Journal of Bacteriology最新文献

{"title":"Revisiting bacterial spore germination in the presence of peptidoglycan fragments.","authors":"Rosa Heydenreich, Juliana Nacita, Chia-Wei Lin, Finn O'Dea, Stéphane Mesnage, Graham Christie, Alexander Mathys","doi":"10.1128/jb.00146-25","DOIUrl":"https://doi.org/10.1128/jb.00146-25","url":null,"abstract":"<p><p>Bacterial spores of <i>Bacillus</i> species are metabolically inert cell types formed in response to nutrient starvation. Spores must undergo the process of germination to resume vegetative growth. This process is stimulated by the interaction of various nutrient molecules with specialized clusters of membrane-localized germinant receptors (GRs) present within spores. A second route to spore germination involving the stimulation of the PrkC Ser/Thr kinase by soluble peptidoglycan fragments was proposed in 2008 and has been subject to much less scrutiny. The current study examined the germinative response of spores of <i>Bacillus subtilis</i>, <i>Bacillus cereus,</i> and <i>Bacillus megaterium</i> when incubated in the presence of complex mixtures of peptidoglycan fragments or purified peptidoglycan fragments previously identified as germinants. The spore suspensions did not show any appreciable germination, as determined by fluorometric dipicolinic acid release, flow cytometry, or microscopy. However, the purified peptidoglycan fragments displayed a stimulatory effect on germination triggered by amino acids and nucleosides with spore GRs. In contrast, GR-mediated germination was inhibited to varying degrees by unidentified components of the complex peptidoglycan fragment mixtures derived from enzymatic digests of <i>B. subtilis</i> vegetative sacculi. Collectively, our results indicate that soluble peptidoglycan fragments cannot initiate spore germination but may influence germination via mechanisms that have yet to be established.IMPORTANCEStimuli and mechanisms that underpin bacterial spore germination are fairly well characterized. The physiological route relies upon the interaction of various small nutrient molecules with receptor proteins buried within spores. An alternative route to germination, whereby fragments of bacterial cell wall material-peptidoglycan-were proposed to stimulate a different receptor system, was proposed more recently (I. M. Shah, M. H. Laaberki, D. L. Popham and J. Dworkin, Cell 135:486-496, 2008, https://doi.org/10.1016/j.cell.2008.08.039). Results from the current study, where spores of several species of <i>Bacillus</i> were exposed to various peptidoglycan fragment-containing solutions, do not support this model of germination. This is significant since knowledge of germination can be exploited in a practical sense, as germinated spores are much easier to eradicate-in food processing and healthcare settings, for example-than their dormant counterparts.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0014625"},"PeriodicalIF":2.7,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144553667","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":"Conjugative delivery of toxin genes <i>ccdB</i> and <i>kil</i> confers synergistic killing of bacterial recipients.","authors":"Yang Grace Li, Daniel Haeusser, William Margolin, Peter J Christie","doi":"10.1128/jb.00168-25","DOIUrl":"https://doi.org/10.1128/jb.00168-25","url":null,"abstract":"<p><p>The bacterial type IV secretion systems (T4SS) are medically problematic for their roles in the dissemination of mobile genetic elements or effector proteins, but they also have great potential for new antimicrobial therapies. Recent studies have deployed the T4SS subfamily of conjugation systems to deliver gene editing CRISPR/Cas systems to disrupt drug resistance genes or kill targeted bacterial recipients. However, the therapeutic potential of conjugative CRISPR/Cas delivery is compromised by mutations or host repair systems that diminish the efficiency with which CRISPR/Cas induces double-strand breaks in new transconjugants. Here, we compared the efficiencies of conjugation-based killing systems based on the delivery of CRISPR-Cas9 elements or toxin genes encoding the bacteriophage lambda Kil peptide or the F plasmid-encoded CcdB. <i>Escherichia coli</i> equipped with one of two efficient conjugation systems, pKM101 (IncN) or F (IncF), served as donors to mobilize plasmids carrying the cognate <i>oriT</i> sequence and one or more toxic elements. Overall, toxin gene delivery proved significantly more effective than CRISPR-Cas9 in killing