Journal of Bacteriology最新文献

{"title":"The extracellular segment of CroS is not required for sensing but fine-tunes the magnitude of CroS signaling to regulate cephalosporin resistance in <i>Enterococcus faecalis</i>.","authors":"Sarah B Timmler, Christopher J Kristich","doi":"10.1128/jb.00274-24","DOIUrl":"10.1128/jb.00274-24","url":null,"abstract":"<p><p>Enterococci are Gram-positive bacteria that colonize the gastrointestinal tract. Clinically relevant enterococci are intrinsically resistant to antibiotics in the cephalosporin family, and prior therapy with cephalosporins is a major risk factor for the acquisition of an enterococcal infection. One important determinant of intrinsic cephalosporin resistance in enterococci is the two-component signal transduction system CroS/R. The CroS sensor kinase senses cephalosporin-induced cell wall stress to become activated and phosphorylates its cognate response regulator CroR, thereby enhancing CroR-dependent gene expression to drive cephalosporin resistance. CroS possesses a short (~30 amino acids) extracellular segment between its two transmembrane domains near the N-terminus, but whether this extracellular segment is important for sensing cephalosporin stress, or possesses any other function, has remained unknown. Here, we explored the role of the CroS extracellular segment through mutagenesis and functional studies. We found that mutations in the CroS extracellular segment biased CroS to adopt a more active state during ceftriaxone stress, which led to an increase in CroR-dependent gene expression and hyper-resistance to ceftriaxone. Importantly, these mutants still responded to ceftriaxone-mediated stress by enhancing CroS activity, indicating that the extracellular segment of CroS does not directly bind a regulatory ligand. Overall, our results suggest that although the extracellular segment of CroS does not directly bind a regulatory ligand, it can modulate the magnitude of CroS signaling for phosphorylation of CroR to regulate cephalosporin resistance through the resulting changes in CroR-dependent gene expression.</p><p><strong>Importance: </strong>Clinically relevant enterococci are intrinsically resistant to antibiotics in the cephalosporin family. The CroS sensor kinase senses cephalosporin-induced cell wall stress to trigger signaling that drives cephalosporin resistance, but the mechanism by which CroS senses stress is unknown. We report the first functional characterization of the CroS extracellular segment, revealing that mutations in the extracellular segment did not prevent CroS from responding to cell wall stress but instead biased CroS to adopt a more active state during cephalosporin stress that led to an increase in CroR-dependent gene expression and hyper-resistance to ceftriaxone. Overall, our results suggest that the extracellular segment of CroS does not directly bind to a regulatory ligand but that it can modulate the magnitude of CroS signaling.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0027424"},"PeriodicalIF":2.7,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11580428/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142500954","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"CodY controls the SaeR/S two-component system by modulating branched-chain fatty acid synthesis in <i>Staphylococcus aureus</i>.","authors":"Shahad Alqahtani, Dennis A DiMaggio, Shaun R Brinsmade","doi":"10.1128/jb.00191-24","DOIUrl":"10.1128/jb.00191-24","url":null,"abstract":"<p><p><i>Staphylococcus aureus</i> is a Gram-positive, opportunistic human pathogen that is a leading cause of skin and soft tissue infections and invasive disease worldwide. Virulence in this bacterium is tightly controlled by a network of regulatory factors. One such factor is the global regulatory protein CodY. CodY links branched-chain amino acid sufficiency to the production of surface-associated and secreted factors that facilitate immune evasion and subversion. Our previous work revealed that CodY regulates virulence factor gene expression indirectly in part by controlling the activity of the SaeRS two-component system (TCS). While this is correlated with an increase in membrane anteiso-15:0 and -17:0 branched-chain fatty acids (BCFAs) derived from isoleucine, the true mechanism of control has remained elusive. Herein, we report that CodY-dependent regulation of SaeS sensor kinase activity requires BCFA synthesis. During periods of nutrient sufficiency, BCFA synthesis and Sae TCS activity are kept relatively low by CodY-dependent repression of the <i>ilv-leu</i> operon and the isoleucine-specific permease gene <i>brnQ2</i>. In a <i>codY</i> null mutant, which simulates extreme nutrient limitation, de-repression of <i>ilv-leu</i> and <i>brnQ2</i> directs the synthesis of enzymes in redundant <i>de novo</i> and import pathways to upregulate production of BCFA precursors. Overexpression of <i>brnQ2,</i> independent of CodY, is sufficient to increase membrane anteiso BCFAs, Sae-dependent promoter activity, and SaeR ~<i>P</i> levels. Our results further clarify the molecular mechanisms by which CodY controls virulence in <i>S. aureus</i>.IMPORTANCEExpression of bacterial virulence genes often correlates with the exhaustion of nutrients, but how the signaling of nutrient availability and the resulting physiological responses are coordinated is unclear. In <i>S. aureus,</i> CodY controls the activity of two major regulators of virulence-the Agr and Sae two-component systems (TCSs)-by unknown mechanisms. This work identifies a mechanism by which CodY controls the activity of the sensor kinase SaeS by modulating the levels of anteiso branched-chain amino acids that are incorporated into the membrane. Understanding the mechanism adds to our understanding of how bacterial physiology and metabolism are linked to virulence and underscores the role virulence in maintaining homeostasis. Understanding the mechanism also opens potential avenues for targeted therapeutic strategies against <i>S. aureus</i> infections.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0019124"},"PeriodicalIF":2.7,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11580410/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142390793","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Environmental alkalization suppresses deployment of virulence strategies in <i>Pseudomonas syringae</i> pv. <i>tomato</i> DC3000.","authors":"Zichu Yang, Haibi Wang, Robert Keebler, Amelia Lovelace, Hsiao-Chun Chen, Brian Kvitko, Bryan Swingle","doi":"10.1128/jb.00086-24","DOIUrl":"10.1128/jb.00086-24","url":null,"abstract":"<p><p>Plant pathogenic bacteria encounter a drastic increase in apoplastic pH during the early stages of plant immunity. The effects of alkalization on pathogen-host interactions have not been comprehensively characterized. Here, we used a global transcriptomic approach to assess the impact of environmental alkalization on <i>Pseudomonas syringae</i> pv. <i>tomato</i> DC3000 <i>in vitro</i>. In addition to the Type 3 Secretion System, we found expression of genes encoding other virulence factors such as iron uptake and coronatine biosynthesis to be strongly affected by environmental alkalization. We also found that the activity of AlgU, an important regulator of virulence gene expression, was induced at pH 5.5 and suppressed at pH 7.8, which are pH levels that this pathogen would likely experience before and during pattern-triggered immunity, respectively. This pH-dependent control requires the presence of periplasmic proteases, AlgW and MucP, that function as part of the environmental sensing system that activates AlgU in specific conditions. This is the first example of pH-dependency of AlgU activity, suggesting a regulatory pathway model where pH affects the proteolysis-dependent activation of AlgU. These results contribute to deeper understanding of the role apoplastic pH has on host-pathogen interactions.IMPORTANCEPlant pathogenic bacteria, like <i>Pseudomonas syringae</i>, encounter many environmental changes including oxidative stress and alkalization during plant immunity, but the ecological effects of the individual responses are not well understood. In this study, we found that transcription of many previously characterized virulence factors in <i>P. syringae</i> pv. <i>tomato</i> DC3000 is downregulated by the level of environmental alkalization these bacteria encounter during the early stages of plant immune activation. We also report for the first time the sigma factor AlgU is post-translationally activated by low environmental pH through its natural activation pathway, which partially accounts for the expression Type 3 Secretion System virulence genes at acidic pH. The results of this study demonstrate the importance of extracellular pH on global regulation of virulence-related gene transcription in plant pathogenic bacteria.