Journal of Bacteriology最新文献

{"title":"<i>Staphylococcus aureus</i> encodes four differentially regulated pyruvate transporters.","authors":"Jennifer L Endres, Cleofes Sarmiento, William Xiao, Marat R Sadykov, Kenneth W Bayles, McKenzie K Lehman","doi":"10.1128/jb.00163-25","DOIUrl":"https://doi.org/10.1128/jb.00163-25","url":null,"abstract":"<p><p>The success of <i>Staphylococcus aureus</i> as a pathogen is attributable, in part, to its ability to exploit the diverse nutrient sources available during infection. Critical to this success are the pathways involving pyruvate that serve as a nexus for energy production, oxidative metabolism, and biosynthetic processes. When available, bacteria acquire pyruvate from the environment to fuel growth. Recently, LrgAB was identified as a pyruvate transporter under microaerobic conditions, leading us to speculate that <i>S. aureus</i> encodes other pyruvate transporters that are active during aerobic growth. In this study, we used the toxic pyruvate analog, 3-fluoropyruvic acid (3-FP), to isolate mutants with impaired pyruvate uptake. Whole-genome sequencing (WGS) of these mutants revealed mutations in two genes, <i>lctP</i> and <i>lldP</i>. Pyruvate uptake was significantly delayed when both <i>lctP</i> and <i>lldP</i> were inactivated. Although LldP and LctP were annotated as L-lactate permeases, ¹⁴C-pyruvate uptake assays confirmed that they function as pyruvate transporters. Despite a reduction in pyruvate uptake, the <i>lctP lldP</i> mutant did not have a growth defect in media with pyruvate, indicating that there may be an additional pyruvate importer. Reassessment of 3-FP susceptibility of the <i>lctP lldP</i> mutant revealed a zone of inhibition, confirming there is another transporter. WGS of 3-FP-resistant <i>lldP lctP</i> mutants identified B7H15_13955, an annotated MFS transporter, as the fourth transporter. Importantly, inactivation of all four genes completely eliminated pyruvate uptake, suggesting we have identified all the pyruvate transporters. These findings reveal that <i>S. aureus</i> employs multiple pyruvate transporters to support pyruvate metabolism under aerobic and anaerobic conditions.IMPORTANCEPyruvate is a key metabolite that supports bacterial energy production in many conditions. While the LrgAB system was previously implicated in pyruvate import under microaerobic conditions, the transporters that enable <i>Staphylococcus aureus</i> pyruvate acquisition during aerobic growth have remained undefined. We identified <i>lctP</i> and <i>lldP</i>, two genes annotated as lactate transporters, and B7H15_13955 as additional pyruvate transporters. Through genetic inactivation, pyruvate consumption, growth, and ¹⁴C-pyruvate uptake assays, we demonstrate that LctP, LldP, and B7H15_13955 are capable of pyruvate import, and with LrgAB, comprise a regulated network for pyruvate acquisition. This discovery fills a critical gap in our understanding of <i>S. aureus</i> metabolic adaptation and reveals that this pathogen is equipped with multiple systems to import pyruvate under diverse environmental conditions.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0016325"},"PeriodicalIF":3.0,"publicationDate":"2025-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145274792","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"<i>Enterococcus faecium sagA</i> mutants have cell envelope defects influencing antibiotic resistance and bacteriophage susceptibility.","authors":"Garima Arya, Pavan Kumar Chodisetti, Juliel Espinosa, Brian C Russo, Howard C Hang, Breck A Duerkop","doi":"10.1128/jb.00302-25","DOIUrl":"https://doi.org/10.1128/jb.00302-25","url":null,"abstract":"<p><p><i>Enterococcus faecium</i> is a gram-positive bacterium that is resident to the intestines of animals including humans. <i>E. faecium</i> is also an opportunistic pathogen that causes multidrug-resistant (MDR) infections. Bacteriophages (phages) have been proposed as therapeutics for the treatment of MDR infections; however, an obstacle for phage therapy is the emergence of phage resistance. Despite this, the development of phage resistance can impact bacterial fitness. Thus, understanding the molecular basis of fitness costs associated with phage resistance can likely be leveraged as an antimicrobial strategy. We discovered that phage-resistant <i>E. faecium</i> harbor mutations in the cell wall hydrolase gene <i>sagA</i>. SagA cleaves crosslinked peptidoglycan (PG) involved in PG remodeling. We show that mutations in <i>sagA</i> compromised <i>E. faecium</i> PG hydrolysis. One <i>sagA</i> mutant, with a defect in cell envelope integrity, increased cellular permeability, and aberrant distribution of penicillin-binding proteins, was also more sensitive to β-lactam antibiotics. These changes correspond to a growth defect where cells have abnormal division septa, membrane blebbing, and aberrant cell shape. The dysregulation of the cell envelope caused by the <i>sagA</i> mutation alters the binding of phages to the <i>E. faecium</i> cell surface, where phage infection of <i>E. faecium</i> requires phages to localize to sites of peptidoglycan remodeling. Our findings show that by altering the function of a single PG hydrolase, <i>E. faecium</i> loses intrinsic β-lactam resistance. This indicates that phage therapy could help revive certain antibiotics when used in combination.IMPORTANCE<i>Enterococcus faecium</i> causes hospital-acquired infections and is frequently resistant to frontline antibiotics, including those that target the cell wall. Bacteriophages represent a promising alternative to combat such infections. However, bacterial adaptation to phage predation often results in resistance. Such resistance is frequently accompanied by fitness trade-offs, most notably altered antibiotic susceptibility. This study provides mechanistic insights into phage resistance-associated antibiotic sensitivity in <i>E. faecium</i>. We show that phage-resistant <i>E. faecium</i> carrying a mutation in the peptidoglycan hydrolase SagA has compromised cell envelope integrity, mislocalized penicillin-binding proteins, and become sensitized to β-lactam antibiotics. These findings highlight the potential of reviving antibiotics when used in combination with phages in the clinical setting.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0030225"},"PeriodicalIF":3.0,"publicationDate":"2025-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145251229","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A flow equilibrium model controlling cytoplasmic transition metal cation pools and preventing mis-metalation as exemplified for zinc homeostasis.","authors":"Dietrich H Nies","doi":"10.1128/jb.00228-25","DOIUrl":"https://doi.org/10.1128/jb.00228-25","url":null,"abstract":"<p><p>The metal cations of the first transition period fill up their 3d orbitals from 3d⁵ for Mn(II) to 3d¹⁰ for Zn(II). Enzymes use these cations as cofactors and exploit their individual chemical features for important catalytic reactions. A prerequisite for this process is metalation of the respective enzyme with the correct cation to form metal complexes, despite the presence of other competing transition metal cations. The first step to avoid mis-metalation requires maintenance of cytoplasmic cation homeostasis, which adjusts not only the concentration of an individual cation but also that of the overall metal-ion pools. This is achieved via a flow equilibrium of metal cation uptake by importers with broad substrate specificity combined with export of unwanted cations by efflux systems. A third group of cation importers with high substrate affinity contributes under metal starvation conditions. Experimental evidence for the existence of such a flow equilibrium comes from studies using the metal-resistant beta-proteobacterium <i>Cupriavidus metallidurans</i>. Central to the calibration of the pool of an individual metal cation are the regulators that control expression of the genes for the import and export pumps. A theoretical model that deduces how metal-cation discrimination may be performed by the respective regulator and the pathway from uptake of an external cation to correct metalation provides new insight into these processes.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0022825"},"PeriodicalIF":3.0,"publicationDate":"2025-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145251261","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Functional analysis of thiamine pyrophosphate-responsive riboswitches in human bacterial pathogens of the ESKAPE group using a dual-luciferase reporter gene assay.","authors":"Anna Hübenthal, Vipul Panchal, Ruth Brenk, Matthias Mack","doi":"10.1128/jb.00308-25","DOIUrl":"https://doi.org/10.1128/jb.00308-25","url":null,"abstract":"<p><p>Thiamine pyrophosphate (TPP)-responsive riboswitches are genetic elements in bacteria that regulate the expression of genes coding for proteins involved in the biosynthesis and transport of thiamine (vitamin B₁). Following uptake, cytoplasmic thiamine is converted to TPP, which serves as a cofactor for enzymes of central metabolic pathways such as