Biology subjects

Daniel, R.

Publications and source records attributed to Daniel, R..

At least 19 recordsLinked to original sources

bioRxiv2026

PopZ is dispensable for cell fitness but required for polar localization of ParB in Zymomonas mobilis.

Chromosome segregation is an essential process in monoploid bacteria, in which faithful inheritance of the genetic material is required for viability of daughter cell. In several alpha-proteobacteria, the polar organizing protein PopZ plays a crucial role in chromosome segregation by anchoring the chromosome partitioning machinery at a cell pole. While this process has been studied in monoploid species, it remains unclear whether this type of segregation mechanisms play a significant role in bacterial cells that carry multiple copies of chromosome. The alpha-proteobacterium Zymomonas mobilis exhibits ethanologenic physiology, and thus, is a promising chassis for biofuel production. Recent studies showed that Z. mobilis may serve as a non-model system for studying bacterial cell biology, owing to its relatively simple physiology and reduced genome size. Z. mobilis has previously been shown to be polyploid, and possesses a homolog of PopZ, a key regulator of chromosome organisation and cell polarity in alpha-proteobacteria. This raises the question of whether PopZ is involved in the organization of multiple chromosome copies. Here, we investigated the function of PopZ in Z. mobilis. Unlike in previously studied alpha-proteobacterial species, PopZ is dispensable for growth and cell morphology in Z. mobilis. However, the loss of PopZ altered the polar accumulation of chromosome segregation protein ParB, indicating an involvement in chromosome organization in Z. mobilis. These findings indicate that Z. mobilis might possess a chromosome segregation machinery that is dispensable under favourable growth conditions but might become important under certain conditions that reduce chomorome copy numbers.

microbiology↗

bioRxiv2026

Hypothetical lytic transglycosylase SleB is important for cell fitness in Zymomonas mobilis

Bacterial peptidoglycan (PG) undergoes a variety of chemical modifications. O-acetylation at the C6 hydroxyl group of N-acetylmuramic acid is a widespread PG-modification found across diverse bacterial phyla. It contributes to virulence in pathogenic bacteria because the O-acetyl group reduces the activity of the PG-degrading host defense enzyme, lysozyme. Beyond its role in host defense evasion, recent studies suggest that PG O-acetylation also regulates the activity of endogenous lytic transglycosylase (LT) autolysins. The ethanologenic alpha-proteobacterium Zymomonas mobilis O-acetylates its PG, which is associated with tolerance to environmental stresses, including salt. To better understand how PG O-acetylation contributes to stress tolerance, we investigated the predicted lytic transglycosylase SleB. Intriguingly, the sleB gene is located adjacent to the pat operon, which encodes the proteins responsible for PG O-acetylation. We showed that loss of SleB caused impaired growth and morphology, and a significant reduction of crosslinks in the PG of Z. mobilis. Furthermore, the sleB mutant was sensitive to environmental stress resembling the sensitivity of the patA mutant. Collectively, our findings unravelled an important role of SleB in PG remodelling and stress resilience.

microbiology↗

bioRxiv2026

Periplasmic SacB as a robust counter-selection tool for genome engineering in the polyploid bacterium Zymomonas mobilis

The alpha-proteobacterium Zymomonas mobilis exhibits exceptional ethanologenic physiology, which makes it a traditional alcoholic beverage producer and a promising chassis for biofuel production. Although genetic tools for this organism have expanded in recent years, a fundamental aspect of its chromosome organization remains to be understood. In particular, Z. mobilis has been suggested to exhibit polyploidy, but this feature is not fully confirmed because of discrepancies among studies reporting the copy number of chromosomes. Here, we tagged the chromosome-partitioning protein ParB with a fluorescent marker to visualise its cellular localisation and estimate chromosome copy number in individual cells. Imaging showed that Z. mobilis exhibits several distinctive ParB foci throughout the cytoplasm and an accumulated focus at the pole, demonstrating that a single Z. mobilis cell contains at >5 copies of the chromosome at the oriC regions. After verifying its polyploidy, we sought to establish an efficient counter-selection system, which is crucial for engineering multiple copies of the chromosome. We assessed the efficacy of levan-sucrase (SacB) toxicity in Z. mobilis. We found that, despite Z. mobilis secreting a native extra-cellular sucrase SacB, heterologous periplasmically-localised Bacillus subtilis SacB rendered Z. mobilis cells sensitive to sucrose. We successfully used this effect for counter-selection when deleting and inserting targeted DNA sequences into the Z. mobilis genome. Together, this work provides important insights and tools for advancing Z. mobilis genetics and its biotechnological applications. ImportanceZymomonas mobilis is a promising industrial bacterium with capacity to convert sugars into ethanol at nearly maximum theoretical yield. With its expanding use in industrial applications, it is crucial to clarify if individual Z. mobilis cells carry multiple copies of chromosome as this has important implications for genome engineering. Two previous studies have used quantitative PCR to address this question, but their reported chromosome copy numbers varied widely from 20 to 100. Here, we used a cell biological approach to estimate the copy number and confirmed that single Z. mobilis cell possesses multiple copies. In addition, we show that a SacB-based counter-selection works in Z. mobilis, enabling efficient and complete mutation of all chromosome copies.

