Microorganism cell death – a new era

The ability of cells to self-destruct appears to be essential for cellular life. However, the existence of genetically programmed death pathways in single-cell organisms has been long debated. Thus, cell death research on microorganisms was sparse while the field focused on human tumor cells, animal models and some plants. In addition, microbial death is most commonly viewed as a consequence of being killed by host immune tactics and antibiotics, rather than intrinsic microorganism cell suicide. However, a new perspective has recently emerged, stemming from elegant delineation of cell suicide mechanisms in diverse prokaryotic and eukaryotic microbes. The molecular details often resemble components of human innate immunity, further suggesting that some early forms of cell death arose in microorganisms as defense mechanisms against their own pathogens.

In this review series, we consider the theoretical origins of programmed cell death (Pierre Durand), the evolution of cell death factors in immunity and multicellularity (L. Aravind) and their conservation between prokaryotes and eukaryotes (Eugene Koonin). Global impacts of microorganism cell death become apparent from studies of cell fate decisions in ocean algal blooms (Assaf Vardi), and from studies of cell death by autophagy in a fungal plant pathogen capable of compromising world food resources (Nick Talbot). Articles in this series also describe examples of microbial cell death mechanisms that serve as self-recognition systems and innate immune mechanisms, including fungal gasdermins (Asen Daskalov) and responses to viruses of fungi (Marc Meneghini and Neta Shlezinger) and bacteria (Laurence van Melderen). Also discussed are mechanisms of cell differentiation, aging, and death of a single-cell organism living in a multicellular colony, as well as the commitment points in yeast cell death pathways and methods to study them (Zdena Palková, Manuela Corte-Real, Libuše Váchová, and Madhura Kulkarni). These and other studies cited here mark a new era of cell death research expected to span a diverse microbial world.