Graduate Students Mini Symposia III and IV / 2019

  • Date: Nov 25, 2019
  • Time: 13:00
  • Location: MPI for Terrestrial Microbiology
  • Room: Lecture hall
  • Host: IMPRS
  • Contact: imprs@mpi-marburg.mpg.de

Program:


13:00 Delia Casas Pastor, AG Fritz

ExtraCytoplasmic Function (ECF) σ factor classification: from phylogenesis to protein regulation

ECFs are the most abundant and diverse subfamily of sigma factors in bacteria. Sigma factors drive the RNA polymerase to specific promoters, from which they initiate transcription. In ECFs this function is dependent upon a signal, transmitted to the ECF via its regulators, which are conserved within ECF groups. In this work we expand the original ECF classification using the full array of genomes in NCBI. Taken together, our ECF classification provides predictions for the regulation of more than 150 ECF groups, covering the full bacterial spectrum, which the community can use as a source for testable hypotheses.

13:30 María Esteban Lopez, AG Sourjik

TBA

Attachment to abiotic and biotic surfaces is an important early step during bacterial infection and during formation of submerged biofilms. Flagella-mediated motility is known to be important for this transition from a planktonic to the sessile state for Escherichia coli and other bacteria, but implications of motility regulation by cellular signalling remain to be understood. Here we show that motility largely promotes attachment of E. coli that is mediated by type 1 fimbriae, by allowing cells to reach, get hydrodynamically trapped at and explore the surface. Genetic or stimulation-induced inactivation of the chemotaxis signalling pathway improves attachment by suppressing cell reorientations and thereby increasing surface residence times. The attachment is further enhanced by deletion of genes encoding the cyclic diguanosine monophosphate (c-di-GMP)-dependent flagellar brake protein YcgR or the diguanylate cyclase DgcE, in contrast to the commonly accepted function of c-di-GMP as a positive regulator of the sessile state. This enhancement is apparently due to the increased swimming speed of E. coli in absence of c-di-GMP-mediated signalling, which strengthens adhesion mediated by the type 1 fimbriae. Thus, both signalling networks that regulate motility of E. coli also control its engagement with both biotic and abiotic surfaces, which has likely implications for infection and biofilm formation.

14:00 Stefano Donati, AG Link

Enzyme-level perturbations by CRISPRi reveal control principles of E. coli primary metabolism

Many metabolic enzymes are essential for bacterial growth, because they catalyse reactions that provide energy and biomass building blocks. We investigated how E. coli responds to decreases of single-enzymes by using an inducible CRISPR interference (CRISPRi) system. Growth of 110 CRISPRi strains showed that E. coli is remarkably robust against downregulation of essential enzymes, thus indicating that they are overabundant. We then measured the metabolome and proteome of 30 strains, revealing that decreases of enzymes are compensated by substrate- and effector-level regulation, transcriptional enzyme-level regulation, or by activation of alternative bypass-pathways.


14:30-14:45 Break


14:45 Yulin Song, AG Brune

The capacity of termite gut spirochetes for reductive acetogenesis

Spirochetes are characteristic members of the gut microbiota that termites harbor for the symbiotic digestion of recalcitrant lignocellulose. They dominate the bacterial gut microbiota in many termite species and can even make up more than one-half of the community. However, their functional roles are still enigmatic due to the fact that most of them remain uncultured. While previous studies suggested the termite cluster spirochetes might be the major agents of gut CO2-reductive acetogenesis, we found the lineages from evolutionary higher termites lack key genes of this pathway. A basal isolate of this cluster is also incomplete in the pathway.

15:15 Adrian Izquierdo Martinez, AG Thanbichler

Regulation of the Autolysins during cell division in Caulobacter crescentus

The bacterial cell wall remodeling critically depends on the action of autolysins, whose enzymatic activity must be tightly regulated to prevent cell lysis. In several organisms, proteins with catalytically inactive LytM domains act as regulators of autolysins. Previous studies show that in Caulobacter crescentus two of such LytM factors (DipM and LdpF) recruit different autolysins at different stages of cell division. Our current research suggest that DipM physically connects several kinds of autolysins with divisome components, building a kind of interaction network never reported before. We are comprehensively characterizing these interactions to better understand how the system works in vivo.

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