Research
Our biological systems
Since our mission is to explore algal (metabolic) diversity, our repertoire of lab organisms includes algae from dry deserts, through the Arctics, to marine cyanobacteria, as we have shown that unique properties must exist in organisms that face and have to cope with extremes. Our current favourite is the desert alga Chlorella ohadii which we have isolated from the harsh Negev desert in Israel. This alga can survive and even thrives in extreme illumination levels where other algae and plants experience severe photodamage, but also, much to our surprise, exhibits the fastest growth rate ever reported for any eukaryotic alga. With such a story, no wonder this alga has already made the news several times (see below). These properties have made it an excellent and exciting new green model, supported by our expanding knowledge on its unique physiology, systems responses, and recently, also its published sequenced genome. A stable transformation system is still a challenge, and is one of the main items on our list for turning this alga into a full model. Beyond its value for basic research, C. ohadii bears a tremendous self-evident biotechnological potential and is currently being explored by our lab and others as a gene source for improving algal and plant properties - Chlorella ohadii, the green model you deserve.
As part of our synthetic biology focus, we also harness the great knowledge and powerful tools on the green algal model Chlamydomonas reinhardtii. Except for providing a versatile genetic chassis (e.g. KO, KD, OE), Chlamydomonas is an optimal system for our metabolic engineering goals as it is relatively slow growing and sensitive to abiotic stress, offering a simpler readout in screening for novel traits. Thanks to our set of technological tools, our main strength lies in our ability to go beyond the ‘Black-box’ view of engineering phenotypes, and look into the metabolic network of engineered strains. This informed strategy improves our chances of reaching a desired phenotype or topology in a step-wise approach.
C. ohadii makes the news!
https://www.mpimp-golm.mpg.de/2493685/what-we-can-learn-from-survivalists
https://www.eurekalert.org/news-releases/940561
https://www.mpimp-golm.mpg.de/2704368/news_publication_18171816_transferred
https://communities.springernature.com/posts/green-gold-from-the-desert
Research
Our Projects
Dissecting the effects of photosynthetic metabolic efficiency on plant growth
Plant growth is a spatio-temporally resolved process, whose dynamics depend on the underlying biochemical, physiological and developmental events or signals as well as biotic and abiotic interactions. Here, we tackle the role of photosynthetic metabolism as a determinant of growth.
Using a tailored microfluidic setup, we were recently able to resolve the very short half-timed metabolic fluxes in photosynthesis in several algae and plants, pointing to potential bottlenecks in plant metabolism. Implementing a synthetic approach, we will import genes associated with these target reactions from fast into slower growing algae, to test their effects on the metabolic network and eventually, on growth rate. In addition, we will upscale this novel setup to study a range of algal species and conditions, and reveal new candidate targets.
Elucidating the role of photosynthetic metabolism in abiotic stress response
When we think of abiotic stress resistance, we typically envision more stable proteins, favorable membrane composition, or durable biophysical designs. However, facing harsh extremes, different properties of metabolic performance, e.g. efficiency, flexibility or capacity, can be a virtue. We applied multi-omics studies to demonstrate that vast basal metabolic capacity renders cells "stress-ready", involving prompt redox-poising and oxidation. We also identified novel response nodes associated with this metabolic robustness under photoinhibitory stress, a process which significantly lowers global productivity. Follow-up studies will aim at manipulating these key regulators to shed light on the cellular mechanisms underlying metabolism-mediated extreme illumination response, and raise promising targets to improve photosynthesis in a changing world.
Exploring algal metabolic adaptations in extreme environments
As outlined in the other sections, algal metabolic diversity, represents a valuable and unexploited resource for photosynthesis research and prospective engineering goals. Further perspectives may emerge from exploring of algal diversity, especially from under-sampled extreme environments, including desert sand crusts, polar habitats and intertidal zones, simply since unique capabilities are more likely to be found in organisms that must cope with severe stress conditions. Merely scratching the surface of this enormous potential, we will conduct a metabolic-phenotype-directed survey of algal isolates from the Negev desert and Mediterranean tidal-pools alongside selected strains provided by our partners working in the McMurdo Dry Valleys lakes, Antarctica.
Our technology
13CO2 labeling setups
To support isotopically non-stationary metabolic flux analysis (INST-MFA), we developed a set of tailor-made metabolic-phenotyping setups based on combining gas mixers with microfluidics for liquid cultures (algae, cyanobacteria) or gas chambers for higher plants. Label is supplied via medium pre-bubbled with 13CO2-based synthetic air mixture (algae) or with the air mixture itself (plants).
Plant Metabolomics
The analytical infrastructure in the lab includes metabolomics analysis of most photosynthetic intermediates, including the CBC, sucrose and starch synthesis, photorespiration, C4 photosynthesis, and additional downstream central C metabolism pathways. Focusing mostly on polar metabolites, our main setup is a bio-compatible uHPLC system linked to a high-end tandem MS (Sciex Qtrap 6500+) equipped with Ion Mobility technology (SelexION).
A major effort is currently dedicated to implementing new separation techniques (HILIC, Anion-exchange) which will bypass the use of ion-pairing reagents involved in the separation of phosphorylated intermediates of photosynthesis, in order to extend the pool of studied metabolites and analytical applications.
Photobioreactors
Our basic experimental setups for growth and physiology analyses, are state-of-the-art photobioreactors which allow full and accurate control and monitoring of algal growth over a wide range of conditions. Following the development of our microfluidic setups, we are currently designing the next generation of this system, which will allow high-throughput pulse-labeling via an automated and controlled auto-sampler.