Microsporidia (Phylum Microsporidia Balbiani 1882) are ubiquitous parasites within the Animal Kingdom. The phylum includes 1400 described species belonging to 200 genera. The host range, as well as molecular data, strongly suggest that microsporidia evolved as parasites of invertebrates and, to a lesser extent, fish. Only about 1% of microsporidia species have been found in endothermic vertebrates, birds and mammals. Microsporidiosis in humans has been observed worldwide mainly in patients with HIV infection and now increasingly in other groups such as children, immunosuppressed individuals (e.g. organ transplant recipients), contact lens wearers, travelers, and the elderly. Among AIDS patients, microsporidiosis is listed as the third important opportunistic infection causing gastrointestinal disorders, after Cytomegalovirus and Cryptosporidium. In fact, only four species belonging to two genera can be considered true mammalian parasites: Enterocytozoon bieneusi, Encephalitozoon cuniculi, E. intestinalis, and E. hellem. These represent a serious threat to human populations as zoonotic infections. Findings of other microsporidia (as a rule, parasites of arthropods or close relatives of those) in humans, are accidental. At the same time these records demonstrate the consecutive stages of microsporidia adaptation to parasitism in humans: from transient arthropodrelated microsporidia known by sequences in stools of AIDS patients, through accidental surface infections in immunocompromised patients (Endoreticulatuslike Microsporidium sp., Tubulinosema) and development in immune privileged tissues of eyes (Vittaforma), skin, and muscles due to accidental exposure to spores of a “generalist” microsporidium (Trachipleistaphora, Anncaliia), to specialized infections of gut epithelium (Enterocytozoon), and systemic microsporidiosis disseminated by macrophages (Encephalitozoon). The review is addressing the following questions. What is special about the microsporidia that are able to infect warm-blooded animals? How high are the risks of acquisition of new microsporidia parasites by humans, given abundance of microsporidia in invertebrates, many of which may traverse food chains leading to humans and other mammals?
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Current state and perspectives of single-cell studies in ecophysiology of protists
Olga Matantseva, Sergei Skarlato
Protists (eukaryotic microbes) play a tremendous role in aquatic and terrestrial ecosystems worldwide, because their physiological activity is important for biogeochemical cycling of elements. For a long time studies of microbial physiology have been carried out with the focus on populations. However, nowadays development and application of new techniques lead to rapid accumulation of data obtained at the single-cell level. Single-cell approaches have already brought a lot of invaluable information about prokaryotic microbes, whereas protists are still less studied in this respect. In this paper, we review the range of single-cell studies in the field of ecophysiology of eukaryotic microbes published to the date and discuss future prospects of individual-based protist research.
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Annual variation of protozoan communities and its relationship to environmental conditions in a sub-tropic urban wetland ecosystem, southern China
Xinlu Shi, Xiangwei Meng, Guijie Liu, Yong Jiang, Songlu Liu, Cuicui Hou, Qingjuan Meng, Henglong Xu
With ease of collection, short life cycles, lack of complex developmental stages, and rapid response to environmental changes, protozoa attract the increasing attention as suitable indicators for bioassessment. In order to reveal the annual variation of protozoan communities and its relation to the environmental conditions in a subtropic urban wetland, the protozoan species composition, abundance, diversity, and their correlations with abiotic factors were studied in Xixi wetland, Hangzhou, China. A total of 89 protozoan species comprising 34 ciliates, 13 flagellates, and 42 rhizopods were recorded; 7 of those were the dominant species. The protozoan abundance ranged from 3×104 ind. l-1 to 19.65×104 ind. l-1; ciliates (69.3%) were the primary contributors in terms of relative abundance. The cluster analysis discriminated the protozoan communities into three annual stages: spring, summerautumn and winter at a 30% similarity level with significant difference. Multivariate correlation analysis showed that temporal variation in protozoan communities was significantly related to the changes of environmental variables, especially water temperature, dissolved oxygen, chemical oxygen demand (COD) and nutrients. Three diversity indices (species richness, diversity and evenness) were significantly correlated with the COD and nutrients. The results demonstrated that the annual variation in protozoan abundance represented a clear seasonal shift in response to environmental changes and thus may be used as a potential indicator for assessing water quality in a sub-tropic urban wetland ecosystem.