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Revista Chilena de Infectologia :... Jun 2016
Topics: Actinomycetales; Actinomycetales Infections
PubMed: 27598282
DOI: 10.4067/S0716-10182016000300011 -
Research in Microbiology Oct 1993The actinomycetes are well known as a group of filamentous, Gram-positive bacteria that produce many useful secondary metabolites, including antibiotics and enzymes.... (Review)
Review
The actinomycetes are well known as a group of filamentous, Gram-positive bacteria that produce many useful secondary metabolites, including antibiotics and enzymes. Although they have been intensively studied for both theoretical and practical objectives, there is much scope for developing our basic knowledge of the means of detection and isolation of these microbes. This session concentrated on new methods for the detection and identification of novel actinomycetes from a range of environments. Approaches to the detection of actinomycetes ranged from investigations of neglected habitats and extreme environments (e.g. alkaline soils and oil drills) to the analysis of DNA extracted from the environment and use of specific phages. The continuing problems of the identification of actinomycete isolates were also considered. Topics discussed included use of phage typing, DNA probes, and correlation between phenetic and genotypic species of Streptomyces.
Topics: Actinomycetales; Bacteriophage Typing; DNA, Bacterial; In Vitro Techniques; Polymerase Chain Reaction; Soil Microbiology
PubMed: 8140283
DOI: 10.1016/0923-2508(93)90069-e -
Clinical Microbiology Reviews Jul 1994The aerobic actinomycetes are soil-inhabiting microorganisms that occur worldwide. In 1888, Nocard first recognized the pathogenic potential of this group of... (Review)
Review
The aerobic actinomycetes are soil-inhabiting microorganisms that occur worldwide. In 1888, Nocard first recognized the pathogenic potential of this group of microorganisms. Since then, several aerobic actinomycetes have been a major source of interest for the commercial drug industry and have proved to be extremely useful microorganisms for producing novel antimicrobial agents. They have also been well known as potential veterinary pathogens affecting many different animal species. The medically important aerobic actinomycetes may cause significant morbidity and mortality, in particular in highly susceptible severely immunocompromised patients, including transplant recipients and patients infected with human immunodeficiency virus. However, the diagnosis of these infections may be difficult, and effective antimicrobial therapy may be complicated by antimicrobial resistance. The taxonomy of these microorganisms has been problematic. In recent revisions of their classification, new pathogenic species have been recognized. The development of additional and more reliable diagnostic tests and of a standardized method for antimicrobial susceptibility testing and the application of molecular techniques for the diagnosis and subtyping of these microorganisms are needed to better diagnose and treat infected patients and to identify effective control measures for these unusual pathogens. We review the epidemiology and microbiology of the major medically important aerobic actinomycetes.
Topics: AIDS-Related Opportunistic Infections; Actinomycetales; Actinomycetales Infections; Animals; Anti-Bacterial Agents; Bacteria, Aerobic; Humans; Microbial Sensitivity Tests; Nocardia; Nocardia Infections; Virulence
PubMed: 7923055
DOI: 10.1128/CMR.7.3.357 -
Journal of Clinical Microbiology Jun 2013The clinical significance of Dietzia papillomatosis is for the moment limited to the rare skin disease confluent and reticulated papillomatosis. We present a case of...
The clinical significance of Dietzia papillomatosis is for the moment limited to the rare skin disease confluent and reticulated papillomatosis. We present a case of infection with D. papillomatosis in a 2-year-old boy with known syringomyelia. The microbiological diagnosis was done using 16S rRNA gene sequencing. This is the first report of bacteremia with D. papillomatosis.
Topics: Actinomycetales; Actinomycetales Infections; Bacteremia; Child, Preschool; DNA, Bacterial; DNA, Ribosomal; Humans; Male; RNA, Ribosomal, 16S; Sequence Analysis, DNA
PubMed: 23536398
DOI: 10.1128/JCM.03313-12 -
Antimicrobial Agents and Chemotherapy 2014Synthesis of peptidoglycan precursors ending in D-lactate (D-Lac) is thought to be responsible for glycopeptide resistance in members of the order Actinomycetales that...