glycolysis, the tricarboxylic acid cycle, and the pentose phosphate pathway, and it is the level of TPP (and not thiamine) that is sensed by TPP riboswitches. TPP riboswitches are the most widespread riboswitches in bacteria. Their key roles in metabolism combined with their absence in humans make them potential targets for antibiotics, whereby the focus of the present study was pathogenic bacteria of the ESKAPE group: <i>Enterococcus faecium</i>, <i>Staphylococcus aureus</i>, <i>Klebsiella pneumoniae</i>, <i>Acinetobacter baumannii</i>, <i>Pseudomonas aeruginosa,</i> and <i>Enterobacter</i> spp. As a first step toward the development of novel TPP riboswitch-targeting antimicrobials to treat infections caused by ESKAPE organisms, we characterized various TPP riboswitches present in these bacteria. We developed a dual-luciferase reporter gene assay to monitor riboswitch activity and found that most of the predicted TPP riboswitches indeed were functional regulators and responded to TPP. In contrast to the <i>Escherichia coli thiC</i> TPP riboswitch, TPP riboswitches from ESKAPE bacteria were found not to respond to the synthetic thiamine analog pyrithiamine. One TPP riboswitch of <i>K. pneumoniae</i> was examined in detail with regard to the effect of pyrithiamine. Site-directed mutagenesis experiments identified specific nucleotides responsible for the non-response to pyrithiamine, and this should be useful in developing novel TPP riboswitch-targeting antimicrobials.</p><p><strong>Importance: </strong>Riboswitches are RNA molecules that control important processes in bacteria. Infections with pathogens of the ESKAPE group are common, and we are trying to find new ways to fight these bacteria. Small molecules can be designed to bind to riboswitches and optimally block their activity. In the present work, we have analyzed the thiamine pyrophosphate (TPP) riboswitches of ESKAPE pathogens with respect to small molecule binding. For this purpose, we developed a dual-luciferase reporter gene assay. Most of the predicted TPP riboswitches were indeed functional regulators and are thus targets for new anti-infectives. The small molecule pyrithiamine does not block all TPP riboswitches tested, and we found a structural basis for this behavior.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0030825"},"PeriodicalIF":3.0,"publicationDate":"2025-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145251269","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Compositional analysis of bacterial peptidoglycan: insights from peptidoglycomics into structure and function.","authors":"Erin M Anderson, Dyanne Brewer, Matthew T Sorbara, Cezar M Khursigara","doi":"10.1128/jb.00359-25","DOIUrl":"https://doi.org/10.1128/jb.00359-25","url":null,"abstract":"<p><p>Peptidoglycan (PG) is a critical component of bacterial cell walls that stabilizes the cell membrane while performing diverse physiological roles. It consists of a polysaccharide backbone cross-linked by peptide side chains forming a lattice-like sacculus that encases the entire cell. The fundamental structural component known as a muropeptide is well characterized, although modifications to this structure are common and often linked to specific physiological functions. Recent advancements in mass spectrometry and bioinformatics now facilitate a detailed examination of the global composition of this essential biopolymer. We can deepen our understanding of its dynamic roles by employing peptidoglycomics to analyze how PG composition changes in response to physiological or environmental stimuli. This minireview will discuss the key physiological functions of peptidoglycan, introduce the peptidoglycomic approach, and highlight research where an omics-based perspective could significantly benefit future studies. By enabling a comprehensive, sensitive, and non-biased detection of PG modifications, peptidoglycomics provides a powerful lens to uncover novel structural variants and functional insights that were previously inaccessible using classical methodologies.