of transconjugant population, but the highest levels of growth suppression of both <i>E. coli</i> and <i>Klebsiella pneumoniae</i> recipients were achieved by a combination of CRISPR-Cas9 plus one or two toxin genes. By contrast, capsule production conferred no or very slight protective effects on plasmid acquisition and killing of either species. We propose that the conjugative co-transfer of two or more toxic elements with distinct mechanisms of action has strong potential for growth suppression of targeted species in environmental or clinical settings.IMPORTANCEThe prevalence of antibiotic resistance emphasizes the need for alternative antimicrobial intervention strategies. We engineered <i>Escherichia coli</i> for conjugative transmission of plasmids encoding CRISPR-Cas9 elements or genes encoding the cell division inhibitor Kil or gyrase poisoner CcdB. Delivery of toxin genes more effectively suppressed the growth of <i>E. coli</i> recipients than CRISPR-Cas9, but the combinatorial delivery of CRISPR-Cas9 and a toxin gene or two toxin genes elicited the strongest killing effects. Capsule production by <i>E. coli</i> or <i>Klebsiella pneumoniae</i> recipient cells had no or little protective effect on plasmid acquisition or growth suppression. Our findings suggest that probiotic donor strains equipped for conjugative delivery of two or more toxic elements may prove effective as an alternative or adjunct to traditional antimicrobials.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0016825"},"PeriodicalIF":2.7,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144553660","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":"DdiA, an XRE family transcriptional regulator, is a co-regulator of the DNA damage response in <i>Myxococcus xanthus</i>.","authors":"Jana Jung, Timo Glatter, Marco Herfurth, Lotte Søgaard-Andersen","doi":"10.1128/jb.00184-25","DOIUrl":"https://doi.org/10.1128/jb.00184-25","url":null,"abstract":"<p><p>Repair of DNA damage is essential for genome integrity. DNA damage elicits a DNA damage response (DDR) that includes error-free and error-prone, i.e., mutagenic, repair. The SOS response is a widely conserved system in bacteria that regulates the DDR and depends on the recombinase RecA and the transcriptional repressor LexA. However, RecA/LexA-independent DDRs have been identified in several bacterial species. Here, using a whole-cell, label-free quantitative proteomics approach, we map the proteomic response in <i>Myxococcus xanthus</i> to mitomycin C treatment and the lack of LexA. In doing so, we demonstrate a LexA-independent proteomic DDR in <i>M. xanthus</i>. Using a candidate approach, we identify <u>D</u>NA <u>d</u>amage-<u>i</u>nduced protein <u>A</u> (DdiA), a transcriptional regulator of the Xenobiotic Response Element (XRE) family, and demonstrate that it is involved in regulating the abundance of a subset of the LexA-independent DDR proteins. <i>ddiA</i> is expressed heterogeneously in a subpopulation of cells in the absence of exogenous genotoxic stress and reversibly induced population wide in response to such stress. DdiA, indirectly or directly, activates the expression of <i>dnaE2</i>, which encodes the DnaE2 error-prone DNA polymerase, and inhibits the expression of <i>recX</i>, which encodes RecX, a negative regulator of RecA. Accordingly, the Δ<i>ddiA</i> mutant not only has a lower mutation frequency than the wild type but also a fitness defect, suggesting that DdiA mediates a trade-off between fitness and mutagenesis. We speculate that the DdiA-dependent response is tailored to counter replication stress, thereby preventing the induction of the complete RecA/LexA-dependent DDR in the absence of exogenous genotoxic stress.IMPORTANCEDNA damage repair is essential for genome integrity and depends on the DNA damage response (DDR). While the RecA/LexA-dependent SOS response is widely conserved in bacteria, there are also RecA/LexA-independent DDRs. Here, we identify the DNA damage-induced transcriptional regulator DdiA in <i>Myxococcus xanthus</i> and demonstrate that it regulates part of a LexA-independent DDR. DdiA activates the expression of <i>dnaE2</i>, which encodes the DnaE2 error-prone DNA polymerase, and inhibits the expression of <i>recX</i>, which encodes RecX, a negative regulator of RecA. Because the Δ<i>ddiA</i> mutant has a lower mutation frequency than the wild type but also a fitness defect, we suggest that DdiA mediates a trade-off between fitness and mutagenesis, and the DdiA-dependent DDR is specifically tailored to counter replication stress.