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0008624"},"PeriodicalIF":2.7,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11580431/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142500953","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"<i>E. coli</i> cells advance into phase-separated (biofilm-simulating) extracellular polymeric substance containing DNA, HU, and lipopolysaccharide.","authors":"Archit Gupta, Purnananda Guptasarma","doi":"10.1128/jb.00309-24","DOIUrl":"10.1128/jb.00309-24","url":null,"abstract":"<p><p>We have previously shown that the nucleoid-associated protein, HU, uses its DNA-binding surfaces to bind to bacterial outer-membrane lipopolysaccharide (LPS), causing HU to act as a glue aiding the adherence of DNA to bacteria, e.g., in biofilms. We have also previously shown that HU and DNA coacervate into a state of liquid-liquid phase separation (LLPS), within bacterial cells and also <i>in vitro</i>. Here, we show that HU and free LPS (which is ordinarily shed by bacteria) also condense into a state of phase separation. Coacervates of HU, DNA, and free LPS are less liquid-like than coacervates of HU and DNA. <i>Escherichia coli</i> cells bearing LPS on their surfaces are shown to adhere to (as well as advance into) coacervates of HU and DNA. HU appears to play a role, therefore, in maintaining both intracellular and extracellular states of phase separation with DNA that are compatible with LPS and LPS-bearing <i>E. coli,</i> with LPS determining the liquidity of the biofilm-simulating coacervate.</p><p><strong>Importance: </strong>Understanding the constitution and behavior of biofilms is crucial to understanding how to deal with persistent biofilms. This study, together with other recent studies from our group, elucidates a novel aspect of the extracellular polymeric substance (EPS) of <i>Escherichia coli</i> biofilms, by creating a simulacrum of the EPS and then demonstrating that its formation involves liquid-liquid phase separation (LLPS) of HU, DNA, and lipopolysaccharide (LPS) components, with LPS determining the liquidity of this EPS simulacrum. The findings provide insight into the nature of biofilms and into how the interplay of HU, DNA, and LPS could modulate the structural integrity and functional dynamics of biofilms.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0030924"},"PeriodicalIF":2.7,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11580401/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142500952","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Corrinoid salvaging and cobamide remodeling in bacteria and archaea.","authors":"Elizabeth A Villa, Jorge C Escalante-Semerena","doi":"10.1128/jb.00286-24","DOIUrl":"10.1128/jb.00286-24","url":null,"abstract":"<p><p>Cobamides (Cbas) are cobalt-containing cyclic tetrapyrroles used by cells from all domains of life as co-catalyst of diverse reactions. There are several structural features that distinguish Cbas from one another. The most relevant of those features discussed in this review is the lower ligand, which is the nucleobase of a ribotide located in the lower face of the cyclic tetrapyrrole ring. The above-mentioned ribotide is known as the nucleotide loop, which is attached to the ring by a short linker. In Cbas, the nucleobase of the ribotide can be benzimidazole or derivatives of it, purine or derivatives of it, or phenolic compounds. Given the importance of Cbas in prokaryotic metabolism, it is not surprising that prokaryotes have evolved enzymes that cleave part or the entire nucleotide loop. This function is advantageous when Cbas contain nucleobases that somehow interfere with the function of Cba-dependent enzymes in the organism. After cleavage, Cbas are rebuilt via the nucleotide loop assembly (NLA) pathway, which includes enzymes that activate the nucleobase and the ring intermediate, followed by condensation of activated intermediates and a final dephosphorylation reaction. This exchange of nucleobases is known as Cba remodeling. The NLA pathway is used to salvage Cba precursors from the environment.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0028624"},"PeriodicalIF":2.7,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11580458/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142466180","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Impact of high-speed nanodroplets on various pathogenic bacterial cell walls.","authors":"Yurina Tamura, Masato Kawamura, Takehiko Sato, Tomoki Nakajima, Siwei Liu, Takumi Sato, Shigeru Fujimura","doi":"10.1128/jb.00139-24","DOIUrl":"10.1128/jb.00139-24","url":null,"abstract":"<p><p>Although the development of disinfection technologies with novel mechanisms has stagnated, we demonstrate the bactericidal effects and mechanisms of high-speed nanodroplet generation technology. The first development of this technology in 2017 gushes out a water droplet of 10 nm in size at 50 m/s; however, the target surface does not become completely wet. Nanodroplets were exposed to biofilm models of <i>Staphylococcus aureus</i>, <i>Pseudomonas aeruginosa</i>, <i>Escherichia coli</i>, and <i>Serratia marcescens</i>. This phenomenon was verified when the nanodroplets collide with the surface of the bacteria at an impact pressure of ~75 MPa. <i>S. aureus</i> was exposed to nanodroplets