Unravelling the mysteries of complex life
Massey Uni microbiologist is working on big questions tied to endosymbiosis
Few of us have heard of endosymbiosis. But it’s responsible for nearly every living thing that surrounds us. It can be simply described as the collision of two organisms, forming a relationship where one lives inside the other and creates new life.
One example is photosynthesis — where plants harness energy from sunlight and convert it into chemical energy they can use later.
Another are the tiny generators found in nearly every complex cell, including the trillions that form our own bodies. What are called mitochondria also represent the earliest case of endosymbiosis that we know about.
While scientists now have a good understanding of endosymbiosis, some of the biggest questions haven’t yet been completely answered.
Just how such partnerships are able to form and stabilise is one mystery a New Zealand microbiologist is now on the way to solving.
Massey University’s Dr Heather Hendrickson was essentially trying to recreate the first steps of endosymbiosis — all in a lab, and in real-time.
What she discovered could widen what we know about the origin of complex life on Earth. Working with colleagues Dr Elizabeth Ostrowski and Professor Ant Poole, Hendrickson will run a series of evolution experiments using two separate “predator-prey” pairs of cells.
Over the course of 10,000 generations, predators — in this case amoeba — and prey — bacteria — will be mixed together under different conditions.
“By isolating certain types of single-celled amoebae from nature, it has been shown that endosymbiosis has happened many times and continues to take place in nature between amoebae and their bacterial prey,” Hendrickson said.
“We will be setting up longterm co-evolution experiments using well-studied amoebae and genetically amenable bacteria to try to capture this event in the lab.”
The team will examine the routes these cells take in adapting towards endosymbiosis and monitor them for collaborative or antagonistic effects on each other, using a cutting-edge mix of novel molecular, genomic and imaging techniques.
“Ideally, we will be able to sequence the genomes of these new partnerships as they form and study the mutations that allow this intimate association to form.”
One of the most exciting parts about the study, supported with an $884,000 grant from the Marsden Fund, was the fact it had never been attempted before — and Hendrickson said it was possible endosymbiosis might not even be observed.
“However, co-evolving these organisms will tell us a lot about how they develop their positive and negative relationships in nature — and that is something we have never observed either.
“So this is going to be an exciting project either way.”
A pilot study Hendrickson already led suggested these predator-prey relationships could have effects on increasing bacterial virulence.
“It looks like these naturally occurring microbial relationships are driving behaviours that affect all of us in the long run.”
What might we gain? “Getting insight into the first steps in endosymbiosis will allow us to understand what allows these surprising interactions to stabilise,” Hendrickson said.
“Why would any organism ever give up its independence and partner with another?
“These events have been a jumping-off point for the incredible diversity on the planet.
“It is very exciting to have the opportunity to figure out what makes that possible.”
And because the bestknown examples of endosymbionts are instrumental in powering cells they are linchpins of biological life.
“Understanding how endosymbionts evolve will give us the fundamental tools we would need to adapt them to a changing climate, specifically target them in agricultural pests or build new ones in the future,” Hendrickson said.
“There are a huge number of problems that we might be able to approach in entirely new ways if we could understand the basis of this phenomenon.”