microbiology↗

bioRxiv2025

Spore type-specific gene expression profiles underlying development and leaf infection processes of Colletotrichum graminicola

Colletotrichum graminicola causes significant losses of the staple crop maize worldwide. The fungus produces two distinct asexual spore types, oval and falcate conidia, which show unique processes in development and plant interaction. Based on genome resequencing of our laboratory strain (CgM2/ M1.001), we investigated the gene expression profiles of oval and falcate conidia during development and early leaf infection using RNA-seq. Our results reveal specific gene expression profiles between the two spore types, indicating fundamental differences in their developmental programs that reflect different modes of infection. We identified expression patterns discriminating both conidia types from mycelium and spore type-specific ones for genes encoding transcription factors, conserved fungal developmental genes, transporters, genes of secondary metabolite clusters, and pathogenicity-related functions, including effectors and carbohydrate-active enzymes (CAZymes). Our study shows that despite the identical genomic basis, oval and falcate conidia show unique transcriptomes across vegetative development and early plant interaction. Taking together, these results provide new insights into the molecular mechanisms determining the biology of C. graminicola and its interaction with the plant host.

microbiology↗

bioRxiv2025

Time-resolved effects of cold atmospheric plasma on E. coli GW-AmxH19 transcriptome and proteome in an emulated wastewater environment

Cold atmospheric plasma (CAP) has been shown to be effective against a variety of microorganisms. In this study, we described effects on an Escherichia coli strain isolated from hospital wastewater caused by a treatment with physical plasma. E. coli GW-AmxH19 was incubated in artificial wastewater and treated for 15 minutes with CAP. Transcriptomes and proteomes were monitored at different timepoints within a 24 h period to differentiate between immediate physiological responses and adaptations in the recovery phase. Reduction of viable cells was on average at 90%. The short-term response of the surviving cells to physical plasma aims at repairing and protecting cellular structures from plasma-induced damages, mainly provoked by reactive oxygen and nitrogen species. Notably, CAP induced a temporary transcription of genes from a conjugative plasmid carrying antibiotic resistance determinants. The late response during recovery phase is dominated by a massive activation of two prophages turning cold plasma treatment into a novel possible strategy to induce the lytic cycle of prophages. This study is the first report on the combined analysis of transcriptional and translational effects of CAP on an environmental bacterial isolate in a time-resolved manner. Chances and risks of considering CAP as an additional purification step in wastewater treatment plants are depicted and discussed.

microbiology↗

bioRxiv2025

Polyethylene terephthalate (PET) primary degradation products affect c-di-GMP-, cAMP-signaling and quorum sensing (QS) in Vibrio gazogenes DSM 21264

