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2.
Free Radic Biol Med ; 178: 295-307, 2022 01.
Artigo em Inglês | MEDLINE | ID: mdl-34890769

RESUMO

The role and coexistence of oxidative stress (OS) and inflammation in type C hepatic encephalopathy (C HE) is a subject of intense debate. Under normal conditions the physiological levels of intracellular reactive oxygen species are controlled by the counteracting antioxidant response to maintain redox homeostasis. Our previous in-vivo1H-MRS studies revealed the longitudinal impairment of the antioxidant system (ascorbate) in a bile-duct ligation (BDL) rat model of type C HE. Therefore, the aim of this work was to examine the course of central nervous system (CNS) OS and systemic OS, as well as to check for their co-existence with inflammation in the BDL rat model of type C HE. To this end, we implemented a multidisciplinary approach, including ex-vivo and in-vitro electron paramagnetic resonance spectroscopy (EPR) spin-trapping, which was combined with UV-Vis spectroscopy, and histological assessments. We hypothesized that OS and inflammation act synergistically in the pathophysiology of type C HE. Our findings point to an increased CNS- and systemic-OS and inflammation over the course of type C HE progression. In particular, an increase in the CNS OS was observed as early as 2-weeks post-BDL, while the systemic OS became significant at week 6 post-BDL. The CNS EPR measurements were further validated by a substantial accumulation of 8-Oxo-2'-deoxyguanosine (Oxo-8-dG), a marker of oxidative DNA/RNA modifications on immunohistochemistry (IHC). Using IHC, we also detected increased synthesis of antioxidants, glutathione peroxidase 1 (GPX-1) and superoxide dismutases (i.e.Cu/ZnSOD (SOD1) and MnSOD (SOD2)), along with proinflammatory cytokine interleukin-6 (IL-6) in the brains of BDL rats. The presence of systemic inflammation was observed already at 2-weeks post-surgery. Thus, these results suggest that CNS OS is an early event in type C HE rat model, which seems to precede systemic OS. Finally, our results suggest that the increase in CNS OS is due to enhanced formation of intra- and extra-cellular ROS rather than due to reduced antioxidant capacity, and that OS in parallel with inflammation plays a significant role in type C HE.


Assuntos
Encefalopatia Hepática , Animais , Ductos Biliares , Encéfalo , Modelos Animais de Doenças , Encefalopatia Hepática/etiologia , Inflamação , Estresse Oxidativo , Ratos , Ratos Wistar
3.
Lett Appl Microbiol ; 74(3): 311-333, 2022 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-34714944

RESUMO

Cadmium (Cd) is considered a toxic heavy metal; nevertheless, its toxicity fluctuates for different organisms. Cadmium-tolerant bacteria (CdtB) are diverse and non-phylogenetically related. Because of their ecological importance these bacteria become particularly relevant when pollution occurs and where human health is impacted. The aim of this review is to show the significance, culturable diversity, metabolic detoxification mechanisms of CdtB and their current uses in several bioremediation processes applied to agricultural soils. Further discussion addressed the technological devices and the possible advantages of genetically modified CdtB for diagnostic purposes in the future.


Assuntos
Metais Pesados , Poluentes do Solo , Agricultura , Bactérias/genética , Biodegradação Ambiental , Cádmio/toxicidade , Humanos , Metais Pesados/análise , Solo , Poluentes do Solo/análise , Poluentes do Solo/toxicidade
4.
J Appl Microbiol ; 128(5): 1497-1502, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31834654

RESUMO

INTRODUCTION: This study explores the uses of microcalorimetry to detect Mycobacterium tuberculosis (TB) in sputum. Microcalorimetry measures metabolic heat evolution during cellular proliferation of tuberculosis (TB) and is considered as a possible alternative to conventional diagnostic tools. OBJECTIVES: To compare the time to detection (TTD) from the BACTEC™ MGIT™ 960 and the calScreener™ calorimetric system. METHODS: Sixty-four sputa samples were selected from patients with confirmed pulmonary tuberculosis. Those sample were then decontaminated and analysed using calorimetry and BACTEC MGIT 960 system. RESULTS: The incubation period until detection of M. tuberculosis in the sample was 8·5 ± 3·7 days for the MGIT system and 10·1 ± 4·1 days (mean ± SD) for calorimetry. CONCLUSIONS: The microincubations in the 48-well format calScreener offers potential for rapid and accurate diagnostic of TB in different samples. Although TTD from calorimetry is still longer than with the MGIT, our findings suggest that several improvements are possible. Still, the instrument is ideal for continuous, real-time analysis of net metabolic heat release of limited sample numbers. SIGNIFICANCE AND IMPACT OF THE STUDY: Our result emphasizes that with further optimization, calorimetry can become an alternative detection method for tuberculosis.


