RESUMEN
A Gram-negative, aerobic bacterial strain RR6T was isolated from the sea sand to produce lipase and proposed as a novel species of Halopseudomonas. The optimum growth occurred at 2837 °C, and the pH was 6.08.0. The optimum growth occurred at 3.0 -6.5% (w/v) NaCl. The major cellular fatty acids were C10:0 3OH, C12:0, C16:1 ω7c/16:1 ω6c, 18:1 ω7c and/or 18:1 ω6c, and C16:0. The predominant polar lipids were phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, unidentified phospholipid, and unidentified lipids. The genome is 3.93 Mb, and the G + C content is 61.3%. The 16S rRNA gene sequences shared 99.7399.87% sequence similarity with the closely related type strains of Halopseudomonas. The average nucleotide identity and average amino acid identity of strain RR6T with reference type strains were below 9596%, and the corresponding in-silico DNADNA hybridization values were below 70%. Strain RR6T clustered with Halopseudomonas gallaeciensis V113T and Halopseudomonas pachastrellae CCUG 46540 T in the phylogenetic tree. Further, lipase produced by this bacterium belongs to α/β hydrolase lipase family and exhibits structural similarity to the lactonizing lipase. Based on the polyphasic analysis, the new isolates RR6T represent a novel species of Halopseudomonas for which Halopseudomonas maritima sp. nov. is proposed. The type strain is RR6T (= NBRC 115418 T = TBRC 15628 T).(AU)
Asunto(s)
Humanos , Filogenia , 24975/microbiología , Técnicas de Tipificación Bacteriana , Lipasa/genética , Fosfolípidos/química , Bacterias Aerobias Gramnegativas , Microbiología , Técnicas Microbiológicas , Genoma , ADN Bacteriano/genéticaRESUMEN
Bacterial outer membrane vesicles (OMVs) are nanometer-scale, spherical vehicles released by Gram-negative bacteria into their surroundings throughout growth. These OMVs have been demonstrated to play key roles in pathogenesis by delivering certain biomolecules to host cells, including toxins and other virulence factors. In addition, this biomolecular delivery function enables OMVs to facilitate intra-bacterial communication processes, such as quorum sensing and horizontal gene transfer. The unique ability of OMVs to deliver large biomolecules across the complex Gram-negative cell envelope has inspired the use of OMVs as antibiotic delivery vehicles to overcome transport limitations. In this review, we describe the advantages, applications, and biotechnological challenges of using OMVs as antibiotic delivery vehicles, studying both natural and engineered antibiotic applications of OMVs. We argue that OMVs hold great promise as antibiotic delivery vehicles, an urgently needed application to combat the growing threat of antibiotic resistance.
Asunto(s)
Antibacterianos/administración & dosificación , Membrana Externa Bacteriana/metabolismo , Portadores de Fármacos , Vesículas Extracelulares/metabolismo , Bacterias Aerobias Gramnegativas/metabolismo , Animales , Antibacterianos/metabolismo , Composición de Medicamentos , Vesículas Extracelulares/genética , Bacterias Aerobias Gramnegativas/genética , HumanosRESUMEN
Epicotripeptin (1), a new cyclic tripeptide along with four known cyclic dipeptides (2-5) and one acetamide derivative (6) were isolated from seagrass-associated endophytic fungus Epicoccum nigrum M13 recovered from the Red Sea. Additionally, two new compounds, cyclodidepsipeptide phragamide A (7) and trioxobutanamide derivative phragamide B (8), together with eight known compounds (9-16), were isolated from plant-derived endophyte Alternaria alternata 13A collected from a saline lake of Wadi El Natrun depression in the Sahara Desert. The structures of the isolated compounds were determined based on the 1D and 2D NMR spectroscopic data, HRESIMS data, and a comparison with the reported literature. The absolute configurations of 1 and 7 were established by advanced Marfey's and Mosher's ester analyses. The antimicrobial screening indicated that seven of the tested compounds exhibited considerable (MIC range of 2.5-5 µg/mL) to moderate (10-20 µg/mL) antibacterial effect against the tested Gram-positive strains and moderate to weak (10-30 µg/mL) antibacterial effect against Gram-negative strains. Most of the compounds exhibited weak or no activity against the tested Gram-negative strains. On the other hand, four of the tested compounds showed considerable antibiofilm effects against biofilm forming Gram-positive and Gram-negative strains.