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0018425"},"PeriodicalIF":2.7,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144553661","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":"Reductive activation of the disulfide-containing antibiotic thiolutin is mediated by both bacillithiol and FAD-dependent disulfide reductases.","authors":"Ahmed Gaballa, Yesha Patel, John D Helmann","doi":"10.1128/jb.00181-25","DOIUrl":"https://doi.org/10.1128/jb.00181-25","url":null,"abstract":"<p><p>Metal ions are universally essential for life and are required for critical enzymes throughout metabolism. Metalloenzymes rely on metal import and trafficking pathways for loading of the desired metal. Many microbes produce natural products that serve as metal chelators, both for their own nutrition and to serve as antimicrobials. In response to infection, our immune cells restrict bacterial growth by deploying proteins that chelate metal ions as part of nutritional immunity. Cells respond to metal depletion by the activation of pathways that prioritize metal delivery to the most essential enzymes. Dithiolopyrrolone (DTP) class natural products are prodrugs that are reduced in cells to generate a potent, dithiol-containing zinc chelator. Here, we identify the cellular reductants, bacillithiol and the FAD-dependent oxidoreductases TrxB and AhpF, that activate the DTP antibiotic thiolutin in <i>Bacillus subtilis</i>. Genetic studies reveal that loss of the Spx transcription factor also increases thiolutin resistance, consistent with the known role of Spx in transcriptional activation of thioredoxin reductase (<i>trxB</i>) and genes required for bacillithiol synthesis. Collectively, our results support a model in which several parallel pathways all contribute to the reductive activation of DTP class prodrugs <i>in vivo</i>.IMPORTANCEMetal ion chelators (metallophores) are deployed by microbes to obtain nutrient metals, sequester excess metals, and act as antimicrobials to inhibit the growth of other organisms. Dithiolopyrrolones (DTPs) are a class of natural products that inhibit bacterial growth by the intracellular chelation of zinc and iron, two metal ions essential for growth. Thiolutin, a model DTP antibiotic, is activated by reduction inside cells and selectively chelates intracellular metals. Here, we demonstrate that the activation of the thiolutin prodrug is mediated by several parallel pathways, which greatly reduces the ability of cells to evolve antibiotic resistance. Since DTP antibiotics appear to primarily target zinc enzymes, they provide a powerful tool for exploring how cells adapt to zinc deficiency.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0018125"},"PeriodicalIF":2.7,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144553666","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":"Beyond movement: the dynamic roles of Type IV pili in cyanobacterial life.","authors":"Jonas Hammerl, Nils Schuergers, Gen Enomoto, Conrad W Mullineaux, Annegret Wilde","doi":"10.1128/jb.00086-25","DOIUrl":"https://doi.org/10.1128/jb.00086-25","url":null,"abstract":"<p><p>Type IV pili are versatile prokaryotic cell appendages that are extremely widespread in the bacterial and archaeal domains of life. The structure, dynamics, and functions of type IV pili have been most intensively studied in several species of heterotrophic bacteria, but these appendages also appear universal in cyanobacteria. Cyanobacterial type IV pili have much in common with those found in other bacteria, but they also show some unique features that may be crucial for facilitating the photoautotrophic lifestyles of cyanobacteria. Here, we discuss what is known of the structure and dynamic organization of cyanobacterial type IV pili. We discuss the multiple roles of cyanobacterial type IV pili in motility and phototaxis, sensory signal transduction, DNA uptake, and the formation of cell aggregates and biofilms. We conclude with some ideas on the likely importance of cyanobacterial type IV pilus functions in the natural environment and for biotechnological applications.