Search results for "ribosomal DNA"
showing 10 items of 137 documents
Acanthamoeba isolates belonging to T1, T2, T3, T4 and T7 genotypes from environmental freshwater samples in the Nile Delta region, Egypt.
2006
The free-living amoebae of the genus Acanthamoeba include non-pathogenic and pathogenic species and has been recently classified into 15 different genotypes, T1–T15. In this study, a survey was conducted in order to determine the presence and pathogenic potential of free-living amoebae of Acanthamoeba genus in freshwater sources associated with human activities in the Nile Delta region, Egypt. Identification of Acanthamoeba was based on the morphology of cyst and trophozoite forms and PCR amplification with a genus specific primer pair. The pathogenic potential of Acanthamoeba isolates was characterized using temperature and osmotolerance assays and PCR reactions with two primer pairs speci…
Typing of anastomosis groups of Rhizoctonia solani by restriction analysis of ribosomal DNA.
2003
A method based on restriction analysis of polymerase chain reaction (PCR)-amplified ribosomal DNA was developed for the rapid characterization of large populations of Rhizoctonia solani at the anastomosis group (AG) level. The restriction maps of the internal transcribed spacers (ITS) sequences were compared for 219 isolates of R. solani belonging to AG-1 to AG-12 and AG-BI, representing diverse geographic and host range origins. Four discriminant restriction enzymes (MseI, AvaII, HincII, and MunI) resolved 40 restriction fragment length polymorphism (RFLP) types among the 219 ITS sequences of R. solani. Each RFLP type could be assigned to a single AG except for two RFLP types, which were c…
Isolation of Desulfovibrio intestinalis sp. nov. from the hindgut' of the lower termite Mastotermes darwiniensis.
1999
A Gram-negative, anaerobic sulfate-reducing bacterium was isolated from hindgut contents of the lower termite Mastotermes darwiniensis Froggatt (strain KMS2). Strain KMS2 is motile by a single polar flagellum. The isolate possesses desulfoviridin and catalase activity. The G+C content of its DNA is in the range of 54.5-55.5 mol% (strain KMS2). It respires hydrogen and different low molecular weight organic compounds in the presence of sulfate, thiosulfate, and sulfite, and also oxygen. The isolated strain ferments pyruvate. Fastest growth with a doubling time of 12.5 h was obtained at 37°C and not at 28°C, the temperature at which the termites were grown. The isolate showed a 16S rDNA seque…
Incomplete sequence homogenization in 45S rDNA multigene families: intermixed IGS heterogeneity within the single NOR locus of the polyploid species …
2014
† Background and Aims Ribosomal sequences have become the classical example of the genomic homogenization of nuclear multigene families. Despite theoretical advantages and modelling predictions that support concerted evolution of the 45S rDNA, several reports have found intragenomic polymorphisms. However, the origins and causes of these rDNA polymorphisms are difficult to assess because seed plants show a wide range of 45S rDNA loci number variation, especially in polyploids. Medicago arborea is a tetraploid species that has a single 45S rDNA locus. This feature makes this species a suitable case study to assess the fate of ribosomal IGS homogenization in polyploid species showing nucleolu…
Characterization of three different clusters of 18S-26S ribosomal DNA genes in the sea urchin P. lividus: Genetic and epigenetic regulation synchrono…
2015
We previously reported the characterization 5S ribosomal DNA (rDNA) clusters in the common sea urchin Paracentrotus lividus and demonstrated the presence of DNA methylation-dependent silencing of embryo specific 5S rDNA cluster in adult tissue. In this work, we show genetic and epigenetic characterization of 18S-26S rDNA clusters in this specie. The results indicate the presence of three different 18S-26S rDNA clusters with different Non-Transcribed Spacer (NTS) regions that have different chromosomal localizations. Moreover, we show that the two largest clusters are hyper-methylated in the promoter-containing NTS regions in adult tissues, as in the 5S rDNA. These findings demonstrate an an…