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0035925"},"PeriodicalIF":3.0,"publicationDate":"2025-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145251264","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Intracellular glutamine fluctuates with nitrogen availability and regulates <i>Mycobacterium smegmatis</i> biofilm formation.","authors":"Elizabeth Varner, Mitchell Meyer, Jocelyn Whalen, Yu-Hao Wang, Carlos Rodriguez, Ifra Malik, Steven J Mullet, Stacy L Gelhaus, William H DePas","doi":"10.1128/jb.00252-25","DOIUrl":"https://doi.org/10.1128/jb.00252-25","url":null,"abstract":"<p><p>Nontuberculous mycobacteria (NTM) can form biofilms during human infection and in household plumbing systems, so understanding biofilm regulation could help us better treat and prevent NTM infections. Glucose drives NTM aggregation <i>in vitro</i>, and ammonium inhibits it, but the regulatory systems controlling this early step in biofilm formation are not understood. Here, in the model NTM <i>Mycobacterium smegmatis</i>, we show that multiple carbon and nitrogen sources have similar impacts on aggregation as glucose and ammonium , suggesting that the response to these nutrients is general and likely sensed through downstream, integrated signals. Next, we performed a transposon screen in <i>M. smegmatis</i> to uncover these putative regulatory nodes. Our screen revealed that mutating specific genes in the purine and pyrimidine biosynthesis pathways caused an aggregation defect, but supplementing with adenosine and guanosine had no impact on aggregation either in a <i>purF</i> mutant or WT. Realizing that the only genes we hit in purine or pyrimidine biosynthesis were those that utilized glutamine as a nitrogen donor, we pivoted to the hypothesis that intracellular glutamine could be a nitrogen-responsive node affecting aggregation. We tested this hypothesis in a defined M63 medium using targeted mass spectrometry. Indeed, intracellular glutamine increased with nitrogen availability and correlated with planktonic growth. Furthermore, a <i>garA</i> mutant, which has an artificially expanded glutamine pool in the growth phase, grew solely as planktonic cells even without nitrogen supplementation. Altogether, these results establish that intracellular glutamine controls <i>M. smegmatis</i> aggregation, and they introduce flux-dependent sensors as key components of the NTM biofilm regulatory system.IMPORTANCEA subset of nontuberculous mycobacteria (NTM), including <i>Mycobacterium abscessus</i>, are opportunistic pathogens that can cause severe pulmonary infections. Biofilm formation renders <i>M. abscessus</i> more tolerant to antibiotics; hence, the ability to inhibit NTM biofilm formation could help us better prevent and treat NTM infections. However, the regulatory systems controlling NTM biofilm formation, which could include targets for anti-biofilm therapeutics, are poorly understood. The significance of this work is that it reveals intracellular glutamine as an important node controlling the initiation of biofilm formation in the model NTM <i>Mycobacterium smegmatis</i>. Building on this foundation, future studies will investigate how NTM biofilms can be dispersed by altering glutamine levels and will describe how NTM translates intracellular glutamine to the alteration of surface adhesins.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0025225"},"PeriodicalIF":3.0,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145251216","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"<i>Pseudomonas aeruginosa-</i>secreted respiratory toxin HQNO triggers fatty acid accumulation in respiring <i>Staphylococcus aureus,</i> decreasing SaeRS-dependent transcriptional regulation.","authors":"Franklin Roman-Rodriguez, Nupur Tyagi, Hassan Al-Tameemi, Jeffrey M Boyd","doi":"10.1128/jb.00395-25","DOIUrl":"https://doi.org/10.1128/jb.00395-25","url":null,"abstract":"<p><p><i>Staphylococcus aureus</i> and <i>Pseudomonas aeruginosa</i> are the two pathogens that colonize the airway of cystic fibrosis patients. As patients age, <i>P. aeruginosa</i> outcompetes <i>S. aureus</i> to become the predominant organism in the airway, which overlaps with worsening symptoms. This inverse correlation is partly due to the ability of <i>P. aeruginosa</i> to secrete secondary metabolites and virulence factors that are antagonistic to the host cells and other bacteria present. Several of these secondary metabolites inhibit <i>S. aureus</i> respiration. SaeRS is a two-component regulatory system that promotes the transcription of numerous virulence genes in <i>S. aureus</i>. The transcription of SaeRS-regulated genes is decreased as a function of respiratory status. The accumulation of intracellular fatty acids also negatively impacts the activity of SaeRS. Incubation of <i>S. aureus</i> with <i>P. aeruginosa</i> cell-free conditioned culture medium decreased the transcriptional output of the SaeRS system. Further analyses using <i>P. aeruginosa</i> mutant strains and chemical genetics determined that 2-heptyl-4-quinolone N-oxide (HQNO) was responsible