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At least 415 records · Page 23Linked to original sources
PubMed1997

Hemagglutinin specificity and neuraminidase coding capacity of neuraminidase-deficient influenza viruses.

Neuraminidase (NA)-deficient mutant virus stocks have been obtained by passaging A/NWS/33HA-tern/Australia/G70c/75NA (H1N9) influenza virus in medium containing neuraminidase from Micromonospora viridifaciens and antiserum against the influenza NA. Growth of the resulting mutants is dependent on addition of bacterial neuraminidase to the medium. Nucleotide sequence analysis showed large single deletions in the NA genes, with both ends of the NA gene segments conserved. These RNA fragments all have the capacity to code for a peptide that contains the N-terminal "tail" and membrane-anchoring region of the NA, but the presence of this peptide has not been demonstrated in virions or infected cells. In contrast to the ease of selection of NA-deficient mutants from the H1N9 virus, no mutants were selected from three other viruses. The HA-coding segments of parental H1N9 and mutant NWSc-Mvi predict a change of Pro to His at residue 227 (H3 numbering), close to the receptor-binding site of H3 HA, compared to the HA of an H1N2 reassortant that contains the NWS/33 HA gene. This change may contribute to an altered HA specificity that allows selection of mutants that can infect cells in the presence of high levels of NA activity. It appears that the role of NA in influenza infection is to remove sialic acid from the HA rather than to destroy receptors on cells.

Amino Acid Sequence↗
PubMed1990

The chromosomal integration site of the Streptomyces element pSAM2 overlaps a putative tRNA gene conserved among actinomycetes.

The pSAM2 element of Streptomyces ambofaciens integrates site-specifically in the genome of different Streptomyces species by recombination between a 58 bp sequence common to the plasmid (attP) and the chromosome (attB). Southern hybridization analysis showed that sequences similar to the pSAM2 attB site were found in other actinomycetes (Mycobacterium, Nocardia, Micromonospora) as well as unrelated bacteria (Bacillus circulans, Escherichia coli, Clostridium botulinum, Bordetella pertussis, and Legionella pneumophila). Hybridizing fragments from B. circulans and Mycobacterium tuberculosis were cloned and sequenced. Comparison of these sequences with the sequence of the integration zone of S. ambofaciens revealed a conserved region of 76 bp which overlapped with the attB site. This conserved sequence was similar to the Salmonella typhimurium and E. coli tRNA(pro1) genes as well as a number of eucaryotic tRNA genes and had a proline-tRNA-like cloverleaf structure. Furthermore, the Streptomyces lividans attB site of the Streptomyces glaucescens element pIJ408 was also found to overlap a potential tRNA gene (tRNA(thr)). We note here that these two putative tRNA genes as well as those which overlap the attB site of the elements SLP1 of Streptomyces coelicolor and pMEA100 of Nocardia mediterranei all contain the site where integrative recombination takes place. These presumptive actinomycete tRNA genes lack the 3' terminal CCA sequence found in most procaryotic tRNA genes.

Actinomycetales↗
PubMed2004

The kgmB gene, encoding ribosomal RNA methylase from Streptomyces tenebrarius, is autogenously regulated.

The KgmB methylase (the kanamycin-gentamicin resistance methylase from Streptomyces tenebrarius) acts at G-1405 of 16S rRNA within the sequence CGUCA that is also found 6 bp in front of ribosomal binding site of the kgmB gene. The kgmBColon, two colonslacZ gene and operon fusions were used in order to test for translational autoregulation of kgmB gene. Overexpression of kgmB either in cis or in trans drastically decreased the level of expression of the fusion protein. However, mutagenesis eliminated any role for the CGUCA sequence in translational autoregulation. Hence, the role of second putative regulatory sequence (CGCCC) that was shown to be involved in regulation of another methylase, Sgm (sisomicin-gentamicin methylase gene from Micromonospora zionensis) was examined. It was shown that the Sgm methylase can also decrease the level of expression of the kgmBColon, two colonslacZ fusion protein.

Artificial Gene Fusion↗
PubMed2006

Diversity of actinomycetes isolated from Challenger Deep sediment (10,898 m) from the Mariana Trench.

