Mechanisms underlying microbial symbiosis

Abstract Like many miniscule phenomena in biology, the importance of intimate, host-associated microbes lay hidden until the timely collaboration between a microscope and a curious mind. Chronicled early in insect groups such as termites, ants, and both sap- and blood-feeders, recent research within the 'omics era has completely transformed our understanding of symbiosis within the hexapods. Bacteria, protists, and fungi shape a range of insect phenotypes, complementing their endogenous abilities for resource acquisition and defence. Other microbes exploit chinks in insect armour, manipulating conserved features of insect cell biology to selfishly spread within host populations. Through the use of ever-improving technology, combined with conceptual and experimental advances, scientists now understand a number of key mechanisms underpinning the function, regulation, and transmission of insect-associated microbes across a range of systems. In this volume of Advances in Insect Physiology we present eight chapters focused on symbiont mechanism, including those involved in resource acquisition among herbivores, detritivores and blood-feeding insects, and those associated with reproductive manipulation and host defence. Within the present introduction, we sandwich summaries of each chapter between a brief historical perspective on insect-microbe symbiosis and a discussion on the implications of growing mechanistic knowledge. We conclude that understanding mechanism brings the potential to manage insects—and their impacts—in a changing world, whether aiding those that are beneficial, or suppressing pest-transmitted diseases. This understanding also promises a powerful, wide-ranging comprehension of complex biological phenomena emerging from symbiosis, spanning the biological spectrum from genes, molecules, cells, organisms, populations, communities, and ecosystems.