Assuntos
Técnicas Bacteriológicas/métodos , Mycobacterium tuberculosis/isolamento & purificação , Mycobacterium tuberculosis/metabolismo , Escarro/microbiologia , Técnicas Bacteriológicas/instrumentação , Calorimetria , Humanos , Mycobacterium tuberculosis/crescimento & desenvolvimento , Fatores de Tempo , Tuberculose Pulmonar/microbiologia
5.
Geobiology ; 16(4): 378-398, 2018 07.
Artigo em Inglês | MEDLINE | ID: mdl-29573198

RESUMO

In modern stromatolites, mineralization results from a complex interplay between microbial metabolisms, the organic matrix, and environmental parameters. Here, we combined biogeochemical, mineralogical, and microscopic analyses with measurements of metabolic activity to characterize the mineralization processes and products in an emergent (<18 months) hypersaline microbial mat. While the nucleation of Mg silicates is ubiquitous in the mat, the initial formation of a Ca-Mg carbonate lamina depends on (i) the creation of a high-pH interface combined with a major change in properties of the exopolymeric substances at the interface of the oxygenic and anoxygenic photoautotrophic layers and (ii) the synergy between two major players of sulfur cycle, purple sulfur bacteria, and sulfate-reducing bacteria. The repetition of this process over time combined with upward growth of the mat is a possible pathway leading to the formation of a stromatolite.


Assuntos
Chromatiaceae/crescimento & desenvolvimento , Chromatiaceae/metabolismo , Sedimentos Geológicos/microbiologia , Minerais/metabolismo , Bactérias Redutoras de Enxofre/crescimento & desenvolvimento , Bactérias Redutoras de Enxofre/metabolismo
6.
Int J Parasitol Drugs Drug Resist ; 8(2): 159-164, 2018 08.
Artigo em Inglês | MEDLINE | ID: mdl-29587237

RESUMO

Trypanosoma congolense is a protozoan parasite that is transmitted by tsetse flies, causing African Animal Trypanosomiasis, also known as Nagana, in sub-Saharan Africa. Nagana is a fatal disease of livestock that causes severe economic losses. Two drugs are available, diminazene and isometamidium, yet successful treatment is jeopardized by drug resistant T. congolense. Isothermal microcalorimetry is a highly sensitive tool that can be used to study growth of the extracellular T. congolense parasites or to study parasite growth inhibition after the addition of antitrypanosomal drugs. Time of drug action and time to kill can be quantified in a simple way by real time heat flow measurements. We established a robust protocol for the microcalorimetric studies of T. congolense and developed mathematical computations in R to calculate different parameters related to growth and the kinetics of drug action. We demonstrate the feasibility and benefit of the method exemplary with the two standard drugs, diminazene aceturate and isometamidium chloride. The method and the mathematical approach can be translated to study other pathogenic or non-pathogenic cells if they are metabolically active and grow under axenic conditions.


Assuntos
Antiprotozoários/farmacologia , Calorimetria/métodos , Temperatura , Tripanossomicidas/farmacologia , Trypanosoma congolense/efeitos dos fármacos , Trypanosoma congolense/crescimento & desenvolvimento , Animais , Cultura Axênica , Bovinos , Sistemas Computacionais , Diminazena/análogos & derivados , Diminazena/farmacologia , Descoberta de Drogas , Resistência a Medicamentos , Modelos Teóricos , Fenantridinas/farmacologia , Trypanosoma congolense/fisiologia , Tripanossomíase Bovina/diagnóstico , Tripanossomíase Bovina/parasitologia
7.
J Appl Microbiol ; 124(5): 1175-1194, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29345852