Global plastic pollution in oceans and estuaries is increasing rapidly and its well known that bacteria colonize plastic particles of all sizes. Vibrio spp. are frequently found as part of the plastisphere. We recently showed that Vibrio gazogenes DSM 21264 harbors a promiscuous esterase designated PET6. We now provide evidence that the pet6 gene is expressed under a wide range of environmental conditions in its native host. However, in PET- and PE-grown biofilms the pet6 gene expression was not affected by the type of surface. The pet6 transcription was sufficient to allow enzyme production and release of {micro}M amounts of mono-(2-hydroxyethyl) terephthalate (MHET) and terephthalic acid (TPA) already after 24 hours of incubation on PET foil. Notably, the highest pet6 gene transcription was observed in planktonic lifestyle in the presence of bis(2-hydroxyethyl) terephthalate (BHET) one of the primary degradation products of PET. BHET was further hydrolyzed by PET6 and UlaG, a lactonase that had not been known to be involved in BHET degradation. Elevated concentrations of BHET affected the major signaling circuits involved in bacterial quorum sensing (QS), c-di-GMP and cAMP-CRP signaling. This resulted in failure to form biofilms, synthesis of the red pigment prodigiosin and altered colony morphologies. While BHET had a very wide impact, TPA interfered mainly with the bacterial QS by attenuating the expression of the CAI-I autoinducer synthase gene. These observations imply a potential role of BHET and TPA as nutritional signals in Vibrio gazogenes and that may affect its growth and survival in the plastisphere. IMPORTANCEThis study provides first evidence that Vibrio gazogenes DSM 21264 secretes an active PET hydrolase and degrades the polymer using PET6 when growing in biofilms on foils and microplastic particles. The study further provides evidence that the primary PET degradation products BHET and TPA may have a profound impact on the global QS, c-di-GMP and cAMP-CRP signaling of V. gazogenes and its capability to colonize plastic particles in the marine environment.

microbiology↗

bioRxiv2025

A single pathogen-secreted protein reprograms plants for drought resilience

Climate change-enforced drought stress conditions and diseases caused by pathogens often co-occur and represent one of the greatest challenges in plant science1-3. Wilt pathogens that colonize water-conducting plant tissues can aggravate the problem and affect a wide range of agricultural crops4,5. However, whilst fungal infections with the vascular pathogen Verticillium dahliae are typically associated with wilt symptoms due to occlusion of xylem tissues, the related V. longisporum induces de novo formation of tracheary elements6,7. This promotes not only its virulence but also enables elevated water storage capacity of the infected host plant and resilience against drought stress conditions6,7. Here, we identified a secreted Verticillium protein, TRANSDIFFERENTIATION EFFECTOR (TRADE), which triggers cell identity switches of bundle sheath cells into tracheary elements. We show that TRADE interacts with the intracellular plant protein VARICOSE (VCS), a conserved component of the mRNA turnover machinery and ortholog of the metazoan protein ENHANCER OF DECAPPING 4 (EDC4/HEDLS/Ge-1)8. The TRADE-VCS interaction induces SUCROSE NON-FERMENTING 1 (SNF1)-related protein kinase (SRK)-dependent phosphorylation and thus dysfunction of VCS. This affects the abundance of mRNAs encoding master regulators of xylem differentiation and demonstrates how a single pathogen effector protein triggers complex tissue-specific developmental reprogramming and thus promotes abiotic stress resilience.

plant biology↗

bioRxiv2024

Nanoparticles co-delivering siRNA and mRNA for simultaneous restoration and silencing of gene/protein expression in vitro and invivo

RNA-based agents such as siRNA, miRNA, and mRNA can selectively manipulate gene expression/proteins and have the potential to revolutionize the current therapeutic strategies for various diseases, including cancer. To address the poor stability and inherent limitations of RNA agents, nanoparticle (NP) platforms have been developed to deliver functional mRNA or siRNA inside the cells. Recent studies have focused on either siRNA to knock down proteins causing drug resistance or mRNA technology to introduce tumor suppressors. However, complex diseases like cancer need multi-targeted approaches to selectively target multiple gene expressions/proteins. In this proof-of-concept study, we developed co-delivery nanoparticles containing Luc-mRNA and siRNA-GFP as model RNA agents ((M+S)-NPs) and assessed their effects in vitro and in vivo. Our studies show that NPs can effectively deliver both functional mRNA and siRNA together, simultaneously impacting the expression of two genes/proteins in vitro. Additionally, after in vivo administration, co-delivery NPs successfully knocked down GFP while introducing luciferase in a TNBC mouse model, indicating our NPs have the potential to develop RNA-based anticancer therapeutics. These studies pave the way to develop RNA-based, multitargeted, multi-delivery approaches for complex diseases like cancer. TOC O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=90 SRC="FIGDIR/small/600196v1_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@1668ae2org.highwire.dtl.DTLVardef@1283491org.highwire.dtl.DTLVardef@9336daorg.highwire.dtl.DTLVardef@f654c5_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2024

