FREE-LIVING AMEBA - INTERACTIONS WITH ENVIRONMENTAL PATHOGENIC BACTERIA

Free-living amoeba live in close association with other microorganisms in the same ecological niches, feeding on bacteria and fungi. The eff iciency of consumption is different, depending on protozoan type and g rowth state, temperature, bacterial abundance, and size and nature of bacterial prey. Many of the bacteria are digested, especially enteroba cteria which are used as nutriment. Gram positive bacteria seem to be digested slower, owing to their thick cell wall. Some bacteria may avo id digestion by liberation out of the phagosome before lysosomal fusio n or resist the cellular mechanisms of digestion in phagosomes and esc ape into the host cell cytoplasm where they multiply. A number of bact eria have been reported to survive as parasites or endosymbionts of fr ee-living amoeba, and some of these bacteria are also potential pathog ens to vertebrates. Free-living amoeba are incriminated in the ecology and epidemiology of legionellosis. They are also likely to be natural hosts for well-known pathogens like Vibrio cholerae and Listeria mono cytogenes, or nosocomial new pathogens, like Xanthomonas maltophilia a nd Flavobacterium sp. Their interacting with protozoa in biofilms asso ciated to intracellular replication and inclusion of pathogen bacteria in cysts give these pathogens a possibility of survival and transmiss ion in unfavourable conditions.