RESUMO

AIMS: This research aims to assess total-cadmium soil content and microbiological aspects to understand the dynamics of culturable cadmium-tolerant bacteria (CdtB) in cacao soils from northeastern Colombia. METHODS AND RESULTS: An integration of inverted dish plating, Cd determination and a microcalorimetry assay (IMC) was carried out. A farm in Boyacá showed the highest level of total soil Cd (3·74 mg kg-1 ) followed by farms in Santander and Arauca (2·76 and 1·16 mg kg-1 , respectively). Coefficient of determination between total soil Cd and CFU of CdtB was high (R2  = 0·83) for the farm in Boyacá. Moreover, a pool of 129 CdtB was isolated, and phylogeny of 21 CdtB was discussed. Among CdtB strains isolated, Enterobacter sp. CdDB41 showed major Cd immobilization capacity (Qmax of 2·21 and 2·32 J at 6 and 24 mg l-1 of CdCl2 ), with an immobilization rate of 0·220 mg kg-1  h-1 . CONCLUSIONS: Among CdtB strains isolated, Enterobacter sp. CdDB41 showed major Cd immobilization capacity (Qmax of 2·21 and 2·32 J at 6 and 24 mg l-1 of CdCl2 ), with an immobilization rate of 0·220 mg kg-1  h-1 . SIGNIFICANCE AND IMPACT OF THE STUDY: Nothing is known about soil CdtB in cacao. Our data showed that CdtB such as Enterobacter sp. has high immobilization capacity. Furthermore, the otavite found in situ might be mineralized due to the bacterial metabolic activity of CdtB.


Assuntos
Bactérias/isolamento & purificação , Bactérias/metabolismo , Cacau/química , Cacau/microbiologia , Cádmio/análise , Cádmio/metabolismo , Produtos Agrícolas/microbiologia , Microbiologia do Solo , Colômbia , Produtos Agrícolas/química , Poluentes do Solo/análise , Poluentes do Solo/metabolismo
8.
J Appl Microbiol ; 123(3): 773-779, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28776899

RESUMO

AIMS: Production and release of injectable drug solutions are highly regulated since the administration of injectables bypasses natural body barriers. The sterility test is the last opportunity of product quality assessment. However, sterility is currently assessed by visual inspection (VI) that is time consuming and somewhat subjective. Therefore, we assessed isothermal microcalorimetry (IMC) as a replacement for the VI of the filtration based state-of-the-art sterility control. METHODS AND RESULTS: We used ATCC strains and house isolates to artificially contaminate frequently produced monoclonal antibodies (Avastin, Mabthera, Herceptin). After filtration, growth was assessed with IMC. Growth of all micro-organisms was reliably and reproducibly detected 4 days after inoculation, which was significantly faster than with VI. CONCLUSIONS: The reliability and the sensitivity of IMC have a large potential to improve sterility controls. Further evaluation of this alternative method is therefore highly recommended. SIGNIFICANCE AND IMPACT OF THE STUDY: Drug safety is of great concern for public health. Faster and safer drug production could be achieved using the technique described here. All the tests were performed with real manufactured drugs and complied with pharmaceutical standards. This suggests that drug sterility testing can be improved with potentially increased safety and cost reduction.


Assuntos
Calorimetria/métodos , Contaminação de Medicamentos , Preparações Farmacêuticas/análise , Contaminação de Medicamentos/estatística & dados numéricos , Filtração , Infertilidade , Reprodutibilidade dos Testes
9.
Geobiology ; 15(2): 259-279, 2017 03.
Artigo em Inglês | MEDLINE | ID: mdl-27935656

