Biology subjects

Aeby, S.

Publications and source records attributed to Aeby, S..

5 recordsLinked to original sources

bioRxiv2026

Microbial community profiles of the snake cloaca in the presence and absence of Chlamydiota

Chlamydiota are obligate intracellular bacteria detected in snake cloacal microbiota, yet their biological significance remains poorly understood. Members range from recognised pathogens, such as Chlamydia serpentis, to potential environmental symbionts, raising questions about whether they represent transient contaminants, persistent colonisers, or subclinical infectious agents. Despite the cloaca serving as a primary site of chlamydial shedding in snakes, its interaction with the broader cloacal microbiota remains unexplored. Following pan-Chlamydiota PCR screening of 137 captive snakes across five collections, 52 samples (caenophidian snakes) (27 Chlamydiota-positive, 25 Chlamydiota-negative) were retained after V3-V4 16S rRNA sequencing and quality filtering. Presence of Chlamydiota was not associated with significant differences in alpha diversity or overall community composition, though it was related to greater within-community compositional heterogeneity. Differential abundance and multivariate analyses identified several enriched and depleted genera, with Lachnospiraceae and Copromonas consistently negatively associated with Chlamydiota across all three methods. Co-occurrence network analysis recovered more associations and a higher proportion of positive edges in the presence of Chlamydiota, with an expansion of anaerobic taxa. Inferred functional composition did not differ globally between groups; however, elastic net stability selection identified subtle pathway-specific differences, including enrichment of proteolytic and mycobacterial pathways in infected snakes. Our findings suggest subtle infection-associated community shifts that do not fully conform to established mammalian paradigms in which Chlamydia species behave either as gastrointestinal commensals or as cervicovaginal pathogens, highlighting the need for multi-omics approaches in larger cohorts of caenophidian and henophidian wild and captive snakes to better characterise the mechanistic basis and generalisability of these associations.

microbiology↗

bioRxiv2026

Comparative analysis of cloacal microbiota in Henophidia (non-venomous) and Caenophidia (venomous) snakes

The evolutionary divergence between Henophidia (non-venomous) and Caenophidia (venomous) snakes has produced distinct cranial morphologies, digestive strategies, and presence of specialised venom systems in Caenophidia, yet the extent to which these long-standing diverging trajectories have shaped cloacal microbiota assembly remains poorly understood. We characterised cloacal microbiota in 70 captive snakes (52 Caenophidia, 18 Henophidia) by 16S rRNA amplicon sequencing. Beta diversity was tested by PERMANOVA, differential abundance by ANCOM-BC2, community types by Dirichlet Multinomial Mixture modelling (DMM), and microbial interactions by SparCC co-occurrence networks. Predicted functional potential (PICRUSt2) was analysed by ALDEx2 differential abundance testing and elastic net feature selection. Henophidia exhibited significantly higher bacterial richness and greater compositional variability than Caenophidia. Community composition showed clade-associated differences (PERMANOVA) and partitioned into two distinct DMM community types. The Henophidia network was 11.9-fold denser and more modular, with Burkholderiaceae as a keystone hub, whereas the Caenophidia network was sparse. Henophidia showed predicted enrichment in C1 metabolic pathways (ethylmalonyl-CoA, formaldehyde assimilation I, glycine betaine degradation I, methylaspartate cycle), aromatic compound catabolism, and nitrogen recycling, whilst Caenophidia showed enrichment in allantoin and glucuronate degradation. This multi-method analysis suggests Burkholderiaceae as a candidate keystone taxon in Henophidia and indicates that phylogenetic clade is a major contributor to cloacal microbiota structure. The lower richness in Caenophidia raises a testable hypothesis that broad-spectrum antimicrobial activity of their venom components may selectively filter susceptible microbial lineages, motivating future shotgun metagenomic studies in wild populations of snakes.

ecology↗

bioRxiv2022

An NlpC/P60 protein catalyzes a key step in peptidoglycan recycling at the intersection of energy recovery, cell division and immune evasion in the intracellular pathogen Chlamydia trachomatis