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0008625"},"PeriodicalIF":2.7,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144553659","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":"EzrA promotes Z-ring formation through interaction of its QNR motif with FtsA.","authors":"Tingting Li, Xiujian Liu, Liangsheng Zhang, Haotian Li, Minghui Ni, Wenjin Zou, Menglei Liang, Ruotong Gong, Qiao Hu, Lelin Zhao, Zhe Hu, Lu Li, Qi Huang, Rui Zhou","doi":"10.1128/jb.00125-25","DOIUrl":"https://doi.org/10.1128/jb.00125-25","url":null,"abstract":"<p><p>Bacterial cell division requires precise placement and formation of the division machinery to ensure the accurate generation of identical daughter cells. This process is canonically initiated by the highly conserved FtsZ but also needs the involvement of a variety of FtsZ-binding proteins to orchestrate the spatial and temporal positioning and assembly of the Z-ring. However, the underlying molecular mechanisms remain poorly understood. In this study, we characterized the roles of an important FtsZ binding protein EzrA in the cell division of <i>Streptococcus suis</i>, an emerging zoonotic bacterial pathogen. Our results revealed that EzrA shares high subcellular dynamics with FtsZ during the entire cell division cycle and functions primarily as a positive regulator for Z-ring formation. Co-immunoprecipitation and bacterial two-hybrid data suggest that EzrA interacts with FtsZ and several early division proteins. Importantly, the conserved QNR motif in EzrA directly contributes to its interaction with FtsA. Disrupting this motif results in the mislocalization of EzrA itself at the division site rather than the localization of FtsA, which remains concentrated localization at the division site. Moreover, the interaction of EzrA through the QNR motif with FtsA is conserved among the <i>Firmicutes</i>. Taken together, these findings demonstrate EzrA as a regulator of Z-ring positioning to the division site through the interaction of its conserved QNR motif with FtsA.IMPORTANCEBacteria replicate through binary fission in which the FtsZ-ring positioning and assembly is a crucial process requiring precise spatial and temporal regulation. However, the mechanism of this process remains largely unknown, especially in ovoid-shaped bacteria, such as <i>Streptococci,</i> in which many members are important human and animal pathogens. In this study, we characterize the critical role of the cell division regulator EzrA in the formation of the Z-ring. Our data reveal a model in which EzrA interacts through its QNR motif with FtsA to be properly localized to the septum so as to facilitate the positioning and formation of the Z-ring of <i>Streptococcus suis</i>. This regulatory mechanism could be conserved in <i>Firmicutes</i>. This research provides insights into the regulation mechanism of the Z-ring formation and will contribute to the understanding of the cell division process in <i>Streptococci</i>.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0012525"},"PeriodicalIF":2.7,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144553665","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":"Bacterial evolution in the oral microbiome: the role of conjugative elements and horizontal gene transfer.","authors":"Allison J Renno, Robert C Shields, Lisa K McLellan","doi":"10.1128/jb.00066-25","DOIUrl":"https://doi.org/10.1128/jb.00066-25","url":null,"abstract":"<p><p>As one of the most diverse bacterial populations within the human body, the oral microbiome encodes a wealth of genetic information. Horizontal gene transfer, driven by mobile genetic elements, takes advantage of this information to influence bacterial evolution and the spread of phenotypes (antibiotic resistances, virulence attributes, and metabolic capabilities) among oral microbes. Although widespread within microbial communities, fundamental aspects of the mobile elements that drive horizontal gene transfer within the oral cavity remain poorly understood. In this review, we explore what is known about the role of horizontal gene transfer in bacterial evolution within the oral microbiome and the elements that facilitate this transfer, with a specific focus on conjugative DNA transfer. Conjugative elements are found in virtually all bacterial phylogenetic clades, and some can mediate genetic exchange between distantly related organisms. This is of particular interest in the diverse microcosm of the oral cavity, specifically how it drives the evolution and virulence of dental pathogens. Finally, we highlight advances in our understanding of the unique biology within dental plaque and how these might influence our understanding of bacterial gene transfer, and thus human health and disease.