RESUMO

The use of metals as biosignatures in the fossil stromatolite record requires understanding of the processes controlling the initial metal(loid) incorporation and diagenetic preservation in living microbialites. Here, we report the distribution of metals and the organic fraction within the lithifying microbialite of the hypersaline Big Pond Lake (Bahamas). Using synchrotron-based X-ray microfluorescence, confocal, and biphoton microscopies at different scales (cm-µm) in combination with traditional geochemical analyses, we show that the initial cation sorption at the surface of an active microbialite is governed by passive binding to the organic matrix, resulting in a homogeneous metal distribution. During early diagenesis, the metabolic activity in deeper microbialite layers slows down and the distribution of the metals becomes progressively heterogeneous, resulting from remobilization and concentration as metal(loid)-enriched sulfides, which are aligned with the lamination of the microbialite. In addition, we were able to identify globules containing significant Mn, Cu, Zn, and As enrichments potentially produced through microbial activity. The similarity of the metal(loid) distributions observed in the Big Pond microbialite to those observed in the Archean stromatolites of Tumbiana provides the foundation for a conceptual model of the evolution of the metal distribution through initial growth, early diagenesis, and fossilization of a microbialite, with a potential application to the fossil record.


Assuntos
Microbiologia Ambiental , Fósseis , Metais/análise , Microbiota , Salinidade , Bahamas , Técnicas de Química Analítica
10.
Methods ; 76: 27-34, 2015 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-25461776

RESUMO

Isothermal microcalorimetry measures the heat released or consumed by physical or chemical processes. Metabolic activity releases heat that can be measured. However the calorimetric signal can be difficult for new users to interpret. This paper compares microcalorimetry to other techniques and reviews its application to different fields where microbiological activity is important. We also describe different ways to analyze the data and translate it into meaningful (micro)biological equivalents. This paper aims at providing non-specialist reader the tools to understand how isothermal microcalorimetry can be used for microbiological applications.


Assuntos
Bactérias/crescimento & desenvolvimento , Calorimetria/métodos , Bactérias/metabolismo , Temperatura Alta
11.
Placenta ; 35(1): 44-9, 2014 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-24280234

RESUMO

INTRODUCTION: Intrauterine Growth Restriction (IUGR) is a multifactorial disease defined by an inability of the fetus to reach its growth potential. IUGR not only increases the risk of neonatal mortality/morbidity, but also the risk of metabolic syndrome during adulthood. Certain placental proteins have been shown to be implicated in IUGR development, such as proteins from the GH/IGF axis and angiogenesis/apoptosis processes. METHODS: Twelve patients with term IUGR pregnancy (birth weight < 10th percentile) and 12 CTRLs were included. mRNA was extracted from the fetal part of the placenta and submitted to a subtraction method (Clontech PCR-Select cDNA Subtraction). RESULTS: One candidate gene identified was the long non-coding RNA NEAT1 (nuclear paraspeckle assembly transcript 1). NEAT1 is the core component of a subnuclear structure called paraspeckle. This structure is responsible for the retention of hyperedited mRNAs in the nucleus. Overall, NEAT1 mRNA expression was 4.14 (±1.16)-fold increased in IUGR vs. CTRL placentas (P = 0.009). NEAT1 was exclusively localized in the nuclei of the villous trophoblasts and was expressed in more nuclei and with greater intensity in IUGR placentas than in CTRLs. PSPC1, one of the three main proteins of the paraspeckle, co-localized with NEAT1 in the villous trophoblasts. The expression of NEAT1_2 mRNA, the long isoform of NEAT1, was only modestly increased in IUGR vs. CTRL placentas. DISCUSSION/CONCLUSION: The increase in NEAT1 and its co-localization with PSPC1 suggests an increase in paraspeckles in IUGR villous trophoblasts. This could lead to an increased retention of important mRNAs in villous trophoblasts nuclei. Given that the villous trophoblasts are crucial for the barrier function of the placenta, this could in part explain placental dysfunction in idiopathic IUGR fetuses.


Assuntos
Retardo do Crescimento Fetal/fisiopatologia , Placenta/fisiopatologia , RNA Longo não Codificante/metabolismo , Trofoblastos/metabolismo , Adulto , Núcleo Celular/metabolismo , Feminino , Humanos , Gravidez
12.
J Appl Microbiol ; 115(5): 1186-93, 2013 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-23865534

