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Diversidade metabólica em solo tratado com biossólidos.; Metabolic diversity in a soil amended with biosolids.

Lopes, Elizabeth Barretto de Menezes
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 21/01/2002 PT
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A aplicação de biossólidos em solos agrícolas e/ou florestais é uma prática aceitável, tanto como forma de disposição destes materiais, quanto de melhorar as características físicas, químicas e biológicas do solo. No entanto, pouco se sabe dos impactos decorrentes desta utilização e dos seus efeitos sobre a estrutura das comunidades microbianas dos solos e sua capacidade metabólica. Assim, o objetivo deste trabalho foi determinar alterações quanti-qualitativas na diversidade metabólica dos microrganismos do solo após a adição de biossólidos e identificar possíveis indicadores de alteração de qualidade do solo. O delineamento experimental constituiu-se de 4 doses de biossólidos da ETE-Franca, equivalentes à 6, 12, 24 e 48 Mg ha-1, mantendo-se um controle sem adição de biossólido. Foram utilizadas 4 repetições por tratamento, compreendendo 20 sub-parcelas. Estas sub-parcelas foram incubadas por 1, 2, 4, 8 e 16 semanas, perfazendo um total de 120 parcelas. Após o período de incubação, amostras de solo foram coletadas para as determinações de pH, C-biomassa, Respiração Basal (RB), Respiração Induzida pelo Substrato (RIS), Quociente Metabólico (qCO2) e Diversidade Metabólica. Houve um aumento transiente do pH nos tratamentos com as maiores doses de biossólido...

Fornecimento de uréia na dieta de catetos (Pecari tajacu) e uso de isótopo estável 15N como marcador para estimativa da síntese de nitrogênio microbiano; Provision of urea in diet peccary collared (Pecari tajacu) and use of stable isotope 15N how to marker to estimate of microbial nitrogen synthesis

Mendes, Alcester
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 22/10/2008 PT
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A utilização racional da fauna silvestre é um processo benéfico, por resultar em vantagens econômicas e sociais, e ao mesmo tempo auxiliar no processo de conservação das espécies silvestres. Entre as espécies silvestres brasileiras com potencial zootécnico, destaca-se o cateto (Pecari tajacu), um animal que consome diversos tipos de alimentos e que produz carne e couro com elevada demanda nos mercados nacional e internacional, respectivamente. Uma característica desta espécie é a presença de um pré-estômago, onde ocorre fermentação microbiana que confere a esta espécie capacidade para digerir alimentos volumosos. Objetivou-se com o presente trabalho: (i) medir a capacidade digestiva usando doses crescentes de uréia como fonte de nitrogênio não protéico (NNP) na dieta de catetos; (ii) avaliar a eficiência da microbiota do pré-estômago de catetos em proceder à fermentação anaeróbica da dieta, através da técnica de produção de gases para diferentes doses de uréia; (iii) estimar a síntese de nitrogênio microbiano in vitro utilizando o isótopo estável 15N como marcador. O trabalho foi dividido em três capítulos. No primeiro foi utilizado delineamento com distribuição inteiramente aleatória, no qual as possíveis seqüências dos tratamentos (doses de uréia: 0...

Microbial community composition and function in wastewater treatment plants

Wagner, Michael; Loy, Alexander; Nogueira, R.; Purkhold, Ulrike; Lee, Natuschka; Daims, Holger
Fonte: Kluwer Academic Publishers Publicador: Kluwer Academic Publishers
Tipo: Artigo de Revista Científica
Publicado em //2002 ENG
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Biological wastewater treatment has been applied for more than a century to ameliorate anthropogenic damage to the environment. But only during the last decade the use of molecular tools allowed to accurately determine the composition, and dynamics of activated sludge and biofilm microbial communities. Novel, in many cases yet not cultured bacteria were identified to be responsible for filamentous bulking and foaming as well as phosphorus and nitrogen removal in these systems. Now, methods are developed to infer the in situ physiology of these bacteria. Here we provide an overview of what is currently known about the identity and physiology of some of themicrobial key players in activated sludge and biofilm systems.; Deutsche Forschungsgemeinschaft - project WA1558/1.