Thirty-eight actinomycetes were isolated from sediment collected from the Mariana Trench (10,898 m) using marine agar and media selective for actinomycetes, notably raffinose-histidine agar. The isolates were assigned to the class Actinobacteria using primers specific for members of this taxon. The phylogenetic analysis based on 16S rRNA gene sequencing showed that the isolates belonged to the genera Dermacoccus, Kocuria, Micromonospora, Streptomyces, Tsukamurella and Williamsia. All of the isolates were screened for genes encoding nonribosomal peptide and polyketide synthetases. Nonribosomal peptide synthetase sequences were detected in more than half of the isolates and polyketide synthases type I (PKS-I) were identified in five out of 38 strains. The Streptomyces isolates produced several unusual secondary metabolites, including a PKS-I associated product. In initial testing for piezotolerance, the Dermacoccus strain MT1.1 grew at elevated hydrostatic pressures.

Actinobacteria↗
PubMed2005

Diversity of cultivable actinobacteria in geographically widespread marine sediments.

Reports describing actinobacteria isolated from marine environments have been dominated by Micromonospora, Rhodococcus and Streptomyces species. Recent culture-independent studies have shown that marine environments contain a high diversity of actinobacterial species that are rarely, if at all, recovered by cultivation-based methods. In this study, it is shown that cultivation-independent methods can be used to guide the application of selective isolation methods. The detection of marine-derived actinobacterial species that have previously only been reported from terrestrial habitats is highlighted. This study provides good evidence that the previously described low diversity of actinobacterial species isolated from marine environments does not reflect an actual low species diversity, and that the use of informed selective isolation procedures can aid in the isolation of members of novel taxa.

Actinobacteria↗
PubMed2005

Marine actinomycetes as a source of novel secondary metabolites.

A set of 600 actinomycetes strains which were isolated from marine sediments from various sites in the Pacific and Atlantic Oceans were screened for the production of bioactive secondary metabolites. Marine streptomycete strains were found to be producers of well known chemically diverse antibiotics isolated from terrestrial streptomycetes, as in the case of marine Micromonospora strains. New marine members of the rare genus Verrucosispora seem to be a promising source for novel bioactive secondary metabolites as shown in the case of the abyssomicin producing strain AB-18-032.

Actinomycetales↗
PubMed2006

Culturable actinobacteria from the marine sponge Hymeniacidon perleve: isolation and phylogenetic diversity by 16S rRNA gene-RFLP analysis.

A total of 106 actinobacteria associated with the marine sponge Hymeniacidon perleve collected from the Yellow Sea, China were isolated using eight different media. The number of species and genera of actinobacteria recovered from the different media varied significantly, underlining the importance of optimizing the isolation conditions. The phylogenetic diversity of the actinobacteria isolates was assessed using 16S rRNA gene amplification-restriction fragment length polymorphism (RFLP) analysis of the 106 strains with different morphologies. The RFLP fingerprinting of selected strains by HhaI-digestion of the 16S rRNA genes resulted in 11 different patterns. The HhaI-RFLP analysis gave good resolution for the identification of the actinobacteria isolates at the genus level. A phylogenetic analysis using 16S rRNA gene sequences revealed that the isolates belonged to seven genera of culturable actinobacteria including Actinoalloteichus, Micromonospora, Nocardia, Nocardiopsis, Pseudonocardia, Rhodococcus, and Streptomyces. The dominant genus was Streptomyces, which represented 74% of the isolates. Three of the strains identified are candidates for new species.

Actinobacteria↗
PubMed1987

Sites of action of two ribosomal RNA methylases responsible for resistance to aminoglycosides.

Methylation of either of two residues (G-1405 or A-1408) within bacterial 16 S ribosomal RNA results in high level resistance to specific combinations of aminoglycoside antibiotics. The product of a gene that originated in Micromonospora purpurea (an actinomycete that produces gentamicin) gives resistance to kanamycin plus gentamicin by converting residue G-1405 to 7-methylguanosine. Resistance to kanamycin plus apramycin results from conversion of residue A-1408 to 1-methyladenosine catalysed by the product of a gene from Streptomyces tenjimariensis.

