Biology subjects

Kretschmer, D.

Publications and source records attributed to Kretschmer, D..

3 recordsLinked to original sources

bioRxiv2024

Probiotic Lactobacilli activate Formyl-Peptide Receptor 2

Changes in the composition of the human microbiota can negatively impact human health. Probiotic bacteria like many lactobacilli help prevent or repair dysbiosis but it is largely unclear which molecules of these bacteria mediate the probiotic effects. Given the extensive crosstalk between the immune system and microbiome members, we investigated whether lactobacilli activate the formyl-peptide receptor 2 (FPR2), a pattern recognition receptor that is expressed on the surface of intestinal epithelial cells and known to promote wound healing and immune homeostasis. Probiotic strains of Lacticaseibacillus paracasei, Lactiplantibacillus plantarum, and Lacticaseibacillus rhamnosus were isolated from probiotic compounds and sequenced. Calcium influx experiments in FPR1 or FPR2 overexpressing HL60 cells, and primary human neutrophils, along with pharmacological inhibition of FPR2, revealed that culture filtrates of the isolated lactobacilli strongly activate FPR2, promote killing of the methicillin resistant S. aureus USA300 and induce neutrophil chemotaxis. Pretreatment of culture filtrates with proteinase K reduced FPR2 activity, indicating that the FPR2 ligands are peptides. In silico analysis of the amphipathic properties of the signal peptides of lactic acid bacteria identified selected signal peptides of L. plantarum with the ability to predominantly activate FPR2 in vitro. Thereby, via targeted activation of FPR2, peptides released by some lactobacilli are likely to positively influence the outcome of inflammatory gut diseases and could be used to treat inflammatory diseases.

microbiology↗

bioRxiv2023

An interbacterial lipase toxin with an unprecedented reverse domain arrangement defines a new class of type VII secretion system effector

The type VII protein secretion system (T7SS) is found in many Gram-positive bacteria and in pathogenic mycobacteria. All T7SS substrate proteins described to date share a common helical domain architecture at the N-terminus that typically interacts with other helical partner proteins, forming a composite signal sequence for targeting to the T7SS. The C-terminal domains are functionally diverse and in Gram-positive bacteria such as Staphylococcus aureus often specify toxic anti-bacterial activity. Here we describe the first example of a new class of T7 substrate, TslA, that has an unexpected reverse domain organisation. TslA is widely found across Bacillota including Staphylococcus, Enterococcus and Listeria. We show that the S. aureus TslA N-terminal domain is a phospholipase A with anti-staphylococcal activity that is neutralised by the immunity lipoprotein TilA. Two small helical partner proteins, TlaA1 and TlaA2 are essential for T7-dependent secretion of TslA and at least one of these interacts with the TslA C-terminal domain to form a helical stack. Cryo-EM analysis of purified TslA complexes indicate that they share structural similarity with canonical T7 substrates. Our findings suggest that the T7SS has the extraordinary feature of recognising a secretion signal present at either end of a substrate.

microbiology↗

bioRxiv2023

Lipase-mediated detoxification of host-derived antimicrobial fatty acids by Staphylococcus aureus

Long-chain fatty acids with antimicrobial properties are abundant on the skin and mucosal surfaces, where they are essential to restrict the proliferation of opportunistic pathogens such as Staphylococcus aureus. These antimicrobial fatty acids (AFAs) elicit bacterial adaptation strategies, which have yet to be fully elucidated. Characterizing the pervasive mechanisms used by S. aureus to resist AFAs could open new avenues to prevent pathogen colonization. Here, we identify the S. aureus lipase Lip2 as a novel resistance factor against AFAs. Lip2 detoxifies AFAs via esterification with cholesterol. This is reminiscent of the activity of the fatty acid-modifying enzyme (FAME), whose identity has remained elusive for over three decades. In vitro, Lip2-dependent AFA-detoxification was apparent during planktonic growth and biofilm formation. Our genomic analysis revealed that prophage-mediated inactivation of Lip2 was more common in blood and nose isolates than in skin strains, suggesting a particularly important role of Lip2 for skin colonization. Accordingly, in a mouse model of S. aureus skin colonization, bacteria were protected from sapienic acid - a human-specific AFA - in a cholesterol- and lipase-dependent manner. These results suggest Lip2 is the long-sought FAME that exquisitely manipulates environmental lipids to promote bacterial growth. Our data support a model in which S. aureus exploits and/or exacerbates lipid disorders to colonize otherwise inhospitable niches.

microbiology↗