Symbiont modulates expression of specific gene categories in Angomonas deanei

Trypanosomatids are parasites that cause disease in humans, animals, and plants. Most are non-pathogenic and some harbor a symbiotic bacterium. Endosymbiosis is part of the evolutionary process of vital cell functions such as respiration and photosynthesis. Angomonas deanei is an example of a symbiont-containing trypanosomatid. In this paper, we sought to investigate how symbionts influence host cells by characterising and comparing the transcriptomes of the symbiont-containing A. deanei (wild type) and the symbiont-free aposymbiotic strains. The comparison revealed that the presence of the symbiont modulates several differentially expressed genes. Empirical analysis of differential gene expression showed that 216 of the 7625 modulated genes were significantly changed. Finally, gene set enrichment analysis revealed that the largest categories of genes that downregulated in the absence of the symbiont were those involved in oxidation-reduction process, ATP hydrolysis coupled proton transport and glycolysis. In contrast, among the upregulated gene categories were those involved in proteolysis, microtubule-based movement, and cellular metabolic process. Our results provide valuable information for dissecting the mechanism of endosymbiosis in A. deanei.

Microsporidia: emerging ocular pathogens.

Microsporidia are eukaryotic, spore forming obligate intracellular parasites, first recognized over 100 years ago. Microsporidia are becoming increasingly recognized as infectious pathogens causing intestinal, ocular, sinus, pulmonary, muscular and renal diseases, in both immunocompetent and immunosuppressed patients. Ocular microsporidiosis, though uncommon, could be isolated or part of systemic infections. It occurs mainly in two forms: keratoconjunctivitis form, mostly seen in immunocompromised individuals; stromal keratitis form seen in immunocompetent individuals. Recent reports indicate increasing number of cases of ocular microsporidiosis in immunocompetent individuals. The ocular cases present as superficial keratitis in AIDS patients, and these differ in presentation and clinical course from the cases seen in immunocompetent individuals which mainly appear to be as deep stromal keratitis. For most patients with infectious diseases, microbiological isolation and identification techniques offer the most rapid and specific determination of the etiologic agent, however this does not hold true for microsporidia, which are obligate intracellular parasites requiring cell culture systems for growth. Therefore, the diagnosis of microsporidiosis currently depends on morphological demonstration of the organisms themselves, either in scrapings or tissues. Although the diagnosis of microsporidiosis and identification of microsporidia by light microscopy have greatly improved during the last few years, species differentiation by these techniques is usually impossible and electron microscopy may be necessary. Immuno fluorescent-staining techniques have been developed for species differentiation of microsporidia, but the antibodies used in these procedures are available only at research laboratories at present. During the last 10 years, molecular techniques have been developed for the detection and species differentiation of microsporidia.

Detection of Enterocytozoon bieneusi (Microsporidia) by polymerase chain reaction (PCR) using species-specific primer in stool samples of HIV patients.

BACKGROUND & OBJECTIVE: Microsporidia are obligate intracellular parasites causing infections predominantly in immunocompromised patients. Enterocytozoon bieneusi is the most important microsporidian causing chronic diarrhoea in AIDS patients. The current method used for diagnosing the microsporidia spores is based on light microscopy using stained smears, which do not differentiate spores at species level. The present study was undertaken to detect microsporidia and confirm at species level (E. bieneusi) by PCR from stool samples of HIV positive patients. METHODS: During September 2002 to April 2003, stool samples from 153 HIV-positive patients (with chronic diarrhoea n = 105; without diarrhoea n=48) were collected and examined microscopically for microsporidia spores using modified Weber's chromotrope stain. Stool samples were subjected to PCR assay using species-specific primer EBIEFI/EBIER1, which amplifies small subunit ribosomal RNA (SSU rRNA) of this microsporidian RESULTS: A total of 10 HIV positive patients with chronic diarrhoea were positive for microsporidia by microscopic analysis and confirmed as Enterocytozoon bieneusi by PCR. No false positive results were observed. A diagnostic DNA fragment of 607 bp of the unique SSU rRNA was amplified from all samples infected with E. bieneusi. INTERPRETATION & CONCLUSION: The study revealed that polymerase chain reaction is a useful tool for accurate species identification of microsporidia in stool samples, which serves the benefit of treatment to the patients.