for the SaeRS-dependent changes in gene regulation. Treatment with HQNO increased the abundance of cell-associated fatty acids. HQNO inhibits cell respiration, and the SaeRS system did not respond to HQNO treatment in a respiration-impaired <i>S. aureus</i> strain, which accumulates fatty acids. The data presented are consistent with a working model wherein treatment of <i>S. aureus</i> with HQNO inhibits respiration, increasing free fatty acid accumulation, which negatively impacts SaeRS signaling. This results in decreased expression of the SaeRS regulon, which has significant roles in pathogenesis.IMPORTANCE<i>Pseudomonas aeruginosa</i> and <i>Staphylococcus aureus</i> are often co-isolated from the airways of cystic fibrosis patients. <i>P. aeruginosa</i> secretes non-essential metabolites that alter <i>S. aureus</i> physiology, providing <i>P. aeruginosa</i> with a competitive advantage. <i>S. aureus</i> can adapt to the presence of these metabolites, but the genetic mechanisms used to sense these <i>P. aeruginosa</i>-produced metabolites and/or the induced physiological changes are largely unknown. The <i>S. aureus</i> SaeRS two-component regulatory system positively regulates the expression of various virulence factors, including toxins and proteases, that facilitate adaptation to and survival in hostile host environments. This study demonstrates that the <i>P. aeruginosa</i>-produced respiratory toxin 2-heptyl-4-quinolone N-oxide inhibits respiration, decreasing the transcription of SaeRS-regulated genes and thereby decreasing virulence factor production. These findings could be exploited to decrease the ability of <i>S. aureus</i> to express virulence factors in various infection settings.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0039525"},"PeriodicalIF":3.0,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145251292","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The effect of MurM and a branched cell wall structure on penicillin resistance in <i>Streptococcus pneumoniae</i>.","authors":"Ragnhild Sødal Gjennestad, Maria Victoria Heggenhougen, Anja Ruud Winther, Johanne Moldstad, Vegard Eldholm, Morten Kjos, Leiv Sigve Håvarstein, Daniel Straume","doi":"10.1128/jb.00141-25","DOIUrl":"https://doi.org/10.1128/jb.00141-25","url":null,"abstract":"<p><p>The aminoacyltransferase MurM is an important penicillin resistance determinant in <i>Streptococcus pneumoniae</i>. This enzyme attaches a serine or alanine to the side chain of lysine, the third residue of the pentapeptide of lipid II, resulting in branched muropeptides that can be crosslinked to stem peptides in peptidoglycan by penicillin binding proteins (PBPs). Deletion of <i>murM</i> results in only linear muropeptides, and more importantly, a significant reduction in resistance. Highly penicillin-resistant pneumococci express low-affinity PBPs, an altered MurM protein, and possess a highly branched cell wall. It has therefore been hypothesized that MurM, and thus branched muropeptides, are essential for resistance because they are better substrates for low-affinity PBPs. In this study, we found that neither the version of <i>murM</i> nor elevated levels of cell wall branching affected resistance levels. To further support this, we investigated whether branched muropeptide substrates compete better than linear versions with penicillin at the active site of low-affinity PBPs and quantified changes to the stem peptide composition of the resistant Pen6 strain in response to subinhibitory concentrations of penicillin. We found that the level of cell wall branching decreased during penicillin exposure. Together, our results do not support the idea that elevated levels of branched muropeptides (more active MurM) are important for either the function of low-affinity PBPs or the cell's response to penicillin. Nevertheless, since a functional MurM enzyme is important for resistance, we speculate that it might indirectly influence other functions related to cell wall synthesis and remodeling needed for a resistant phenotype.IMPORTANCEA fundamental understanding of the mechanisms behind antibiotic resistance is needed to find strategies to extend the clinical relevance of existing drugs. This study explores the relationship between cell wall composition and penicillin resistance in <i>Streptococcus pneumoniae</i>. Here, we confirm that branched peptide crosslinks in the cell wall are crucial for resistance but found no correlation between elevated branching levels and resistance. Our data suggest that the function of low-affinity penicillin binding proteins is not influenced by the lack of branched cell wall precursors. Instead, a branched cell wall might contribute to resistance via other cell wall biosynthesis and remodeling mechanisms. These insights could offer new perspectives on why a branched cell wall is important for penicillin resistance in pneumococci.