for 30 seconds at 75 MPa, which exploded the bacterial body and completely sterilized. Eighteen MPa damaged the bacterial surface, causing peptidoglycan leakage. <i>S. aureus</i> was repaired and survives in this state. In contrast, in Gram-negative bacteria, nanodroplets with 18 MPa penetrated some biofilm-forming bacteria but did not hit all of them, and the viable count was not significantly reduced. Although all three bacterial species were completely sterilized at 75 MPa, the disinfectant effect was affected by the biomass of the biofilm formed. In summary, our findings prove that nanodroplets at 18 MPa on the bacterial surface were ineffective in killing bacteria, whereas at 75 MPa, all four bacterial species were completely sterilized. The disinfection mechanism involved a high-velocity collision of nanodroplets with the bacteria, physically destroying them. Our results showed that disinfection using this technology could be an innovative method that is completely different from existing disinfection techniques.</p><p><strong>Importance: </strong>Although existing disinfection techniques demonstrate bactericidal effects through chemical reactions, concerns regarding human toxicity and environmental contamination have been raised. To the best of our knowledge, this study is the first in the world to reveal that the use of this technology, with nanodroplets of less than 100 nm, can destroy and sterilize bacterial cells by colliding with biofilm-forming bacteria at 75 MPa. Furthermore, because this technology uses only water, it can solve the problems of human toxicity and environmental contamination caused by existing disinfection techniques. Because of its minimal water usage, it can be employed for sanitation worldwide without being limited to specific regions. Our report proposes an unprecedented physical disinfection approach that utilizes a high-speed nanodroplet generation technology.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0013924"},"PeriodicalIF":2.7,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11580407/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142390794","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Identification of an ArgR-controlled promoter within the outermost region of the IS<i>10</i>R mobile element.","authors":"Oscar J Vázquez-Ciros, Adrián F Alvarez, Dimitris Georgellis","doi":"10.1128/jb.00264-24","DOIUrl":"10.1128/jb.00264-24","url":null,"abstract":"<p><p>The transposon Tn<i>10</i> is a prevalent composite element often detected in enteric bacteria, including those obtained from clinical samples. The Tn<i>10</i> is flanked by two IS<i>10</i> elements that work together in mediating transposition. IS<i>10</i>-right (IS<i>10</i>R) promotes transposition, while IS<i>10</i>-left lacks a functional transposase and cannot transpose independently. IS<i>10</i>R contains a weak promoter crucial for transposase transcription (pIN), along with two outward-oriented promoters, pOUT and OUTIIp, which may influence the expression of adjacent genes flanking the transposition site. Here, we report the identification of a novel outward-facing promoter, pOUT70, and a functional translation initiation region (TIR) within the last 70 nucleotides of IS<i>10</i>R. Furthermore, we show that pOUT70 is negatively regulated by ArgR and positively controlled by IHF, and we demonstrate that pOUT70 enables growth phase-dependent expression of a truncated yet constitutively active version of the histidine kinase BarA. These findings underscore the significance of IS elements in enhancing downstream gene expression, and highlights the role of outward-facing promoters in derepressing virulence factors or acquiring antibiotic resistance.</p><p><strong>Importance: </strong>Mobile genetic elements are small DNA fragments that can relocate within the genome, causing either gene inactivation or enhanced gene expression. Our research identified a new functional promoter and mRNA translation region within the IS10R element, which is part of the widely distributed <i>Tn10</i> transposon. We found that the global regulators ArgR and IHF control the activity of this promoter. Additionally, insertion of this mini-<i>Tn10</i> derivative into the <i>barA</i> gene resulted in the expression of a truncated but constitutive active form of the BarA sensor kinase. Overall, our work sheds light on how mobile genetic elements could impact the physiology and virulence of opportunistic pathogenic bacteria.