Nature Index 25 September 2021 Science cities 2021 . Many of the world’s leading science cities are active in research related to the United Nations Sustainable Development Goals. Image: Sam Chivers Collection 24 September 2021 Chemical Biology of Microbiomes . Interspecies communication in complex microbiome environments occurs through the small molecules, peptides, and proteins produced by both the host and the microbial residents, as highlighted ...