant close to the root surface and for plants grown under elevated pCO2. Putative denitrifiers harbored mainly the membrane-bound (NAR) form of nitrate reductase. Finally, both narG and napA sequences displayed a high level of diversity. Anyway, this diversity was correlated neither with the root proximity nor with the pCO2 treatment.


Assuntos
Variação Genética , Nitrato Redutases/genética , Raízes de Plantas/microbiologia , Poaceae/microbiologia , Pseudomonas/genética , Microbiologia do Solo , Dióxido de Carbono/metabolismo , Contagem de Colônia Microbiana , Primers do DNA , Proteínas de Membrana/metabolismo , Proteínas Periplásmicas/metabolismo , Reação em Cadeia da Polimerase , Polimorfismo de Fragmento de Restrição , Pseudomonas/enzimologia , Suíça
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