302 resultados para `Candidatus Liberibacter americanus`


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"Interspersed with many curious and useful observations, respecting their uses in medicine, diet, and mechanics."

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Amer. journ. sci. 1838. 34. 225-266. pl. 3-5.

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A field-applicable assay for testing anthelmintic sensitivity is required to monitor for anthelmintic resistance. We undertook a study to evaluate the ability of three in vitro assay systems to define drug sensitivity of clinical isolates of the human hookworm parasite Necator americanus recovered from children resident in a village in Madang Province, Papua New Guinea. The assays entailed observation of drug effects on egg hatch (EHA), larval development (LDA), and motility of infective stage larvae (LMA). The egg hatch assay proved the best method for assessing the response to benzimidazole anthelmintics, while the larval motility assay was suitable for assessing the response to ivermectin. The performance of the larval development assay was unsatisfactory on account of interference caused by contaminating bacteria. A simple protocol was developed whereby stool samples were subdivided and used for immediate egg recovery, as well as for faecal culture, in order to provide eggs and infective larvae, respectively, for use in the egg hatch assay and larval motility assay systems. While the assays proved effective in quantifying drug sensitivity in larvae of the drug-susceptible hookworms examined in this study, their ability to indicate drug resistance in larval or adult hookworms remains to be determined. (c) 2005 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.

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The gastrointestinal tracts of multi-cellular blood-feeding parasites are targets for vaccines and drugs. Recently, recombinant vaccines that interrupt the digestion of blood in the hookworm gut have shown efficacy, so we explored the intestinal transcriptomes of the human and canine hookworms, Necator americanus and Ancylostoma caninum, respectively. We used Laser Microdissection Microscopy to dissect gut tissue from the parasites, extracted the RNA and generated cDNA libraries. A total of 480 expressed sequence tags were sequenced from each library and assembled into contigs, accounting for 268 N. americanus genes and 276 A. caninum genes. Only 17% of N. americanus and 36% of A. caninum contigs were assigned Gene Ontology classifications. Twenty-six (9.8%) N. americanus and 18 (6.5%) A. caninum contigs did not have homologues in any databases including dbEST-of these novel clones, seven N. americanus and three A. caninum contigs had Open Reading Frames with predicted secretory signal peptides. The most abundant transcripts corresponded to mRNAs encoding cholesterol-and fatty acid-binding proteins, C-type lectins, Activation-Associated Secretory Proteins, and proteases of different mechanistic classes, particularly astacin-like metallopeptidases. Expressed sequence tags corresponding to known and potential recombinant vaccines were identified and these included homologues of proteases, anti-clotting factors, defensins and integral membrane proteins involved in cell adhesion. (c) 2006 Australian Society for Parasitology Inc Published by Elsevier Ltd. All fights reserved.

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The bacteria that mediate the anaerobic oxidation of ammonium (anammox) are detected worldwide in natural and man-made ecosystems, and contribute up to 50% to the loss of inorganic nitrogen in the oceans. Two different anammox species rarely live in a single habitat, suggesting that each species has a defined but yet unknown niche. Here we describe a new anaerobic ammonium oxidizing bacterium with a defined niche: the co-oxidation of propionate and ammonium. The new anammox species was enriched in a laboratory scale bioreactor in the presence of ammonium and propionate. Interestingly, this particular anammox species could out-compete other anammox bacteria and heterotrophic denitrifiers for the oxidation of propionate in the presence of ammonium, nitrite and nitrate. We provisionally named the new species Candidatus "Anammoxoglobus propionicus".

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Despite differences in their morphologies, comparative analyses of 16S rRNA gene sequences revealed high levels of similarity (> 94 %) between strains of the filamentous bacterium 'Candidatus Nostocoida limicola' and the cocci Tetrasphaera australiensis and Tetrasphaera japonica and the rod Tetrasphaera elongata, all isolated from activated sludge. These sequence data and their chemotaxonomic characters, including cell wall, menaquinone and lipid compositions and fingerprints of their 16S-23S rRNA intergenic regions, support the proposition that these isolates should be combined into a single genus containing six species, in the family Intrasporangiaceae in the Actinobacteria. This suggestion receives additional support from DNA-DNA hybridization data and when partial sequences of the rpoC1 gene are compared between these strains. Even though few phenotypic characterization data were obtained for these slowly growing isolates, it is proposed, on the basis of the extensive chemotaxonomic and molecular evidence presented here, that 'Candidatus N. limicola' strains Ben 17, Ben 18, Ben 67, Ben 68 and Ben 74 all be placed into the species Tetrasphaera jenkinsii sp. nov. (type strain Ben 74(T) = DSM 17519(T) = NCIMB 14128(T)), 'Candidatus N. limicola' strain Ben 70 into Tetrasphaera vanveenii sp. nov. (type strain Ben 70(T) = DSM 17518(T) = NCIMB 14127(T)) and 'Candidatus N. limicola' strains Ver 1 and Ver 2 into Tetrasphaera veronensis sp. nov. (type strain Ver 1(T) = DSM 17520(T) = NCIMB 14129(T)).

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Candidatus Accumulibacter Phosphatis is widely considered to be a polyphosphate accumulating organism (PAO) of prime importance in enhanced biological phosphorus removal (EBPR) systems. This organism has yet to be isolated, despite many attempts. Previous studies on the biochemical and physiological aspects of this organism, as well as its response to different EBPR operational conditions, have generally relied on the use of mixed culture enrichments. One frequent problem in obtaining highly enriched cultures of this organism is the proliferation of glycogen accumulating organisms (GAO) that can compete with PAOs for limited carbon sources under similar operational conditions. In this study, Candidatus Accumulibacter Phosphatis has been enriched in a lab-scale bioreactor to a level greater than 90% as quantified by fluorescence in situ hyrbridisation (FISH). This is the highest enrichment of this organism that has been reported thus far, and was obtained by alternating the sole carbon source in the feed between acetate and propionate every one to two sludge ages, and operating the bioreactor within a pH range of 7.0-8.0. Simultaneously, the presence of two known groups of GAOs was eliminated under these operational conditions. Excellent phosphorus removal performance and stability were maintained in this system, where the phosphorous concentration in the effluent was below 0.2 mg/L for more than 7 months. When a disturbance was introduced to this system by adding sludge from an enriched GAO culture, Candidatus Accumulibacter Phosphatis once again became highly enriched, while the GAOs were out-competed. This feeding strategy is recommended for future studies focused on describing the physiology and biochemistry of Accumulibacter, where a highly-enriched culture of this organism is of high importance. (c) 2006 Elsevier Ltd. All rights reserved.