Physiological role and complex regulation of O-reducing enzymes in the obligate anaerobe .

Unlabelled: , the major cause of antibiotic-associated diarrhea, is a strict anaerobic, sporulating Firmicutes. However, during its infectious cycle, this anaerobe is exposed to low oxygen (O) tensions, with a longitudinal decreasing gradient along the gastrointestinal tract and a second lateral gradient with higher O tensions in the vicinity of the cells. A plethora of enzymes involved in oxidative stress detoxication has been identified in , including four O-reducing enzymes: two flavodiiron proteins (FdpA and FdpF) and two reverse rubrerythrins (revRbr1 and revRbr2).

From ubiquity to specificity: The diverse functions of bacterial thioredoxin systems.

The thioredoxin (Trx) system, found universally, is responsible for the regeneration of reversibly oxidized protein thiols in living cells. This system is made up of a Trx and a Trx reductase, and it plays a central role in maintaining thiol-based redox homeostasis by reducing oxidized protein thiols, such as disulfide bonds in proteins. Some Trxs also possess a chaperone function that is independent of thiol-disulfide exchange, in addition to their thiol-disulfide reductase activity.

SpoIVA is an essential morphogenetic protein for the formation of heat- and lysozyme-resistant spores in NBRC 14293.

is an anaerobic spore-forming bacterium genetically related to but lacks toxin genes. The sporulation mechanism and spore structures of anaerobic bacteria, including , have not been comprehensively analyzed. Based on 16S rRNA gene analysis, it has been determined that NBRC 14293 belongs to Group I.

The multiplicity of thioredoxin systems meets the specific lifestyles of Clostridia.

Cells are unceasingly confronted by oxidative stresses that oxidize proteins on their cysteines. The thioredoxin (Trx) system, which is a ubiquitous system for thiol and protein repair, is composed of a thioredoxin (TrxA) and a thioredoxin reductase (TrxB). TrxAs reduce disulfide bonds of oxidized proteins and are then usually recycled by a single pleiotropic NAD(P)H-dependent TrxB (NTR).

The absence of surface D-alanylation, localized on lipoteichoic acid, impacts the way of life and antibiotic resistance.

Introduction: The operon encodes proteins responsible for the esterification of positively charged D-alanine on the wall teichoic acids and lipoteichoic acids of Gram-positive bacteria. This structural modification of the bacterial anionic surface in several species has been described to alter the physicochemical properties of the cell-wall. In addition, it has been linked to reduced sensibilities to cationic antimicrobial peptides and antibiotics.

The Tolerance of Gut Commensal to Oxidative Stress Is Strain Dependent and Relies on Detoxifying Enzymes.

Obligate anaerobic bacteria in genus are among the most dominant taxa in the colon of healthy individuals and contribute to intestinal homeostasis. A decline in the abundance of this genus is associated with the occurrence of various gastrointestinal disorders, including inflammatory bowel diseases. In the colon, these diseases are accompanied by an imbalance between the generation and elimination of reactive oxygen species (ROS), and oxidative stress is closely linked to disruptions in anaerobiosis.

In-Depth Characterization of the Clostridioides difficile Phosphoproteome to Identify Ser/Thr Kinase Substrates.

Clostridioides difficile is the leading cause of postantibiotic diarrhea in adults. During infection, the bacterium must rapidly adapt to the host environment by using survival strategies. Protein phosphorylation is a reversible post-translational modification employed ubiquitously for signal transduction and cellular regulation.

Oxygen response and tolerance mechanisms in Clostridioides difficile.

While the gut is typically thought of as anoxic, there are two intersecting and decreasing oxygen gradients that are observed in the gut: oxygen decreases from the small to the large intestine and from the intestinal epithelium toward the colon lumen. Gut oxygen levels also increase following antibiotic induced-dysbiosis. While dysbiosis favors growth of Clostridioides difficile, the oxygen increase also causes stress to this anaerobic enteropathogen.

Responses of Clostridia to oxygen: from detoxification to adaptive strategies.