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0014125"},"PeriodicalIF":3.0,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145251290","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A clarifying perspective on bacterial pseudo-receiver domains.","authors":"Robert B Bourret, Emily N Kennedy, Rita Tamayo, Clay A Foster","doi":"10.1128/jb.00261-25","DOIUrl":"https://doi.org/10.1128/jb.00261-25","url":null,"abstract":"<p><p>Two-component regulatory systems typically consist of a sensor kinase and a response regulator. Phosphorylation of the receiver domain controls response regulator activity. Pseudo-receivers (PsRs) are identified computationally as receivers but lack key residues to catalyze phosphotransfer reactions. Although PsRs are common, molecular mechanisms that activate and inactivate bacterial PsRs remain a mystery. We untangled four potentially related but distinct concepts: bacterial PsRs, receivers with regulatory mechanisms in addition to phosphorylation, receivers that are active without phosphorylation, and orphan receivers without an obvious partner sensor kinase. We also analyzed bacterial PsR sequences and structures to identify regions of likely functional significance.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0026125"},"PeriodicalIF":3.0,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145251213","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Control of the <i>Pseudomonas aeruginosa</i> LbcA•CtpA proteolytic complex and its substrates.","authors":"Kévin J Rome, Andrew J Darwin","doi":"10.1128/jb.00169-25","DOIUrl":"https://doi.org/10.1128/jb.00169-25","url":null,"abstract":"<p><p><i>Pseudomonas aeruginosa</i> is a highly adaptable bacterial pathogen with a resilient cell envelope. This envelope must be elongated as cells grow, which requires coordinated biosynthesis of the inner and outer membranes and the peptidoglycan cell wall. Cell wall endopeptidases are essential to expand the peptidoglycan sacculus, and the LbcA•CtpA proteolytic complex controls the activity of multiple endopeptidases by degrading them. Here, we report an investigation into control of the LbcA•CtpA proteolytic complex and its substrates. LbcA and CtpA levels were unaffected by growth rate, which corresponded with constitutive expression of their genes. For CtpA, this was explained by its arrangement in a complex operon containing an internal <i>ctpA</i> promoter. Despite constitutive LbcA and CtpA production, the LbcA•CtpA substrate levels were higher when cells were growing rapidly. In most cases, this correlated with modestly higher substrate gene expression in the exponential phase. However, most of the control came from reduced CtpA activity when cells were growing rapidly. Our data suggest that CtpA activity might be affected by phospholipid transport and related processes in the cell envelope. A similar phenomenon was reported to affect the <i>Escherichia coli</i> NlpI•Prc complex, even though there are major sequence and structural differences between the NlpI•Prc and LbcA•CtpA complexes. This makes it likely that growth-rate-dependent autolysin control by these proteolytic complexes is widely conserved, even if they are composed of non-orthologous proteins in some cases.IMPORTANCECarboxyl-terminal processing proteases occur in all domains of life. Some are associated with bacterial virulence, including <i>P. aeruginosa</i> CtpA, which works with the outer membrane lipoprotein LbcA to degrade cell wall endopeptidases. We report that the LbcA•CtpA complex activity is coordinated with growth rate, ensuring appropriate levels of its substrates for cell wall expansion. The mechanism appears to be connected to phospholipid transport, much like a phenomenon reported for <i>Escherichia coli</i> NlpI•Prc complex. However, the NlpI•Prc and LbcA•CtpA complexes are not orthologs. Therefore, growth-rate-dependent control by analogous but dissimilar complexes might be a widely conserved mechanism, and one that could perhaps be targeted for therapeutic intervention.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0016925"},"PeriodicalIF":3.0,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145251258","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}