Destabilisation of the holobiont macroalga and induction of bacterial pathogenesis due to increasing environmental stress conditions

• Applicant: Dr. Tim Lachnit
• Subject Area: Microbial Ecology and Applied Microbiology
• Term: from 2011 to 2013
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 199722763

Surfaces of marine macroalgae (seaweeds) are colonised by complex bacterial communities. It has recently been demonstrated that the composition of these epibacterial communities are specific to the host alga. Disturbances or shifts in this association can compromise the health of the whole entity. The kelp seaweed Ecklonia radiata has undergone high rates of mortality in the last decade. Pathogenic infections as well as increased environmental stress conditions, such as elevated seawater temperature due to climate change, are possibly causative for the tremendous loss of the dominant habitat forming kelp species in Australia, and more generally in temperate regions of the planet. Understanding the seaweed holobiont and how it is affected by global warming trends, in-depth knowledge of the bacterial holobiont members and the factors contributing to this specific host-microbe association is urgently required. This proposal aims to investigate the composition and stability of the holobiont E. radiata on a seasonal and regional scale along an increasing water temperature gradient beginning in the south of Australia towards the northern distributional limit of this alga. In combination with a temperature manipulated mesocosm experiment, this investigation will identify the factors contributing to the stability of the algal holobiont and elucidate how this system can be destabilized by environmental stress conditions. The overall goal of this proposal is to verify the hypothesis that elevated environmental stress conditions directly affect the surface exudation of algal metabolites which will destabilise the natural balance between host alga and its associated bacteria. This in turn will provide space for pathogens resulting in infection or will induce pathogenesis in natural associates.

• DFG Programme: Research Fellowships
• International Connection: Australia
• Host: Professor Peter Steinberg