Physiology and Nutrition of Lampropedia hyalina

Puttlitz, Donald H.; Seeley, H. W.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1968 EN
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A detailed study of the physiology and nutrition of Lampropedia hyalina revealed that it is an aerobic, cytochrome-containing chemoheterotroph which is limited in its energy sources to a few intermediates (and close derivatives) of the Krebs cycle. Reducing compounds at low levels are potent growth inhibitors. The microbe has no photosynthetic ability (despite its previous taxonomic position with the sulfur purple bacteria). The results of a general investigation of its physiology are reported. Added biotin and thiamine are needed for growth in defined media; pantothenate is strongly stimulatory. Alanine, arginine, and tyrosine, as well as NH4Cl, serve as sole nitrogen sources. A unique motion exhibited by cells of a rapidly growing culture is described. Aspects of its metabolism of poly-β-hydroxybutyrate and limiting aspects of its physiology as related to its ecology are discussed.

Susceptibility and Resistance of Several Fungi to Microbial Lysis1

Potgieter, H. J.; Alexander, M.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /04/1966 EN
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Potgieter, H. J. (Cornell University, Ithaca, N.Y.), and M. Alexander. Susceptibility and resistance of several fungi to microbial lysis. J. Bacteriol. 91:1526–1532. 1966.—Strains of Streptomyces, Nocardia, and Pseudomonas capable of lysing hyphae of Fusarium solani or Neurospora crassa were obtained by selective culture, but attempts to isolate an organism lysing Rhizoctonia solani failed. When provided with F. solani or N. crassa as carbon sources, the actinomycetes tested produced β-(1 → 3) glucanase and chitinase. A mixture containing purified chitinase and β-(1 → 3) glucanase induced spheroplast formation in F. solani, caused some morphological changes in N. crassa, but had almost no effect on R. solani hyphae. The polysaccharides in R. solani walls, which contain a large amount of glucose as well as galactose, mannose, and glucosamine, were not hydrolyzed appreciably by the two enzymes. Laminaribiose and laminaritriose were released by enzymatic hydrolysis of F. solani and N. crassa walls, and gentiobiose was liberated from R. solani and N. crassa walls. Melaninlike materials were found in R. solani walls, accounting for 8.50% of the wall weight. A role for melanin in protecting hyphae from microbial lysis is suggested.

Physiology of Growth and Sporulation in Bacillus cereus I. Effect of Glutamic and Other Amino Acids

Buono, F.; Testa, R.; Lundgren, D. G.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /06/1966 EN
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Buono, F. (Syracuse University, Syracuse, N.Y.), R. Testa, and D. G. Lundgren. Physiology of growth and sporulation in Bacillus cereus. I. Effect of glutamic and other amino acids. J. Bacteriol. 91:2291–2299. 1966.—Growth and sporulation were studied in Bacillus cereus by use of an active culture technique and a synthetic medium. A high level of glutamic acid (70 mm) was required for optimal growth and glucose oxidation followed by sporulation even though relatively little glutamic acid was consumed (14 mm). Optimal growth occurred with a combination of 14 mm glutamic acid and 56 mm (NH4)2SO4, aspartic acid, or alanine. Ornithine or arginine at 70 mm could replace glutamic acid in the synthetic medium without affecting the normal growth cycle. Glutamic acid was not replaced by any other amino acid, by (NH4)2SO4, or by a combination of either α-ketoglutarate or pyruvate plus (NH4)2SO4. Enzyme assays of cell-free extracts prepared from cells harvested at different times were used to study the metabolism of glutamic acid. Glutamic-oxaloacetic and glutamic-pyruvate transaminases were completely activated (or derepressed) during early stages of sporulation (period of 6 to 8 hr). Alanine dehydrogenase responded in a similar manner, but the levels of this enzyme were much higher throughout the culture cycle. Neither glutamic dehydrogenase nor α-ketoglutarate dehydrogenase was detected. Sporulation in a replacement salts medium was studied with cells harvested at different times from the synthetic medium. Cultures 2 to 6 hr old were unable to sporulate in the replacement salts medium unless glutamic acid (7.0 mm) was present. By the 6th hr...

Analysis of Structural and Physiological Profiles To Assess the Effects of Cu on Biofilm Microbial Communities

Massieux, B.; Boivin, M. E. Y.; van den Ende, F. P.; Langenskiöld, J.; Marvan, P.; Barranguet, C.; Admiraal, W.; Laanbroek, H. J.; Zwart, G.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /08/2004 EN
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We investigated the effects of copper on the structure and physiology of freshwater biofilm microbial communities. For this purpose, biofilms that were grown during 4 weeks in a shallow, slightly polluted ditch were exposed, in aquaria in our laboratory, to a range of copper concentrations (0, 1, 3, and 10 μM). Denaturing gradient gel electrophoresis (DGGE) revealed changes in the bacterial community in all aquaria. The extent of change was related to the concentration of copper applied, indicating that copper directly or indirectly caused the effects. Concomitantly with these changes in structure, changes in the metabolic potential of the heterotrophic bacterial community were apparent from changes in substrate use profiles as assessed on Biolog plates. The structure of the phototrophic community also changed during the experiment, as observed by microscopic analysis in combination with DGGE analysis of eukaryotic microorganisms and cyanobacteria. However, the extent of community change, as observed by DGGE, was not significantly greater in the copper treatments than in the control. Yet microscopic analysis showed a development toward a greater proportion of cyanobacteria in the treatments with the highest copper concentrations. Furthermore...

