Amoebophagous Fungi as Predators and Parasites of Potentially Pathogenic Free-living Amoebae

Patrick L Scheid

doi:10.2174/1874421401806010075

Abstract

There are numerous case reports indicating that naked Free-Living Amoebae (FLA) can relatively easily get to humans or animals. The presence of pathogenic amoebae in habitats related to human activities supports the public health relevance of FLA. Acanthamoebae, Naegleria fowleri, Balamuthia mandrillaris and several other FLA have proved to be facultative human pathogenic microorganisms. Additionally, a wide range of FLA is known as vectors of pathogenic microorganisms (endocytobionts). Within their biocoenosis, FLA and fungi (and other microorganisms) live sympatrically. It is known that fungi serve as food sources for the phagocytotic active (mycophagous) trophozoite stages of FLA. In contrast, amoebophagous fungi may use FLA as prey organisms. Endoparasitic and predaceous fungi prove that there are numerous different interactions between FLA and fungi. The man-made introduction of suitable fungi into a habitat (soil or water) with human pathogenic FLA may overcome any ecological effects or limits. While nematophagous fungi have already been brought into action against harmful nematodes, the usage of amoebophagous fungi against FLA has not been widely considered. Nevertheless, the results from in vitro studies are promising concerning the targeted use of amoebophagous fungi as biological control measures against FLA in limited natural areas, in soil and in aquatic habitats.

Highlights

Naked Free-Living Amoebae (FLA) inhabit soil and aquatic habitats
A wide range of FLA is known as vectors of pathogenic microorganisms
Penicillium spp. and Aspergillus spp. have been studied interacting with FLA: It has been shown that Aspergillus fumigatus conidia are capable of escaping from the food vacuoles and of germinating inside the cytoplasm of Acanthamoeba castellanii

Summary

INTRODUCTION

Naked Free-Living Amoebae (FLA) inhabit soil and aquatic habitats Some of these FLA are able to form cysts as dormant stages resisting adverse environmental conditions. Throughout the years, a whole range of examples for microorganisms resisting this phagocytotic uptake was detected Among those microorganisms surviving the uptake and escaping digestion, are numerous bacteria, viruses (especially the giant viruses) and fungi [1]. This kind of interaction of FLA with other microorganisms is of particular importance with respect to Environmental Health. (a fungus causing several types of aspergillosis in humans) have been studied interacting with FLA: It has been shown that Aspergillus fumigatus conidia are capable of escaping from the food vacuoles and of germinating inside the cytoplasm of Acanthamoeba castellanii. Studies on Acanthamoebae and Fusarium sharing the same environment revealed that the fungal conidia were internalized by Acanthamoeba castellanii strains and were able to germinate inside the amoebae [6 - 8]

AMOEBOPHAGOUS FUNGI

Microsporidian - Like Fungi as Endoparasites of FLA

Parasitic Fungi Developing Intracellularly

Predaceous Fungi Predating FLA

Findings

CONCLUSION