Asunto(s)
Alternaria/metabolismo , Antibacterianos/farmacología , Ascomicetos/metabolismo , Biopelículas/efectos de los fármacos , Bacterias Aerobias Gramnegativas/efectos de los fármacos , Bacterias Grampositivas/efectos de los fármacos , Antibacterianos/aislamiento & purificación , Biopelículas/crecimiento & desarrollo , Fermentación , Bacterias Aerobias Gramnegativas/crecimiento & desarrollo , Bacterias Grampositivas/crecimiento & desarrollo , Pruebas de Sensibilidad Microbiana , Estructura Molecular , Relación Estructura-ActividadRESUMEN
The spreading of carbapenemase-producing gram-negative bacilli (GNB) must be considered as an "urgent" threat. The aim of this study was to determine the prevalence of extended spectrum ß-lactamase (ESBL), plasmid-mediated quinolone resistance (PMQR), and carbapenemase-producing GNB and to characterize the supporting genes in GNB specimens isolated from patients and healthy volunteers in Burkina Faso. From April to June 2016, carbapenemase-producing GNB screening was performed in 1,230 consecutive clinical specimens, and 158 fecal samples from inpatients and healthy volunteers without digestive pathology at Souro Sanou University Hospital, Bobo Dioulasso. Strains were identified by matrix-assisted laser desorption ionization-time of flight and antimicrobial susceptibility was tested with the disk diffusion method on Müller-Hinton agar. The presence of carbapenemase, ESBL, and PMQR genes was assessed by multiplex PCR. The molecular epidemiological study was performed using multilocus sequence typing analysis. From the 1,230 clinical samples, 443 GNB strains were isolated among which 4 (0.9%) were carbapenemase-producing isolates (Escherichia coli, n = 1; Acinetobacter baumannii, n = 3). Among the 158 fecal samples tested for carbapenemase-producing Enterobacteriaceae carriage, 13 (8.2%) were carbapenemase-producing isolates (E. coli, n = 4; Klebsiella pneumoniae, n = 6; A. baumannii, n = 2; Acinetobacter nosocomialis, n = 1; Acinetobacter bereziniae, n = 1). The strains from the two groups were resistant to broad-spectrum cephalosporins (100% for both), gentamicin (100% and 64.3%), levofloxacin (100% and 85.7%), and to amikacin (0% and 7.1%). The carbapenemase-encoding genes blaNDM-1, blaOxa-58, blaOxa-181, and blaVIM-2 were detected in clinical and in fecal samples. The majority (10/11) of the enterobacterial strains carried also blaCTX-M-15. The majority of the strains belonged to ST692 for E. coli, to ST147 for K. pneumoniae and to ST2 for A. baumannii. This study confirms the presence of carbapenemase-producing GNB in samples from patients and healthy volunteers. More effective active surveillance activities are needed.
Asunto(s)
Antibacterianos/farmacología , Bacterias Aerobias Gramnegativas/efectos de los fármacos , Bacterias Aerobias Gramnegativas/genética , Infecciones por Bacterias Gramnegativas/epidemiología , beta-Lactamasas/genética , Proteínas Bacterianas/genética , Burkina Faso/epidemiología , Relación Dosis-Respuesta a Droga , Farmacorresistencia Bacteriana Múltiple , Femenino , Fluoroquinolonas/farmacología , Infecciones por Bacterias Gramnegativas/genética , Humanos , Masculino , Pruebas de Sensibilidad Microbiana , Plásmidos/efectos de los fármacos , Reacción en Cadena de la PolimerasaRESUMEN
Achromatium is large, hyperpolyploid and the only known heterozygous bacterium. Single cells contain approximately 300 different chromosomes with allelic diversity far exceeding that typically harbored by single bacteria genera. Surveying all publicly available sediment sequence archives, we show that Achromatium is common worldwide, spanning temperature, salinity, pH, and depth ranges normally resulting in bacterial speciation. Although saline and freshwater Achromatium spp. appear phylogenetically separated, the genus Achromatium contains a globally identical, complete functional inventory regardless of habitat. Achromatium spp. cells from differing ecosystems (e.g., from freshwater to saline) are, unexpectedly, equally functionally equipped but differ in gene expression patterns by transcribing only relevant genes. We suggest that environmental adaptation occurs by increasing the copy number of relevant genes across the cell's hundreds of chromosomes, without losing irrelevant ones, thus maintaining the ability to survive in any ecosystem type. The functional versatility of Achromatium and its genomic features reveal alternative genetic and evolutionary mechanisms, expanding our understanding of the role and evolution of polyploidy in bacteria while challenging the bacterial species concept and drivers of bacterial speciation.
