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Rapid ribosequencing--an effective diagnostic tool for detecting microbial infection.

BACKGROUND: Rapid and reliable identification of microorganisms is a prerequisite for the diagnosis and subsequent treatment of infectious diseases. The identification of pathogenic bacteria is traditionally based on their isolation from clinical samples and propagation on culture medium in the routine laboratory. However, despite clinical signs of infection, culture of the pathogenic agent often fails. This may be due to a low number of microorganisms, prior antibiotic treatment, nonculturable microorganisms or specific culture requirements for presently unknown pathogens. Amplification and sequencing of the entire prokaryotic 16S-rRNA is time consuming, labor intensive and expensive. MATERIALS AND METHODS: We describe here a procedure for the identification of a wide range of known and unknown clinically relevant microorganisms by sequencing a small, but highly informative region of the prokaryotic 16S-rRNA gene. This rapid ribosequencing method was evaluated with various reference strains and with clinical samples including eye anterior chamber fluid, cerebrospinal fluid (CSF) and blood cultures. RESULTS: All sequences obtained from the reference strains corresponded to the sequences in databases. We correlated severe eye infection with the isolation of Pseudomonas putida, neurological disorder with Tropheryma whippelii and disseminated visceral abscesses in a child with Blastobacter denitrificans. CONCLUSION: We consider the rapid ribosequencing method as a promising new tool for the analysis of infectious agents in primarily sterile body fluids where conventional culturing of microorganisms fails.

Bacteria↗

Improved protocol for isolation and characterization of human thymic epithelial cells.

Thymic epithelial cells (TECs) play a vital role in the generation of immunocompetent and immunotolerant T cells. The understanding of TEC biology in model animals such as mice has advanced thanks to the cellular and molecular analyses of purified TEC populations, including cortical TECs (cTECs) and medullary TECs (mTECs). On the other hand, studies of human TECs have fallen behind because of the lack of a well-established method for purifying TEC populations. Here, we show that using 0.5 U/mL liberase to digest thymus tissue into single cells is quicker than using collagenase D or 0.1 U/mL liberase. Thymus digestion with 0.5 U/ml liberase preserves CD205 expressed by cTECs. RNA sequencing analysis of TEC populations isolated from 0.5 U/mL liberase-digested human thymic tissue revealed the expression of molecules known as cTEC- and mTEC-specific genes in mouse thymus in each human TEC population. Our study is expected to fuel further cellular and molecular studies of human TECs, including those related to the collapse of immune tolerance in humans.

Flow cytometry↗

Tangier disease. The complete mRNA sequence encoding for preproapo-A-I.

A cDNA library of Tangier liver mRNA has been established, and two apo-A-I-containing clones were identified. The complete derived amino acid sequence of preproapo-A-I has been established by nucleic acid sequence analysis of cloned apo-A-I cDNA and specific primer extensions on Tangier liver RNA. Sequence analysis of the longest cDNA clone, pMDB136T, established the derived amino acid sequence of residues 116-243 of plasma apo-A-I. The remaining portion of the sequence of Tangier preproapo-A-I mRNA was established by sequence analysis of specific primer extensions of synthetic oligonucleotides on Tangier liver mRNA. This latter technique provided the derived amino acid sequence of residues -24 to 116, thus completing the entire preproapo-A-I structure. The structure of Tangier preproapo-A-I was identical to normal preproapo-A-I except for a single base substitution (G----T) which resulted in the isosteric replacement of a glutamic acid residue at position 120 to aspartic acid. These results are interpreted as indicating that there is no major structural defect in Tangier apo-A-I, and the rapid rate of catabolism of apo-A-I in Tangier disease is due to a post-translational defect in apo-A-I metabolism.

Amino Acid Sequence↗

Phylogenetic heterogeneity of the genus Williopsis as revealed by 18S rRNA gene sequences.

A phylogenetic investigation of the ascomycetous yeast genus Williopsis was performed by using 18S rRNA gene sequence analysis. Comparative sequence analysis revealed the genus to be phylogenetically heterogeneous. The five varieties of Williopsis saturnus [var. mrakii, var. sargentensis, var. saturnus (type), var. suaveolens and var. subsufficiens] were found to have identical 18S rRNA gene sequences and formed a distinct group, quite separate from all other Williopsis and non-Williopsis species examined. Williopsis mucosa was found to be the closet phylogenetic relative to the Williopsis saturnus group, however a sequence divergence of approximately 2.3% suggests this species may belong to a separate genus. The recently described species Williopsis salicorniae was found to exhibit a relatively close association with Ogataea minuta (identical to Pichia minuta), the type species of the genus Ogataea. The remaining two members of the genus, Williopsis californica and Williopsis pratensis, were found to form distinct lineages, displaying no specific association with any other Williopsis or non-Williopsis species. Based on comparative analysis of 18S rRNA genes it is apparent that the genus Williopsis as presently constituted is not monophyletic, and that the five currently recognized species form separate sublines each potentially worthy of separate generic status. The genus Williopsis should be restricted to the type species Williopsis saturnus and its five varieties. Despite the five varieties of Williopsis saturnus being genealogically indistinguishable at the 18S rRNA gene level, sequence analysis of the Internal transcribed spacer (ITS) region revealed that the five varieties could be differentiated on both their ITS1 and their ITS2 sequences, providing further evidence of the value of ITS sequences for discrimination of yeasts at the subspecies level.