Interspecies Interactions within Oral Microbial Communities

Kuramitsu, Howard K.; He, Xuesong; Lux, Renate; Anderson, Maxwell H.; Shi, Wenyuan
Fonte: American Society for Microbiology (ASM) Publicador: American Society for Microbiology (ASM)
Tipo: Artigo de Revista Científica
Publicado em /12/2007 EN
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Summary: While reductionism has greatly advanced microbiology in the past 400 years, assembly of smaller pieces just could not explain the whole! Modern microbiologists are learning “system thinking” and “holism.” Such an approach is changing our understanding of microbial physiology and our ability to diagnose/treat microbial infections. This review uses oral microbial communities as a focal point to describe this new trend. With the common name “dental plaque,” oral microbial communities are some of the most complex microbial floras in the human body, consisting of more than 700 different bacterial species. For a very long time, oral microbiologists endeavored to use reductionism to identify the key genes or key pathogens responsible for oral microbial pathogenesis. The limitations of reductionism forced scientists to begin adopting new strategies using emerging concepts such as interspecies interaction, microbial community, biofilms, polymicrobial disease, etc. These new research directions indicate that the whole is much more than the simple sum of its parts, since the interactions between different parts resulted in many new physiological functions which cannot be observed with individual components. This review describes some of these interesting interspecies-interaction scenarios.

Real-Time Microsensor Measurement of Local Metabolic Activities in Ex Vivo Dental Biofilms Exposed to Sucrose and Treated with Chlorhexidine▿

von Ohle, Christiane; Gieseke, Armin; Nistico, Laura; Decker, Eva Maria; deBeer, Dirk; Stoodley, Paul
Fonte: American Society for Microbiology (ASM) Publicador: American Society for Microbiology (ASM)
Tipo: Artigo de Revista Científica
EN
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Dental biofilms are characterized by structural and functional heterogeneity. Due to bacterial metabolism, gradients develop and diverse ecological microniches exist. The aims of this study were (i) to determine the metabolic activity of microorganisms in naturally grown dental biofilms ex vivo by measuring dissolved oxygen (DO) and pH profiles with microelectrodes with high spatial resolution and (ii) to analyze the impact of an antimicrobial chlorhexidine (CHX) treatment on microbial physiology during stimulation by sucrose in real time. Biofilms were cultivated on standardized human enamel surfaces in vivo. DO and pH profiles were measured in a flow cell system in sterile human saliva, after sucrose addition (10%), again after alternative treatment of the sucrose exposed biofilms with CHX (0.2%) for 1 or 10 min or after being killed with paraformaldehyde (4%). Biofilm structure was visualized by vitality staining with confocal microscopy. With saliva as the sole nutrient source oxygen consumption was high within the superficial biofilm layers rendering deeper layers (>220 μm) anoxic. Sucrose addition induced the thickness of the anaerobic zone to increase with a concurrent decrease in pH (7.1 to 4.4). CHX exposure reduced metabolic activity and microbial viability at the biofilm surface and drove metabolic activity deeper into the biofilm. CHX treatment led to a reduced viability at the biofilm surface with minor influence on overall biofilm physiology after 1 min; even after 10 min there was measurable respiration and fermentation inside the biofilm. However...