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0026424"},"PeriodicalIF":2.7,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11580472/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142545639","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Identification of a novel NADPH generation reaction in the pentose phosphate pathway in <i>Escherichia coli</i> using mBFP.","authors":"Koichiro Ueno, Shogo Sawada, Mai Ishibashi, Yoshiki Kanda, Hiroshi Shimizu, Yoshihiro Toya","doi":"10.1128/jb.00276-24","DOIUrl":"10.1128/jb.00276-24","url":null,"abstract":"<p><p>NADPH is a redox cofactor that drives the anabolic reactions. Although major NADPH generation reactions have been identified in <i>Escherichia coli</i>, some minor reactions have not been identified. In the present study, we explored novel NADPH generation reactions by monitoring the fluorescence dynamics after the addition of carbon sources to starved cells, using a metagenome-derived blue fluorescent protein (mBFP) as an intracellular NADPH reporter. Perturbation analyses were performed on a glucose-6-phosphate isomerase (PGI) deletion strain and its parental strain. Interestingly, mBFP fluorescence increased not only in the parental strain but also in the ΔPGI strain after the addition of xylose. Because the ΔPGI strain cannot metabolize xylose through the oxidative pentose phosphate pathway, this suggests that an unexpected NADPH generation reaction contributes to an increase in fluorescence. To unravel this mystery, we deleted the NADPH generation enzymes including transhydrogenase, isocitrate dehydrogenase, NADP⁺-dependent malic enzyme, glucose-6-phosphate dehydrogenase (G6PDH), and 6-phosphogluconate dehydrogenase (6PGDH) in the ΔPGI strain, and revealed that G6PDH and 6PGDH contribute to an increase in fluorescence under xylose conditions. <i>In vitro</i> assays using purified enzymes showed that G6PDH can produce NADPH using erythrose-4-phosphate (E4P) as a substitute for glucose-6-phosphate. Because the <i>Km</i> (0.65 mM) for E4P was much higher than the reported intracellular E4P concentrations in <i>E. coli</i>, little E4P must be metabolized through this bypass in the parental strain. However, the flux would increase when E4P accumulates in the cells owing to genetic modifications. This finding provides a metabolic engineering strategy for generating NADPH to produce useful compounds using xylose as a carbon source.IMPORTANCEBecause NADPH is consumed during the synthesis of various useful compounds, enhancing NADPH regeneration is highly desirable in metabolic engineering. In this study, we explored novel NADPH generation reactions in <i>Escherichia coli</i> using a fluorescent NADPH reporter and found that glucose-6-phosphate dehydrogenase can produce NADPH using erythrose-4-phosphate as a substrate under xylose conditions. Xylose is an abundant sugar in nature and is an attractive carbon source for bioproduction. Therefore, this finding contributes to novel pathway engineering strategies using a xylose carbon source in <i>E. coli</i> to produce useful compounds that consume NADPH for their synthesis.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0027624"},"PeriodicalIF":2.7,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11580446/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142466182","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Discovery and synthesis of leaderless bacteriocins from the Actinomycetota.","authors":"David Hourigan, Felipe Miceli de Farias, Paula M O'Connor, Colin Hill, R Paul Ross","doi":"10.1128/jb.00298-24","DOIUrl":"10.1128/jb.00298-24","url":null,"abstract":"<p><p>Leaderless bacteriocins are a unique class of bacteriocins that possess antimicrobial activity after translation and have few cases of documented resistance. Aureocin A53 and lacticin Q are considered two of the most well-studied leaderless bacteriocins. Here, we used <i>in silico</i> genome mining to search for novel aureocin A53-like leaderless bacteriocins in GenBank and MGnify. We identified 757 core peptides across 430 genomes with 75 species found currently without characterized leaderless bacteriocin production. These include putative novel species containing bacteriocin gene clusters (BGCs) from the genera <i>Streptomyces</i> (sp. NBC_00237) and <i>Agrococcus</i> (sp. SL85). To date, all characterized leaderless bacteriocins have been found within the phylum Bacillota, but this study identified 97 core peptides within the phylum Actinomycetota. Members of this phylum are traditionally associated with the production of antibiotics, such is the case with the genus <i>Streptomyces</i>. Actinomycetota is an underexplored phylum in terms of bacteriocin production with no characterized leaderless bacteriocin production to date. The two novel leaderless bacteriocins arcanocin and arachnicin from Actinomycetota members <i>Arcanobacterium</i> sp. and <i>Arachnia</i> sp., respectively, were chemically synthesized and antimicrobial activity was