Banana microbiome evolution in a warming world
Key Questions
Will microbial commensals adapt and benefit banana health during global climate change?
Background
Managing the impacts of climate change is one of the biggest challenges of the 21st century. Climate change is predicted to threaten wild bananas and production at banana plantations. Understanding the implications of global warming to banana growth requires knowledge of how changing environmental conditions will affect banana microbial commensals. We will use a commensal community isolated from banana pseudostems in Cape Verde, West Africa – the nematode, Caenorhabditis tropicalis, and its natural parasite Leucobacter spp. – to characterize the potential for banana commensal adaptation to a warming world.
Aims of the Project
By examining the potential for adaptation of the banana microbiome to warming environmental conditions, this doctoral project will illuminate whether commensals will accompany bananas, and potentially benefit their growth, under global climate change.
Project Description
Managing the impacts of climate change is one of the biggest challenges of the 21st century. With increased warming – for example, heatwaves (defined as ≥3 consecutive days with maximum temperatures ≥ 26 oC) now more likely than in the past (1981-2000) – and reduced wetness duration impacting many parts of the world, the growth of plant-based food is being affected. Bananas are a crop staple for millions of people, and as the world warms, annual yields now stand at about 10-40 tonnes per hectare. However, climate change is predicted to threaten wild bananas and production at banana plantations.
Understanding the implications of global warming to banana growth requires knowledge of how changing environmental conditions will affect banana microbial commensals. Research into the microbiomes of banana plants has revealed that, in addition to providing protection from infectious diseases, commensal microbes can improve the effects of soils and fertilizers, and generally contribute to plant growth and health. Higher temperatures and shorter wet seasons may cause the extinction of certain microbes, but could also encourage microbial adaptation to the new conditions. The latter outcome has beneficial implications for successful banana growth in the future, as commensals accompanying bananas into novel conditions could improve their survival.
We will focus on a commensal community isolated from banana pseudostems in Cape Verde, West Africa – the nematode, Caenorhabditis tropicalis, and its natural parasite Leucobacter spp. – to characterize the potential for banana commensal adaptation to a warming world. Both microbes distributed across the globe as commensal components of plant microbiota. Two Leucobacter species were isolated from Caenhorabditis tropicalis on rotting banana trunks in Cape Verde, which use the nematodes as hosts. In C.elegans, infection by one species, Verde 2, causes 30% host mortality within 24h in dry conditions whilst in wet conditions, a second species Verde 1, causes hosts to fuse together by their tails forming aggregated “worm stars”, with 100% of trapped individuals dying (Fig. 1). Worm-stars were also observed to form under simulations of natural conditions, such as when rain falls on rotting fruit or during or periods of high humidity. C.elegans can also transmit these microbial parasites under dry conditions to others in a population causing mass mortality within days. Thus, temperature and duration of wetness in the environment can be predicted to alter the costs and benefits of this host-parasite interaction occurring on bananas.
Figure 1. C.elegans infected by Leucobacter Verde1 aggregated in “worm-star” formation in wet environments
More specifically, the project will address the following questions:
1) How do higher temperatures (mean and variance) and reduced moisture impact the fitness of Caenorhabditis tropicalis and Leucobacter spp.? We will examine a range of fitness-related traits for several genotypes of Caenorhabditis tropicalis and Leucobacter spp. on media made from stems across the current and predicted environmental conditions across the geographic distribution of bananas. This experiment will tell us the degree to which there is genetic variation or plasticity in the response of this commensal community to environmental conditions.
2) Can these microbial commensals adapt to the changing environmental conditions? We will test and track the impact of the different temperatures and wetness durations on commensal population dynamics and fitness-related traits across 15 generations (60 days) in a passage experiment. This experiment will establish a proof of principle and indicate the potential for this community of commensals to evolve in response to a warming world. We will determine how quickly adaptation occurs and reveal the changes in fitness-related traits, as well as in real-time. Any drastic reductions in population size and genetic diversity, with major consequences for commensal ecology and evolution, will be detected.
3) Are these patterns of adaptation consistent across other commensals in the banana microbiome? We will collate other bacterial commensals isolated from Musa plants. We will passage these species under increased temperatures and assess changes in their fitness-related traits.
By examining the potential for adaptation of the banana microbiome to warming environmental conditions, this doctoral project will illuminate whether commensals will accompany bananas, and potentially benefit their growth, under global climate change.
Methods to be used
Experimental evolution, microbe culturing, working with catalogued specimens. Potential for field work.
Specialised skills required
All skills will be taught in my lab
Please contact Kayla King on kayla.king@zoo.ox.ac.uk if you are interested in this project
