scholarly journals Work horse strain Clostridioides difficile 630Δerm is oblivious to its anaerobic lifestyle

2020 ◽  
Author(s):  
Daniel Troitzsch ◽  
Hao Zhang ◽  
Silvia Dittmann ◽  
Dorothee Düsterhöft ◽  
Annika-Marisa Michel ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Reference Strain ◽  
Oxidative Stress Response ◽  
Dna Binding Domain ◽  
Human Pathogen ◽  
Amino Acid Exchange ◽  
Anaerobic Conditions ◽  
Clostridioides Difficile ◽  
Laboratory Reference ◽  
Acid Exchange

AbstractThe laboratory reference strain 630Δerm of the anaerobic human pathogen Clostridioides difficile is characterized by a remarkable high oxygen tolerance. We show that an amino acid exchange in the DNA binding domain of the hydrogen peroxide sensor PerR results in a constitutive derepression of PerR-controlled genes and thus in an oxidative stress response even under anaerobic conditions. This questions the model status, strain 630Δerm claims in C. difficile research.

scholarly journals A Point Mutation in the Transcriptional Repressor PerR Results in a Constitutive Oxidative Stress Response in Clostridioides difficile 630Δerm

mSphere ◽  
2021 ◽  
Vol 6 (2) ◽  
Author(s):  
Daniel Troitzsch ◽  
Hao Zhang ◽  
Silvia Dittmann ◽  
Dorothee Düsterhöft ◽  
Timon Alexander Möller ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Stress Response ◽  
Reference Strain ◽  
Transcriptional Repressor ◽  
Oxidative Stress Response ◽  
Detailed Knowledge ◽  
Single Nucleotide ◽  
Content Type ◽  
Clostridioides Difficile ◽  
Model Strain

ABSTRACT The human pathogen Clostridioides difficile has evolved into the leading cause of nosocomial diarrhea. The bacterium is capable of spore formation, which even allows survival of antibiotic treatment. Although C. difficile features an anaerobic lifestyle, we determined a remarkably high oxygen tolerance of the laboratory reference strain 630Δerm. A mutation of a single nucleotide (single nucleotide polymorphism [SNP]) in the DNA sequence (A to G) of the gene encoding the regulatory protein PerR results in an amino acid substitution (Thr to Ala) in one of the helices of the helix-turn-helix DNA binding domain of this transcriptional repressor in C. difficile 630Δerm. PerR is a sensor protein for hydrogen peroxide and controls the expression of genes involved in the oxidative stress response. We show that PerR of C. difficile 630Δerm has lost its ability to bind the promoter region of PerR-controlled genes. This results in a constitutive derepression of genes encoding oxidative stress proteins such as a rubrerythrin (rbr1) whose mRNA abundance under anaerobic conditions was increased by a factor of about 7 compared to its parental strain C. difficile 630. Rubrerythrin repression in strain 630Δerm could be restored by the introduction of PerR from strain 630. The permanent oxidative stress response of C. difficile 630Δerm observed here should be considered in physiological and pathophysiological investigations based on this widely used model strain. IMPORTANCE The intestinal pathogen Clostridioides difficile is one of the major challenges in medical facilities nowadays. In order to better combat the bacterium, detailed knowledge of its physiology is mandatory. C. difficile strain 630Δerm was generated in a laboratory from the patient-isolated strain C. difficile 630 and represents a reference strain for many researchers in the field, serving as the basis for the construction of insertional gene knockout mutants. In our work, we demonstrate that this strain is characterized by an uncontrolled oxidative stress response as a result of a single-base-pair substitution in the sequence of a transcriptional regulator. C. difficile researchers working with model strain 630Δerm should be aware of this permanent stress response.

scholarly journals Single amino acid exchange in ACTIN2 confers increased tolerance to oxidative stress in Arabidopsis der1-3 mutant

2020 ◽  
Author(s):  
Lenka Kubenova ◽  
Tomas Takac ◽  
Jozef Samaj ◽  
Miroslav Ovecka
Keyword(s):  
Oxidative Stress ◽  
Amino Acid ◽  
Actin Cytoskeleton ◽  
Actin Filaments ◽  
Plant Biomass ◽  
Plant Defence ◽  
Single Amino Acid ◽  
Single Point Mutation ◽  
Amino Acid Exchange ◽  
Acid Exchange

Single-point mutation in the ACTIN2 gene of der1-3 mutant revealed that ACTIN2 is an essential actin isovariant required for root hair tip growth, and leads to shorter, thinner and more randomly oriented actin filaments in comparison to wild-type C24 genotype. Actin cytoskeleton has been linked to plant defence against oxidative stress, but it is not clear how altered structural organization and dynamics of actin filaments may help plants to cope with oxidative stress. In this study, we characterized seed germination, root growth, plant biomass, actin organization and antioxidant activity of der1-3 mutant under oxidative stress induced by paraquat and H2O2. Under these conditions, plant growth was better in der1-3 mutant, while actin cytoskeleton in der1-3 carrying pro35S::GFP:FABD2 construct showed lower bundling rate and higher dynamicity. Biochemical analyses documented lower degree of lipid peroxidation, elevated capacity to decompose superoxide and hydrogen peroxide. These results support the view that der1-3 mutant is more resistant to oxidative stress. Single amino acid exchange in mutated ACTIN2 protein (Cys to Arg at the position 97) is topologically exposed to the protein surface and we propose that this might alter protein post-translational modifications and/or protein-protein interactions, leading to enhanced tolerance of der1-3 mutant against oxidative stress.

