An increasing number of microorganisms, including bacteria but also viruses and eukaryotes, have been described as benefiting from interaction with free-living amoebae (FLA). Beneficial interaction can be due to resistance to predation conferring ecological advantage, intracellular survival and/or intracellular proliferation. This review highlights the potential risk associated with amoebae by listing all known pathogenic microbial species for which growth and/or survival promotion by FLA (mainly Acanthamoeba spp.) has been demonstrated. It focuses on the susceptibility of amoebal and intra-amoebal bacteria to various categories of biocides, the known mechanisms of action of these biocides against trophozoites and cysts and the various methods used to demonstrate efficacy of treatments against FLA. Brief descriptions of FLA ecology and prevalence in domestic/institutional water systems and their intrinsic pathogenicity are also presented. The intention is to provide an informed opinion on the environmental risks associated with the presence of FLA and on the survival of cysts following biocidal treatments, while also highlighting the need to conduct research on the roles of amoebae in aquatic ecosystems.

Free-living amoebae and their intracellular pathogenic microorganisms: risks for water quality.

Local and spatially coordinated movements in Dictyostelium discoideum amoebae during chemotaxis

© The Authors, 2010. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in PLoS One 5 (2010): e9688, doi:10.1371/journal.pone.0009688.

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Transcriptome profiling of a toxic dinoflagellate reveals a gene-rich protist and a potential impact on gene expression due to bacterial presence.

I . Introduction . . . . . . . . . . . . . I1 . Synchrony in naturally occurring multinucleate cells . . . . . . . A . Protozoa . . . . . . . . . . . . . . . B . Algae . . . . . . . . . . . . . . . C . Fungi . . . . . . . . . . . . . . . D . Invertebrate somatic tissues . . . . . . . . . . . E . Germ cell formation . . . . . . . . . . . . F . Fertilization and co-ordination of pronuclei G . Early embryonic development . . . . . . . . . . . H . Cell multiplication in viwo and in witro

Nucleo-cytoplasmic interactions in the achievement of nuclear synchrony in dna synthesis and mitosis in multinucleate cells

Nuclei and cytoplasm were transferred between a normal strain anda variant strain of Amoeba discoides heavily infected with bacteria. After 5 years of infection, the infective bacteria that were initially harmful to the host cells became harmless, and the nucleus of the host cell became dependent on the infective organisms for its normal functions.

Development of Cellular Dependence on Infective Organisms: Micrurgical Studies in Amoebas

Unusual intra-cellular bacterial infection in large, free-living amoebae☆

A SIMPLE method has been developed whereby micrurgy on living cells such as nuclear transplantation and cytoplasmic injection in amoebae can be performed with greater ease and rapidity. The present method differs from those used currently1–4 in that the need for a micro-hook to hold cells and the use of mineral oil (liquid paraffin) to prevent the evaporation of culture medium are eliminated. This is done by placing the cells on an agar surface. When the excess medium surrounding the cells is withdrawn, they remain firmly attached during operations. The agar gel apparently replaces the medium that evaporates, and there is no damage to the cells during the period required for micrurgy. Thus, for example, nuclei are transplanted between amoebae in open drops with a micro-probe alone.

New Simple Method of Micrurgy on Living Cells

Lethal effect of heterologous nuclei in amoeba heterokaryons.

Nuclear control of cell movement in amoebae: Nuclear transplantation study

A strain-specific antimitotic substance is present in large mononucleate amoebae. It inhibits mitosis when injected into amoebae of heterologous strains. The antimitotic substance has been isolated from homogenized cells, and some of its properties have been studied. The results obtained show that the active factor is a protein(s) of molecular weight between 200,000 and one million. The activity of this substance differs from other known antimitotic agents in that its action is strain-specific.

K.W. Jeon

Papers

Unusual intra-cellular bacterial infection in large, free-living amoebae☆

New Simple Method of Micrurgy on Living Cells

Lethal effect of heterologous nuclei in amoeba heterokaryons.

Nuclear control of cell movement in amoebae: Nuclear transplantation study

Strain-specific mitotic inhibition in large mononucleate amoebae.