Asunto(s)
Evolución Biológica , Genoma Bacteriano , Sedimentos Geológicos/microbiología , Bacterias Aerobias Gramnegativas/genética , Microbiología del Agua , Ecosistema , Bacterias Aerobias Gramnegativas/metabolismo , Heterocigoto , Filogenia , PoliploidíaRESUMEN
Achromatium is a long known uncultured giant gammaproteobacterium forming intracellular CaCO3 that impacts C and S geochemical cycles functioning in some anoxic sediments and at oxic-anoxic boundaries. While intracellular CaCO3 granules have first been described as Ca oxalate then colloidal CaCO3 more than one century ago, they have often been referred to as crystalline solids and more specifically calcite over the last 25 years. Such a crystallographic distinction is important since the respective chemical reactivities of amorphous calcium carbonate (ACC) and calcite, hence their potential physiological role and conditions of formation, are significantly different. Here, we analyzed the intracellular CaCO3 granules of Achromatium cells from Lake Pavin using a combination of Raman microspectroscopy and scanning electron microscopy. Granules in intact Achromatium cells were unequivocally composed of ACC. Moreover, ACC spontaneously transformed into calcite when irradiated at high laser irradiance during Raman analyses. Few ACC granules also transformed spontaneously into calcite in lysed cells upon cell death and/or sample preparation. Overall, the present study supports the original claims that intracellular Ca-carbonates in Achromatium are amorphous and not crystalline. In that sense, Achromatium is similar to a diverse group of Cyanobacteria and a recently discovered magnetotactic alphaproteobacterium, which all form intracellular ACC. The implications for the physiology and ecology of Achromatium are discussed. Whether the mechanisms responsible for the preservation of such unstable compounds in these bacteria are similar to those involved in numerous ACC-forming eukaryotes remains to be discovered. Last, we recommend to future studies addressing the crystallinity of CaCO3 granules in Achromatium cells recovered from diverse environments all over the world to take care of the potential pitfalls evidenced by the present study.
Asunto(s)
Carbonato de Calcio , Bacterias Aerobias Gramnegativas , Carbonatos , Lagos , Microscopía Electrónica de RastreoRESUMEN
Gram-negative Antarctic bacteria adopt survival strategies to live and proliferate in an extremely cold environment. Unusual chemical modifications of the lipopolysaccharide (LPS) and the main component of their outer membrane are among the tricks adopted to allow the maintenance of an optimum membrane fluidity even at particularly low temperatures. In particular, the LPS' glycolipid moiety, the lipid A, typically undergoes several structural modifications comprising desaturation of the acyl chains, reduction in their length and increase in their branching. The investigation of the structure of the lipid A from cold-adapted bacteria is, therefore, crucial to understand the mechanisms underlying the cold adaptation phenomenon. Here we describe the structural elucidation of the highly heterogenous lipid A from three psychrophiles isolated from Terra Nova Bay, Antarctica. All the lipid A structures have been determined by merging data that was attained from the compositional analysis with information from a matrix-assisted laser desorption ionization (MALDI) time of flight (TOF) mass spectrometry (MS) and MS2 investigation. As lipid A is also involved in a structure-dependent elicitation of innate immune response in mammals, the structural characterization of lipid A from such extremophile bacteria is also of great interest from the perspective of drug synthesis and development inspired by natural sources.