Clostridia comprise bacteria of environmental, biotechnological and medical interest and many commensals of the gut microbiota. Because of their strictly anaerobic lifestyle, oxygen is a major stress for Clostridia. However, recent data showed that these bacteria can cope with O better than expected for obligate anaerobes through their ability to scavenge, detoxify and consume O .

Metabolic adaption to extracellular pyruvate triggers biofilm formation in Clostridioides difficile.

Clostridioides difficile infections are associated with gut microbiome dysbiosis and are the leading cause of hospital-acquired diarrhoea. The infectious process is strongly influenced by the microbiota and successful infection relies on the absence of specific microbiota-produced metabolites. Deoxycholate and short-chain fatty acids are microbiota-produced metabolites that limit the growth of C.

Ser/Thr Kinase-Dependent Phosphorylation of the Peptidoglycan Hydrolase CwlA Controls Its Export and Modulates Cell Division in Clostridioides difficile.

Cell growth and division require a balance between synthesis and hydrolysis of the peptidoglycan (PG). Inhibition of PG synthesis or uncontrolled PG hydrolysis can be lethal for the cells, making it imperative to control peptidoglycan hydrolase (PGH) activity. The synthesis or activity of several key enzymes along the PG biosynthetic pathway is controlled by the Hanks-type serine/threonine kinases (STKs).

Impact of subinhibitory concentrations of metronidazole on proteome of Clostridioides difficile strains with different levels of susceptibility.

Clostridioides difficile is responsible for various intestinal symptoms from mild diarrhea to severe pseudomembranous colitis and is the primary cause of antibiotic-associated diarrhea in adults. Metronidazole was the first-line treatment for mild to moderate C. difficile infections for 30 years.

Transcriptomic and Phenotypic Analysis of a Mutant in .

SpoIIE is a phosphatase involved in the activation of the first sigma factor of the forespore, σ , during sporulation. A Δ mutant of NCIMB 8052, previously generated by CRISPR-Cas9, did not sporulate but still produced granulose and solvents. Microscopy analysis also showed that the cells of the Δ mutant are elongated with the presence of multiple septa.

Genome-Wide Transcription Start Site Mapping and Promoter Assignments to a Sigma Factor in the Human Enteropathogen .

The emerging human enteropathogen is the main cause of diarrhea associated with antibiotherapy. Regulatory pathways underlying the adaptive responses remain understudied and the global view of promoter structure is still missing. In the genome of 630, 22 genes encoding sigma factors are present suggesting a complex pattern of transcription in this bacterium.

How the Anaerobic Enteropathogen Tolerates Low O Tensions.

is a major cause of diarrhea associated with antibiotherapy. After germination of spores in the small intestine, vegetative cells are exposed to low oxygen (O) tensions. While considered strictly anaerobic, is able to grow in nonstrict anaerobic conditions (1 to 3% O) and tolerates brief air exposure indicating that this bacterium harbors an arsenal of proteins involved in O detoxification and/or protection.

-Cresol Production Is Induced by the Precursor -Hydroxyphenylacetate.

is an etiological agent for antibiotic-associated diarrheal disease. produces a phenolic compound, -cresol, which selectively targets gammaproteobacteria in the gut, facilitating dysbiosis. decarboxylates -hydroxyphenylacetate (-HPA) to produce -cresol by the action of the HpdBCA decarboxylase encoded by the operon.

Discovery of novel bacterial queuine salvage enzymes and pathways in human pathogens.

Queuosine (Q) is a complex tRNA modification widespread in eukaryotes and bacteria that contributes to the efficiency and accuracy of protein synthesis. Eukaryotes are not capable of Q synthesis and rely on salvage of the queuine base (q) as a Q precursor. While many bacteria are capable of Q de novo synthesis, salvage of the prokaryotic Q precursors preQ and preQ also occurs.

A microbiota-generated bile salt induces biofilm formation in .

is a major cause of nosocomial infections. Bacterial persistence in the gut is responsible for infection relapse; sporulation and other unidentified mechanisms contribute to this process. Intestinal bile salts cholate and deoxycholate stimulate spore germination, while deoxycholate kills vegetative cells.