Editorial for Article Collection on "Bacterial Survival Strategies".

The question of how bacteria cope with harmful conditions and which strategies they employ to maintain viability in unfavorable environments represents one of the most fundamental issues in microbiology. In an ideal environment, where substrates and nutrients are abundantly available and metabolic end-products are constantly removed, bacterial populations grow exponentially. Research in classical microbial physiology has for long focused on deciphering cellular processes during this phase of a bacterial life. However, in most natural environments, bacteria face – at least temporarily – adverse conditions, which limit their growth or where the viability of bacteria is challenged. Abiotic conditions stressing viability could be severe lack of essential nutrients, the presence of toxic compounds or unfavorable physicochemical environmental conditions. Moreover, the surrounding organisms challenge bacterial survival as predators or competitors for resources and niche occupation. Bacteria have been subjected to these selective pressures during their entire evolution. As a result, they acquired elaborate strategies that allow them to cope with such challenges. Thus, bacterial survival strategies are fundamental to understand key aspects of bacterial behavior, from the long-term survival of nutrient-starved cyanobacteria and their stunning recovery capabilities to the strategies of pathogenic bacteria to survive and resist host defense or to withstand competing microorganisms. We can assume that the survival strategies of bacteria are based on fundamental principles acquired early in evolution and therefore common in most bacteria, as well as on lifestyle specific and highly adapted programs, acquired during niche evolution of the various bacterial genera. These manifold survival strategies are essential to successfully compete in the various ecological niches and to colonize new habitats and hosts. Therefore, this topic is of greatest relevance for bacterial ecology and physiology, for the spread of bacterial pathogens, and for the development of antibacterial compounds and, hence, it is a central area of microbiological research. Nine years ago, the DFG-funded research training group “Molecular Principles of Bacterial Survival Strategies” (RTG1708) was initiated at the University of Tübingen with the aim to elucidate fundamental and niche specific principles of bacterial survival strategies in an interdisciplinary research group, by combining the expertise of research teams with a strong background in molecular physiology, genetics, chemical analytics, environmental microbiology or medical microbiology. On the occasion of the end of the RTG1708 program, a final symposium on “bacterial survival strategies” was organized from October 7 to 9, 2020, together with invited international guests included via remote video access. The present article collection on bacterial survival strategies includes both primary research papers as well as review articles from contributors of this symposium. The papers in this article collection reflect the breadth of the research spectrum. A fundamental challenge to