RESUMO

AIMS: Urinary tract infection (UTI) caused by Candida spp. is an increasing problem in clinical practice. Risk factors include diabetes mellitus, extremes of age, urinary tract abnormalities and indwelling catheters. Here, we determined the applicability of isothermal microcalorimetry (IMC) for the detection and antifungal drug susceptibility testing of Candida albicans in artificial urine. METHODS AND RESULTS: Isothermal microcalorimetry was used to monitor the metabolic heat production rates of C. albicans at 37 °C (µW = µJ s(-1) ). The influence of increasing concentrations of glucose and antifungal drugs on the growth of C. albicans was investigated. The growth rate increased linearly from 0.024 ± 0.010 to 0.203 ± 0.006 h(-1) with increasing concentration of glucose from 20 to 1640 mg l(-1) . The minimum inhibitory concentrations (MIC) against C. albicans were determined at a fixed glucose concentration of 560 mg l(-1) . These MIC were 0.5 µg ml(-1) for amphotericin B, 5 µg ml(-1) for flucytosine, 0.8 µg ml(-1) for fluconazole and 0.5 µg ml(-1) for tioconazole, respectively. CONCLUSIONS: IMC is able to detect and quantify growth of C. albicans in artificial urine and to determine the MIC of antifungal drugs against C. albicans. This study demonstrated that IMC can be used for basic research on Candida-UTI and opens promising avenue for the use of IMC as rapid drug resistance screening tool and diagnostic tool. SIGNIFICANCE AND IMPACT OF STUDY: Little is known on the growth of C. albicans in urine. Our study provides measurements of the growth rate of this yeast in urine with various glucose concentrations. Thus, important insights are gathered for risk group such as patients with diabetes or patients with prolonged parenteral nutrition resulting in higher urinary glucose concentration.


Assuntos
Antifúngicos/farmacologia , Candida albicans/efeitos dos fármacos , Glucose/química , Urina/microbiologia , Anfotericina B/farmacologia , Calorimetria , Candida albicans/crescimento & desenvolvimento , Fluconazol/farmacologia , Flucitosina/farmacologia , Humanos , Imidazóis/farmacologia , Testes de Sensibilidade Microbiana , Infecções Urinárias/tratamento farmacológico , Infecções Urinárias/microbiologia
13.
Urologe A ; 52(8): 1092-6, 2013 Aug.
Artigo em Alemão | MEDLINE | ID: mdl-23699913

RESUMO

Isothermal microcalorimetry (IMC) is a nonspecific analytical tool for measurement of heat. With sensitivity in the order of 0.2 µW, IMC can detect very small amounts of heat produced by only a small number of microorganisms or eukaryotic cells. This report is intended to introduce IMC to the urological audience and to give an overview about the past, present and future of this cutting edge technology in the urological context.


Assuntos
Calorimetria/métodos , Técnicas de Diagnóstico Urológico , Doenças Urológicas/diagnóstico , Doenças Urológicas/fisiopatologia , Humanos
14.
World J Urol ; 31(6): 1427-32, 2013 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-23358791

RESUMO

PURPOSE: To describe the incidence and drug susceptibility profiles of uropathogenic extended-spectrum-ß-lactamase-producing Escherichia coli (ESBL-EC) during a 10-year period and to identify differences in resistance patterns between urological and non-urological ESBL-EC isolates. METHODS: Retrospective analysis of 191,564 urine samples obtained during 2001 to 2010 at the University Hospital Basel, Switzerland. The computerized database of the Clinical Microbiology Laboratory and the Division of Infectious Diseases and Hospital Epidemiology was used to identify ESBL-EC positive urine samples. ESBL-EC isolates were stratified according their origin into two groups: Urology and non-Urology isolates. RESULTS: The rate of ESBL-EC positive urine samples increased significantly during the study period (3 in 2001 compared to 55 in 2010, p < 0.05). The most active agents were imipenem, meropenem, and fosfomycin (100%), followed by amikacin (99.1%) and nitrofurantoin (84%). The least active substances were ampicillin-clavulanate (20%), sulfamethoxazole (28%), and ciprofloxacin (29.6%). ESBL-EC isolates from urological and non-urological patients showed similar susceptibility profiles. However, ESBL-EC isolates from urological patients were significantly less susceptible to ciprofloxacin compared to non-urological isolates (14.7 vs. 32.7%, p < 0.05). CONCLUSIONS: The rate of urinary ESBL-EC isolates is increasing. Their susceptibility to nitrofurantoin, fosfomycin, and carbapenems is excellent, whereas ampicillin-clavulanate, sulfamethoxazole, and ciprofloxacin demonstrate only low susceptibility. In particular, the use of ciprofloxacin should be strictly avoided in urologic patients with suspicion for an ESBL-EC urinary tract infection as well as routine antibiotic prophylaxis prior to urological interventions if not explicit indicated by current international guidelines or local resistance patterns.