The Binning of Metagenomic Contigs for Microbial Physiology of Mixed Cultures

Strous, Marc; Kraft, Beate; Bisdorf, Regina; Tegetmeyer, Halina E.
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
Publicado em 05/12/2012 EN
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So far, microbial physiology has dedicated itself mainly to pure cultures. In nature, cross feeding and competition are important aspects of microbial physiology and these can only be addressed by studying complete communities such as enrichment cultures. Metagenomic sequencing is a powerful tool to characterize such mixed cultures. In the analysis of metagenomic data, well established algorithms exist for the assembly of short reads into contigs and for the annotation of predicted genes. However, the binning of the assembled contigs or unassembled reads is still a major bottleneck and required to understand how the overall metabolism is partitioned over different community members. Binning consists of the clustering of contigs or reads that apparently originate from the same source population. In the present study eight metagenomic samples from the same habitat, a laboratory enrichment culture, were sequenced. Each sample contained 13–23 Mb of assembled contigs and up to eight abundant populations. Binning was attempted with existing methods but they were found to produce poor results, were slow, dependent on non-standard platforms or produced errors. A new binning procedure was developed based on multivariate statistics of tetranucleotide frequencies combined with the use of interpolated Markov models. Its performance was evaluated by comparison of the results between samples with BLAST and in comparison to existing algorithms for four publicly available metagenomes and one previously published artificial metagenome. The accuracy of the new approach was comparable or higher than existing methods. Further...

Proline Availability Regulates Proline-4-Hydroxylase Synthesis and Substrate Uptake in Proline-Hydroxylating Recombinant Escherichia coli

Falcioni, Francesco; Blank, Lars M.; Frick, Oliver; Karau, Andreas; Bühler, Bruno; Schmid, Andreas
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /05/2013 EN
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Microbial physiology plays a crucial role in whole-cell biotransformation, especially for redox reactions that depend on carbon and energy metabolism. In this study, regio- and enantio-selective proline hydroxylation with recombinant Escherichia coli expressing proline-4-hydroxylase (P4H) was investigated with respect to its interconnectivity to microbial physiology and metabolism. P4H production was found to depend on extracellular proline availability and on codon usage. Medium supplementation with proline did not alter p4h mRNA levels, indicating that P4H production depends on the availability of charged prolyl-tRNAs. Increasing the intracellular levels of soluble P4H did not result in an increase in resting cell activities above a certain threshold (depending on growth and assay temperature). Activities up to 5-fold higher were reached with permeabilized cells, confirming that host physiology and not the intracellular level of active P4H determines the achievable whole-cell proline hydroxylation activity. Metabolic flux analysis revealed that tricarboxylic acid cycle fluxes in growing biocatalytically active cells were significantly higher than proline hydroxylation rates. Remarkably, a catalysis-induced reduction of substrate uptake was observed...

Elemental Economy: microbial strategies for optimizing growth in the face of nutrient limitation

Merchant, Sabeeha S.; Helmann, John D.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em //2012 EN
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Microorganisms play a dominant role in the biogeochemical cycling of nutrients. They are rightly praised for their facility at fixing both carbon and nitrogen into organic matter, and microbial driven processes have tangibly altered the chemical composition of the biosphere and its surrounding atmosphere. Despite their prodigious capacity for molecular transformations, microorganisms are powerless in the face of the immutability of the elements. Limitations for specific elements, either fleeting or persisting over eons, have left an indelible trace on microbial genomes, physiology, and their very atomic composition. We here review the impact of elemental limitation on microbes, with a focus on selected genetic model systems and representative microbes from the ocean ecosystem. Evolutionary adaptations that enhance growth in the face of persistent or recurrent elemental limitations are evident from genome and proteome analyses. These range from the extreme (such as dispensing with a requirement for a hard to obtain element) to the extremely subtle (changes in protein amino acid sequences that slightly, but significantly, reduce cellular carbon, nitrogen, or sulfur demand). One near universal adaptation is the development of sophisticated acclimation programs by which cells adjust their chemical composition in response to a changing environment. When specific elements become limiting...

Microbial growth and physiology: a call for better craftsmanship

Egli, Thomas
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
Publicado em 14/04/2015 EN
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Virtually every microbiological experiment starts with the cultivation of microbes. Consequently, as originally pointed out by Monod (1949), handling microbial cultures is a fundamental methodology of microbiology and mastering different cultivation techniques should be part of every microbiologist’s craftsmanship. This is particularly important for research in microbial physiology, as the composition and behavior of microbes is strongly dependent on their growth environment. It has been pointed out repeatedly by eminent microbiologists that we should give more attention to the media and culturing conditions. However, this is obviously not adhered to with sufficient rigor as mistakes in basic cultivation principles are frequently found in the published research literature. The most frequent mistakes are the use of inappropriate growth media and little or no control of the specific growth rate, and some examples will be discussed here in detail. Therefore, this is a call for better microbiological craftsmanship when cultivating microbial cultures for physiological experiments. This call is not only addressed to researchers but it is probably even more important for the teaching of our discipline.

