Naslov
Amoebae as Training Grounds for Intracellular Bacterial Pathogens

Autori
Molmeret, Maelle ; Horm, Matthias ; Wagner, Michael ; Šantić, Marina ; Abu Kwaik, Yousef

Izvornik
Applied and environmental microbiology (0099-2240) 71 (2005), 1; 20-28

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, pregledni rad, znanstveni

Ključne riječi
Legionella pneumophila; environment; symbiotic interaction

Sažetak
Free-living amoebae are important predators that control microbial communities. They are ubiquitous and have been isolated from various natural sources such as soil, freshwater, salt water, dust, and air. Although their abundance in soil is only limited, they have been implicated in the stimulation of phosphorus and nitrogen turnover and thus play an important role in soil ecosystems. Free-living amoebae are also frequently isolated from anthropogenic ecosystems such as tap water, air-conditioning units, and cooling towers, feeding on the microbial biofilm present in those systems. However, several bacteria have developed mechanisms to survive phagocytosis by free-living amoebae and are able to exploit them as hosts. Transient association with amoebae have been reported for a number of different bacteria including Legionella pneumophila, many Mycobacterium spp., Francisella tularensis, and Escherichia coli O157, among others. As most of these bacteria are pathogens of humans, amoebae have been suggested to represent their environmental reservoirs, acting as "Trojan horses" of the microbial world. To date, only the interaction of L. pneumophila with free-living amoebae has been studied in greater detail. L. pneumophila is an intracellular pathogen of humans causing Legionnaires' disease. L. pneumophila multiplies within its host cell (human macrophages and amoebae) but can also grow outside its host cell and can be cultured by routine methodologies. Therefore, it is considered as a facultative intracellular pathogen. In addition to those facultative intracellular bacteria, various obligate endosymbionts have been observed in free-living amoebae. In this context, it should be noted that the term endosymbiont implies neither a mutualistic nor a parasitic relationship between the bacteria and their host cells. According to the broad concept of symbiosis suggested originally by Anton de Bary and consistent with the recent awareness of the variability of symbiotic interactions, we consider bacteria as endosymbionts when they manage to establish their replicative niche within eukaryotic host cells. Approximately 20% of isolates of ubiquitous Acanthamoeba spp. Recovered from clinical and environmental sources are found to harbor such bacterial endosymbionts. These endosymbionts have been shown to maintain a stable interaction with their hosts, but in contrast to L. pneumophila, they cannot be cultured outside their host cells, a primary reason why their identification and analysis have been hampered. This review examines the impact of the interaction between bacteria and amoebae on the evolution of intracellular bacterial pathogens of humans (i.e., bacteria capable of causing disease) by focusing on recent findings on the stable association of free-living

Izvorni jezik
Engleski

Znanstvena područja
Temeljne medicinske znanosti

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