Assuntos
Ciprofloxacina/uso terapêutico , Farmacorresistência Bacteriana , Infecções por Escherichia coli/epidemiologia , Escherichia coli/isolamento & purificação , Infecções Urinárias/epidemiologia , Sistema Urinário/microbiologia , beta-Lactamases/metabolismo , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Antibacterianos/farmacologia , Antibacterianos/uso terapêutico , Carbapenêmicos/farmacologia , Carbapenêmicos/uso terapêutico , Ciprofloxacina/farmacologia , Contraindicações , Escherichia coli/efeitos dos fármacos , Escherichia coli/metabolismo , Infecções por Escherichia coli/tratamento farmacológico , Feminino , Fosfomicina/farmacologia , Fosfomicina/uso terapêutico , Humanos , Masculino , Pessoa de Meia-Idade , Nitrofurantoína/farmacologia , Nitrofurantoína/uso terapêutico , Prevalência , Estudos Retrospectivos , Falha de Tratamento , Resultado do Tratamento , Infecções Urinárias/tratamento farmacológico , Infecções Urinárias/microbiologia , Adulto Jovem
15.
World J Urol ; 31(3): 579-84, 2013 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-23053214

RESUMO

BACKGROUND: Microbial ureteral stent colonisation (MUSC) is one leading risk factor for complications associated with ureteral stent placement. As MUSC remains frequently undetected by standard urine cultures, its definitive diagnosis depends on microbiological investigation of the stent. However, a standard reference laboratory technique for studying MUSC is still lacking. MATERIALS AND METHODS: A total of 271 ureteral stents removed from 199 consecutive patients were investigated. Urine samples were obtained prior to device removal. Stents were divided into four parts. Each part was separately processed by the microbiology laboratory within 6 h. Ureteral stents were randomly allocated to roll-plate or sonication, respectively, and analysed using standard microbiological techniques. Demographic and clinical data were prospectively collected using a standard case-report form. RESULTS: Overall, roll-plate showed a higher detection rate of MUSC compared with sonication (35 vs. 28 %, p < 0.05) and urine culture (35 vs. 8 %, p < 0.05). No inferiority of Maki's technique was observed even when stents were stratified according to indwelling time below or above 30 days. Compared with roll-plate, sonication commonly failed to detect Enterococcus spp., coagulase-negative staphylococci (CoNS) and Enterobacteriaceae. In addition, sonication required more hands-on time, more equipment and higher training than roll-plate in the laboratory. CONCLUSIONS: This prospective randomised study demonstrates the superiority of Maki's roll-plate technique over sonication in the diagnosis of MUSC and that urine culture is less sensitive than both methods. The higher detection rate, simplicity and cost-effectiveness render roll-plate the methodology of choice for routine clinical investigation as well as basic laboratory research.


Assuntos
Infecções Relacionadas a Cateter/diagnóstico , Infecções por Enterobacteriaceae/diagnóstico , Enterobacteriaceae/isolamento & purificação , Enterococcus/isolamento & purificação , Técnicas Microbiológicas/métodos , Infecções Estreptocócicas/diagnóstico , Cateteres Urinários/microbiologia , Adulto , Idoso , Infecções Relacionadas a Cateter/microbiologia , Contagem de Colônia Microbiana , Análise Custo-Benefício , Infecções por Enterobacteriaceae/microbiologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Sensibilidade e Especificidade , Sonicação/métodos , Infecções Estreptocócicas/microbiologia , Urina/microbiologia
16.
Geobiology ; 10(6): 518-30, 2012 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-22925453