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0006625"},"PeriodicalIF":2.7,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144540336","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":"Unexpected contribution of the Fak system and the thioesterase TesE to the growth and membrane physiology of <i>Enterococcus faecalis</i>.","authors":"R D Johnston, T A Getty, B M Woodall, S Maharjan, N L Arnold, W B Seaton, M Stevenson, S R Campagna, E M Fozo","doi":"10.1128/jb.00121-25","DOIUrl":"https://doi.org/10.1128/jb.00121-25","url":null,"abstract":"<p><p><i>Enterococcus faecalis</i> is a native of the intestine and a hospital-acquired pathogen that uses host fatty acids to form its membrane. We investigated the utilization of exogenous fatty acids via the fatty acid kinase (Fak) system to understand the varied impacts fatty acids have on physiology. FakB proteins bind fatty acids, and FakA then phosphorylates them for lipid synthesis. Network analysis indicated that two of the four FakB proteins of <i>E. faecalis</i> OG1RF cluster with described proteins of <i>Staphylococcus aureus</i> and <i>Streptococcus pneumoniae</i> (FakB1, FakB2). However, two additional <i>E. faecalis</i> FakB proteins clustered separately and distinctly from characterized proteins; these were subsequently denoted as FakB4 and FakB5. A strain deleted for three of the four genes (<i>ΔfakB1,2,5</i> strain) had severe morphological defects when grown in rich media. Deletion of all four <i>fakB</i>-encoding genes was not possible unless a thioesterase encoding gene, <i>tesE</i>, was also deleted (<i>Δquint</i> strain). The <i>Δquint</i> strain behaved similarly to wild-type OG1RF in rich media, indicating that the combination of free fatty acids from the growth environment and those liberated via TesE was detrimental to the <i>ΔfakB1,2,5</i> strain. The <i>Δquint</i> strain grew unimpeded in saturated fatty acids that are normally toxic to <i>E. faecalis,</i> indicating that incorporation of these fatty acids into phospholipids mediates their toxicity. While saturated fatty acids reduced the membrane fluidity of wild-type OG1RF, they had no impact on the <i>Δquint</i> strain. Our combined data support that the Fak system in <i>E. faecalis</i> plays a critical role in maintaining membrane fluidity and driving enterococcal physiology.IMPORTANCEBacteria living within humans encounter a variety of fatty acids that they can use to synthesize their own cellular material. However, different fatty acids can have a variety of effects on the same bacterial species. Within, we examined how <i>Enterococcus faecalis</i>, which naturally lives in human intestines but can also cause disease, uses fatty acids from its environment. We discovered unexpectedly that fatty acid binding proteins contribute to many aspects controlling bacterial growth, shape, and behavior.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0012125"},"PeriodicalIF":2.7,"publicationDate":"2025-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144528104","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":"Community living causes changes in metabolic behavior and is permitted by specific growth conditions in two bacterial co-culture systems.","authors":"Elizabeth Ellis, Sam Fulte, Skyler Boylan, Alaina Flory, Katherine Paine, Sophia Lopez, Grace Allen, Kanwar Warya, Javier Ortiz-Merino, Sadie Blacketer, Samantha Thompson, Sierra Sanchez, Kayla Burdette, Audrey Duchscherer, Nick Pinkham, Joseph D Shih, Lilah Rahn-Lee","doi":"10.1128/jb.00075-25","DOIUrl":"10.1128/jb.00075-25","url":null,"abstract":"<p><p>Although bacteria exist in complex microbial communities in the environment, their features and behavior are most often studied in monoculture. While environmental enrichments or complex co-cultures with tens or hundreds of members might more accurately represent the natural communities of bacteria, we sought to create simple pairs of organisms to learn what conditions create successful co-culture and how bacteria change transcriptionally when a partner species is present. We grew two pairs of organisms in co-culture, <i>Pseudomonas aeruginosa</i> and <i>Escherichia coli</i> and <i>Lacticaseibacillus rhamnosus</i> and <i>Bacteroides thetaiotaomicron</i>. At first, both co-cultures failed, with one organism outcompeting the other. However, through manipulating media and environmental conditions, we created co-cultures with stable member ratios over many generations for each community. We then show that changes in the expression of metabolic genes are present in all studied species, with key catabolic and anabolic pathways often upregulated in the presence of another organism. These changes in gene expression fail to occur in conditions that will not lead to successful co-culture, suggesting they are essential for adapting to and surviving in the presence of others.