Abstract

Earth’s oceans are immense, covering much of our planet’s surface and filled with microbial communities that make up ∼70% of all marine biomass. These microbes thrive from the sunlit coral reefs to the frigid Arctic ice to hot hydrothermal vents, yet sparingly few are growing in our laboratories. Extreme gradients in temperature, pH, nutrient availability, and pressure present innumerable challenges to growing and studying these microbes on land. However, innovations in creative culturing are opening up the high seas to microbiologists, revealing new metabolisms, novel branches on the tree of life, and clever strategies for surviving at the extremes. Consider SAR11, the most abundant bacteria in the plankton, finally coaxed into lab growth using specific methods developed for slow-growing, oligotrophs with unusual nutrient requirements or the anaerobic methane oxidizing archaea, maintained and studied in the lab via mixed enrichments with syntrophic partners. Still others may never grow on terra firma, including the deep sediment microbe with estimates for cell division over millennia or the tubeworm endosymbiont that operates as efficiently as a laboratory chemostat, but only with its host. For these especially wild types, microbiologists will continue to study them in their salty homes, using new instruments and analytical tools to measure their activity and decipher their genomes. Whether we study them growing solo in our labs or in their watery milieu, the coming years are certain to expand our understanding of how these amazing organisms thrive in our vast ocean world.