Biology subjects

Rehner, J.

Publications and source records attributed to Rehner, J..

3 recordsLinked to original sources

bioRxiv2026

The phosphodiesterase NbdA links c-di-GMP signaling to type IV pili function in Pseudomonas aeruginosa PAO1

The phosphodiesterase (PDE) NbdA (NO-induced biofilm dispersion locus A) consists of a membrane-integrated MHYT domain, a degenerated diguanylate cyclase (DGC) AGDEF domain and an EAL domain. The integral membrane domain MHYT is proposed to sense a so far unknown extracellular signal and transfers the information to the cytosolic enzyme domains to modulate cellular c-di-GMP level. Here, we show that full length NbdA from Pseudomonas aeruginosa PAO1 is an active PDE in vivo. In line with its PDE activity, overexpression leads to slightly reduced global c-di-GMP levels, and reduced twitching motility. Surprisingly, overexpression of truncated cytosolic NbdA variants exhibited increased c-diGMP levels, suggesting previously uncharacterized DGC activity despite lacking a canonical GGDEF motif. While full-length NbdA overexpression resulted in only slight c-di-GMP reduction, cytosolic variants induced a significant increase, indicating a potential for nonenzymatic effects like protein-protein interactions. Further investigation revealed a connection between NbdA and type IV pilus (T4P) function. Overexpression of NbdA conferred resistance to the T4P-dependent phage DMS3vir, suggesting interference with T4P assembly or function. Microscopic analysis demonstrated dynamic localization of NbdA, partially co-localizing with T4P components, supporting a role in T4P regulation. However, no clear link was re-established with flagellar motor switching or chemotaxis signaling. These findings position NbdA in the complex signaling network of c-diGMP and T4P-mediated surface behavior in P. aeruginosa. Future work will focus on elucidating the precise mechanisms of NbdAs PDE activity and its interplay with other DGC/PDE networks. ImportanceIn this work, we show the in vivo activity of the membrane-bound phosphodiesterase NbdA of Pseudomonas aeruginosa, its role in c-di-GMP homeostasis, cellular localization and implications in surface behavior. Using strains overexpressing NbdA and truncated protein variants, we detected a strong defect in growth on solid surfaces and an altered phage susceptibility. Co-localization experiments supported further the hypothesis of interaction with the type IV pilus apparatus. We propose for NbdA to be part of the protein network responsible for c-di-GMP level modulation at the cell pole and thereby regulating the function of type IV pilus apparatus.

microbiology↗

bioRxiv2025

Joint bacterial traces in the gut and oral cavity of Colitis patients provide evidence for saliva as rich microbial biomarker source

The human microbiome, distributed across various anatomical sites, holds promise for identifying diagnostic biomarkers and therapeutic targets in disease. In inflammatory bowel disease (IBD), including ulcerative colitis (UC), interactions between the gut and oral microbiomes are crucial for understanding disease mechanisms and guiding interventions. The IMAGINE study sequenced 1,931 specimens from saliva, plaque, stool, and other sources in patients and healthy controls. Here, we assess whether the oral (saliva/plaque) or gut microbiota provides greater diagnostic potential in IBD and examine shared dysregulation across sample types. Among 177 oral samples (102 healthy, 75 IBD) and 92 stool samples (57 healthy, 35 IBD), we identified 240 distinct strains in plaque, 229 in saliva, and 231 in stool, with 46 strains present in all three. Saliva showed a significantly higher average effect size (0.2) than stool (0.04) and plaque (0.06). Notably, Actinomyces sp., Bifidobacterium dentium, and Veillonella parvula exhibited increased effect sizes, suggesting their potential as diagnostic markers or therapeutic targets. These findings indicate that microbiome profiling in IBD may improve diagnostics and treatment strategies.

microbiology↗

bioRxiv2023

Time series of chicken stool metagenomics and egg metabolomics in changing production systems

Different production systems of livestock animals influence various factors, including the gut microbiota. We investigated whether changing the conditions from barns to free-range impacts the microbiome over the course of three weeks. We compared the stool microbiota of chicken from industrial barns after introducing them either in community or separately to a free-range environment. Over the six time points, 12 taxa - mostly lactobacilli - changed significantly. As expected, the former barn chicken cohort carries more resistances to common antibiotics. These, however, remained positive over the observed period. At the end of the study, we collected eggs and compared metabolomic profiles of the egg white and yolk to profiles of eggs from commercial suppliers. Here, we observed significant differences between commercial and fresh collected eggs as well as differences between the former barn chicken and free-range chicken. Our data suggest that the gut microbiota can change over time following a change in production systems. This change also influences the metabolites in the eggs. We understand the study as a proof-of-concept that justifies larger scale observations with more individual chicken and longer observation periods.

zoology↗