Isolation and characterization of Sporomusa carbonis sp. nov., a carboxydotrophic hydrogenogen in the genus of Sporomusa isolated from a charcoal burning pile

A Gram-negative bacterial strain, designated ACPtT, was isolated from the covering top soil of an active charcoal burning pile. Cells of ACPtT were strictly anaerobic, rod-shaped and grew optimally at 40{degrees}C and pH 7. The substrates ribose, glucose, sucrose, raffinose, melezitose, pyruvate, vanillate, syringate, methanol and CO were utilized for growth. Phylogenomic analysis of the 4.1 Mb genome showed that strain ACPt represented a novel species of the genus Sporomusa. The most closely related species to ACPtT was Sporomusa malonica with an average amino acid identity of 80.1%. The genome of ACPtT encoded cytochromes, ubiquinones, the Wood-Ljungdahl gene cluster and an Rnf complex, which were identified as common features all Sporomusa type strains. However, strain ACPt did not ferment H2 + CO2 via acetogenesis as other Sporomusa species, but employed the metabolism of a carboxydotrophic hydrogenogen converting CO to H2 + CO2. Based on the genomic, morphological and physiological features presented in this study, strain ACPtT is proposed as a novel species in the genus Sporomusa with the name Sporomusa carbonis sp. nov. (DSM 116159T and CCOS 2105T).

microbiology↗

bioRxiv2024

Knock-down of genes essential for homoacetogenic growth using sugar inducible promoters in the thermophile Thermoanaerobacter kivui

Given recent interest in hydrogen (H2) as a medium for storing and transporting renewable energy, the ability of acetogenic bacteria to use H2 to directly fix carbon dioxide (CO2) shows great promise. Thermophilic bacteria have long been of interest as industrial strains due to their resistance to contamination. Thermoanaerobacter kivui is among the most thermophilic acetogens. It can be genetically manipulated, but as yet only in an all-or-nothing manner, either complete gene knockouts or very strong constitutive promoters leading to protein overexpression. The sugar inducible promoters characterized here provide the finer control necessary to close remaining gaps in understanding of T. kivuis energy metabolism and for controlled expression of recombinant genes of industrial relevance. Acetogenic bacteria are capable of growing on mixtures of the gasses H2, CO2, and CO using the Wood-Ljungdahl pathway, the most energy efficient CO2 fixation pathway. T. kivui is a thermophilic (Topt = 66{degrees}C) acetogen also capable of growth on sugars including glucose, mannitol, and fructose. RNA-sequencing indicated an operon of phosphotransferase import genes up-regulated on mannitol, and growth on a mixture of glucose and mannitol was diauxic. Given this evidence for sugar responsive transcriptional regulation, the promoter region from the mannitol operon, and a similar operon involved in fructose uptake were used to control expression of a thermostable {beta}-galactosidase reporter gene. Both promoters resulted in higher reporter gene activity when grown on their inducing sugar relative to glucose. The inducible promoters were used to create "knock-down" mutants of the proton-pumping Ech1 hydrogenase. Ech1 is believed to be essential because repeated attempts to knock-out the gene operon have failed. The resulting sugar-inducible Ech1 expression strains grew better on their inducing sugar than on glucose. The mannitol inducible promoter was also used to control expression of an essential gene of the Wood-Ljungdahl pathway, formyl-THF synthetase (fhs), involved in consuming the metabolic intermediate formate. When fhs repressed by growth on glucose significantly more formate accumulated in the culture medium than during growth on mannitol, clear evidence of a metabolic bottleneck under the knock-down condition. The promoters characterized here provide finer control of recombinant or native gene expression in T. kivui, while the thermostable reporter gene allows for rapid characterization of new promoters.

