Density and Diversity of Protozoa in Some Arid Australian Soils

Abstract

This is the first extensive study of soil protozoa of arid lands. Twenty-six samples from litters, soils, termitaria, and a cyanobacterial crust, collected from central and south Australian arid lands, were analyzed for numbers and species of gymnamoebae, ciliates, and testacea. Amoebae ranged from 1,000-5,000/g of material, and were two orders of magnitude more abundant than ciliates. Both groups increased in abundance and species richness from bare soils through spinifex to mulga to chenopod vegetations. Testacea ranged 900-5,000/g with similar species richness throughout vegetations, but reached 11,900/g with a doubling of species in a refugium in Kings Canyon. The most prevalent species of amoebae, ciliates, and testacea were taxa associated with ephemeral and disturbed habitats (r-selection). The cyanobacterial crust might be considered a micro-refugium because it contained a number of non-encysting protozoa, including Thecamoeba sp. and Nassula picta, feeding on cyanobacterial filaments. The numbers and species richness of protozoa under shrubs were greater than in bare soils, supporting the resource island hypothesis that desert plants create soil heterogeneity by localizing soil fertility under their canopies.

Metatranscriptomic census of active protists in soils

“…However, SSU rRNA sequences of Amoebozoa dominated over those of Alveolata in all non-peat soils. This is in line with cultivation-based studies, which show that small flagellates, especially cercomonads and glissomonads (Rhizaria) (Finlay et al, 2000;Ekelund et al, 2001;Howe et al, 2009) and amoebae represent the numerically dominant soil protists (Schaefer and Schauermann, 1990;Finlay et al, 2000;Robinson et al, 2002). Similarly, other taxonomically highly divergent heterotrophic protist taxa especially abundant in cultivation-based studies such as bodonid and euglenid euglenozoans (Finlay et al, 2000;Geisen et al, 2014a), chrysophytes (Finlay et al, 2000;Boenigk et al, 2005;Chatzinotas et al, 2013), bicosoecids (Ekelund and Patterson, 1997;Lentendu et al, 2014) and heteroloboseans (Geisen et al, 2014a) were identified, but contributed relatively little to the entire protist community.…”

Molecular comparison of cultivable protozoa from a pristine and a polycyclic aromatic hydrocarbon polluted site

“…All 10 isolates obtained had an identical 18S rDNA gene sequence, suggesting a close relationship to A. castellani. The apparent lack of Acanthamoeba in the unpolluted soil, though, is rather surprising, since Acanthamoeba species are considered very common in soils (Page, 1988;Rodrı´guez-Zaragoza and Garcı´a, 1997;Robinson et al, 2002). It could be explained, however, by the large food requirements of this amoeba (Bryant et al, 1982), which are probably not met in the unpolluted, mineral soil.…”

Biogeography of soil archaea and bacteria along a steep precipitation gradient

“…In waterlimited environments, one of the most widely accepted theories is the 'fertility' or 'resource island' hypothesis, which states that shrubs create heterogeneity in soils by localizing soil fertility under their canopies (Schlesinger et al, 1996). Indeed, heterotrophic bacteria (Herman et al, 1995) and protozoa (Robinson et al, 2002) have been found to be more abundant under shrubs than in their interspaces. The links between microbial biogeography, local diversity of microorganisms and the factors that shape them represent largely unexplored territory.…”