Antibiotic tolerance and the alternative lifestyles of .

has an incredible ability to survive, either by adapting to environmental conditions or defending against exogenous stress. Although there are certainly important genetic traits, in part this ability is provided by the breadth of modes of growth can adopt. It has been proposed that while within their host, survives host-generated and therapeutic antimicrobial stress via alternative lifestyles: a persister sub-population, through biofilm growth on host tissue or by growing as small colony variants (SCVs). Key to an understanding of chronic and relapsing infections is determining the molecular basis for its switch to these quasi-dormant lifestyles. In a multicellular biofilm, the metabolically quiescent bacterial community additionally produces a highly protective extracellular polymeric substance (EPS). Furthermore, there are bacteria within a biofilm community that have an altered physiology potentially equivalent to persister cells. Recent studies have directly linked the cellular ATP production by persister cells as their key feature and the basis for their tolerance of a range of antibiotics. In clinical settings, SCVs of have been observed for many years; when cultured, these cells form non-pigmented colonies and are approximately ten times smaller than their counterparts. Various genotypic factors have been identified in attempts to characterize SCVs and different environmental stresses have been implicated as important inducers.