verified. These peptides were encoded in human gut (PRJNA485056) and oral (PRJEB43277) microbiomes, respectively. This research highlights the biosynthetic potential of Actinomycetota in terms of leaderless bacteriocin production and describes the first antimicrobial peptides encoded in the genera <i>Arcanobacterium</i> and <i>Arachnia</i>.IMPORTANCEBacteriocins are gathering attention as alternatives to current antibiotics given the increasing incidence of antimicrobial resistance. Leaderless bacteriocins are considered a commercially attractive subclass of bacteriocins due to the ability to synthesize active peptide and low levels of documented resistance. Therefore, in this work, we mined publicly available data to determine how widespread and diverse leaderless bacteriocins are within the domain of bacteria. Actinomycetota, known for its antibiotic producers but lacking described and characterized bacteriocins, proved to be a rich source of leaderless bacteriocins-97 in total. Two such peptides, arcanocin and arachnicin, were chemically synthesized and have antimicrobial activity. These bacteriocins may provide a novel source of novel antimicrobials that could aid in the development of future alternative antimicrobials and highlight that the Actinomycetota are an underexplored resource of bacteriocin peptides.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0029824"},"PeriodicalIF":2.7,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11580447/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142466181","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A flagellar accessory protein links chemotaxis to surface sensing.","authors":"Rachel I Salemi, Ana K Cruz, David M Hershey","doi":"10.1128/jb.00404-24","DOIUrl":"10.1128/jb.00404-24","url":null,"abstract":"<p><p>Bacteria find suitable locations for colonization by sensing and responding to surfaces. Complex signaling repertoires control surface colonization, and surface contact sensing by the flagellum plays a central role in activating colonization programs. <i>Caulobacter crescentus</i> adheres to surfaces using a polysaccharide adhesin called the holdfast. In <i>C. crescentus</i>, disruption of the flagellum through interactions with a surface or mutation of flagellar genes increases holdfast production. Our group previously identified several <i>C. crescentus</i> genes involved in flagellar surface sensing. One of these, <i>fssF</i>, codes for a protein with homology to the flagellar C-ring protein FliN. We show here that a fluorescently tagged FssF protein localizes to the flagellated pole of the cell and requires all components of the flagellar C-ring for proper localization, supporting the model that FssF associates with the C-ring. Deleting <i>fssF</i> results in a severe motility defect, which we show is due to a disruption of chemotaxis. Epistasis experiments demonstrate that <i>fssF</i> promotes adhesion through a stator-dependent pathway when late-stage flagellar mutants are disrupted. Separately, we find that disruption of chemotaxis through deletion of <i>fssF</i> or other chemotaxis genes results in a hyperadhesion phenotype. Key genes in the surface sensing network (<i>pleD</i>, <i>motB</i>, and <i>dgcB</i>) contribute to both ∆<i>flgH-</i>dependent and ∆<i>fssF-</i>dependent hyperadhesion, but these genes affect adhesion differently in the two hyperadhesive backgrounds. Our results support a model in which the stator subunits of the flagella incorporate both mechanical and chemical signals to regulate adhesion.IMPORTANCEBacterial biofilms pose a threat in clinical and industrial settings. Surface sensing is one of the first steps in biofilm formation. Studying surface sensing can improve our understanding of biofilm formation and develop preventative strategies. In this study, we use the freshwater bacterium <i>Caulobacter crescentus</i> to study surface sensing and the regulation of surface attachment. We characterize a previously unstudied gene, <i>fssF</i>, and find that it localizes to the cell pole in the presence of three proteins that make up a component of the flagellum called the C-ring. Additionally, we find that <i>fssF</i> is required for chemotaxis behavior but dispensable for swimming motility. Lastly, our results indicate that deletion of <i>fssF</i> and other genes required for chemotaxis results in a hyperadhesive phenotype. These results support that surface sensing requires chemotaxis for a robust response to a surface.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0040424"},"PeriodicalIF":2.7,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11580411/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142466178","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}