A brief history of bacterial growth physiology

Schaechter, Moselio
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
Publicado em 21/04/2015 EN
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Arguably, microbial physiology started when Leeuwenhoek became fascinated by observing a Vorticella beating its cilia, my point being that almost any observation of microbes has a physiological component. With the advent of modern microbiology in the mid-19th century, the field became recognizably distinctive with such discoveries as anaerobiosis, fermentation as a biological phenomenon, and the nutritional requirements of microbes. Soon came the discoveries of Winogradsky and his followers of the chemical changes in the environment that result from microbial activities. Later, during the first half of the 20th century, microbial physiology became the basis for much of the elucidation of central metabolism. Bacterial physiology then became a handmaiden of molecular biology and was greatly influenced by the discovery of cellular regulatory mechanisms. Microbial growth, which had come of age with the early work of Hershey, Monod, and others, was later pursued by studies on a whole cell level by what became known as the “Copenhagen School.” During this time, the exploration of physiological activities became coupled to modern inquiries into the structure of the bacterial cell. Recent years have seen the development of a further phase in microbial physiology...

Expression and Putative Function of Innate Immunity Genes under In Situ Conditions in the Symbiotic Hydrothermal Vent Tubeworm Ridgeia piscesae

Nyholm, Spencer V.; Song, Pengfei; Dang, Jeanne; Bunce, Corey; Girguis, Peter R.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
EN_US
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The relationships between hydrothermal vent tubeworms and sulfide-oxidizing bacteria have served as model associations for understanding chemoautotrophy and endosymbiosis. Numerous studies have focused on the physiological and biochemical adaptations that enable these symbioses to sustain some of the highest recorded carbon fixation rates ever measured. However, far fewer studies have explored the molecular mechanisms underlying the regulation of host and symbiont interactions, specifically those mediated by the innate immune system of the host. To that end, we conducted a series of studies where we maintained the tubeworm, Ridgeia piscesae, in high-pressure aquaria and examined global and quantitative changes in gene expression via high-throughput transcriptomics and quantitative real-time PCR (qPCR). We analyzed over 32,000 full-length expressed sequence tags as well as 26 Mb of transcript sequences from the trophosome (the organ that houses the endosymbiotic bacteria) and the plume (the gas exchange organ in contact with the free-living microbial community). R. piscesae maintained under conditions that promote chemoautotrophy expressed a number of putative cell signaling and innate immunity genes, including pattern recognition receptors (PRRs)...

Evolution after Introduction of a Novel Metabolic Pathway Consistently Leads to Restoration of Wild-Type Physiology

Carroll, Sean; Marx, Christopher J
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
EN_US
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Organisms cope with physiological stressors through acclimatizing mechanisms in the short-term and adaptive mechanisms over evolutionary timescales. During adaptation to an environmental or genetic perturbation, beneficial mutations can generate numerous physiological changes: some will be novel with respect to prior physiological states, while others might either restore acclimatizing responses to a wild-type state, reinforce them further, or leave them unchanged. We examined the interplay of acclimatizing and adaptive responses at the level of global gene expression in Methylobacterium extorquens AM1 engineered with a novel central metabolism. Replacing central metabolism with a distinct, foreign pathway resulted in much slower growth than wild-type. After 600 generations of adaptation, however, eight replicate populations founded from this engineered ancestor had improved up to 2.5-fold. A comparison of global gene expression in wild-type, engineered, and all eight evolved strains revealed that the vast majority of changes during physiological adaptation effectively restored acclimatizing processes to wild-type expression states. On average, 93% of expression perturbations from the engineered strain were restored, with 70% of these occurring in perfect parallel across all eight replicate populations. Novel changes were common but typically restricted to one or a few lineages...

Physiology and Evolution of Methylamine Metabolism across Methylobacterium extorquens strains

Nayak, Dipti Dinkar
Fonte: Harvard University Publicador: Harvard University
Tipo: Thesis or Dissertation
EN_US
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The interplay between physiology and evolution in microorganisms is extremely relevant from the stand-point of human health, the environment, and biotechnology; yet microbial physiology and microbial evolution largely continue to grow as disjoint fields of research. The goal of this dissertation was to use experimental evolution to study methylamine metabolism in Methylobacterium extorquens species. Methylotrophs like the M. extorquens species grow on reduced single carbon compounds and are the largest biological sink for methane. M. extorquens AM1, the model system for the study of aerobic methylotrophy, has an unstable genome and severe growth defects as a result of laboratory domestication. First, I describe the genomic, genetic, and phenotypic characterization of a new model system for the study of aerobic methylotrophy: M. extorquens PA1. This strain has a stable genome, was recently isolated from a known ecological niche, and is closely related to AM1. Whereas PA1 grew 10-50% faster than AM1on most substrates, it was five-fold slower on methylamine. The PA1 genome encodes a poorly characterized but ecologically relevant N-methylglutamate pathway whereas AM1 also encodes the well-characterized methylamine dehydrogenase for methylamine oxidation. I characterized the genetics of the N-methylglutamate pathway in PA1 to resolve a linear topology that requires the formation of two...

