7th joint conference "Joint Microbiology & Infection Conference 2024" of the DGHM and VAAM

Prof.

Chair

Professor

Prof. Dr.

Dynamic interplay: chemotaxis, quorum sensing and metabolism affect Escherichia coli interactions during gut colonization

Sensing, Signaling & Communicating Microbes

Bacteria communicate and coordinate their behavior at the intra- and inter-species levels by producing and sensing extracellular small molecules called autoinducers. Autoinducer 2 (AI-2) is produced and detected by a variety of bacteria, thus playing an important role in interspecies communication. Although AI-2 is a major autoinducer molecule present in the mammalian gut, its role in bacteria-bacteria and bacteria-host interactions during gut colonization remains unclear. Through competitive infections in C57BL/6 mice, along with microscopy and bioinformatic approaches, we show that chemotaxis and AI-2 signalling promote gut colonization by Escherichia coli, which is in turn connected to the ability of the bacteria to utilize fructoselysine. Additionally, we show that the genomic diversity of E. coli strains with respect to AI-2 signaling allows ecological niche segregation and stable co-existence of different E. coli strains in the mammalian gut.Furthermore, we demonstrate that E. coli competes with enteric pathogen Salmonella Typhimurium in AI-2 chemotaxis-dependent manner. Utilizing a genetically tagged library of S. Tm gene knockouts, we conducted high-throughput analysis to identify metabolic genes that contribute to E. coli-S. Tm competition during the murine gut colonization. Preliminary data suggests the involvement of genes related to glycerol metabolism and fumarate respiration. In summary, our results pinpoint the importance of quorum sensing- and metabolic pathways involved in both intra- and inter-species interactions of E. coli during gut colonization.Reference: Laganenka, L. et al. 2022. Chemotaxis and autoinducer-2 signalling mediate colonization and co-existence of Escherichia coli strains in the murine gut // Nat Microbiol. 8 (2), 204-217. doi: 10.1038/s41564-022-01286-7.

Oral Presentation

Microalgae and Bacteria Interaction—Evidence for Division of Diligence in the Alga Microbiota

Microalgae are one of the most dominant forms of life on earth that is tightly associated with a distinct and specialized microbiota. We have previously shown that the microbiota of Scenedesmus quadricauda harbors less than 10 distinct microbial species. Here, we provide evidence that dominant species are affiliated with the genera of Variovorax, Porphyrobacter, and Dyadobacter. Experimental and transcriptome-based evidence implies that within this multispecies interaction, Dyadobacter is a key to alga growth and fitness and is highly adapted to live in the phycosphere. While presumably under light conditions the alga provides the energy source to the bacteria, Dyadobacter produces and releases mainly a large variety of polysaccharides modifying enzymes. This is coherent with high-level expression of the T9SS in alga cocultures. The transcriptome data further imply that quorum-quenching proteins (QQ) and biosynthesis of vitamins B1, B2, B5, B6, and B9 are expressed by Dyadobacter at high levels in comparison to Variovorax and Porphyrobacter. Notably, Dyadobacter produces a significant number of leucine-rich repeat (LRR) proteins and enzymes involved in bacterial reactive oxygen species (ROS) tolerance. Complementary to this, Variovorax expresses the genes of the biosynthesis of vitamins B2, B5, B6, B7, B9, and B12, and Porphyrobacter is specialized in the production of vitamins B2 and B6. Thus, the shared currency between partners are vitamins, microalgae growth-promoting substances, and dissolved carbon. This work significantly enlarges our knowledge on alga-bacteria interaction and demonstrates physiological investigations of microalgae and associated bacteria, using microscopy observations, photosynthetic activity measurements, and flow cytometry.

Novel Inhibitors of the Two-Component System VanRS Re-Sensitize Enterococcus Faecalis to Vancomycin

Two-component systems (TCS) are the main signalling system in bacteria and are involved in adaptation, virulence, antimicrobial resistance, etc. TCS are formed by a sensor Histidine Kinase (HK) that detects a specific stimuli and undergoes an autophosphorylation via an ATP bound to the catalytic domain (CA). The phosphate is transferred to the Response Regulator (RR) that then changes gene expression accordingly to the detected stimuli. TCS have been proposed as good targets for antibiotics due to their presence in all bacteria, each bacteria possess multiple TCS, their catalytic domains are conserved and they are absent in mammalian cells. In this research we used a fragment-based drug design approach to develop inhibitors that compete with ATP for the ATP-binding pocket on the CA domain of TCS.Following a fragment-based drug design approach, a series of fragments were screened in silico for binding to the ATP-pocket of different HK. Promising fragments were synthesized and protein binding was confirmed via X-crystallography. The most promising fragment CT14 was rationally and virtually grown into a compound library. This library was synthesized, and screened for in vitro binding to the HKs CheA from Thermotoga maritima and PhoR from Staphylococcus aureus. Best compounds bound with Kds in the low μM range. The library was then screened for inhibition of VanRS TCS mediated vancomycin resistance in E. faecalis and E. faecium. Surprisingly, compound 752 completely re-sensitized E. faecalis vanA and vanB to vancomycin. Expression analysis showed a significant downregulation of vanA induction from vancomycin treatment when 752 was present. Even though 752 failed to re-sensitize E. faecium vancomycin, it led to a similar reduction in vanA induction.In summary, TCS inhibitor 752 re-sensitizes E. faecalis to vancomycin treatment by, at least partially, inhibiting VanRS TCS. Compound 752 also reduces VanRS related pathways in E. faecium but this inhibition is not enough to re-sensitize it to vancomycin. However, optimization for complete inhibition of VanRS could serve to also re-sensitize E. faecium to vancomycin, with great implications in nosocomial infections.

Raum 13

Oral Session

Oral Sessions

Oral Session
Sensing, Signaling & Communicating Microbes

Appointment

Chair

Topic

Programme

Oral SessionSensing, Signaling & Communicating Microbes

Appointment

Chair

Topic

Programme

Oral Session
Sensing, Signaling & Communicating Microbes