Animal-microbe symbioses in pest insects


Sequencing technologies have fuelled a rapid rise in descriptions of microbial communities associated with hosts, but what is often harder to ascertain is the evolutionary significance of these symbioses. In recent research we found that mixed modes of microbial transmission play an underappreciated role in the establishment of animal host-microbe relationships. The goal of this project is to test this idea empirically and thus define fundamental rules governing such associations.

The student will use the Mediterranean fruit fly (medfly, Ceratitis capitata) and its putative stable gut symbiont Klebsiella oxytoca. This represents a powerful system in which the composition of the symbiotic microbiome can be experimentally manipulated in multiple ways. The student will apply a combination of metagenomics, transmission studies, forward genetics and modelling, to test the mechanisms which promote host-symbiont associations.

The project has aims to (i) test the transmission mechanisms that facilitate gut colonisation by symbionts, (ii) determine the extent of, and mechanisms underlying, host fitness benefits, and (iii) conduct genome-wide screens to identify essential genes of symbiotic bacteria required for colonisation and mutualism in medfly.

The student will train at the interface of molecular genetics, genomics and mathematical theory, to test fundamental concepts of symbioses. They will gain key insights into the development and application of transferrable technologies via collaboration with colleagues at the Pirbright Institute. They will also receive excellent training and career development from the thriving Norwich Biosciences Doctoral Training Partnership.


Leftwich PT, Edgington MP & Chapman T. (2020) Transmission efficiency drives host-microbe associations. Proc Roy Soc B accepted. bioRxiv 2020.07.23.216366; doi:

Leftwich PT*, Nash, WJ*, Friend LA, & Chapman T. (2019) Contribution of maternal effects to dietary selection in the medfly. Evolution, 73: 278-292.

Leftwich PT, Hutchings MI & Chapman T. (2018) Diet, gut microbes and mate choice: understanding the significance of microbiome effects on host mate choice requires a case by case evaluation. BioEssays, 40: 1800053.