Editorial: Microbial Responses to Environmental Changes

Earth is teeming with taxonomically, phylogenetically, and metabolically highly diverse microorganisms ; organisms that are crucial for sustaining life on our planet in that they carry out processes of great biogeochemical significance. The processes and mechanisms underlying their diversity and distribution are, thus, of great interest, yet—despite their importance—only poorly understood. Microbial communities may be structured by a large number of factors among which are environmental conditions: local, contemporary environmental conditions select and sort microorganisms according to their ecological niche (Hutchinson, 1957). This corresponds to the so-called Baas-Becking hypothesis for microbial organisms " everything is everywhere: but the environment selects " (Baas Becking, 1934) that formed the basis of the later formulated species-sorting paradigm/perspective (Leibold et al., 2004; Holyoak et al., 2005). Species sorting has been repeatedly shown to be an important determinant for the assembly of microbial communities (e.g., Van der Gucht et al., 2007; Logue and Lindström, 2008). It has been suggested that the response of microbes to environmental conditions and changes thereof is mediated by a complex combination of adjustment (e.g., high adaptability and plasticity but also ability to horizontally transfer genetic material), replacement (e.g., high dispersal rates) and species interaction mechanisms, all facilitated by their fast population growth rates (Allison and Martiny, 2008; Comte and del Giorgio, 2011). Yet, the factors that determine the type and magnitude of the response of microbial communities remain unclear (de Vries and Shade, 2013). Given that many ecosystems are undergoing rapid and major environmental changes, obtaining a quantitative and process-level understanding of the mechanisms that affect microbes and microbial communities is pivotal for predicting the responses of microbial communities to novel or changing selective forces and their implications at the local, regional and global scale. Advances in molecular biology have revolutionized our ability to describe microbial communities with regard to composition and biogeography, diversity and processing, but also the mechanisms of adaptation and evolution (Pedrós-Alió, 2006). In addition, the integration of theory into microbial ecology has greatly improved our understanding of the roles microorganisms play across a wide range of biomes by providing researchers with organization, structure, mechanistic insight, and predictive power (Prosser et al., 2007). Technical advances and theoretical integration will advance our understanding of how microbial organisms may respond and evolve in a changing environment. The aim of this Research Topic " Microbial responses to environmental changes " is to provide the reader with a selection of studies …