Base Sequence↗

A reassortant H1N1 influenza A virus caused fatal epizootics among camels in Mongolia.

In the autumn of 1979 a severe influenza epizootic started among camels in Mongolia (Lvov et al., 1982; Viprosi Virusol. 27, 401-405.) Between 1980 and 1983 13 independent isolates of H1N1 viruses were obtained from diseased camels, which were virtually indistinguishable from the human A/USSR/90/77 strain by serological means. Two hundred and seventy-one samples of camel sera collected between 1978 and 1983 contained antibodies against the human A/USSR/90/77 isolate. After experimental infection of camels with some of these isolates, the animals developed similar symptoms as those found during natural infection: coughing, bronchitis, fever, discharge from nose and eyes. A genetic sequence analysis revealed that among the eight segments (genes) the PB1, HA, and NA genes were almost identical with allelic genes of the USSR/77 strain, and the PB2, PA, NP, M, and NS genes were almost identical with those of the A/PR/8/34 strain.

Animals↗

Sequence and phylogenetic analysis of the sigmaA-encoding gene of avian reovirus.

The full-length sigmaA-encoding gene nucleotide sequences (1251 bp) of ten avian reovirus (ARV) field-isolates and three vaccine strains were determined and analyzed to study the degree of genetic divergence and evolution. Strains were isolated over a 23-year period from different hosts, pathotypes, and geographic locations. A phylogenetic tree constructed from variation in the sigmaA nucleotide sequences among ARV isolates showed that Taiwanese isolates from different dates of isolation were grouped into two distant groups, indicating that they have evolved in nature. In paired identity analysis, there was over 97.3% nucleotide sequence identity in the sigmaA-encoding genes between group I Taiwanese isolates (T6, 750505, 919, and 918) and Japanese isolate OS161 as well as three US vaccine strains, suggesting that they might have descended from a common ancestor. However, the nucleotide sequences of these sigmaA-encoding genes varied extensively from those of group II Taiwanese isolates (601SI, R2/TW, 1017-1, 916, and 601G), displaying only 86% identity. These results revealed that the genetic diversity in the sigmaA-encoding gene of ARV correlated with the date of isolation and geographic locations.

Amino Acid Sequence↗

[A study on taxonomy of Rhizobia isolated from Astragalus sp].

Thirty-six strains isolated from root nodule of Astragalus spp., in comparison with 31 reference strains of Rhizobium, Bradyrhizobium and Sinorhizobium species, and some other strains isolated from legumes in Xinjiang and Hainian Province, were classified by performing numberical taxonomy, DNA-DNA hybrization and partial 16S rRNA gene sequencing. Results of herichical analysis showed most of trains isolated from Astragalus spp. fell into subgroups 8 and 9, Also the DNA homolgy among strains of subgroups 8 and 9 are more than 70%, with the exception of strains CA8593 and SX044, and the DNA homology between strain CA8561, JL84 and type strains of all described rhizobial species are less than 56%. These results indicated that these two subgroups 8 and 9 were unique DNA homologous groups, distinguishing from all described rhizobial species. Sequencing of partial 16S rRNA gene showed that cetrostrain CA8561 of subgroup 8 is phylogenetically far from all know species of Rhizobium, Bradyrhizobium, Sinorhizobium, Azorhizobium and Agrobacterium, and it is a unique geneline. The cetrostrain JL84 of subgroup 9 has a unique position in the phylogenetic branch consisted of species of Rhizobium and Agrobacterium.

Fabaceae↗

Caenorhabditis elegans embryos contain only one major species of Ro RNP.

