Highlights of MiCROPe 2019

Marie Legein, 06/02/2020, Antwerp 

Plants interact closely with microbes. These microbes can have an influence on plant health by supplying plants with extra nutrients, protecting plants against pathogens or helping plants cope with abiotic stress. A number of scientists are focusing on these microbial communities since they can provide us with vital solutions to make our food production more sustainable. Many of these scientists came together in Vienna last December during the MiCROPe conference. As a PhD student at the LebeerLab, I was lucky enough to receive a FEMS travel grant to be part of this event. Here, I will share with you some of the interesting new developments in the field.  

I will start with the quest for the perfect consortium of microbes. This is a question that occupies many microbiologists from other fields as well. In the field of plant microbiology, these consortia are often called syncoms (short for “synthetic communities”). Syncoms are interesting since they have the potential to be more successful then single microbes in conferring a health benefit to the host. The challenge, however, is to pick a good set of microbes. Some researchers choose to make combinations with bacteria that occur in plant environments with high frequency or abundance (e.g. Dr. Rafael de Souza). Others focus on combining microbes with plant growth promoting traits such as antipathogenic activity (e.g. Dr. Maria Isabella Prigigallo), or a large overlap in carbon source utilization with the pathogen and a small overlap amongst the syncom members (e.g. Jie Hu). But, even when using one or more of these guiding principles, there exists a practically unlimited number of possible microbe-microbe combinations and an even larger number of microbe-microbe-plant combinations. Therefore, trial and error (still) plays a big role in syncom assembly and inevitably, many syncoms are unsuccessful. Prof. Jos Raaijmakers admitted that they have done many experiments with syncoms that failed to live up to expectations. Unfortunately, journals do not seem to be interested in publishing these deficient consortia. Knowledge on what combinations are not successful is however crucial in the quest for the perfect syncom.  

Secondly, the plant’s immune system still holds secrets for us. In brief, plants detect microbes by detecting microbe-associated molecular patterns (MAMPs) and this triggers the defense system. Some microbes have evolved to evade detection, by injecting effectors into the host cell that prevent MAMP detection. In response, plants have evolved to detect these effectors and this usually triggers a stronger immune response. How the plant is able to differentiate between beneficial and pathogenic microbes is not fully understood. Effectors are usually associated with pathogens but several scientists are now focusing on the role of effectors in beneficial bacteria and fungi (e.g. Jemma Roberts is looking into effectors that activate beneficial plant pathways and Johannes Herpell found Type 3 Secretion Systems, which are needed to inject effectors into host cells, in the genome of a beneficial bacterium). Understanding host-microbe interactions is highly relevant in this field but also in other microbiome research.  

Thirdly, I would like to mention the research on quorum sensing molecules such as N-acyl homoserine lactones (AHLs). These molecules are used by bacteria to communicate and regulate their behavior according to their population size. Interestingly, plants are also able to detect and respond to AHLs. It makes sense that plants are interested in the population size of the microbes around them and to respond to that signal if necessary. For example, Adam Schikora looks into how genetically different barley cultivars respond differently to AHLs. I wonder if other host organisms (e.g. humans) are also able to detect and respond to AHLs? 

Finally, I would like to focus on the phyllosphere, the above ground surface of plants. This habitat is very different from the rhizosphere and microbes living there need specific adaptations. Prof. Steven Lindow demonstrated that rhizosphere bacteria are not good inoculi for the phyllosphere. He also emphasized that other plants, in the surroundings of the crops, are an important source of well-adapted bacteria. Agricultural management practices, such as cover cropping or weed control, thus play an important role in shaping phyllosphere communities.

The MiCROPe conference was a wonderful opportunity to learn about the latest developments in the field. It was also set in a very inspiring location, the orangery of the Schönbrunn palace. A guided visit to this impressive palace was organized and we even had the chance to explore it calmly outside visiting hours. The weekend after, I visited the surrounding park and greenhouses. The greenhouse dates back to 1882 and houses an impressive number of plants (4 500 according to wikipedia) from different climatic regions. I couldn’t help but wonder if the microbes on these plants were as exotic as the plants themselves.  


Dag van de Wetenschap

Sunday the 24th of November, a couple of members from the team were present at the ‘Dag van de Wetenschap’ in Antwerp to show some of the research done at the lab. People from all ages were able to look through the microscope, admire some agar art, make their own bacteria using Play-Doh and taste some fermented foods/drinks such as Yakult, fermented carrot juice, kombucha and blue cheese.

Dag van de Wetenschap