Graduate Students Mini Symposium IV 2021


16:00 Giovanni Scarinci (RG Sourjik)

Study and implementation of metabolic interactions in natural and semi-synthetic systems

Metabolic interconnections between diverse organisms are common in microbial consortia. Community members often excrete the exchanged metabolites in the environment, making them available to the other partners. However, the availability of these free compounds in the environment might favor community members that do reciprocate with any benefit to the community but exploit the costly “public goods” generated by other members (cheaters). In nature, several strategies are adopted by partners to reduce cheating and aggregative structures are thought to be one of those. We use synthetic communities that combine an aggregative behavior together with metabolic dependencies between community members to investigate the effects of partner proximity on microbial communities.

16:30 Benedikt Steinfeld (RG Bischof-Pfeifer)

Phenotypic heterogeneity in bacteria: Understanding mixed populations

Phenotypic heterogeneity is an important concept in understanding bacterial populations. In growing populations, B. subtilis forms two mutually exclusive cell types, namely short motile cells and chains of connected sessile cells. In order to understand these mixed populations, we employ a mixture of single-cell and bulk measurements to demonstrate that motile and sessile cells have different resistance traits under stress and that the composition of the population is influenced by cell-cell communication. Furthermore, we present a novel approach to analyse both cell types at an OMICS-level.

17:00 Break

17:05 Miriam Bayer (RG Drescher)

A novel method for spatiotemporal RNA-seq of Vibrio cholerae biofilm subpopulations

Most bacteria have the ability to grow into 3D structural assemblages called biofilms, in which closely packed cells are held together by a self-produced extracellular matrix. In contrast to a well-mixed planktonic culture, cells in a biofilm experience spatially distinct microenvironments due to the formation of chemical gradients. Our knowledge about heterogeneous behavior of biofilm subpopulations however is limited due to the inaccessibility of cells in 3D aggregates. We developed a novel method to collect transcriptomes of spatial subpopulations from V. cholerae biofilms in different developmental stages. Our method allows us to uncover heterogeneity in gene expression of before undescribed subpopulations by performing spatiotemporal RNA-seq.

17:35 Christopher Felderwert (RG Brune)

Endosymbiotic Opitutales in termite gut flagellates are highly specialized energy parasites

Cellulolytic gut flagellates play a key role in lignocellulose digestion by termites. They are consistently associated with a variety of endosymbiotic bacteria, which are often cospeciating with their host. Despite a massive genome reduction, all endosymbionts studied so far have retained the biosynthetic pathways for most amino acids, which led to the hypothesis that they supply the flagellate with essential nutrients. Here, we report a novel group of endosymbionts from the phylum Verrucomicrobia, which were localized in several flagellate species by fluorescence in-situ hydridization (FISH). Phylogenomic analysis of metagenome-assembled genomes (MAGs) from 21 lower termite species yielded 83 MAGs representing several family-level clades of unclassified Opitutales. Functional analysis of the MAGs revealed highly reduced genomes with an impaired glycolysis and a carbon metabolism driven by the uptake of sugar phosphates. Most MAGs encoded an ATP transporter with homologs in Rickettsiales that was most likely acquired by lateral gene transfer from other gut bacteria. In view of the absence of all pathways for the biosynthesis of amino acids, it seems likely that the flagellate-associated Opitutales are not mutualistic endosymbionts but energy parasites. The recovery of additional, less-reduced MAGs of more basal lineages of Opitutales from termite guts allows first insights into the evolutionary transition from a free-living to an endosymbiotic lifestyle.

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