Adaptation strategies of mutualistic rhizobacteria on Arabidopsis roots

Kuramae, E. (Examiner)

NIOO - Microbial Ecology (ME)

Activity: Teaching/Examination/Supervision › PhD candidate reviewing/examination

Period	03 Jul 2023
Examinee	Hao Zhang
Examination held at	Utrecht University
Degree of Recognition	International

Documents & Links

Beneficial microorganisms that live near plant roots play important roles in helping the plants grow and stay healthy. In our study, we wanted to understand how certain bacteria adapt to living in the area around plant roots. We conducted experiments using a type of bacteria called Pseudomonas protegens, which lives in the roots of a plant called Arabidopsis thaliana. We found that these bacteria had undergone changes in their genes, with 35 mutations occurring in 28 different genes. Some of these mutations affected the way the bacteria decorate their outer surface. We focused on a group of genes called OBC3, which are involved in making a substance called O-antigen, a part of the bacteria's outer layer. We discovered that four specific mutations in the OBC3 genes (oafA, galE, and RS09880) were related to changes in the O-antigen decoration. Interestingly, we also found similar mutations in other strains of Pseudomonas protegens found in the environment, even those not associated with plants. We observed that the mutated bacteria, especially those with changes in oafA and RS09880, were better at attaching to plant roots, leading to enhanced colonization. The oafA gene encodes a protein that helps with the O-antigen decoration, and the mutations caused the protein to be cut short, affecting its function. Additionally, two mutants with changes in galE and RS09880 had alterations in the structure of their outer layer and were less susceptible to a type of virus that infects bacteria. Our findings suggest that the decoration of the O-antigen plays a role in how bacteria colonize plant roots by influencing their attachment. These mutations in the OBC3 genes also occur naturally in environmental strains of Pseudomonas protegens and can provide resistance to viruses. Overall, this study helps us understand how bacteria interact with plants and adapt to their environment, which can have important implications for plant health and agriculture.