scholarly journals Pseudo-Outbreak ofClostridium sordelliiInfection following Probable Cross-Contamination in a Hospital Clinical Microbiology Laboratory

2010 ◽  
Vol 31 (6) ◽  
pp. 640-642 ◽  
Author(s):  
David M. Aronoff ◽  
Tennille Thelen ◽  
Seth T. Walk ◽  
Kathleen Petersen ◽  
Julia Jackson ◽  
...  
Keyword(s):  
Quality Control ◽  
Clinical Microbiology ◽  
Reference Strain ◽  
Clinical Microbiology Laboratory ◽  
Cross Contamination ◽  
Microbiology Laboratory ◽  
Human Pathogen ◽  
Anaerobic Culture ◽  
Clostridium Sordellii ◽  
Laboratory Reference

We report a pseudo-outbreak of infection caused byClostridium sordellii, an uncommon human pathogen. The pseudo-outbreak involved 6 patients and was temporally associated with a change by the clinical microbiology laboratory in the protocol of handling anaerobic culture specimens. All isolates were genetically indistinguishable from a laboratory reference strain used for quality control.

scholarly journals OxyR2 Modulates OxyR1 Activity and Vibrio cholerae Oxidative Stress Response

2017 ◽  
Vol 85 (4) ◽  
Author(s):  
Hui Wang ◽  
Nawar Naseer ◽  
Yaran Chen ◽  
Anthony Y. Zhu ◽  
Xuewen Kuai ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Stress Response ◽  
Vibrio Cholerae ◽  
Diarrheal Disease ◽  
Transcriptional Regulator ◽  
Cysteine Residue ◽  
Oxidative Stress Response ◽  
Human Pathogen ◽  
Content Type ◽  
Low Levels

ABSTRACT Bacteria have developed capacities to deal with different stresses and adapt to different environmental niches. The human pathogen Vibrio cholerae, the causative agent of the severe diarrheal disease cholera, utilizes the transcriptional regulator OxyR to activate genes related to oxidative stress resistance, including peroxiredoxin PrxA, in response to hydrogen peroxide. In this study, we identified another OxyR homolog in V. cholerae, which we named OxyR2, and we renamed the previous OxyR OxyR1. We found that OxyR2 is required to activate its divergently transcribed gene ahpC, encoding an alkylhydroperoxide reductase, independently of H2O2. A conserved cysteine residue in OxyR2 is critical for this function. Mutation of either oxyR2 or ahpC rendered V. cholerae more resistant to H2O2. RNA sequencing analyses indicated that OxyR1-activated oxidative stress-resistant genes were highly expressed in oxyR2 mutants even in the absence of H2O2. Further genetic analyses suggest that OxyR2-activated AhpC modulates OxyR1 activity by maintaining low intracellular concentrations of H2O2. Furthermore, we showed that ΔoxyR2 and ΔahpC mutants were less fit when anaerobically grown bacteria were exposed to low levels of H2O2 or incubated in seawater. These results suggest that OxyR2 and AhpC play important roles in the V. cholerae oxidative stress response.

scholarly journals The Mycoplasma genitalium MG_454 Gene Product Resists Killing by Organic Hydroperoxides

2009 ◽  
Vol 191 (21) ◽  
pp. 6675-6682 ◽  
Author(s):  
Sankaralingam Saikolappan ◽  
Smitha J. Sasindran ◽  
Hongwei D. Yu ◽  
Joel B. Baseman ◽  
Subramanian Dhandayuthapani
Keyword(s):  
Oxidative Stress ◽  
Response Regulator ◽  
Cumene Hydroperoxide ◽  
Mycoplasma Genitalium ◽  
Oxidative Stress Response ◽  
Human Pathogen ◽  
Reverse Transcription Pcr ◽  
Organic Hydroperoxides ◽  
Elevated Expression ◽  
Catalase Peroxidase

ABSTRACT Mycoplasma genitalium is the smallest self-replicating organism and a successful human pathogen associated with a range of genitourinary maladies. As a consequence of its restricted genome size, genes that are highly conserved in other bacteria are absent in M. genitalium. Significantly, genes that encode antioxidants like superoxide dismutase and catalase-peroxidase are lacking. Nevertheless, comparative genomics has revealed that MG_454 of M. genitalium encodes a protein with putative function as an organic hydroperoxide reductase (Ohr). In this study, we found that an M. genitalium transposon mutant that lacks expression of MG_454 was sensitive to killing by t-butyl hydroperoxide and cumene hydroperoxide. To understand whether this sensitivity to hydroperoxides was linked to MG_454, we cloned this gene behind an arabinose-inducible PBAD promoter in plasmid pHERD20T and transformed this construct (pHERDMG454) into a Pseudomonas aeruginosa strain having deletion in its ohr gene (ohr mutant) and showing sensitivity to organic hydroperoxides. The P. aeruginosa ohr mutant harboring pHERDMG454, when induced with arabinose, was able to reverse its sensitivity to organic hydroperoxides, thus supporting the notion that the product of MG_454 resists organic hydroperoxides in M. genitalium. Surprisingly, real-time reverse transcription-PCR showed that expression of MG_454 in M. genitalium was not elevated in response to oxidative stress but was elevated in response to physical stresses, like salt (NaCl) and heat. Although failure of MG_454 to respond to oxidative stress in M. genitalium implies the absence of a known oxidative stress response regulator in the genome of M. genitalium, elevated expression of MG_454 due to physical stress suggests its control by an unidentified regulator.

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