RESUMO

Mineral precipitation in microbial mats may have been the key to their preservation as fossil stromatolites, potentially documenting evidence of the earliest life on Earth. Two factors that contribute to carbonate mineral precipitation are the saturation index (SI) and the presence of nucleation sites. Both of these can be influenced by micro-organisms, which can either alter SI through their metabolisms, or produce and consume organic substances such as extracellular polymeric substances (EPS) that can affect nucleation. It is the balance of individual metabolisms within the mat community that determines the pH and the dissolved inorganic carbon concentration, thereby potentially increasing the alkalinity and consequently the SI. Sulfate-reducing bacteria (SRB) are an important component of this 'alkalinity engine.' The activity of SRB often peaks in layers where CaCO(3) precipitates, and mineral precipitation has been demonstrated in SRB cultures; however, the effect of their metabolism on the alkalinity engine and actual contribution to mineral precipitation is the subject of controversy. Here, we show through culture experiments, theoretical calculations, and geochemical modeling studies that the pH, alkalinity, and organomineralization potential will vary depending on the type of electron donor. Specifically, hydrogen and formate can increase the pH, but electron donors like lactate and ethanol, and to a lesser extent glycolate, decrease the pH. The implication of this for the lithification of mats is that the combination of processes supplying electron donors and the utilization of these compounds by SRB may be critical to promoting mineral precipitation.


Assuntos
Bactérias/metabolismo , Carbonato de Cálcio/metabolismo , Sulfatos/metabolismo , Precipitação Química , Microbiologia Ambiental , Concentração de Íons de Hidrogênio , Modelos Biológicos , Modelos Teóricos , Oxirredução
17.
J Clin Microbiol ; 50(1): 16-20, 2012 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-22090404

RESUMO

Mycobacterium tuberculosis is a global public health concern, particularly with the emergence of drug-resistant strains. Immediate identification of drug-resistant strains is crucial to administering appropriate treatment before the bacteria are allowed to spread. However, developing countries, which are most affected by drug resistance, are struggling to combat the disease without the facilities or funds for expensive diagnostics. Recent studies have emphasized the suitability of isothermal microcalorimetry (IMC) for the rapid detection of mycobacteria. In this study, we investigate its suitability for rapid and reliable M. tuberculosis drug susceptibility testing. Specifically, IMC was used to determine the MICs of three drugs, namely, isoniazid, ethambutol, and moxifloxacin, against three mycobacteria, namely, Mycobacterium smegmatis, Mycobacterium avium, and Mycobacterium tuberculosis. The Richards growth model was used to calculate growth parameters, namely, the maximum bacterial growth rate and the lag phase duration from integrated heat flow-versus-time results. For example, MICs of isoniazid, ethambutol, and moxifloxacin were determined to be 1.00, 8.00, and 0.25 µg/ml, respectively. IMC, as described here, could be used not just in industrialized countries but also in developing countries because inexpensive and sensitive microcalorimeters are now available.


Assuntos
Compostos Aza/farmacologia , Etambutol/farmacologia , Isoniazida/farmacologia , Testes de Sensibilidade Microbiana/métodos , Mycobacterium avium/efeitos dos fármacos , Mycobacterium smegmatis/efeitos dos fármacos , Mycobacterium tuberculosis/efeitos dos fármacos , Quinolinas/farmacologia , Antituberculosos/farmacologia , Calorimetria/métodos , Fluoroquinolonas , Humanos , Moxifloxacina
18.
Biotechnol Bioeng ; 108(12): 3019-24, 2011 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-21769860

RESUMO

Isothermal microcalorimeters (IMC) are highly sensitive instruments that allow the measurement of heat flow in the microwatt range. Due to their detection of minute thermal heat, IMC techniques have been used in numerous biological applications, including the study of fermentation processes, pharmaceutical development, and cell metabolism. In this work, with the ultimate goal of establishing a rapid and real-time method to predict the proliferative capacity of human articular chondrocytes (HAC), we explored to use of IMC to characterize one of the crucial steps within the process of cartilage tissue engineering, namely the in vitro expansion of HAC. We first established an IMC-based model for the real-time monitoring of heat flow generated by HAC during proliferation. Profiles of the heat and heat flow curves obtained were consistent with those previously shown for other cell types. The average heat flow per HAC was determined to be 22.0 ± 5.3 pW. We next demonstrated that HAC proliferation within the IMC-based model was similar to proliferation under standard culture conditions, verifying its relevance for simulating the typical cell culture application. HAC growth and HAC heat over time appeared correlated for cells derived from particular donors. However, based on the results from 12 independent donors, no predictive correlation could be established between the growth rate and the heat increase rate of HAC. This was likely due to variability in the biological function of HAC derived from different donors, combined with the complexity of tightly couple metabolic processes beyond proliferation. In conclusion, IMC appears to be a promising technique to characterize cell proliferation. However, studies with more reproducible cell sources (e.g., cell lines) could be used before adding the complexity associated with primary human cells.