Synthesis of peptidoglycan precursors ending in D-lactate (D-Lac) is thought to be responsible for glycopeptide resistance in members of the order Actinomycetales that produce these drugs and in related soil bacteria. More recently, the peptidoglycan of several members of the order Actinomycetales was shown to be cross-linked by L,D-transpeptidases that use tetrapeptide acyl donors devoid of the target of glycopeptides. To evaluate the contribution of these resistance mechanisms, we have determined the peptidoglycan structure of Streptomyces coelicolor A(3)2, which harbors a vanHAX gene cluster for the production of precursors ending in D-Lac, and Nonomuraea sp. strain ATCC 39727, which is devoid of vanHAX and produces the glycopeptide A40296. Vancomycin retained residual activity against S. coelicolor A(3)2 despite efficient incorporation of D-Lac into cytoplasmic precursors. This was due to a D,D-transpeptidase-catalyzed reaction that generated a stem pentapeptide recognized by glycopeptides by the exchange of D-Lac for D-Ala and Gly. The contribution of L,D-transpeptidases to resistance was limited by the supply of tetrapeptide acyl donors, which are essential for the formation of peptidoglycan cross-links by these enzymes. In the absence of a cytoplasmic metallo-D,D-carboxypeptidase, the tetrapeptide substrate was generated by hydrolysis of the C-terminal D-Lac residue of the stem pentadepsipeptide in the periplasm in competition with the exchange reaction catalyzed by D,D-transpeptidases. In Nonomuraea sp. strain ATCC 39727, the contribution of L,D-transpeptidases to glycopeptide resistance was limited by the incomplete conversion of pentapeptides into tetrapeptides despite the production of a cytoplasmic metallo-D,D-carboxypeptidase. Since the level of drug production exceeds the level of resistance, we propose that L,D-transpeptidases merely act as a tolerance mechanism in this bacterium.
Topics: Actinomycetales; Anti-Bacterial Agents; Drug Resistance, Bacterial; Glycopeptides; Peptidoglycan; Streptomyces coelicolor
PubMed: 24395229
DOI: 10.1128/AAC.02329-13 -
Research in Microbiology Oct 1993Actinomycetes are widespread in the environment and are mainly organotrophic. Studies of their ecology have been primarily focussed on their detection and isolation,... (Review)
Review
Actinomycetes are widespread in the environment and are mainly organotrophic. Studies of their ecology have been primarily focussed on their detection and isolation, with comparatively little attention to the control mechanisms that determine their occurrence and behaviour in their natural environments. This session provided some diverse examples of approaches to this problem. Several actinomycete genera produce motile spores. The significance of flagella proteins and factors influencing spore motility and germination are considered. The genus Frankia forms nitrogen-fixing associations with non-leguminous plants. Molecular techniques have been used to clarify the endophyte-host relationships. Micromonospora species are common in the environment. The growth and physiology of a gentamicin-producing strain are described. Thermophilic actinomycetes in the genus Thermoactinomyces are common in composts and other self-heating environments. Novel isolates from acid soil, which grow and produce enzymes active at high temperatures and in acidic conditions, are discussed.
Topics: Actinomycetales; Gentamicins; In Vitro Techniques; Micromonosporaceae; Polymerase Chain Reaction; RNA, Ribosomal, 16S; Soil Microbiology; Spores, Bacterial
PubMed: 8140284
DOI: 10.1016/0923-2508(93)90070-i -
Applied Microbiology Feb 1975Mesophilic Actinomycetales were isolated from whole corn, brewers grits, and break flour received from three different mills. In addition, strains were isolated from...
Mesophilic Actinomycetales were isolated from whole corn, brewers grits, and break flour received from three different mills. In addition, strains were isolated from high-moisture (27 per cent) field corn; high-moisture, silo-stored corn (untreated); and high-moisture corn treated with ammonia, ammonium isobutyrate, or propionic-acetic acid. According to standard techniques, 139 strains were extensively characterized and 207 additional strains were partially characterized. On the basis of these characterizations, the streptomycete strains were identified by both the systems of Pridham et al. and Hütter because these systems are rapid and accurate. In general, only Streptomyces griseus (Krainsky) Waksman and Henrici was isolated from high-moisture whole corn (treated or untreated) except from grain exposed to ammonium isobutyrate. Strains isolated from high-moisture corn subjected to that treatment represented both S. griseus and S. albus (Rossi Doria) Waksman and Henrici. The strains isolated from corn and corn products from the three mills were identified with a number of streptomycete species. Of all Actinomycetales isolated, only three were not streptomycetes--two from brewer's grits and one from break flour.
Topics: Actinomycetales; Bacteriological Techniques; Bucrylate; Flour; Food Microbiology; Humidity; Pimelic Acids; Streptomyces; Streptomyces griseus; Zea mays
PubMed: 803819
DOI: No ID Found -
CA: a Cancer Journal For Clinicians 1990Livingston-Wheeler's cancer treatment is based on the belief that cancer is caused by a bacterium she has named Progenitor cryptocides. Careful research using modern...
Livingston-Wheeler's cancer treatment is based on the belief that cancer is caused by a bacterium she has named Progenitor cryptocides. Careful research using modern techniques, however, has shown that there is no such organism and that Livingston-Wheeler has apparently mistaken several different types of bacteria, both rare and common, for a unique microbe. In spite of diligent research to isolate a cancer-causing microorganism, none has been found. Similarly, Livingston-Wheeler's autologous vaccine cannot be considered an effective treatment for cancer. While many oncologists have expressed the hope that someday a vaccine will be developed against cancer, the cause(s) of cancer must be determined before research can be directed toward developing a vaccine. The rationale for other facets of the Livingston-Wheeler cancer therapy is similarly faulty. No evidence supports her contention that cancer results from a defective immune system, that a whole-foods diet restores immune system deficiencies, that abscisic acid slows tumor growth, or that cancer is transmitted to humans by chickens.