Asunto(s)
Frío , Bacterias Aerobias Gramnegativas/metabolismo , Lípido A/química , Termotolerancia , Regiones Antárticas , Hielo , Lípido A/aislamiento & purificación , Estructura Molecular , Agua de Mar/microbiología , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción , Microbiología del AguaRESUMEN
Planctomycetes of the family Gemmataceae are characterized by large genome sizes and cosmopolitan distribution in freshwater and terrestrial environments but their ecological functions remain poorly understood. In this study, we characterized a novel representative of this family, strain PL17T, which was isolated from a littoral tundra wetland and was capable of growth on xylan and cellulose. Cells of this isolate were represented by pink-pigmented spheres that multiplied by budding and occurred singly or in short chains and aggregates. Strain PL17T was obligately aerobic, mildly acidophilic chemoorganotrophic bacterium, which displayed good tolerance of low temperatures. The major fatty acids were C18:0, C16:1ω5, and ßOH-C16:1; the major polar lipid was trimethylornithine. The genome of strain PL17T consisted of a 9.83 Mb chromosome and a 24.69kb plasmid. The G+C contents of the chromosomal and plasmid DNA were 67.4 and 62.3mol%, respectively. Over 8900 potential protein-coding genes were identified in the genome including a putative cellulase that contains a domain from the GH5 family of glycoside hydrolases. The genome of strain PL17T contained one linked and one unlinked rRNA operons with 16S rRNA gene sequences displaying 94.5% similarity to that in Gemmata obscuriglobus UQM2246T. Based on the results of comparative phenotypic, chemotaxonomic and phylogenomic analyses, we propose to classify strain PL17T (= CECT 9407T=VKM B-3467T) as representing a novel genus and species of the family Gemmataceae, Frigoriglobus tundricola gen. nov., sp. nov.
Asunto(s)
Bacterias Aerobias Gramnegativas/clasificación , Bacterias Aerobias Gramnegativas/aislamiento & purificación , Tundra , Humedales , Bacterias , Técnicas de Tipificación Bacteriana , Composición de Base , Celulosa/metabolismo , Frío , ADN Bacteriano/química , ADN Bacteriano/genética , Ácidos Grasos/análisis , Genes Bacterianos , Genes de ARNr , Genoma Bacteriano , Bacterias Aerobias Gramnegativas/genética , Bacterias Aerobias Gramnegativas/fisiología , Lípidos/análisis , Redes y Vías Metabólicas/genética , Filogenia , Planctomycetales/clasificación , Planctomycetales/genética , ARN Ribosómico 16S/genética , Xilanos/metabolismoRESUMEN
No disponible
Asunto(s)
Humanos , Masculino , Anciano , Infecciones por Bacterias Gramnegativas/diagnóstico , Infecciones por Bacterias Gramnegativas/tratamiento farmacológico , Infecciones por Bacterias Grampositivas/diagnóstico , Bacterias Aerobias Gramnegativas , Bacteriemia/diagnóstico , Infecciones por Bacterias Grampositivas/tratamiento farmacológico , Bacterias/efectos de los fármacos , Bacteriemia/tratamiento farmacológico , Linezolid/uso terapéutico , Cultivo de Sangre , Cromatografía de Gases y Espectrometría de Masas , Factores de RiesgoRESUMEN
We evaluated the Copan Eswab transport system for the quantitative recovery of Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa after 1, 2, 3, 5, and 7â¯days of storage at room and refrigerator temperatures, and 7 and 30â¯days of storage at -80⯰C and -20⯰C using mono- and polymicrobial samples. The study was based on Clinical and Laboratory Standards Institute (CLSI) M40-A2 standard procedures on the quality control of microbiological transport systems. Eswab met the CLSI standards at room and refrigerator temperatures for all (combinations of) bacterial strains tested. At room temperature, after 24â¯h, bacterial growth was observed. At -80⯰C, bacterial viability was maintained in monomicrobial samples; however, in polymicrobial samples, P. aeruginosa recovery was compromised. Storage at -20⯰C was unsuitable. We conclude that specimens collected using Eswab should be transported to the laboratory as soon as possible. If transport or processing is delayed, specimens should preferably be stored at refrigerator temperatures.