The obligate intracellular Chlamydiaceae do not need to resist osmotic challenges and thus lost their cell wall in the course of evolution. Nevertheless, these pathogens maintain a rudimentary peptidoglycan machinery for cell division. They build a transient peptidoglycan ring, which is remodeled during the process of cell division and degraded afterwards. Uncontrolled degradation of peptidoglycan poses risks to the chlamydial cell, as essential building blocks might get lost or trigger host immune response upon release into the host cell. Here, we provide evidence that a primordial enzyme class prevents energy intensive de novo synthesis and uncontrolled release of immunogenic peptidoglycan subunits in Chlamydia trachomatis. Our data indicate that the homolog of a Bacillus NlpC/P60 protein is widely conserved among Chlamydiales. We show that the enzyme is tailored to hydrolyze peptidoglycan-derived peptides, does not interfere with peptidoglycan precursor biosynthesis, and is targeted by cysteine protease inhibitors in vitro and in cell culture. The peptidase plays a key role in the underexplored process of chlamydial peptidoglycan recycling. Our study suggests that chlamydiae orchestrate a closed-loop system of peptidoglycan ring biosynthesis, remodeling, and recycling to support cell division and maintain long-term residence inside the host. Operating at the intersection of energy recovery, cell division and immune evasion, the peptidoglycan recycling NlpC/P60 peptidase could be a promising target for the development of drugs that combine features of classical antibiotics and anti-virulence drugs. Author SummaryFree-living bacteria are wrapped by a peptidoglycan cell wall. This envelope provides shape and protects from osmotic stress, while also triggering human immune defense. Chlamydial pathogens live inside human cells and dispensed with a cell wall in their isotonic niche. Instead, they produce a transient peptidoglycan ring that is essentially involved in cell division. Recycling of peptidoglycan is likely important for chlamydiae to maintain a complete cycle of peptidoglycan ring synthesis and cell division. Moreover, the process may help to save energy and to protect from recognition through the immune system. Despite a potentially central role in cell viability and pathogenicity almost nothing is known about recycling of peptidoglycan in chlamydiae. The minimalist organisms lack all enzymes known to catalyze the process in model organism Escherichia coli. Here, we found an NlpC/P60 enzyme to serve a critical step in decomposing peptidoglycan ring derived peptides in Chlamydia trachomatis. Our data indicate that the peptidase recycles energy cost intensive components and breaks down the minimal recognition motif of innate immune factor NOD1. We also identified a natural lead compound to inhibit the NlpC/P60 enzyme opening the way for innovative anti-chlamydial drug development at the intersection of energy recovery, cell division, and immune evasion.

microbiology↗

bioRxiv2020

Nested species distribution models of Chlamydiales in tick host Ixodes ricinus in Switzerland

The tick Ixodes ricinus is the vector of various pathogens, including Chlamydiales bacteria, potentially causing respiratory infections. In this study, we modelled the spatial distribution of I. ricinus and associated Chlamydiales over Switzerland from 2009 to 2019. We used a total of 2293 ticks and 186 Chlamydiales occurrences provided by a Swiss Army field campaign, a collaborative smartphone application and a prospective campaign. For each tick location, we retrieved from Swiss federal datasets the environmental factors reflecting the topography, climate and land cover. We then used the Maxent modelling technique to estimate the suitability for I. ricinus and to subsequently build the nested niche of Chlamydiales bacteria. Results indicate that I. ricinus high habitat suitability is determined by higher temperature and vegetation index (NDVI) values, lower temperature during driest months and a higher percentage of artificial and forests areas. The performance of the model was increased when extracting the environmental variables for a 100 m-radius buffer around the sampling points and when considering the data over the two years previous sampling date. For Chlamydiales bacteria, the suitability was favoured by lower percentage of artificial surfaces, driest conditions, high precipitation during coldest months and short distances to wetlands. From 2009 to 2018, we observed an extension of tick and Chlamydiales suitable areas, associated with a shift towards higher altitude. The importance to consider spatio-temporal variations of the environmental conditions for obtaining better prediction was also demonstrated. ImportanceIxodes ricinus is the vector of pathogens, including the agent of Lyme disease, the tick borne encephalitis virus and the less known Chlamydiales bacteria at the origin of some respiratory infections. In this study, we identified the environmental factors influencing the presence of I. ricinus and Chlamydiales in Switzerland and generated maps of their distribution from 2009 to 2018. We found an important expansion of suitable areas for both the tick and the bacteria during the last decade. Results provided also the environmental factors that determine the presence of Chlamydiales within ticks. Distribution maps as generated here are expected to bring valuable informations for decision-makers to control tick-borne diseases in Switzerland and establish prevention campaigns. The methodological framework presented could be used to predict the distribution and spread of other host-pathogen couples, to identify environmental factors driving their distribution and to develop control or prevention strategies accordingly.

microbiology↗

bioRxiv2018

Indication of spatially random infection of chlamydia-like organisms in Bufo bufo tadpoles from ponds located in the Geneva metropolitan area

Occurrence of bacteria belonging to the order Chlamydiales was investigated for the first time in common toad (Bufo bufo) tadpole populations collected from 41 ponds in the Geneva metropolitan area, Switzerland. A Chlamydiales-specific Real-Time PCR was used to detect and amplify the Chlamydiales 16S rRNA-encoding gene from the tails of 375 tadpoles. We found the studied amphibian populations to be infected by \"Chlamydia-like organisms\" (CLOs) attributable to the genera Similichlamydia, Neochlamydia, Protochlamydia and Parachlamydia (belonging to the family Parachlamydiaceae), Simkania (family Simkaniaceae) and Estrella (family Criblamydiaceae); additionally, DNA from the genus Thermoanaerobacter (family Thermoanaerobacteriaceae) was detected. A global autocorrelation analysis did not reveal a spatial structure in the observed CLOs infection rates, and association tests involving land cover characteristics did not evidence any clear effect on CLOs infection rates in B. bufo. Despite preliminary, these results suggest a random and ubiquitous distribution of CLOs in the environment, which would support the biogeographical expectation \"everything is everywhere\" for the concerned microorganisms and their amoeba vectors.

epidemiology↗