As Tassos Economou and colleagues point out on page 839, and Bitter and colleagues reinforce on page 883, secreting proteins from the bacterial cytoplasm into the extracellular environment is a complex problem that requires the coordination of a myriad of individual reactions. Ever-resourceful, bacteria have evolved many different solutions to this problem that can be used for different substrates or in different situations. The specific topic of the Review by Economou and colleagues is the Sec pathway, a protein-secretion pathway that also forms the entry point for many of the other secretion pathways and which is conserved in all three domains of life. At the core of the Sec pathway is the translocase, which comprises the membrane protein SecYEG, the SecA ATPase and a subset of partner proteins. Over the past 30 years, the steady accumulation of genetic, biochemical and structural data has revealed many of the secrets of this 'dynamic nanomachine'. The topic of the Opinion by Bitter and colleagues is the mycobacterial ESX secretion system, which the authors propose should be called type VII secretion.

The third in our series of supplements on evaluating diagnostics, which we are producing in conjunction with our partners at TDR, is supplied with this issue. The aim of the supplements is to provide practical, user-friendly guides that explain how to evaluate diagnostic tests for infectious diseases that mainly affect people in the developing world. The topic of this supplement is the evaluation of diagnostics for visceral leishmaniasis. The supplement will be published online on 22 October as our journal's contribution to the Council of Science Editors Global Theme Issue on Poverty and Human Development (http://www.councilscienceeditors.org/globalthemeissue.cfm) and can be accessed free online at http://www.nature.com/nrmicro/supplements