Abstract

The ability to grow as surface-associated communities or biofilms is seen as a microbial life-style widely spread in all biomes on planet Earth, including the extremely acidic natural ecosystems. Within these harsh and constantly changing habitats the biofilm mode of growth is thought to offer the microbial community a regular condition so as to cope the adverse scenery. Though acidophilic biofilms communities are mainly dominated by bacterial species, archaeal and eukaryotic populations appear to play a crucial role broadening metabolic diversity in order to maintain the community structure. To date, environmental signals and molecular mechanisms accomplishing the biofilm life-style have been largely characterized for bacteria that colonize human cavities. In contrast the genetic bases that enable environmental acidophilic bacteria and archaea to form and develop biofilms are far to be comprehended. Nonetheless, several molecular mechanisms that govern the biofilm developmental process of some acidophile have just begun to come into sight. This chapter describes what is currently known on the cellular and molecular mechanisms that promote biofilm formation of bacteria and archaea inhabiting extremely acidic ecosystems.