Asunto(s)
Técnicas Bacteriológicas/métodos , Bacterias Aerobias Gramnegativas/crecimiento & desarrollo , Manejo de Especímenes/métodos , Recuento de Colonia Microbiana , Medios de Cultivo , Escherichia coli/crecimiento & desarrollo , Heces/microbiología , Humanos , Klebsiella pneumoniae/crecimiento & desarrollo , Viabilidad Microbiana , Pseudomonas aeruginosa/crecimiento & desarrollo , Refrigeración , Temperatura , Factores de TiempoRESUMEN
The worldwide spread of multidrug-resistant Enterobacterales is a serious threat to public health. Here, we compared the MICs of plazomicin, amikacin, gentamicin, and tobramycin against 303 multinational multidrug-resistant Gram-negative bacilli. We followed Clinical and Laboratory Standards Institute (CLSI) guidelines and applied CLSI breakpoints as well as those of the European Committee on Antimicrobial Susceptibility Testing (EUCAST) for amikacin, gentamicin, and tobramycin and of the U.S. Food and Drug Administration for plazomicin. Overall, the highest percentage of susceptible isolates (80.2%) was demonstrated for plazomicin, which had the lowest MIC50 (1 µg/ml) of the aminoglycosides studied. Of the 42 isolates resistant to plazomicin, 34 had MICs of ≥128 µg/ml, with 33 of the 34 having MICs of >128 µg/ml for amikacin, gentamicin, and tobramycin. Among the 42 blaNDM-positive isolates, 35.7% were plazomicin susceptible, with the percentage of isolates susceptible to amikacin being 38.1% or 35.7% when applying the CLSI or EUCAST breakpoint, respectively. The 20 blaOXA-48-like-positive isolates showed 50.0% susceptibility to plazomicin. Among 35 isolates with blaCTX-M as their only characterized resistance mechanism, 68.6% were plazomicin susceptible, while the percentage susceptible to amikacin was 74.3% or 62.9% when applying the CLSI or EUCAST breakpoint, respectively. Among the 117 blaKPC-positive isolates, 94.9% were susceptible to plazomicin, whereas when the CLSI and EUCAST breakpoints were applied, 43.6% and 25.6%, respectively, were susceptible to amikacin; 56.4% and 44.4%, respectively, were susceptible to gentamicin; and 5.1% and 4.3%, respectively, were susceptible to tobramycin.
Asunto(s)
Antibacterianos/farmacología , Farmacorresistencia Bacteriana Múltiple/efectos de los fármacos , Bacterias Aerobias Gramnegativas/efectos de los fármacos , Sisomicina/análogos & derivados , Amicacina/farmacología , Gentamicinas/farmacología , Bacterias Aerobias Gramnegativas/enzimología , Pruebas de Sensibilidad Microbiana , Sisomicina/farmacología , Tobramicina/farmacología , beta-Lactamasas/genética , beta-Lactamasas/metabolismoRESUMEN
Achromatium oxaliferum is a large sulfur bacterium easily recognized by large intracellular calcium carbonate bodies. Although these bodies often fill major parts of the cells' volume, their role and specific intracellular location are unclear. In this study, we used various microscopy and staining techniques to identify the cell compartment harboring the calcium carbonate bodies. We observed that Achromatium cells often lost their calcium carbonate bodies, either naturally or induced by treatments with diluted acids, ethanol, sodium bicarbonate and UV radiation which did not visibly affect the overall shape and motility of the cells (except for UV radiation). The water-soluble fluorescent dye fluorescein easily diffused into empty cavities remaining after calcium carbonate loss. Membranes (stained with Nile Red) formed a network stretching throughout the cell and surrounding empty or filled calcium carbonate cavities. The cytoplasm (stained with FITC and SYBR Green for nucleic acids) appeared highly condensed and showed spots of dissolved Ca2+ (stained with Fura-2). From our observations, we conclude that the calcium carbonate bodies are located in the periplasm, in extra-cytoplasmic pockets of the cytoplasmic membrane and are thus kept separate from the cell's cytoplasm. This periplasmic localization of the carbonate bodies might explain their dynamic formation and release upon environmental changes.