microbiology↗

bioRxiv2024

Aldehydic load as an objective imaging biomarker of mild traumatic brain injury

Concussion is a mild traumatic brain injury (mTBI) defined as complex neurological impairment induced by biomechanical forces without structural brain damage. There does not yet exist an objective diagnostic tool for concussion. Downstream injury from mTBI stems from oxidative damage leading to the production of neurotoxic aldehydes. A collagen-based 3D corticomimetic scaffold was developed affording an in vitro model of concussion, which confirmed increased aldehyde production in live neurons following impact. To evaluate total aldehyde levels in vivo following mTBI, a novel CEST-MRI contrast agent, ProxyNA3, has been implemented in a new model of closed-head, awake, single-impact concussion developed in aged and young mice with aldehyde dehydrogenase 2 (ALDH2) deficiency. Behavioural tests confirm deficits immediately after injury. ProxyNA3-MRI was performed before impact, and on days two- and seven- post-impact. MRI signal enhancement significantly increased at two days post-injury and decreased to baseline seven days post-injury in all mice. An increase in astrocyte activation at seven days post-injury confirms the onset of a neuroinflammatory response following aldehyde production in the brain. The data suggest that advanced age and ALDH2 deficiency contribute to increased aldehydic load following mTBI. Overall, ProxyNA3 was capable of mapping concussion-associated aldehydes, supporting its application as an objective diagnostic tool for concussion.

biochemistry↗

bioRxiv2023

Control of three-carbon amino acid homeostasis by promiscuous importers and exporters in Bacillus subtilis: Role of the sleeping beauty family of amino acid exporters

The Gram-positive model bacterium Bacillus subtilis can acquire amino acids by import, de novo biosynthesis, or by degradation of proteins and peptides. The accumulation of several amino acids inhibits growth of B. subtilis, probably due to misincorporation into cellular macromolecules such as proteins or peptidoglycan or due to interference with other amino acid biosynthetic pathways. Here, we studied the adaptation of B. subtilis to toxic concentrations of the three-carbon amino acids L-alanine, {beta}-alanine, and 2,3-diaminopropionic acid as well as glycine. Resistance to the non-proteinogenic amino acid {beta}-alanine, which is a precursor for the vitamin B5 and thus for coenzyme A biosynthesis is achieved by mutations that either activate a cryptic amino acid exporter, AexA (previously YdeD), or inactivate the amino acid importers AimA, AimB (previously YbxG), and BcaP. The aexA gene is very poorly expressed under most conditions studied. However, mutations afecting the transcription factor AerA (previously YdeC), can result in strong constitutive aexA expression. AexA is the founding member of a conserved family of amino acid exporters in B. subtilis, which are all very poorly expressed. Therefore, we suggest to call this family "sleeping beauty family of amino acid exporters". 2,3-Diaminopropionic acid can also be exported by AexA, and this amino acid also seems to be a natural substrate of AerA/ AexA, as it can cause a slight but significant induction of aexA expression, and AexA also provides some natural resistance towards 2,3-diaminopropionic acid. Moreover, our work shows how low specificity amino acid transporters contribute to amino acid homeostasis in B. subtilis. IMPORTANCEEven though B. subtilis is of of the most-studied bacteria, amino acid homeostasis in this organism is not fully understood. We have identified import and export systems for the C2 and C3 amino acids. Our work demonstrates that the responsible amino acid permeases contribute in a rather promiscuitive way to amino acid uptake. In addition, we have discovered AexA, the first member of a family of very poorly expressed amino acid exporters, that we call "sleeping beauty amino acid exporters". The expression of these transporters is typically triggered by mutations in corresponding regulator genes that are acquired upon exposure to toxic amino acids. These exporters are ubiquitous in all domains of life. It is tempting to speculate that many of them are not expressed until the cells experience a selective pressure by toxic compounds and that the protect the cells from rare but potentially dangerous accounters with such compounds.

microbiology↗

bioRxiv2023

Profiling age and body fluid DNA methylation markers using nanopore adaptive sampling

