Journal of Bacteriology最新文献

{"title":"<i>Borrelia burgdorferi</i> loses essential genetic elements and cell proliferative potential during stationary phase in culture but not in the tick vector.","authors":"Jessica Zhang, Constantin N Takacs, Joshua W McCausland, Elizabeth A Mueller, Jeline Buron, Yashna Thappeta, Jenny Wachter, Patricia A Rosa, Christine Jacobs-Wagner","doi":"10.1128/jb.00457-24","DOIUrl":"10.1128/jb.00457-24","url":null,"abstract":"<p><p>The Lyme disease agent <i>Borrelia burgdorferi</i> is a polyploid bacterium with a segmented genome in which both the chromosome and over 20 distinct plasmids are present in multiple copies per cell. This pathogen can survive for at least 9 months in its tick vector in an apparent dormant state between blood meals, without losing cell proliferative capability when re-exposed to nutrients. Cultivated <i>B. burgdorferi</i> cells grown to stationary phase or resuspended in nutrient-limited media are often used to study the effects of nutrient deprivation. However, a thorough assessment of the spirochete's ability to recover from nutrient depletion has been lacking. Our study shows that starved <i>B. burgdorferi</i> cultures rapidly lose cell proliferative ability. Loss of genetic elements essential for cell proliferation contributes to the observed proliferative defect in stationary phase. The gradual decline in copies of genetic elements is not perfectly synchronized between chromosomes and plasmids, generating cells that harbor one or more copies of the essential chromosome but lack all copies of one or more non-essential plasmids. This phenomenon likely contributes to the well-documented issue of plasmid loss during <i>in vitro</i> cultivation of <i>B. burgdorferi</i>. In contrast, <i>B. burgdorferi</i> cells from ticks starved for 14 months showed no evidence of reduced cell proliferative ability or plasmid loss. Beyond their practical implications for studying <i>B. burgdorferi</i>, these findings suggest that the midgut of the tick vector offers a unique environment that supports the maintenance of <i>B. burgdorferi</i>'s segmented genome and cell proliferative potential during periods of tick fasting.IMPORTANCE<i>Borrelia burgdorferi</i> causes Lyme disease, a prevalent tick-borne illness. <i>B. burgdorferi</i> must survive long periods (months to a year) of apparent dormancy in the midgut of the tick vector between blood meals. Resilience to starvation is a common trait among bacteria. However, this study reveals that, in laboratory cultures, <i>B. burgdorferi</i> poorly endures starvation and rapidly loses viability. This decline is linked to a gradual loss of genetic elements required for cell proliferation. These results suggest that the persistence of <i>B. burgdorferi</i> in nature is likely shaped more by unique environmental conditions in the midgut of the tick vector than by an innate ability of this bacterium to endure nutrient deprivation.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0045724"},"PeriodicalIF":2.7,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11925233/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143414277","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":"Sucrose and malic acid in the tobacco plant induce <i>hrp</i> regulon in a phytopathogen <i>Ralstonia pseudosolanacearum</i>.","authors":"Yuzhu Cao, Masayuki Tsuzuki, Akinori Kiba, Yasufumi Hikichi, Yong Zhang, Kouhei Ohnishi","doi":"10.1128/jb.00273-24","DOIUrl":"10.1128/jb.00273-24","url":null,"abstract":"<p><p>Genes encoding a type III secretion system in <i>Ralstonia pseudosolanacearum</i> are regulated by HrpB as an <i>hrp</i> regulon and induced only in plants. This study aimed to identify the plant signals that induce the <i>hrp</i> regulon and confirm the signal recognition mechanism. Signaling molecules that induce <i>hrpB</i> expression were screened using resting cells of the <i>hrpB-lacZ</i> reporter strain. Only the soluble fraction of smashed tobacco seedlings induced <i>hrpB</i> expression. The heated soluble fraction retained its <i>hrpB</i>-inducing activity, indicating that the signaling molecules were not proteins. When the soluble fraction was fractionated into acidic, neutral, and basic components, both the acidic and neutral fractions induced <i>hrpB</i> expression. As neutral compounds, sucrose, glucose, and fructose have been found to induce <i>hrpB</i> expression. Sucrose-induced <i>hrpB</i> expression was greatly reduced in the <i>prhA</i> mutant, indicating that the TonB-dependent receptor PrhA perceives sugars. Among the organic acids found in the acidic fractions, malic acid most efficiently induced <i>hrpB</i> expression, which was reduced by the mutation of a hybrid histidine kinase gene of a two-component