Asunto(s)
Carbonato de Calcio/metabolismo , Bacterias Aerobias Gramnegativas/metabolismo , Periplasma/metabolismo , Calcio/metabolismo , Citoplasma/metabolismo , Bacterias Aerobias Gramnegativas/citología , Azufre/metabolismoRESUMEN
Bacteremia is associated with high morbidity and mortality, which contribute substantially to health care costs. A beneficial influence of appropriate empirical antimicrobial therapy (EAT) on patient outcome is evidenced; However, the evidence highlighting a comparison of clinical manifestations and of the effects of inappropriate EAT between Gram-positive and Gram-negative bacteremia is insufficient. In a retrospective 6-year cohort study, the total 2053 adults (Gram-positive, 566; Gram-negative 1487) presenting with community-onset monomicrobial aerobes bacteremia were recruited. Inappropriate EAT was defined as the first dose of an appropriate antimicrobial agent not being administered within the first 24 h after blood cultures were drawn. Although the bacteremia severity (a Pitt bacteremia score) at onset, comorbidity severity (the McCabe-Johnson classification), and 28-day mortality rate were similar in the two groups. Furthermore, after adjustment of independent predictors of 28-day mortality respectively recognized by the multivariate regression model in Gram-negative and Gram-positive groups, the Kaplan-Meier curve and Cox regression analysis revealed a significant difference (adjust odds ratio [AOR], 2.68; P < 0.001) between appropriate and inappropriate EAT in the Gram-negative group, but not in the Gram-positive group (AOR, 1.54; P = 0.06). Conclusively, patients with Gram-positive and Gram-negative bacteremia exhibited the similar presentation in bacteremia severity, but a greater impact of inappropriate EAT on survival of patients with Gram-negative aerobe bacteremia was evidenced.
Asunto(s)
Antibacterianos/uso terapéutico , Bacteriemia/tratamiento farmacológico , Bacterias Aerobias , Infecciones por Bacterias Gramnegativas/tratamiento farmacológico , Infecciones por Bacterias Grampositivas/tratamiento farmacológico , Prescripción Inadecuada , Adulto , Anciano , Bacteriemia/microbiología , Bacteriemia/mortalidad , Estudios de Cohortes , Femenino , Bacterias Aerobias Gramnegativas , Infecciones por Bacterias Gramnegativas/microbiología , Infecciones por Bacterias Gramnegativas/mortalidad , Infecciones por Bacterias Grampositivas/microbiología , Infecciones por Bacterias Grampositivas/mortalidad , Humanos , Masculino , Persona de Mediana Edad , Estudios RetrospectivosRESUMEN
Sarecycline is a novel, narrow-spectrum, once-daily tetracycline-derived oral antibiotic that is FDA-approved in the US to be taken with or without food for moderate-to-severe acne vulgaris for ages 9 years of age and older. Sarecycline possesses anti-inflammatory properties and potent activity against Gram-positive bacteria, including activity against multiple strains of Cutibacterium acnes, while exhibiting minimal activity against enteric aerobic Gram-negative bacteria. Unlike many acne studies, sarecycline was investigated for chest and back acne. Significant reduction in inflammatory lesions was seen at week 12 at 1.5 mg/kg/day of sarecycline, with statistically significant improvement seen as early as week 3. No reports of phototoxicity, dizziness, pseudotumor cerebri or lupus but 1.2% nausea and 1.2% vaginal candidiasis was reported in the pivotal Phase III studies.
