WMS/SLS Joint Micro Seminar: How to survive an apocalypse – tales from the microbial world on adaptation, Professor Robert Jackson, School of Biological Sciences, University of Reading
Abstract: Microbes face a multitude of different stresses that impact on their survival and when this happens on a population scale, it might be regarded as a type of apocalypse that could potentially lead to extinction. We know, of course, that microbes are the masters of survival tactics and when faced with such life-threatening conditions, they can rapidly adapt to survive. In this talk I will describe two tales of plant-associated Pseudomonas, facing different kinds of stresses, and show that they can quickly overcome, or bypass, the stress to enable them to survive. In the first tale, I will illustrate how a plant pathogen, Pseudomonas syringae, can adapt to avoid plant host resistance. When it infects a resistant plant, the plant senses the pathogen due to the secretion of a product of a type III effector gene present on a genomic island. The initial response to triggering host immunity is for the genomic island to excise from the chromosome and circularise, leading to downregulation of the effector gene in an attempt to mask it. Over time, the pathogen evolves by ditching the genomic island, and thus effector gene, from the majority of the population – though the island is able to survive within a small sub-population waiting for infection into a susceptible host. Thus, the pathogen, and its selfish element, dynamically change to enable pathogen survival inside the plant. In the second tale, I will describe how a sessile P. fluorescens strain undergoes starvation because it is unable to forage for nutrients. Starvation appears to act as a selective environment for the emergence of mutants that can move to obtain nutrients. These mutants were discovered to have re-purposed a different sensing-signalling system involved in nitrogen homeostasis to reactivate the flagellum system, thereby allowing the bacterium to overcome the starvation conditions. Together, these systems provide key insights to the molecular mechanisms at play that underpin bacterial adaption to potentially extinction-level events.