In virtually all vertebrate cells, Ro RNPs consist of the 60-kDa Ro autoantigen bound to one of several small cytoplasmic RNA molecules known as Y RNAs. Because the 60-kDa Ro autoantigen is also found complexed with defective precursors of 5S rRNA in Xenopus oocytes, we have proposed that this protein functions in a quality control, or discard pathway, for 5S RNA biosynthesis (O'Brien CA, Wolin SL, 1994, Genes & Dev 8:2891-2903). The role of the Y RNAs in this pathway is unknown. To begin a genetic analysis of Ro RNP function, we have characterized these particles in the nematode Caenorhabditis elegans. The C. elegans Ro protein is 12 kDa larger than the vertebrate protein; the larger size is due in part to an N-terminal extension and to two insertions in the RNA recognition motif. In contrast to all previously described vertebrate species, the Ro protein appears bound to a single Y RNA in C. elegans. Similar to vertebrate Y RNAs, the C. elegans Y RNA can be folded to form a pyrimidine-rich internal loop and a long stem in which the 5' and 3' ends are base paired. Within the stem is a conserved bulged helix that is proposed to be the binding site of the Ro protein. Interestingly, although the human protein can bind the nematode Y RNA, the C. elegans protein does not bind human Y RNAs. This is the first description of Ro RNPs in an invertebrate species.

Amino Acid Sequence↗

Nucleotide sequence analysis and development of consensus primers of RT-PCR for detection of Norwalk-like viruses prevailing in Japan.

A total of 177 different nucleotide sequences of the RNA polymerase region of Norwalk-like viruses (NLVs) genomes, collected via a nation-wide survey project in Japan between 1989 and 1998, were examined by reverse transcription-polymerase chain reaction (RT-PCR) employing various primer pairs. The nucleotide sequences of different strains showed great diversity, with a range of 57 to 100% identities among strains. The strains could be classified into five clusters: Norwalk (NV), Snow Mountain agent/Bristol virus (SMA/BV), Toronto virus/Mexico virus (TV/MX), and Japan specific cluster 1 and 2 (JP-1 and JP-2). Within each cluster there is greater than 85% identity of amino acid sequence (more than 75% identity of nucleotide sequences), based on sequence homology analysis. We believe that two of the five clusters, JP-1and JP-2, define new specific clusters found in Japan according to phylogenetic and pair-wise comparison studies. An RT-PCR procedure was designed using new consensus primer pairs, P1/P2, P1/P3, and Y1/Y2 based on multiple alignment of collected nucleotide sequences, that are expected to detect nearly all NLVs prevailing in Japan. The usefulness of the primers was tested by ten different laboratories in Japan using a panel of ten fecal samples containing different virus strains. The identification of these primer pairs will facilitate routine diagnosis of NLV infection by RT-PCR and offers the potential for their direct detection in food and environmental samples.

Caliciviridae Infections↗

Infection with GB virus C/hepatitis G virus in Brazilian hemodialysis and hepatitis patients and asymptomatic individuals.

Recently, sequences from a novel human flavivirus, termed GB virus C (GBV-C) or hepatitis G virus (HGV), have been identified in serum from patients with cryptogenic hepatitis and others. Sera from 116 patients with different clinical backgrounds were tested for the presence of GBV-C/HGV RNA by a reverse transcription-polymerase chain reaction with primers from the nonstructural (NS) 5 region. Ten (15%) patients on maintenance hemodialysis and 5 (19%) non A-C hepatitis patients were GBV-C/HGV RNA positive, along with one patient with chronic hepatitis B, one patient with chronic hepatitis C, and two asymptomatic individuals. Sequence comparison within 354 base pairs in the NS5 region showed homology rates varying from 87% to 97% among five Brazilian isolates, and from 86% to 93% between Brazilian strains and GBV-C/HGV isolates from other countries previously sequenced. Homology rates were higher at the amino acid level since most substitutions occurred at the third nucleotide position of codons without changing the codon meaning.

Adolescent↗

Characterization of virus-like particles assembled in a recombinant baculovirus system expressing the capsid protein of a fish nodavirus.

Betanodaviruses are causative agents of neurological disorders in several species of fish. We cloned and sequenced the RNA2 segment of two grouper viruses isolated from Epinephelus malabaricus (malabaricus grouper nervous necrosis virus, MGNNV) and Epinephelus lanceolatus (dragon grouper nervous necrosis virus, DGNNV). The sequences of the two RNAs were 99% identical and comparison with previously sequenced RNA2 segments of fish nodaviruses striped jack nervous necrosis virus, Atlantic halibut virus, sea bass encephalitis virus, and greasy grouper nervous necrosis virus (GGNNV) revealed that MGNNV and DGNNV were most closely related to GGNNV. No correlation of sequence with geographical habitat was detected. The MGNNV coat protein, the gene product of RNA2, was expressed in Sf21 cells with a recombinant baculovirus system and virus-like particles (VLPs) spontaneously formed. Two types of VLPs were observed: a slower sedimenting particle was RNase-sensitive and stain-permeable, while the faster sedimenting particle survived RNase treatment and was not stain-permeable. An image reconstruction of the latter, obtained with electron cryomicroscopy data, revealed a morphology consistent with T = 3 quasi-symmetry but with features significantly different from insect nodavirus structures at the same resolution. This assembly system allows the first biophysical comparisons of fish and insect nodavirus structure, assembly, and stability.

