Adaptations of prokaryotes to their biotopes and to physicochemical conditions in natural or anthropized environments

Abstract

Microorganisms live in a constantly changing environment and must modify their physiology and morphology to cope with these changes. The main systems for molecular adaptation to modifications of environmental conditions and the behavioral responses of prokaryotes in various habitats, excluding extreme habitats, are discussed. The main regulation systems that are described are transcription, signal transduction, and protein modifications. Three specialized systems are also presented in details: quorum sensing, phase variation, and antibiosis. Quorum sensing allows bacteria to trigger some responses when their density is high enough to permit the function to be successful. Phase variation is an adaptive process by which a bacterial subpopulation undergoes frequent, usually reversible phenotypic changes resulting from genetic or epigenetic alterations, allowing rapid modification of the cells physiology. Antibiosis is the ability to synthesize molecules that will impact other taxa and eventually provide a selective advantage to which some microbes respond by resisting to these molecules. Finally are described the physiological responses to various environmental parameters such as temperature, oxidants, salinity, acidity, pressure, desiccation, and how this translates in different biotopes such as soil, water bodies, sediments, biofilms, mats, air, and manmade biotopes.