We have published a special thematic issue of FEMS Microbiology Ecology on the subsurface microbial world, guest edited by Matthew Stott and Tillmann Lueders. Read their editorial Deep life, kia ora! for an overview of the exciting research in this issue.

Microbial life can be found to occupy every environment on planet earth’s surface, but the microbiome also extends deep into the earth’s crust. This issue presents the latest research in this area. Several articles were also used to inform the science behind this long read by The Scientist.

The subsurface provides a myriad of habitats for microbial life, and the microorganisms that we discover in these environments often exist in complex communities. Subsurface microbiomes are the drivers of many important biogeochemical processes, which we must seek to understand better for the protection and sustainable use of subsurface resources. These include groundwater, fossil and mineral deposits, but also subsurface biodiversity, which in turn can have implications for human health, economic advancements, and local environments.

This Thematic Issue provides exciting recent research outcomes on the ecology, structure, and function of subsurface microbiomes, collated on occasion and amongst delegates of the 10th International Society for Subsurface Microbiology Conference (ISSM 2017) held in Rotorua, New Zealand in early November 2017.

The twenty two papers in this Issue represent a truly global assortment of current subsurface microbiology research, with all its different habitats, processes, and microbes investigated using the latest cutting-edge technologies.