Amino Acid Sequence↗

Sequences at the ends of RNA-2 of I6, a recombinant tobravirus.

Tobravirus isolate I6 is an anomalous strain of tobacco rattle virus (TRV), which has biological properties typical of TRV, but which is serologically related to pea early-browning virus (PEBV). Its RNA-2 species is a natural recombinant molecule which contains internal sequences, including the particle protein gene, resembling those of PEBV, but with some TRV-like sequences at each end. Sequencing of RNA-2 of isolate I6 showed that, at the 3' end, it is almost identical to RNA-2 of PEBV strain SP5, and TRV-like sequences are limited to the 25 residues that are common to both viruses. However, unlike PEBV RNA-2, I6 RNA-2 can be replicated by TRV RNA-1-coded enzymes. Thus, specific recognition of RNA-2 by TRV replicase seems not to involve sequences at the 3' end. About 275 residues at the 5' end of I6 RNA-2 are similar to those in RNA-2 of TRV strain TCM, and are jointed to the PEBV-SP5-like subgenomic promoter and coding sequences by about 100 residues of uncertain origin. These results support the idea that I6 RNA-2 originated by recombination between TRV and PEBV RNA-2 molecules, although the exact position of the junction and therefore the mechanism involved are unclear.

Base Sequence↗

Evolutionary implications of genetic variations in the S1 gene of infectious bronchitis virus.

The large number of phenotypically distinct strains of infectious bronchitis virus (IBV) provide a broad genetic background for examining naturally occurring coronavirus variation. Comparisons of the published nucleotide sequence of S1 genes of strains isolated in Europe, Japan and the USA and four additional American strains described in this report identified 4 genetically distinct groups. The Dutch group was the most divergent sharing only about 60% identity with the American, Mass and European groups which were about 80% homologous with each other. Whereas the strains within the Mass, European and Dutch strains were at least 95% homologous, the strains within the American group were most variable, sharing about 80% identity. The hypervariable region (HVR) which tended to correlate with serotype extended from amino acid residue 53 to 148. In addition to the previously described putative recombination events in the S1 gene of PP14 and SE17, we have now described similar shifts in homology in the corresponding gene of the Gray, Holte, 6/82 (European strain), and Iowa strains. Although minor cross-over sites were identified in the more conserved 3' end at approximately nt 1000 and 1400, a frequently used hot-spot for recombination extended from nt 25 to a region immediately upstream of, but not including, the hypervariable region (HVR). In addition to point mutations, deletions, and insertions, recombination often involving Mass-like and Ark-like sequences, is a commonly used mechanism responsible for the evolution of IBV.

Amino Acid Sequence↗

Selection of genomic target RNAs by iterative screening.

A growing number of proteins are known to exert their regulatory or biological functions via RNA binding. In some cases genetic interactions allow us to infer candidate targets for RNA directed regulation, but in many other cases identification of potential regulatory targets is problematic. We have developed an in vitro biochemical screen, SETIS (SElection of < > Target RNAs by Iterative Screening) that allows screening of a major portion of the genome for identification of potential targets for RNA binding proteins.

Animals↗

Cloning and characterization of the 3'-untranslated region of the human excitatory amino acid transporter 2 transcript.

The 3'-untranslated region (UTR) of the human excitatory amino acid transporter 2 (EAAT2) transcript was cloned and characterized. The full-length EAAT2 cDNA of 11 692 bp was found to contain 283 bp of 5' UTR, a 1725-bp open reading frame and an unusually long 3'-UTR of 9684 bp. The 3'-UTR of EAAT2 cDNA was well conserved among mammals, and human, macaque, rat and mouse cDNA had nearly identical 3' ends. The human EAAT2 transcripts were detected in brain, spinal cord, liver, adrenal gland, placenta and pancreas by northern hybridization, and many ESTs homologous to the human EAAT2 cDNA were found in numerous tissues. To investigate the role of human EAAT2 3'-UTR in gene expression, we constructed luciferase expression vectors containing 3'-UTR fragments spanning the entire length of the region. The individual fragments varied in their effects on reporter gene expression in human astrocytes by a factor of eight to ten suggesting a complex role of the 3'-UTR in post-transcriptional regulation of EAAT2 gene expression.