DNA methylation plays essential roles in regulating physiological processes, from tissue and organ development to gene expression and aging processes and has emerged as a widely used biomarker for the identification of body fluids and age prediction. Currently, methylation markers are targeted independently at specific CpG sites, as part of a multiplexed assay, rather than through a unified assay. Methylation detection is also dependent on divergent methodologies, ranging from enzyme digestion and affinity enrichment to bisulfite treatment, alongside various technologies for high-throughput profiling, including microarray and sequencing. In this pilot study, we test the simultaneous identification of age-associated and body fluid-specific methylation markers using a single technology, nanopore adaptive sampling. This innovative approach enables the profiling of multiple CpG marker sites across entire gene regions from a single sample without the need for specialized DNA preparation or additional biochemical treatments. Our study demonstrates that adaptive sampling achieves sufficient coverage in regions of interest to accurately determine the methylation status, shows a robust consistency with whole-genome bisulfite sequencing data, and corroborates known CpG markers of age and body fluids. Our work also resulted in the identification of new sites strongly correlated with age, suggesting new possible age methylation markers. This study lays the groundwork for the systematic development of nanopore-based methodologies in both age prediction and body fluid identification, highlighting the feasibility and potential of nanopore adaptive sampling while acknowledging the need for further validation and expansion in future research.

genomics↗

bioRxiv2023

Novel insights into phage biology of the pathogen Clostridioides difficile based on the active virome

The global pathogen Clostridioides difficile is a well-studied organism, and researchers work on unravelling its fundamental virulence mechanisms and biology. Prophages have been demonstrated to influence C. difficile toxin expression and contribute to the distribution of advantageous genes. All this underlines the importance of prophages in C. difficile virulence. Although several C. difficile prophages were sequenced and characterized, investigations on the entire active virome of a strain are still missing. Phages were mainly isolated after mitomycin C-induction, which does not resemble natural stressor for C. difficile. We examined active prophages from different C. difficile strains after cultivation in the absence of mitomycin C by sequencing and characterization of particle-protected DNA. Phage particles were collected after standard cultivation, or after cultivation in the presence of the secondary bile salt deoxycholate (DCA). DCA is a natural stressor for C. difficile and a potential prophage-inducing agent. We also investigated differences in prophage activity between clinical and non-clinical C. difficile strains. Our experiments demonstrated that spontaneous prophage release is common in C. difficile, and that DCA presence induces prophages. Fourteen different, active phages were identified by this experimental procedure. We could not identify a definitive connection between clinical background and phage activity. However, one phage exhibited distinctively higher activity upon DCA-induction in the clinical strain than in the corresponding non-clinical strain, although the phage is identical in both strains. We recorded that enveloped DNA mapped to genome regions with characteristics of mobile genetic elements other than prophages. This pointed to mechanisms of DNA mobility that are not well-studied in C. difficile so far. We also detected phage-mediated lateral transduction of bacterial DNA, which is the first described case in C. difficile. This study significantly contributes to our knowledge on prophage activity in C. difficile and revealed novel aspects on C. difficile (phage) biology.

microbiology↗

bioRxiv2023

Genome-based metabolic and phylogenomic analysis of the type strains of Terrisporobacter mayombei, Terrisporobacter petrolearius and Terrisporobacter glycolicus.

To date, three validly published type strains of the genus Terrisporobacter are covered by draft genome sequences, and the genes and pathway responsible for acetogenesis have not been analyzed. Here, we report complete genome sequences of the bacterial type strains Terrisporobacter petrolearius JCM 19845T, Terrisporobacter mayombei DSM 6539T and Terrisporobacter glycolicus DSM 1288T. Functional annotation, KEGG pathway module reconstructions and screening for virulence factors were performed. Various species-specific vitamin, cofactor and amino acid auxotrophies were identified and a model for acetogenesis of Terrisporobacter was constructed. The complete genomes harbored a gene cluster for the reductive proline-dependent branch of the Stickland reaction located on an approximately 21 kb plasmid, which is exclusively found in the Terrisporobacter genus. Phylogenomic analysis of available Terrisporobacter genomes suggested a reclassification of most isolates as T. glycolicus into T. petrolearius.

genomics↗

bioRxiv2023

A patchwork pathway of apparently recent origin enables degradation of the synthetic buffer compound TRIS in bacteria

