Soil Sampling and Methods of Analysis, 2nd edition
M. Carter and E. Gregorich, editors
Protozoa, supplementary material.
S. M. Adl, D. Acosta-Mercado, T. R. Anderson, and D. H. Lynn
Among the microbial groups, it is well established that protozoa are involved in pivotal processes in
both aquatic and terrestrial ecosystems. In soil ecosystems, protozoa are conspicuous (Berthold and
Palzenberger 1995), serving as predators and prey for other soil microorganisms (Clarholm 1981),
influencing the development and metabolic activities of bacterial communities (Griffiths et al. 1999;
Pussard et al. 1994), and concomitantly increasing plant biomass (Alphei et al. 1996; Kuikman et al.
1990). The role and diversity of protozoa in the soil has been the subject of recent reviews (Adl 2003;
Adl and Gupta 2006). An extensive literature was synthesised in two earlier reviews (Darbyshire 1994;
Foissner 1987), and Bonkowski (2004) reviewed the interactions of protozoa with plant roots.
For the purpose of this chapter, protozoa are defined as heterotrophic, non-filamentous protists. The
major role of protozoa in decomposition food webs is usually assumed to be as bacterivores. Although
this is primarily correct, predatory protozoa are more diverse, influencing the rest of the food web by
feeding on each other, fungal components, and even on some soil metazoans. Ingestion of prey through