3' Untranslated Regions↗

Two mRNAs are transcribed from the human gene for choline acetyltransferase.

The product of the choline acetyltransferase (ChAT) gene is the enzyme that synthesizes the neurotransmitter acetylcholine. A 14.4-kb portion of the human ChAT gene contains 7 exons, which are estimated to comprise approximately one-third of the human protein coding sequence by comparison with porcine ChAT mRNA. Two of the exons were used to identify polyadenylated human ChAT gene transcripts on Northern blots. An exon with 84% identity to the region of porcine ChAT mRNA that codes for the amino terminus of the corresponding protein detected 6,000- and 2,300-nucleotide mRNAs in RNA isolated from human CHP134 neuroblastoma cells. Only the 2,300-nucleotide mRNA was detected by a second probe containing an exon with 96% identity to porcine ChAT mRNA in the domain that encodes amino acids 204-263 of the predicted porcine ChAT protein. Further evidence that two species of human mRNA are produced from the human ChAT gene was obtained from nuclease protection assays using an antisense RNA probe prepared from a human ChAT cDNA clone. Total RNA isolated from either CHP134 cells or adult human nucleus basalis protected 525- and 400-nucleotide fragments of this probe, confirming the presence of two species of RNA that differ by the inclusion of an internal exon. cDNA clones of each of these transcripts have been isolated. Their sequences suggest that the 2,300-nucleotide mRNA encodes enzymatically active human ChAT, while translation of the 6,000-nucleotide mRNA would be terminated prematurely by a shift in the reading frame. These results indicate that a complex pattern of transcription produces two mRNAs with different coding potentials from the human ChAT gene.

Blotting, Northern↗

Oligonucleotide probes to the 16S ribosomal RNA: implications of sequence homology and secondary structure with particular reference to the oral species Prevotella intermedia and Prevotella nigrescens.

Eight oligonucleotides based upon regions of the small subunit 16S ribosomal RNA gene sequences were analysed against a background of their position within the molecule and their two-dimensional structure to rationalise their use in recognising Prevotella intermedia and Prevotella nigrescens. The 41 clinical isolates from both oral and respiratory sites and two reference strains were subjected to DNA-DNA hybridisation and multilocus enzyme electrophoresis to confirm their identity. Alignment of oligonucleotide probes designated I Bi-2 to I Bi-6 (for P. intermedia) and 2Bi-2 (for P. nigrescens) with the 16S rRNA suggested that these probes lacked specificity or were constructed from hypervariable regions. A 52-mer oligonucleotide (designated Bi) reliably detected both species. Because of the high degree of concordance between the 16S rRNAs of both species, it was necessary to vary the stringency of hybridisation conditions for detection of both species. Thus probe I Bi-I recognised P. intermedia while I Bi-I detected both P. intermedia and P. nigrescens at low stringency. However, under conditions of high stringency only P. nigrescens was recognised by probe 2Bi-I. These probes were highly specific and did not hybridise with DNA from the closely related P. corporis, nor other periodontal pathogens such as Fusobacterium nucleatum, Actinobacillus actinomycetemcomitans, Treponema denticola and several pigmented species such as Prevotella melaninogenica, P. denticola, P. loescheii, Porphyromonas asaccharolytica, Py. endodontalis, Py. gingivalis, Py. levii, and Py. macacae.

Bacterial Typing Techniques↗

ORP-3, a human oxysterol-binding protein gene differentially expressed in hematopoietic cells.

Using differential display polymerase chain reaction, a gene was identified in CD34(+)-enriched populations that had with low or absent expression in CD34(-) populations. The full coding sequence of this transcript was obtained, and the predicted protein has a high degree of homology to oxysterol-binding protein. This gene has been designated OSBP-related protein 3 (ORP-3). Expression of ORP-3 was found to be 3- to 4-fold higher in CD34(+) cells than in CD34(-) cells. Additionally, expression of this gene was 2-fold higher in the more primitive subfraction of hematopoietic cells defined by the CD34(+)38(-) phenotype and was down-regulated with the proliferation and differentiation of CD34(+) cells. The ORP-3 predicted protein contains an oxysterol-binding domain. Well-characterized proteins expressing this domain bind oxysterols in a dose-dependent fashion. Biologic activities of oxysterols include inhibition of cholesterol biosynthesis and cell proliferation in a variety of cell types, among them hematopoietic cells. Characterization and differential expression of ORP-3 implicates a possible role in the mediation of oxysterol effects on hematopoiesis.

Antigens, CD34↗