Asunto(s)
Acné Vulgar/tratamiento farmacológico , Antibacterianos/uso terapéutico , Bacterias/efectos de los fármacos , Tetraciclinas/uso terapéutico , Acné Vulgar/microbiología , Antiinflamatorios/uso terapéutico , Ensayos Clínicos Fase III como Asunto , Bacterias Aerobias Gramnegativas/efectos de los fármacos , Bacterias Grampositivas/efectos de los fármacos , Humanos , Pruebas de Sensibilidad Microbiana , Propionibacteriaceae/efectos de los fármacosRESUMEN
Auranofin, an FDA-approved arthritis drug, has recently been repurposed as a potential antimicrobial agent; it performed well against many Gram-positive bacteria, including multidrug resistant strains. It is, however, inactive toward Gram-negative bacteria, for which we are in dire need of new therapies. In this work, 40 auranofin analogues were synthesized by varying the structures of the thiol and phosphine ligands, and their activities were tested against ESKAPE pathogens. The study identified compounds that exhibited bacterial inhibition (MIC) and killing (MBC) activities up to 65 folds higher than that of auranofin, making them effective against Gram-negative pathogens. Both thiol and the phosphine structures influence the activities of the analogues. The trimethylphosphine and triethylphosphine ligands gave the highest activities against Gram-negative and Gram-positive bacteria, respectively. Our SAR study revealed that the thiol ligand is also very important, the structure of which can modulate the activities of the AuI complexes for both Gram-negative and Gram-positive bacteria. Moreover, these analogues had mammalian cell toxicities either similar to or lower than that of auranofin.
Asunto(s)
Antibacterianos/farmacología , Antirreumáticos/farmacología , Auranofina/farmacología , Bacterias Aerobias Gramnegativas/efectos de los fármacos , Bacterias Grampositivas/efectos de los fármacos , Células A549 , Antibacterianos/síntesis química , Antibacterianos/química , Antirreumáticos/síntesis química , Antirreumáticos/química , Auranofina/síntesis química , Auranofina/química , Supervivencia Celular/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Humanos , Pruebas de Sensibilidad Microbiana , Estructura Molecular , Relación Estructura-Actividad , Células Tumorales CultivadasRESUMEN
Biological nitrogen fixation plays an important role in nitrogen cycling by transferring atmospheric N2 to plant-available N in the soil. However, the diazotrophic activity and distribution in different types of soils remain to be further explored. In this study, 152 upland soils were sampled to examine the diazotrophic abundance, nitrogenase activity, diversity and community composition by quantitative polymerase chain reaction, acetylene reduction assay and the MiSeq sequencing of nifH genes, respectively. The results showed that diazotrophic abundance and nitrogenase activity varied among the three soil types. The diazotrophic community was mainly dominated by Bradyrhizobium, Azospirillum, Myxobacter, Desulfovibrio and Methylobacterium. The symbiotic diazotroph Bradyrhizobium was widely distributed among soils, while the distribution of free-living diazotrophs showed large variation and was greatly affected by multiple factors. Crop type and soil properties directly affected the diazotrophic É-diversity, while soil properties, climatic factors and spatial distance together influenced the diazotrophic community. Network structures were completely different among all three types of soils, with most complex interactions observed in the Red soil. These findings suggest that diazotrophs have various activities and distributions in the three soil types, which played different roles in nitrogen input in agricultural soil in China, being driven by multiple environmental factors.
Asunto(s)
Bacterias Aerobias Gramnegativas/metabolismo , Bacterias Anaerobias Gramnegativas/metabolismo , Fijación del Nitrógeno/fisiología , Oxidorreductasas/genética , Microbiología del Suelo , Agricultura , Bradyrhizobium , China , Granjas , Bacterias Aerobias Gramnegativas/clasificación , Bacterias Aerobias Gramnegativas/genética , Bacterias Anaerobias Gramnegativas/clasificación , Bacterias Anaerobias Gramnegativas/genética , Nitrógeno/análisis , Suelo/química , SimbiosisAsunto(s)
Antibacterianos/uso terapéutico , Farmacorresistencia Bacteriana Múltiple , Bacterias Aerobias Gramnegativas/efectos de los fármacos , Infecciones por Bacterias Gramnegativas/tratamiento farmacológico , Lipopéptidos/uso terapéutico , Animales , Antibacterianos/farmacología , Humanos , Lipopéptidos/farmacología , RatonesRESUMEN
We investigated the intracellular dynamics of calcite and sulfur in the large sulfur-oxidizing, calcite-accumulating bacterium Achromatium, with an emphasis on oxygen exposure as a physiological control. For this purpose, morphological changes and possible accretion mechanisms of calcite granules in cells that were freshly collected from natural Achromatium-containing sediment were compared to cells from the same source after prolonged exposure to atmospheric oxygen. Intracellular sulfur is oxidized and removed in response to oxygen exposure. Calcite granules also undergo distinct oxygen-related dynamics; they alternate between tightly packaged, smooth granules with narrow but sharply defined interstitial spaces in atmospheric oxygen-exposed cells, and more loosely packaged granules with irregular, bumpy surface texture and larger interstitial spaces in cells that were not artificially exposed to oxygen. These results suggest that morphological changes of the calcite granules reflect their changing physiological role inside the cell. Sulfur oxidation and calcite dissolution appear to be linked in that proton generation during sulfur oxidation is buffered by gradual calcite erosion, visible in the smooth, rounded surface morphology observed after oxygen exposure. Our results support the hypothesis that calcite dynamics buffer the intracellular pH fluctuations linked to electron acceptor limitation during proton-consuming sulfide oxidation to sulfur, and electron acceptor abundance during proton-generating sulfur oxidation to sulfate.