Efecto del cambio climático sobre los microorganismos edáficos; Suelos Ecuatoriales

Varela Ramírez, Amanda
Fonte: Pontifícia Universidade Javeriana Publicador: Pontifícia Universidade Javeriana
Formato: 1-8
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39 - 1; Este artículo tiene como objetivo hacer una revisión sobre el efecto que tiene el cambio climático global sobre la actividad, presencia y diversidad de microorganismos del suelo. En particular se hace referencia al efecto del aumento del CO2 sobre las actividades microbiales involucradas en el ciclaje biogeoquímico de nutrientes en el suelo. Algunos opinan que los organismos simbióticos, los involucrados en procesos de mineralización e inmovilización (especialmente de nitrógeno), los relacionados con los procesos de descomposición de la materia orgánica y los patógenos de plantas deberían estudiarse con más atención ya que pueden ser más afectados. Algunos estudios sobre biomasa microbiana y densidad bacteriana muestran resultados aparentemente contradictorios, pues estas pueden aumentar bajo condiciones de CO2 elevadas o no mostrar diferencias. Sin embargo, estas respuestas parecen estar mediadas por la humedad y cuando esta es baja se encuentran diferencias. Se considera que las medidas de actividad y biomasa no son adecuadas para describir las respuestas de la comunidad microbiana al aumento de CO2 otras herramientas en la biología molecular parecen más prometedoras. Con estas últimas se ha detectado que el efecto del aumento de CO2 es más marcado en las comunidades microbianas de la rizosfera que en las del suelo. Lo anterior hace que el panorama sea más complejo en términos de los efectos que causaría sobre la estructura de la red trófica del suelo. En general...

The Roles of Microcystin and Sulfide in Physiology and Tactic Responses of Pathogenic and Non-Pathogenic Mat-Forming Cyanobacteria

Brownell, Abigael C.
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica Formato: application/pdf
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Planktothricoides raciborskii and Roseofilum reptotaenium are physiologically similar, yet ecologically distinct organisms found in a hot spring outflow and coral black band disease (BBD), respectively. The aim of this study was to elucidate the relationship between R. reptotaenium and sulfide in BBD, to compare microcystin (MC) production in response to environmental factors, and to determine chemotactic responses to MC and sulfide by the two organisms. Results showed that the pathogenicity of R. reptotaenium in BBD is dependent on sulfate-reducing bacteria as secondary pathogens. Roseofilum reptotaenium produced significantly more MC than P. raciborskii, as measured using ELISA. Roseofilum reptotaenium was negatively chemotactic to sulfide, determined using horizontal and vertical gradients in agar, while P. raciborskii was not affected. Neither cyanobacterium was chemotactic to MC in the agar assays. The ecophysiology of P. raciborskii and R. reptotaenium in relation to MC production and response to sulfide reflected their pathogenic versus non-pathogenic status.

Microbial adaptations to envrionmental change: a moving target for global change ecology

Matthew D. Wallenstein; Sarah Evans
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Conferência ou Objeto de Conferência
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Background/Question/Methods As the abiotic conditions that structure biological communities and elicit physiological responses continue to change at an unprecedented rate, we need to understand how biological responses to global change will affect ecosystem functioning. A number of studies have detected shifts in the structure of microbial communities in response to experimental warming, elevated CO2 altered precipitation, and increased N deposition. However, since the links between microbial phylogeny and function are poorly understood, it can be challenging to predict how these changes in community structure will affect the rates of specific processes. It is often assumed that the high diversity of microbial communities makes them functionally redundant, and thus changes in community composition should have no direct effects. This paradigm has resulted in model structures that famously represent microbes as ‘black boxes'. Recently, significant progress has been made in linking microbial community structure to function, and efforts have been made to incorporate microbial physiology into biogeochemical models. Results/Conclusions Most efforts to predict the rates of microbially driven processes under future climates have extrapolated contemporary relationships between abiotic drivers and process rates...