The widely used synthetic buffer compound TRIS was long considered to be biologically inert. Herein, we describe the discovery of a complete bacterial degradation pathway for TRIS. By serendipity, a Pseudomonas strain was isolated from sewage sludge that was able to grow with TRIS as only carbon and nitrogen source. Genome and transcriptome analyses revealed two adjacent gene clusters embedded in a mobile genetic element on a conjugative plasmid to be involved in TRIS degradation. Conjugational transfer of this plasmid into P. putida KT2440 enabled this strain to grow with TRIS, demonstrating that the complete TRIS degradation pathway can be transmitted by horizontal gene transfer. Heterologous gene expression revealed cluster I to encode a TRIS uptake protein, a TRIS alcohol dehydrogenase, and a TRIS aldehyde dehydrogenase, catalyzing the oxidation of TRIS into 2-hydroxymethylserine. Gene cluster II encodes a methylserine hydroxymethyltransferase and a D-serine dehydratase which plausibly catalyze the conversion of 2-hydroxymethylserine into pyruvate. Subsequent enrichments from wastewater purification systems led to the isolation of further TRIS-degrading bacteria from the Pseudomonas and Shinella genera carrying highly similar TRIS degradation gene clusters. Our data indicate that TRIS degradation evolved recently via gene recruitment and enzyme adaptation from multiple independent metabolic pathways and database searches suggest that the TRIS degradation pathway is now globally distributed. Our study illustrates how engineered environments can enhance the emergence of new microbial metabolic pathways in short evolutionary time scales. This knowledge is valuable for developing new water purification processes in times of increasing water scarcity.

microbiology↗

bioRxiv2023

The previously uncharacterized RnpM (YlxR) protein modulates the activity of ribonuclease P in Bacillus subtilis

Even though Bacillus subtilis is one of the most studied organisms, no function has been identified for about 20% of its proteins. Among these unknown proteins are several RNA- and ribosome-binding proteins suggesting that they exert functions in cellular information processing. In this work, we have investigated the RNA-binding protein YlxR. This protein is widely conserved in bacteria and strongly constitutively expressed in B. subtilis suggesting an important function. We have identified the RNA subunit of the essential RNase P as the binding partner of YlxR. The main activity of RNase P is the processing of 5 ends of pre-tRNAs. In vitro processing assays demonstrated that the presence of YlxR results in reduced RNase P activity. Chemical cross-linking studies followed by in silico docking analysis and experiments with site-directed mutant proteins suggest that YlxR binds to the region of the RNase P RNA that is important for binding and cleavage of the pre-tRNA substrate. We conclude that the YlxR protein is a novel interaction partner of the RNA subunit of RNase P that serves to finetune RNase P activity to ensure appropriate amounts of mature tRNAs for translation. We rename the YlxR protein RnpM for RNase P modulator.

microbiology↗

bioRxiv2023

Direct and culture-independent detection of low-abundant Clostridioides difficile in environmental DNA via PCR

Clostridioides difficile represents a major burden to public health. As a well-known nosocomial pathogen whose occurrence is highly associated with antibiotic treatment, most examined C. difficile strains originated from clinical specimen and were isolated under selective conditions emplyoing antibiotics. This suggests a significant bias among analysed C. difficile strains, which impedes a holistic view on this pathogen. In order to support extensive isolation of C. difficile strains from environmental samples, we designed a detection PCR that targets the hpdBCA operon and thereby identifies low abundances of C. difficile in environmental samples. Amplicon-based analyses of diverse environmental samples demonstrated that the designed PCR is highly specific for C. difficile and successfully detected C. difficile despite its absence in general 16S rRNA gene-based detection strategies. Further analyses revealed the potential of the hpdBCA detection PCR sequence for initial phylogenetic classification, which allows assessing C. difficile diversity in environmental samples via amplicon sequencing. Our findings furthermore showed that C. difficile strains isolated under antibiotic treatment from environmental samples were originally dominated by other strains according to detection PCR amplicon results. This provided evidence for selective cultivation of under-represented but antibiotic-resistant isolates. Thereby, we revealed a substantial bias in C. difficile isolation and research. ImportanceClostridioides difficile is mainly responsible for hospital-acquired infections after antibiotic treatment with serious morbidity and mortality worldwide. Research on this pathogen and its virulence focused on bacterial isolation from clinical specimen under antibiotic treatment, which implies a substantial bias in isolated strains. Comprehensive studies however require an unbiased strain collection, which is accomplished by isolation of C. difficile from diverse environmental samples and avoiding antibiotic-based enrichment strategies. Thus, isolation can significantly benefit from our C. difficile-specific detection PCR, which rapidly verifies C. difficile presence in environmental samples and further allows estimation of the C. difficile diversity by using NGS.

microbiology↗