A New PCR-Based Approach Indicates the Range of Clonorchis sinensis Now Extends to Central Thailand

Differentiation of the fish-borne trematodes belonging to the Opisthorchiidae, Heterophyidae and Lecithodendriidae is important from a clinical and epidemiological perspective, yet it is impossible to do using conventional coprological techniques, as the eggs are morphologically similar. Epidemiological investigation therefore currently relies on morphological examination of adult worms following expulsion chemotherapy. A PCR test capable of amplifying a segment of the internal transcribed spacer region of ribosomal DNA for the opisthorchiid and heterophyid flukes eggs taken directly from faeces was developed and evaluated in a rural community in central Thailand. The lowest quantity of DNA that could be amplified from individual adults of Opisthorchis viverrini, Clonorchis sinensis and Haplorchis taichui was estimated at 0.6 pg, 0.8 pg and 3 pg, respectively. The PCR was capable of detecting mixed infection with the aforementioned species of flukes under experimental conditions. A total of 11.6% of individuals in rural communities in Sanamchaikaet district, central Thailand, were positive for ‘Opisthorchis-like’ eggs in their faeces using conventional parasitological detection techniques. In comparison to microscopy, the PCR yielded a sensitivity and specificity of 71.0% and 76.7%, respectively. Analysis of the microscopy-positive PCR products revealed 64% and 23% of individuals to be infected with O. viverrini and C. sinensis, respectively. The remaining 13% (three individuals) were identified as eggs of Didymozoidae, presumably being passed mechanically in the faeces following the ingestion of infected fishes. An immediate finding of this study is the identification and first report of a C. sinensis–endemic community in central Thailand. This extends the known range of this liver fluke in Southeast Asia. The PCR developed herein provides an important tool for the specific identification of liver and intestinal fluke species for future epidemiological surveys.     

Solution spectroscopy of dipicolinic acid interaction with nucleic acids: Role in spore heat resistance

The effect of dipicolinic acid (DPA) or its calcium chelate (CaDPA) on the spectral characteristics of nucleic acids was examined. Dipicolinic acid was found to displace ethidium gromide from DNA; this indicates that it may bind by intercalation. On interaction with DNA, the ultraviolet absorption spectrum revealed downfield shifts and caused progressive diminution in both DNA and dipicolinate chromophores. The strength and type of interaction may be ion-specific but not discriminatory to any type of base pairing. Spectral analysis also indicated that both dipicolinate and calcium dipicolinate bound to different RNA species, although the mechanism of binding was not elucidated. We conclude that the interaction of dipicolinate/ calcium dipicolinate with nucleic acids is a mechanism whereby water can be removed from spore polynucleotides, increasing their stability to denaturation.     

The Location and Protection Status of Earth’s Diminishing Marine Wilderness

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Familial multiple-system tauopathy with presenile dementia is localized to chromosome 17.

An autosomal dominant presenile dementia affecting 39 individuals in a seven-generation, 383-member pedigree has been studied at Indiana University. In the affected members of this family, clinical symptoms occurred early in life, with an average age at onset of 48.8 years. The presenting clinical features include disequilibrium, neck stiffness, dysphagia, and memory loss. As the disease progresses, further cognitive decline, superior-gaze palsy, and dystaxia also are observed. The average duration from onset of symptoms to death is approximately 10 years. Neuropathologic studies of nine affected individuals showed neuronal loss in several areas of the CNS, as well as argentophilic tau-immunopositive inclusions in neurons and in oligodendroglia. A limited genomic screen by use of DNA samples from 28 family members localized the gene for this disorder to a 3-cM region on chromosome 17, between the markers THRA1 and D17S791. The gene for tau also was analyzed, through samples from the family.     

Identification of a distinct, cryptic heparosan synthase from Pasteurella multocida types A, D, and F

The extracellular polysaccharide capsules of Pasteurella multocida types A, D, and F are composed of hyaluronan, N-acetylheparosan (heparosan or unsulfated, unepimerized heparin), and unsulfated chondroitin, respectively. Previously, a type D heparosan synthase, a glycosyltransferase that forms the repeating disaccharide heparosan backbone, was identified. Here, a approximately 73% identical gene product that is encoded outside of the capsule biosynthesis locus was also shown to be a functional heparosan synthase. Unlike PmHS1, the PmHS2 enzyme was not stimulated greatly by the addition of an exogenous polymer acceptor and yielded smaller- molecular-weight-product size distributions. Virtually identical hssB genes are found in most type A, D, and F isolates. The occurrence of multiple polysaccharide synthases in a single strain invokes the potential for capsular variation.     

Diversity of methyl halide-degrading microorganisms in oceanic and coastal waters

Methyl halides have a significant impact on atmospheric chemistry, particularly in the degradation of stratospheric ozone. Bacteria are known to contribute to the degradation of methyl halides in the oceans and marine bacteria capable of using methyl bromide and methyl chloride as sole carbon and energy source have been isolated. A genetic marker for microbial degradation of methyl bromide ( cmuA ) was used to examine the distribution and diversity of these organisms in the marine environment. Three novel marine clades of cmuA were identified in unamended seawater and in marine enrichment cultures degrading methyl halides. Two of these cmuA clades are not represented in extant bacteria, demonstrating the utility of this molecular marker in identifying uncultivated marine methyl halide-degrading bacteria. The detection of populations of marine bacteria containing cmuA genes suggests that marine bacteria employing the CmuA enzyme contribute to methyl halide cycling in the ocean.