Research Challenge Sustainability

Nitrogen pollution from industrial and agricultural wastewater is a growing environmental challenge, threatening water quality and aquatic ecosystems worldwide. This project investigates the molecular mechanisms behind the remarkable ammonium tolerance of resistant green microalgae strains capable of thriving in undiluted landfill leachate where conventional microalgae cannot survive. Using whole-genome sequencing, we identify genetic markers and adaptive mutations responsible for this exceptional resilience. Complementary transcriptomic experiments, in which microalgae are cultivated under varying ammonium concentrations and their RNA subsequently sequenced on the Illumina platform, reveal which genes are differentially expressed between sensitive and resistant strains and which molecular adaptation strategies are activated under stress. Taken together, these analyses will provide a comprehensive picture of the genetic regulation underlying ammonium assimilation - knowledge that is essential for harnessing microalgae as effective, low-energy tools for nitrogen removal from contaminated water.

Frenzen Stiftung: Forschungsgeist! NGS in der Ökosystemforschung

This project investigates the adaptive evolution of key nitrogen utilization components in microalgae. Nitrogen, a crucial macroelement in biomolecules, is assimilated by photoautotrophic eukaryotic organisms in organic and inorganic forms. Anthropogenic activities are reshaping nutrient dynamics, altering both the load and the prevalent form of nitrogen entering freshwater and coastal marine ecosystems. While nitrate, the predominant oxidized form, drives eutrophication in many aquatic systems, chemically reduced nitrogen forms such as ammonium, urea, and dissolved organic nitrogen are increasingly significant due to various environmental and anthropogenic factors.

The goal of this research is to systematically identify core components involved in the uptake and assimilation of organic and inorganic nitrogen, as well as cellular signalling pathways regulating these processes in distant phylogenetic groups of microalgae: green algae, dinoflagellates, diatoms, and euglenophytes, and to trace their evolutionary trajectories. While core components are hypothesized to be evolutionarily conserved, regulatory mechanisms for nitrogen transport and assimilation are expected to show variability across taxa.

The study employs a multidisciplinary approach at the interface of physiology and evolutionary biology. It integrates comparative genomic analyses of both established and novel algal genomes with experimental studies using stable isotopes and transcriptome sequencing to investigate nitrogen uptake and gene expressional responses to various nitrogen supply scenarios. This dual focus aims to provide a comprehensive understanding of nitrogen utilization strategies and their evolutionary adaptation in microalgae.

CRC RESIST - SFB 1439

The new CRC RESIST aims to understand and explain the mechanisms underlying the degradation of and recovery from multiple stressors in stream ecosystems. More information on the CRC can be found on its website: https://sfb-resist.de/.

Subproject A04: “The roles of bacteria and fungi for CPOM degradation during stressor increase and release: A metatranscriptomic approach”

The subproject A04 focuses on the role of different fungal and bacterial groups in enzymatic decomposition of coarse particulate organic matter (CPOM) - leaf decompositions - in the presence and absence of stressors. To determine the stressor effect on molecular level we will use metatranscriptome sequencing. In two experimental systems experiments will be run in collaboration with all CRC members. Here we will evaluate the effect of stressor increase and release for both fungi and bacteria. In particular, we will test whether functions recover faster than community composition to a pre‐degradation stage, due to partial functional redundancy among taxa. We expect that functions are shared between bacteria and fungi, and among different taxa within these microbial groups. Thus, if species or other taxonomic groups disappear following stressor exposure, their metabolic activity will be compensated for by other taxa. However, such compensatory mechanisms might be limited if a succession of taxa is necessary for the decomposition of CPOM. First, we will determine the bacterial and fungal community composition contributing to the decomposition of leaf litter by stable isotope probing and amplicon and metatranscriptome sequencing in the absence of stressors. Thereupon, we will analyse via metatranscriptomics: i) the taxa involved in the decomposition of leaf litter, ii) their specific functional roles, iii) their interactions and redundancies and iv) the effect of multiple stressors on all of the previous aspects.

Subproject Z-INF: “Data management and integration”

The Z-INF subproject represents the backbone for data management and data integration to facilitate collaboration inside RESIST. Data storage and data exchange between RESIST’s individual projects and with external institutions will be coordinated by Z-INF, for which a respective infrastructure will be established. Central data storage facilities will ensure archiving and accessibility of raw and processed data of RESIST. Management of research data for exchange between projects, for publications and future internal and external use will be provided and maintained. For the provided data, data type descriptors with respect to file format, content, sample and experimental affiliation, generation of the data (hardware, software, versions, parameters) will be developed and applied. With mandatory documentation of the generated data, in form of metadata and the introduction of an electronic laboratory notebook connected to the data management system, we will contribute to ensuring reproducible research. In the scope of further utilisation of the data, pipelines and tools for data integration will be developed to analyse multiple data sources in conjunction with regard to stressor effects across experimental systems and analysed organisms. This involves the development of methods to integrate heterogeneous types.