Aminoglycosides↗
PubMed1996

Characteristics of 45Ca2+ release induced by quinolidomicin A1, a 60-membered macrolide from skeletal muscle sarcoplasmic reticulum.

Quinolidomicin A1, a 60-membered macrolide purified from an actinomycete Micromonospora sp. markedly induced 45Ca2+ release from the heavy fraction of skeletal muscle sarcoplasmic reticulum (HSR), but induced only slightly from the light fraction of sarcoplasmic reticulum (LSR), showing a lack of the ionophoretic activity even at a high concentration (300 microM). This was also confirmed by measuring the 45Ca2+ transport activity of quinolidomicin A1 across an organic solvent barrier. Quinolidomicin A1 (3-300 microM) increased 45Ca2+ release from HSR with an EC50 value of approx. 20 microM. The potency of quinolidomicin A1 was approx. 100-fold higher than that of caffeine. The bell-shaped profile of Ca2+ dependence for quinolidomicin A1 was different from that for caffeine. Blockers of Ca2+ release channels such as Mg2+ (10 mM), procaine (10 mM) and ruthenium red (10 microM) partially blocked quinolidomicin A1 (30 microM)-induced 45Ca2+ release from HSR. At 0 degrees C, quinolidomicin A1-induced 45Ca2+ release was ascertained not to be due to the inhibition of Ca2+ ATPase by the ATPase assay. Quinolidomicin A1 potentiated [3H]ryanodine binding to HSR with a decrease in KD but without a change in Bmax. These results suggest that quinolidomicin A1-induced Ca2+ release from HSR is consisted of two components, which are both sensitive and insensitive to blockers of Ca2+ release channels, and that the former component is associated with the ryanodine receptor.

Actinomycetales↗
PubMed1993

Physiology of some actinomycete genera.

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.

Actinomycetales↗
PubMed2004

A gene cluster for biosynthesis of kanamycin from Streptomyces kanamyceticus: comparison with gentamicin biosynthetic gene cluster.

Gene clusters for the biosynthesis of kanamycin (Km) and gentamicin (Gm) were isolated from the genomic libraries of Streptomyces kanamyceticus and Micromonospora echinospora, respectively. The sequencing of the 47 kb-region of S. kanamyceticus genomic DNA revealed 40 putative open reading frames (ORFs) encoding Km biosynthetic proteins, regulatory proteins, and resistance and transport proteins. Similarly, the sequencing of 32.6 kb genomic DNA of M. echinospora revealed a Gm biosynthetic gene cluster flanked by resistant genes. Biosynthetic pathways for the formation of Km were proposed by the comparative study of biosynthetic genes. Out of 12 putative Km biosynthetic genes, kanA was expressed in Escherichia coli and determined its function as a 2-deoxy-scyllo-inosose synthase. Furthermore, the acetylations of aminoglycoside-aminocyclitols (AmAcs) by Km acetyltransferase (KanM) were also demonstrated. The acetylated derivatives completely lost their antibacterial activities against Bacillus subtilis. The comparative genetic studies of Gm, Km, tobramycin (Tm), and butirosin (Bn) reveal their similar biosynthetic routes and provide a framework for the further biosynthetic studies.

Base Sequence↗
PubMed2026

Mechanistic insights into flavor deterioration in bitter sturgeon caviar: Evidence from lipidomics and metagenomics.

This study systematically compared the flavor and multi-omics differences between normal caviar and bitter caviar based on quantitative descriptive analysis (QDA), volatile compounds (VOCs) analysis, untargeted lipidomics, and metagenomics. The results showed that bitter caviar was characterized not only by increased bitterness, but also by decreased positive sensory attributes, including buttery, nutty, and marine fresh. VOCs analysis indicated that the volatile profile of bitter caviar was reorganized. Compounds such as 3-hydroxy-2-butanone, 1-octen-3-ol, and (E, Z)-2,6-nonadienal showed higher relative odor activity values (rOAVs); however, these changes did not improve its overall sensory experience. Untargeted lipidomics identified 492 differential lipids. These changes were mainly characterized by decreased PC and increased DG and LPC in bitter caviar. KEGG pathways analysis showed that these differential lipids were mainly associated with glycerophospholipid metabolism, choline metabolism in cancer, and retrograde endocannabinoid signaling. Metagenomic analysis showed that bacteria dominated the microbial community of caviar. Among them, Bacillus and Micromonospora showed relatively high abundance in the caviar microbiota. They were also closely associated with lipid metabolic changes involving PC, DG, and LPC, suggesting their potential as candidate targets for future microbiota-directed regulation of caviar quality. These findings provide new insights into the mechanisms underlying sensory deterioration and flavor formation in bitter caviar, and offer a theoretical basis for improving caviar quality in industrial production.

