Exploring metabolic dependencies through low and high cell density cultures from the Baltic Sea

For this project, we started cultures with low and high cell densities, called cultivated model communities. Cultivated communities are a powerful tool for studying ubiquitous but hard-to-cultivate microorganisms because they can facilitate their growth alongside metabolic partners. We hypothesize that co-cultivation can improve the cultivation success of these elusive microbes by satisfying their metabolic dependencies.We initiated our study by collecting an environmental water sample from the Baltic Sea, from which we generated two metagenomes using different DNA extraction kits. Using this sample, we established microbial cultures through the dilution-to-extinction method, with cell densities ranging from 2 to 100 cells/mL in 96 well-plates (low cell density) and 200 to 1x10^6 cells per bottle (high cell density).After a four-week incubation period, successful cultures were identified using flow cytometry, resulting in 315 cultures with growing cells. We performed metagenomic characterization from these cultures and obtained metagenome-assembled genomes (MAGs) from 204 cultures.Our analysis will compare the interaction patterns within these cultivated communities to those in extensive publicly available metagenomic data from the Baltic Sea. This comparison aims to provide deeper insights into the ecological mechanisms and interaction networks of aquatic microorganisms, ultimately contributing to a better understanding of their roles in biogeochemical cycles.