</p><p><strong>Importance: </strong>In 1882, Robert Koch and Fanny Hesse developed the agar plate, which enabled microbiologists to separate individual microbial cells from each other and create monocultures of a single strain of bacteria. This powerful tool has been used in the almost 150 years since to develop a robust understanding of how bacterial cells are structured, how they manage and process their information, and how they respond to the environment to produce behaviors that match their circumstances. We were curious about how the behavior of bacteria, as measured by their gene expression, changes between well-studied monoculture conditions and co-culture. We found that only specific growth conditions permit co-culture and that bacteria change their metabolic strategies in the presence of a partner.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0007525"},"PeriodicalIF":2.7,"publicationDate":"2025-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12186488/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144006700","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":"Resisting the resistance: the antimicrobial peptide DGL13K selects for small colony variants of <i>Staphylococcus aureus</i> that show increased resistance to its stereoisomer LGL13K, but not to DGL13K.","authors":"Sven-Ulrik Gorr","doi":"10.1128/jb.00505-24","DOIUrl":"10.1128/jb.00505-24","url":null,"abstract":"<p><p>About 30% of the population are nasal carriers of <i>Staphylococcus aureus</i>, a leading cause of bacteremia, endocarditis, osteomyelitis, and skin and soft tissue infections. Antibiotic-resistant bacteria, in particular, are an increasing problem in both hospital and community settings. In this study, we sought to determine the cellular consequences of long-term exposure of <i>S. aureus</i> to the antimicrobial peptide stereoisomers, DGL13K and LGL13K. Both peptides selected for mutations in the chorismate/menaquinone biosynthetic pathway, which resulted in increased resistance to LGL13K but not DGL13K. DGL13K-selected isolates showed a mutation in <i>aroF</i>, while <i>menA</i> and <i>menH</i> were mutated in LGL13K-selected isolates. The latter also contained a mutation of <i>frsA</i>. The peptide-selected isolates exhibited golden coloration, suggesting increased production of the carotenoid staphyloxanthin, which could enhance resistance to cationic antimicrobial peptides (AMPs). The peptide-selected isolates grew as small colony variants, which have also been associated with resistance to AMPs. Addition of menaquinone to the growth medium reduced the generation time of DGL13K-selected mutants, but not LGL13K-selected mutants. Instead, the latter showed an increased MIC to LGL13K and greatly reduced ATP levels. The peptide-selected isolates showed increased biofilm formation and decreased autolysis, which was further reduced by alkaline shock, consistent with increased Asp23 expression. The mechanisms behind the differential effect of DGL13K and LGL13K on <i>S. aureus</i> resistance remain to be elucidated. The finding that DGL13K induced resistance to the stereoisomer LGL13K but not to DGL13K itself suggests that peptide primary structure is responsible for inducing bacterial defense mechanisms, but the peptide secondary structure determines if the defense mechanisms are effective against each peptide.</p><p><strong>Importance: </strong>This work examines resistance to stereoisomers of the antimicrobial peptide GL13K in <i>Staphylococcus aureus</i>. Both DGL13K and LGL13K isomers cause mutations in the menaquinone pathway. While LGL13K causes resistance to LGL13K, the bacteria remain susceptible to DGL13K. Conversely, DGL13K also raises resistance to LGL13K, but the cells remain susceptible to DGL13K. The resistant isolates exhibit a small colony variant phenotype and overproduce the pigment staphyloxanthin. Menaquinone supplementation decreases the long generation time of DGL13K-selected isolates and increases the MIC of LGL13K-selected isolates.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0050524"},"PeriodicalIF":2.7,"publicationDate":"2025-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12186495/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144215837","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}