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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 44 (1997), S. 0 
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: . The species richness and quantity of naked amebae were determined in the bulk soil and rhizoplane of the desert plant Escontria chiotilla in the Valley of Tehuacan, Mexico. Samples from bulk soil were taken at 10-cm and 30-cm depths in April, May and July, 1993, and from roots and soil at a 10-cm depth in June and July, 1994. Quantity of amebae obtained by Most Probable Number method increased in the rhizoplane by two orders of magnitude after rains. Likewise, the countable population of amebae doubled in numbers at both the 10- and 30-cm depths after rains. We isolated 163 strains from both root and soil environments, which were grouped into 40 bactivorous and/or generalist species belonging to 19 genera. Species richness showed no clear dominance of a particular genus in either bulk soil or root. Acanthamoeba (groups II and III, Pussard & Pons) and Vahlkampfia accounted for 12.5% and 15% of the total number of species, respectively. However, greater species richness was found in bulk soil than on root surfaces. We concluded that the diversity of naked amebae, taken as numbers of individuals (or as biomass) of each species and its evenness, is still needed to assess the ecological roles of Acanthamoeba and Vahlkampfia in the soil environment.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The 18S rRNA gene (Rns) phylogeny of Acanthamoeba is being investigated as a basis for improvements in the nomenclature and taxonomy of the genus. We previously analyzed Rns sequences from 18 isolates from morphological groups 2 and 3 and found that they fell into four distinct evolutionary lineages we called sequence types T1-T4. Here, we analyzed sequences from 53 isolates representing 16 species and including 35 new strains. Eight additional lineages (sequence types T5-T12) were identified. Four of the 12 sequence types included strains from more than one nominal species. Thus, sequence types could be equated with species in some cases or with complexes of closely related species in others. The largest complex, sequence type T4, which contained six closely related nominal species, included 24 of 25 keratitis isolates. Rns sequence variation was insufficient for full phylogenetic resolution of branching orders within this complex, but the mixing of species observed at terminal nodes confirmed that traditional classification of isolates has been inconsistent. One solution to this problem would be to equate sequence types and single species. Alternatively, additional molecular information will be required to reliably differentiate species within the complexes. Three sequence types of morphological group 1 species represented the earliest divergence in the history of the genus and, based on their genetic distinctiveness, are candidates for reclassification as one or more novel genera.
    Type of Medium: Electronic Resource
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