Animals↗
PubMed2005

Mismatched hemagglutinin and neuraminidase specificities in recent human H3N2 influenza viruses.

The hemagglutinin (HA) of influenza viruses initiates infection by binding to sialic acid on the cell surface via alpha2,6 (human) or alpha2,3 (avian) linkage. The influenza neuraminidase (NA) can cleave both alpha2,3- and alpha2,6-linked sialic acids, but all influenza NAs have a marked preference for the non-human alpha2,3 linkage. Recent H3N2 influenza viruses have lost the ability to agglutinate chicken red blood cells. To determine if changes in HA specificity or affinity correlate with NA specificity or activity, we examined red cell binding and elution of a series of H3N2 viruses. We found that the NA activity of many influenza viruses does not release binding by their HA. In some egg-adapted strains, lack of elution correlates with low levels of viral NA activity, and these elute rapidly when bacterial NA is added. However, a Fujian-like virus, A/Oklahoma/323/03, does not elute by its own NA or with Vibrio cholerae sialidase, and it binds to red cells pre-treated with V. cholerae sialidase. It elutes after addition of the broad specificity Micromonospora viridifaciens sialidase. Human glycophorin inhibits A/Oklahoma/323/03 hemagglutination 6-fold better than fetuin. We conclude that specific forms of sialic acid are used as receptor by recent human H3N2 influenza viruses, perhaps involving branched alpha2,6 sialic acid or alpha2,8 sialic acid structures on O-linked carbohydrates. The virus itself has no O-linked glycans, so even though the NA is not able to cleave receptors on cells, the viruses will not self-aggregate. It will be important to monitor efficacy of neuraminidase inhibitors in case there are NA-resistant receptors in the human respiratory tract that allow the viruses to be less dependent on NA activity.

Animals↗
PubMed1977

Separation of gentamicin C-complex into five components by Craig distribution.

A gentamicin C-complex preparation was separated preparatively into five components by Craig distribution. Gentamicins C1, C2, and C1a were the major components, whereas components C2a and C2b represented only 4% of the total C-complex mixture. Paper chromatographic analysis showed that the gentamicin C2b separated by Craig distribution was identical with a gentamicin isolated from Micromonospora purpurea var. JI-33 fermentation broth and identified as 6'-N-methylgentamicin C1a. Similarly, component C2a was identical with a previously separated gentamicin component tentatively identified as the 6'-C epimer of gentamicin C2.

Biological Assay↗
PubMed2003

Structure and ligand binding of carbohydrate-binding module CsCBM6-3 reveals similarities with fucose-specific lectins and "galactose-binding" domains.

Carbohydrate-binding polypeptides, including carbohydrate-binding modules (CBMs) from polysaccharidases, and lectins, are widespread in nature. Whilst CBMs are classically considered distinct from lectins, in that they are found appended to polysaccharide-degrading enzymes, this distinction is blurring. The crystal structure of CsCBM6-3, a "sequence-family 6" CBM in a xylanase from Clostridium stercorarium, at 2.3 A reveals a similar, all beta-sheet fold to that from MvX56, a module found in a family 33 glycoside hydrolase sialidase from Micromonospora viridifaciens, and the lectin AAA from Anguilla anguilla. Sequence analysis leads to the classification of MvX56 and AAA into a family distinct from that containing CsCBM6-3. Whilst these polypeptides are similar in structure they have quite different carbohydrate-binding specificities. AAA is known to bind fucose; CsCBM6-3 binds cellulose, xylan and other beta-glucans. Here we demonstrate that MvX56 binds galactose, lactose and sialic acid. Crystal structures of CsCBM6-3 in complex with xylotriose, cellobiose, and laminaribiose, 2.0 A, 1.35 A, and 1.0 A resolution, respectively, reveal that the binding site of CsCBM6-3 resides on the same polypeptide face as for MvX56 and AAA. Subtle differences in the ligand-binding surface give rise to the different specificities and biological activities, further blurring the distinction between classical lectins and CBMs.