Topics: Actinomycetales; Bacterial Vaccines; Combined Modality Therapy; Diet, Vegetarian; Humans; Levamisole; Neoplasms
PubMed: 2106368
DOI: 10.3322/canjclin.40.2.103 -
Applied and Environmental Microbiology Jan 2019Under general aqueous conditions, xanthan appears in an ordered conformation, which makes its backbone largely resistant to degradation by known cellulases. Therefore,...
Under general aqueous conditions, xanthan appears in an ordered conformation, which makes its backbone largely resistant to degradation by known cellulases. Therefore, the xanthan degradation mechanism is still unclear because of the lack of an efficient hydrolase. Here, we report the catalytic properties of MiXen, a xanthan-degrading enzyme identified from the genus MiXen is a 952-amino-acid protein that is unique to strain XT11. Both the sequence and structural features suggested that MiXen belongs to a new branch of the GH9 family and has a multimodular structure in which a catalytic (α/α) barrel is flanked by an N-terminal Ig-like domain and by a C-terminal domain that has very few homologues in sequence databases and functions as a carbohydrate-binding module (CBM). Based on circular dichroism, shear-dependent viscosity, and reducing sugar and gel permeation chromatography analysis, we demonstrated that recombinant MiXen efficiently and randomly cleaved glucosidic bonds within the highly ordered xanthan substrate. A MiXen mutant free of the C-terminal CBM domain partially lost its xanthan-hydrolyzing ability because of decreased affinity toward xanthan, indicating the CBM domain assisted MiXen in hydrolyzing highly ordered xanthan via recognizing and binding to the substrate. Furthermore, side chain substituents and the terminal mannosyl residue significantly influenced the activity of MiXen via the formation of barriers to enzymolysis. Overall, the results of this study provide insight into the hydrolysis mechanism and enzymatic properties of a novel endotype xanthanase that will benefit future applications. This work characterized a novel endotype xanthanase, MiXen, and elucidated that the C-terminal carbohydrate-binding module of MiXen could drastically enhance the hydrolysis activity of the enzyme toward highly ordered xanthan. Both the sequence and structural analysis demonstrated that the catalytic domain and carbohydrate-binding module of MiXen belong to the novel branch of the GH9 family and CBMs, respectively. This xanthan cleaver can help further reveal the enzymolysis mechanism of xanthan and provide an efficient tool for the production of molecular modified xanthan with new physicochemical and physiological functions.
Topics: Actinomycetales; Amino Acid Sequence; Bacterial Proteins; Catalysis; Polysaccharides, Bacterial; Sequence Alignment
PubMed: 30413476
DOI: 10.1128/AEM.01800-18 -
Applied and Environmental Microbiology Dec 2018Chromate is one of the major anthropogenic contaminants on Earth. is a highly chromate-resistant strain, tolerating chromate concentrations in LB medium of up to 400...
Chromate is one of the major anthropogenic contaminants on Earth. is a highly chromate-resistant strain, tolerating chromate concentrations in LB medium of up to 400 mM. In response to chromate stress, forms biofilms, which are held together via extracellular DNA. Inhibition of biofilm formation leads to drastically decreased chromate tolerance. Moreover, chromate is reduced intracellularly to the less-toxic Cr(III). The oxidation status and localization of chromium in cell aggregates were analyzed by energy-dispersive X-ray spectroscopy coupled to scanning transmission electron microscopy and X-ray absorption spectroscopy measurements. Most of the heavy metal is localized as Cr(III) at the cytoplasmic membrane. As a new cellular response to chromate stress, we observed an increased production of the carotenoid lutein. Carotenoid production could increase membrane stability and reduce the concentration of reactive oxygen species. Bioinformatic analysis of the genome revealed several gene clusters that could enable heavy-metal resistance. The extreme chromate tolerance and the unique set of resistance factors suggest the use of as a new model organism to study microbial chromate resistance. Chromate is a highly toxic oxyanion. Extensive industrial use and inadequate waste management has caused the toxic pollution of several field sites. Understanding the chromate resistance mechanisms that enable organisms to thrive under these conditions is fundamental to develop (micro)biological strategies and applications aiming at bioremediation of contaminated soils or waters. Potential detoxifying microorganisms are often not sufficient in their resistance characteristics to effectively perform, e.g., chromate reduction or biosorption. In this study, we describe the manifold strategies of to establish an extremely high level of chromate resistance. The multitude of mechanisms conferring it make this organism suitable for consideration as a new model organism to study chromate resistance.
Topics: Actinomycetales; Biodegradation, Environmental; Cell Membrane; Chromates; Chromium; Oxidation-Reduction; X-Ray Absorption Spectroscopy
PubMed: 30266727
DOI: 10.1128/AEM.02208-18