Projects

MICROBIAL CHEMOTAXIS IN THE PHYLLOSPHERE

Plant leaves are a major habitat for bacteria in the phyllosphere (i.e. the above ground parts of plants). However, the surface of a leaf is a challenging place to live. In contrast, the interior of a plant contains comparatively abundant nutrients and mild environmental conditions that allow microbial pathogens to thrive and cause disease. Bacterial pathogens of plants are unable to directly penetrate the surface on their own; they must gain entry through natural openings such as stomata or wounds. The molecular basis of how bacteria navigate between these vastly different habitats remains poorly understood.

Motile bacteria are attracted by certain chemicals and repelled by others, a behaviour termed chemotaxis, which enables them to navigate towards favourable conditions. Our research is exploring the ‘what, how and why’ of bacterial chemotaxis in the phyllosphere. Longer-term, these insights may lead to novel plant disease management strategies

ENZYME EVOLUTION IN THE CONTEXT OF CELLULAR METABOLISM

Biochemistry textbooks tell us that enzymes are supremely active and specific catalysts. However, our recent work has shown that many microorganisms use decidedly unimpressive enzymes in essential roles. This implies that speed and specificity are not the dominant factors determining the evolutionary trajectories of enzymes. Instead, we hypothesise that the evolution of individual enzymes is dictated by the constraints of optimising flux through multi-step metabolic pathways. A further layer of complexity arises because environmental conditions alter the metabolic demands on a cell; mutations that are beneficial in one environment can be deleterious in another.

In this project, we are discovering what determines the evolutionary trajectories of enzymes that are embedded in the heart of the metabolic network. We are making every possible single-amino-acid mutation in each of two central metabolic enzymes. We are measuring the effects of these mutations on enzyme activity, and also on cell growth in almost 1,000 different environments. We will measure the flow of metabolites through pathways and individual enzyme-catalysed steps. Ultimately, we hope to gain a comprehensive and integrated understanding of how natural selection works, from enzyme to organism.

MĀTAURANGA MĀORI GUIDED BIODISCOVERY:
NEW TOOLS TO CONTROL KAURI DIEBACK

Phytophthora are microscopic organisms that cause root rot and dieback diseases in thousands of plant species. It was a Phytophthora species which caused the Irish potato famine in the 1840s. Today they continue to devastate native ecosystems and cause billions of dollars in damage annually. Two species of particular importance in New Zealand are Phytophthora agathidicida, which causes kauri dieback disease, and Phytophthora cinnamomi, which causes root rot in avocados and other agricultural crops.

We are collaborating with Mātauranga Māori knowledge holders (Mr. Chris Pairama and Mr. Te Rangi Kaihoro) to identify native plant species with bioactive, anti-pathogen characteristics. Biochemical and microbiological methods are being used to isolate anti-Phytophthora compounds from these native plants, and we are testing their ability to inhibit various stages of the Phytophthora life cycle. The most promising compounds will also be tested for their effectiveness at stopping infections in controlled glasshouse trials with seedlings.

TE KURA O TE KAURI [THE SCHOOL OF THE KAURI]

PRINCIPAL INVESTIGATORS: GERTH & PATRICK

This is an outreach/education project. We are developing a travelling classroom called Te Kura o te Kauri (the School of the Kauri) using the previously developed ‘Lab in a Box’ travelling lab as the base. The classroom will travel around the Auckland and Northland areas (where kauri dieback is the biggest threat) and focus on educating children in Years 5-8. The main goals of the classroom are to encourage kaitiakitanga of our forests, give hands-on experience with both western and mātauranga Māori approaches to the science of a healthy forest, and engage the senses through art, sound, and virtual reality technology.