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Chapter 25 : The Social Life of Legionellae
Legionellae were initially characterized by criteria typically used to describe an autonomous unicellular organism. Bacteria of the genus Legionella were described as gram-negative, aerobic, and rod shaped with one or more polar or lateral flagella. A more complete ecological profile of legionellae will provide the scientific basis for selecting the most appropriate host for pathogenesis studies as well as studies to identify procedures to control amplification of the bacteria in certain environments. Analysis of bacterial group behavior represents the most recent facet in the study of the ecology of legionellae. In building water systems, legionellae are most frequently detected in biofilms of plumbing fixtures and heating, ventilating, and air-conditioning (HVAC) equipment. The complex nutrients available with biofilms have led some researchers to propose that the biofilm might allow the survival and multiplication of legionellae outside a host cell. If legionellae can multiply extracellularly within biofilms, the study and characterization of this phenomenon could have tremendous impact on control strategies for the prevention of legionellosis. Researchers have only begun to characterize the interaction of legionellae with the microbial community. Controlling legionellae within biofilms may lead to the most effective control measures to prevent legionellosis.