Asunto(s)
Carbonato de Calcio/metabolismo , Bacterias Aerobias Gramnegativas/metabolismo , Azufre/metabolismo , Aerobiosis , Oxidación-Reducción , Oxígeno/metabolismoRESUMEN
A Gram-negative, yellow-pigmented, aerobic bacterium, designated strain B51-30T, was isolated from oil-well production liquid in Baolige oilfield, China. The strain was able to grow at pH 6-10 (optimum at pH 7.5), in 0-6% (w/v) NaCl (optimum at 1%, w/v) at 15-55 °C (optimum at 45 °C). Cells of the isolate were non-motile and non-spore-forming rods. The major cellular fatty acids were iso-C15:0, iso-C11:0, iso-C11:0 3OH, iso-C17:1 ω9c, and iso-C17:0. Ubiquinone 8 was the predominant respiratory quinone. The major polar lipids consisted of phosphatidylethanolamine and diphosphatidylglycerol. The genomic DNA G+C content of the isolate was 70.6 mol%. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain B51-30T was most closely related to Coralloluteibacterium stylophorae KCTC 52167T (98.7% similarity). The two strains showed DNA-DNA relatedness values of 58.5%. Genotypic and phenotypic features indicate that strain B51-30T represents a novel species of the genus Coralloluteibacterium, for which the name Coralloluteibacterium thermophilus sp. nov. is proposed. The type strain is B51-30T (= CGMCC 1.13574T = KCTC 62780T).
Asunto(s)
Gammaproteobacteria/aislamiento & purificación , Bacterias Aerobias Gramnegativas/aislamiento & purificación , Yacimiento de Petróleo y Gas/microbiología , Técnicas de Tipificación Bacteriana/métodos , Composición de Base/genética , China , ADN Bacteriano/genética , Ácidos Grasos/genética , Gammaproteobacteria/genética , Bacterias Aerobias Gramnegativas/genética , Fosfolípidos/genética , Filogenia , ARN Ribosómico 16S/genética , Análisis de Secuencia de ADN/métodos , Microbiología del SueloRESUMEN
PURPOSE OF REVIEW: Successful treatment of patients with hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP) remains a difficult and complex undertaking. Better knowledge of the pathogens involved in that setting may allow reassessment of our current modalities of therapy and definition of better protocols. RECENT FINDINGS: Microorganisms responsible for HAP/VAP differ according to geographic areas, ICU patients' specific characteristics, durations of hospital and ICU stays before onset of the disease, and risk factors for MDR pathogens. However, a number of studies have shown that Gram-negative bacilli (GNB) - particularly Pseudomonas aeruginosa and Enterobacteriaceae - cause many of the respiratory infections in this setting, with minimal differences between HAP and VAP, indicating that the cause depends more on the underlying clinical condition of patients rather than previous intubation. SUMMARY: When selecting initial antimicrobial therapy in patients with HAP/VAP, more attention should be paid to individual risk factors for MDR pathogens, severity of the clinical situation, and the local epidemiology than to the type of pneumonia.