Nitrogen-transforming microorganisms shape global biogeochemical nutrient cycles. In this Review, Kuypers, Marchant and Kartal explore the vast diversity of these microorganisms and their enzymes, highlighting novel pathways, and discuss how nitrogen-transforming microorganisms form complex nitrogen-cycling networks in different environments.
Microbial metabolic activity lies at the heart of the myriad of interactions between the environment and microorganisms that shape the dynamics of ecosystems. Earth is a closed system with a finite amount of matter that cycles between the lithosphere (the outer shell of the Earth), atmosphere, hydrosphere and biosphere, and microbial metabolism drives biogeochemical cycling between these spheres. This Focus on microbial biogeochemistry explores microbial metabolism in the context of wider ecosystems. It comprises Reviews that discuss the microbial nitrogen cycling network, the role that bacterial microcompartments have in atmospheric carbon fixation, the symbiotic exchange of nitrogen and carbon compounds between rhizobia and legumes and the function of hopanoid lipids, which are markers of ancient microbial life in sediments and as membrane components, mediate interactions between nitrogen-fixing bacteria and plants. It also features Research Highlights that showcase the latest research into the relationship between microbial metabolism and the environment.
Bacterial microcompartments are self-assembling organelles that consist of an enzymatic core that is encapsulated by a selectively permeable protein shell. In this Review, Kerfeld and colleagues discuss recent insights into the structure, assembly, diversity and function of bacterial microcompartments.
Rhizobia can exist as both free-living soil microbiota and plant-associated endosymbionts, which form N2-fixing root nodules. In this Review, Poole, Ramachandran and Terpolilli explore the drastic lifestyle shift that underlies this transition and the associated plant–bacteria interactions.
Hopanoid lipids are structurally and functionally related to sterols, which are important building blocks of membranes. In this Review, Newman, Silipo and colleagues explore the diversity of bacterial hopanoids and their roles in stress adaptation and plant symbiosis.
News & Comment
This Focus issue on biogeochemistry highlights the metabolic versatility in microbial communities and the significance of microbial contributions to the flow of elements in Earth's biogeochemical cycles.
Two new studies highlight the potential impact of climate change on microbial biogeochemical cycles.
Infection of E. huxleyi by coccolithoviruses facilitates downward vertical flux of both particulate organic and inorganic carbon, thus enhancing the efficiency of carbon export into the deep ocean.
Two new studies explore the diverse microorganisms and their enzymes that contribute to the global sulfur cycle.