Carbohydrates↗
PubMed2003

Influence and persistence of phorate and carbofuran insecticides on microorganisms in rice field.

An experiment was conducted in microplots (4 m x 4 m) with two insecticides, phorate and carbofuran at rates of 1.5 and 1.0 kga.i.ha(-1) respectively, to investigate its effect on the population and distribution of bacteria, actinomycetes and fungi as well as the persistence of the insecticidal residues in rhizosphere soils of rice (Oryza sativa L., variety IR-50). Application of the insecticides stimulated the population of bacteria, actinomycetes and fungi in the rhizosphere soils, and the stimulation was more pronounced with phorate as compared to carbofuran. Both the insecticides did not have marked effect on the numbers of Streptomyces and Nocardia in the rhizosphere soils. However, the growth of Bacillus, Escherichia, Flavobacterium, Micromonospora, Penicillium, Aspergillus and Trichoderma with phorate and that of Bacillus, Corynebacterium, Flavobacterium, Aspergillus and Phytophthora with carbofuran were increased. On the other hand, the numbers of Staphylococcus, Micrococcus, Fusarium, Humicola and Rhizopus under phorate and Pseudomonas, Staphylococcus, Micrococcus, Klebsiella, Fusarium, Humicola and Rhizopus under carbofuran were inhibited. Both the insecticides persisted in the rhizosphere soil for a short period of time and the rate of dissipation of carbofuran was higher than that of phorate in the soil depicting the half-life (T1/2) 9.1 and 10.4 days, respectively.

Bacteria↗
PubMedDate not supplied

Identification and evolution of the cellulolytic microflora present during composting of cattle manure: on the role of Actinomycetes sp.

Population changes in cellulolytic microflora were studied during composting of cattle manure. Six bacterial and nine actinomycetes species were isolated. Among the isolates, two actinomycetes, Micromonospora chalcae and Pseudonocardia thermophila, were cellulolytic strains which were numerically dominant and might therefore play a notable role in the degradation of cellulose in cattle manure. Fungi were practically absent during the process, but two cellulose-degrading bacterial species, Sporocytophaga myxococcoides and Cytophaga hutchinsonii, appeared to coexist in equilibrium with actinomycetes during the maturation phase.

Actinomycetales↗
PubMed1995

Insecticides: their effect on microorganisms and persistence in rice soil.

A field experiment was conducted to investigate the effect of four insecticides, HCH, phorate, carbofuran and fenvalerate, at recommended doses on the preponderance of bacteria, actinomycetes and fungi. We also measured the persistence of the insecticides in the rhizosphere soil of rice. HCH and fenvalerate stimulated the proliferation of all of the microorganisms significantly. Phorate increased the population of bacteria and actinomycetes. Carbofuran accentuated the preponderance of actinomycetes in soil. Insecticides, in general, did not have marked influence on the proliferation of Bacillus, Streptomyces, Aspergillus and Fusarium in soil. However, we observed a stimulation of growth of Staphylococcus, Proteus and Sarcina with HCH, Pseudomonas, Corynebacterium, Erysipelothrix and Rhizopus with phorate, Serratia, Corynebacterium, Klebsiella, Escherichia, Rhizopus and Humicola with carbofuran, and Staphylococcus, Sarcina, Klebsiella and Nocardia with fenvalerate. On the other hand, there was an inhibition in growth of Pseudomonas, Micrococcus, Nocardia and Penicillium with HCH, of Pseudomonas, Micrococcus and Penicillium with carbofuran, and of Pseudomonas, Micrococcus and Micromonospora with fenvalerate. Different types of insecticides exhibited differential patterns of dissipation in soil. HCH had the highest persistence followed by phorate, carbofuran and fenvalerate, respectively.

Actinomycetales↗