Morphology, ultrastructure and molecular characterisation of Spiroxys japonica Morishita, 1926 (Spirurida: Gnathostomatidae) from Pelophylax nigromac…
2014
Gnathostomatid nematodes identified morphologically as Spiroxys japonica Morishita, 1926 were collected from the dark-spotted frog Pelophylax nigromaculatus (Hallowell) (Amphibia: Ranidae) in China. Light and scanning electron microscopy were used to study the morphology of this species in detail. Previously unreported morphological features are revealed and others corrected. In addition, adult nematodes of S. japonica collected from P. nigromaculatus and Spiroxys hanzaki Hasegawa, Miyata & Doi, 1998 collected from Andrias japonicus (Temminck) (Caudata: Cryptobranchidae) in China and Japan, respectively, and the third-stage larva of S. japonica collected from Lithobates catesbeianus (Shaw) …
Evidence for male XO sex-chromosome system in Pentodon bidens punctatum (Coleoptera Scarabaeoidea: Scarabaeidae) with X-linked 18S-28S rDNA clusters
2004
In scarab beetle species of the genus Pentodon, the lack of analysis of sex chromosomes in females along with the poor characterization of sex chromosomes in the males, prevented all previous investigations from conclusively stating sex determination system. In this study, somatic chromosomes from females and spermatogonial chromosomes from males of Pentodon bidens punctatum (Coleoptera: Scarabaeoidea: Scarabaeidae) from Sicily have been analyzed using non-differential Giemsa staining. Two modal numbers of chromosomes were obtained: 2n = 20 and 19 in females and males, respectively. This finding along with other karyological characteristics such as the occurrence of one unpaired, heterotypi…
Case of fatal systemic infection with an Aureobacterium sp.: identification of isolate by 16S rRNA gene analysis
1996
The case of a 75-year-old man who succumbed to a disseminated infection most likely caused by a species of the genus Aureobacterium is reported. Identification of the isolate was achieved by comparative 16S rRNA gene analysis. Aureobacteria are commonly found in the environment. However, only recently have they been recognized as a cause of infections including septicemia and soft tissue infections. To our knowledge, this is the first documentation of a fatal infection caused by an Aureobacterium sp.
ITS-2 rDNA sequencing of Gnathostoma species (Nematoda) and elucidation of the species causing human gnathostomiasis in the Americas.
2000
From several gnathostome species the complete internal transcribed spacer ITS-2 ribosomal DNA (rDNA) repeat sequence and a fragment of the 5.8S rDNA were obtained by direct polymerase chain reaction cycle-sequencing and silver-staining methods. The size of the complete ITS-1 sequence in agarose gel electrophoresis was also obtained. The ITS-2 enabled the differentiation of Gnathostoma spinigerum from Thailand and Gnathostoma binucleatum from Mexico and Ecuador and confirmed the validity of the latter. Gnathostoma turgidum, Gnathostoma sp. I (=Gnathostoma procyonis sensu Almeyda-Artigas et al., 1994), and Gnathostoma sp. II (=G. turgidum sensu Foster, 1939 pro parte), all from Mexico, proved…
Chromosome Analysis and rDNA FISH in The Stag Beetle Dorcus Parallelipipedus L. (Coleoptera: Scarabaeoidea: Lucanidae)
2001
In the present work the chromosome complement (2n = 18; 8AA + XY) of the stag beetle Dorcus parallelipipedus L. (Scarabaeoidea: Lucanidae) is analyzed using conventional Giemsa staining, banding techniques and ribosomal fluorescent in situ hybridization (rDNA FISH). rDNA FISH remains the unique tool for providing a clear-cut identification of Nucleolar Organizer Regions (NORs) when conventional banding methods such as silver- and CMA3-staining proved to be inadequate. The dull, homogeneous CMA3 fluorescence of all chromosomes indicates the absence of markedly GC rich compartmentalized regions in D. parallelipipedus genome. Silver impregnation inadequacy in detecting NOR regions is to be sou…