Assuntos
Proliferação de Células , Condrócitos/fisiologia , Termogênese , Calorimetria/métodos , Células Cultivadas , Humanos , Engenharia Tecidual/métodos
19.
J Mater Sci Mater Med ; 22(10): 2293-300, 2011 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-21786131

RESUMO

In this study, the cytotoxicity evaluation of prepared 63S bioactive glass and bone-derived hydroxyapatite particles with yeast and human chondrocyte cells was carried out using isothermal micro-nano calorimetry (IMNC), which is a new method for studying cell/biomaterial interactions. Bioactive glass particles were made via sol-gel method and hydroxyapatite was obtained from bovine bone. Elemental analysis was carried out by XRF and EDXRF. Amorphous structure of the glass and completely crystalline structure of HA were detected by XRD analysis. Finally, the cytotoxicity of bioactive glass and bone-derived HA particles with yeast and cultured human chondrocyte cells was evaluated using IMNC. The results confirmed the viability, growth and proliferation of human chondrocyte cells in contact with 63S bioactive glass, and bone-derived HA particles. Also the results indicated that yeast model which is much easier to handle, can be considered as a good proxy and can provide a rapid primary estimate of the ranges to be used in assays involving human cells. All of these results confirmed that IMNC is a convenient method which caters to measuring the cell-biomaterial interactions alongside the current methods.


Assuntos
Osso e Ossos/química , Condrócitos/efeitos dos fármacos , Vidro/química , Hidroxiapatitas/toxicidade , Saccharomyces cerevisiae/efeitos dos fármacos , Animais , Materiais Biocompatíveis , Calorimetria , Bovinos , Relação Dose-Resposta a Droga , Humanos , Hidroxiapatitas/química , Difração de Raios X
20.
J Appl Microbiol ; 111(4): 1016-24, 2011 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-21797951

RESUMO

AIMS: The objective of this study was to evaluate the effectiveness of microcalorimetry in rapid detection of mycobacterium species using an inexpensive Isothermal microcalorimetry (IMC) instrument. In addition, we compared microcalorimetry with conventional monitoring techniques. METHODS AND RESULTS: Isothermal microcalorimetry measures heat production rate and can provide rapid detection of living mycobacteria in clinical specimens. Using liquid medium showed that bacterial activity measured by IMC using a TAM Air® agreed with the triphenyl tetrazolium chloride (TTC) assay. Using solid medium to enhance growth, fast-growing mycobacteria detection was achieved between 26 and 53 h and slow-growing mycobacteria detection was achieved between 54 and 298 h. In addition, the calorimetric data were analysed to estimate the growth rate and generation time of the mycobacteria monitored. SIGNIFICANCE AND IMPACT OF THE STUDY: Infections caused by mycobacteria are severe and difficult to treat. With 9·27 million new cases of tuberculosis in 2007, developing countries experience severe health and economic consequences owing to the lack of an affordable, fast detection method. Research-grade IMC instruments are too expensive to use in developing countries. Our study demonstrates that less-expensive instruments such as the TAM air® are adequate for mycobacteria detection and therefore establishes a clear proof of concept.


Assuntos
Técnicas Bacteriológicas/métodos , Calorimetria/métodos , Infecções por Mycobacterium/diagnóstico , Mycobacterium/isolamento & purificação , Tuberculose/diagnóstico , Técnicas Bacteriológicas/economia , Calorimetria/economia , Meios de Cultura , Humanos , Mycobacterium/crescimento & desenvolvimento
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