High Numbers of Naked Amoebae in the Planktonic Waters of a Mangrove Stand in Southern Florida, USA

Abstract

This is the first study to examine the abundance of naked amoebae in the water column of a mangrove stand. A total of 37 different niorphotypes was noted and at least 13 of these are probably new species. Over a one-year sampling interval, amoebae averaged 35.400 cells liter I (range 2,000-104,000) by an indirect enrichment cultivation method. Densities in the upper end of this range are the highest ever reported for any planktonic habitat. Variation between samples was related to the quantity of suspended aggregates (flocs) in the water column emphasizing that amoebae are usually floc-associated. The study also showed that it is essential to disrupt floc material prior to withdrawing sample aliquots for the indirect counting method since several amoebae can occupy the interstices of aggregates. There is concern that indirect enumeration methods that require organisms to be cultured in the laboratory seriously underestimate the true count. A direct counting method using acridine orange staining and epifluorescence microscopy was attempted to assess the possible magnitude of the error associated with indirect counting. While this direct method had limitations, notably the difficulty of unambiguously differentiating between small amoebae and nanoflagellates, the results suggested that the indirect method gave estimates that were close to the true count (within a factor of two). Mangrove waters are rich in heterotrophic protozoa ( -3 X 10" liter I) and while the heterotrophic flagellates are by far the dominant group, naked amoebae outnumber ciliates some 20fold. The ecological consequences of high numbers of amoebae, particularly the common small forms less than 10 pm in length, need to be examined for these important coastal sites.

Replication and Long-Term Persistence of Bovine and Human Strains of Mycobacterium avium subsp. paratuberculosis within Acanthamoeba polyphaga

“…They populate soils and sediments, suspended aggregates in fresh and marine waters, roots and surfaces of plants, and bodies of animals. They are dispersed by the movement of water and wind (1,19,20,(36)(37)(38)(39). They feed by predation on prokaryotes and have a dynamic role in the maintenance and selection of bacterial populations.…”

Molecular Characterization of Ciliate Diversity in Stream Biofilms

“…It remains difficult and time-consuming to reliably detect or identify many protozoan species by these methods, as protozoa may be fragile and inconspicuous and as it may be difficult to determine whether a given morphological feature can be regarded as distinct or not (7,19,38,46). Molecular techniques based upon analysis of small-subunit RNA gene sequences, while not foolproof (18), offer the potential for more-accurate and -efficient methods for detecting and identifying protozoan organisms and characterizing protozoan communities, including unculturable components (3,7).…”

The importance of morphological versus chemical defences for the bloom-forming cyanobacterium Microcystis against amoebae grazing

“…Moreover, the mucilage around Microcystis cells can host a high abundance and diversity of heterotrophic bacteria (Brunberg 1999;Shi et al 2009), some of which are known to even degrade microcystins (Maruyama et al 2003). However, since most amoebae need a substrate to attach to for feeding and thus are mostly associated with suspended particles in the water column (Anderson and Rogerson 1995;Rogerson and Gwaltney 2000;Rogerson et al 2003), the Microcystis-grazing amoebae are probably more efficient grazers on colonies since attachment is easier than on single cells. We hypothesize that amoebae feeding on Microcystis colonies probably spend less energy to search for food and therefore divide at a higher rate in comparison with amoebae feeding on Microcystis single cells in suspension.…”