system, <i>rsc1598</i>, indicating that Rsc1598 may sense malic acid. We demonstrated direct binding of Rsc1598 to malic acid using isothermal titration calorimetry.IMPORTANCESimilar to other Gram-negative plant pathogens, the type III secretion system (T3SS) is the most important virulence factor in <i>Ralstonia pseudosolanacearum</i>. The genes for the T3SS are regulated as an <i>hrp</i> regulon, activated only when the pathogen encounters the plants, indicating that the pathogen must sense plant signals. For the first time, we identified two signaling compounds, sucrose and malic acid, that are abundantly found in tobacco roots. The <i>hrp</i> operon was induced even in non-host plants, possibly because sucrose and malic acid are common in plants. We also found that <i>R. pseudosolanacearum</i> membrane proteins received sucrose and malic acid independently. As a next step, antagonists of signaling molecules can be screened.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0027324"},"PeriodicalIF":2.7,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11925246/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143189405","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":"Quorum sensing LuxR proteins VjbR and BabR jointly regulate <i>Brucella abortus</i> survival during infection.","authors":"Mitchell T Caudill, S Tristan Stoyanof, Clayton C Caswell","doi":"10.1128/jb.00527-24","DOIUrl":"10.1128/jb.00527-24","url":null,"abstract":"<p><p><i>Brucella abortus</i> maintains an <i>N</i>-acetyl homoserine lactone quorum sensing system that consists of two LuxR proteins, VjbR and BabR, as well as two signals, dodecanoyl (C12 AHL) and 3-oxododecanoyl (3-OXO-C12 AHL) homoserine lactone. This system regulates major virulence factors that influence the bacteria's survival during infection. We generated the first strain that lacks both LuxR proteins and found a synergistic interaction for survival in the chronic infection C57BL/6 mouse model. Transcriptomic analyses of the <i>∆vjbR∆babR</i> double-deletion strain, as well as the cognate single-deletion strains, in a rich medium with vehicle control or supplemented with an AHL signal revealed large-scale genetic dysregulation in all conditions. Moreover, the double mutant maintained a limited response to AHL, even in the absence of the LuxR proteins. We additionally found that quorum sensing regulates the denitrification pathway but found no <i>in vitro</i> differences in the ability of quorum sensing deletion strains to clear nitric oxide stress or grow under anoxic denitrifying conditions. Finally, we confirmed that BabR autoregulates its own expression, and that VjbR mildly represses BabR expression. Altogether, these experiments help further characterize the <i>Brucella</i> quorum sensing systems and indicate that further attention should be given to the joint interactions between VjbR and BabR in controlling virulence.IMPORTANCE<i>Brucella abortus</i> is a zoonotic bacterial pathogen that uses its quorum sensing to survive within hosts. This study further characterizes that system and indicates important future lines of inquiry. We found that both quorum sensing proteins, VjbR and BabR, coordinate to maintain survival, as well as document that both quorum sensing systems appear physiologically active.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0052724"},"PeriodicalIF":2.7,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11925318/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143515637","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 novel regulation on the developmental checkpoint protein Sda that controls sporulation and biofilm formation in <i>Bacillus subtilis</i>.","authors":"Yinghao He, Yuxuan Qin, Jennifer Greenwich, Samantha Balaban, Migue Van Louis Darcera, Kevin Gozzi, Yunrong Chai","doi":"10.1128/jb.00210-24","DOIUrl":"10.1128/jb.00210-24","url":null,"abstract":"<p><p>Biofilm formation by <i>Bacillus subtilis</i> is triggered by an unusually simple environmental sensing mechanism. Certain serine codons, the four TCN codons (N for A, T, C, or G), in the gene for the biofilm repressor SinR caused lowered SinR translation and subsequent biofilm induction during transition from exponential to stationary growth. Global ribosome profiling showed that ribosomes pause when translating the four UCN (U for T on the mRNA) serine codons on mRNA, but not the two AGC/AGU serine codons. We proposed a serine codon hierarchy (AGC/AGT vs TCN) in that genes enriched in the TCN serine codons may experience reduced translation efficiency when serine is limited. In this study, we designed an algorithm to score all protein-coding genes in <i>B. subtilis</i> NCIB3610 based on the serine codon hierarchy. We generated a short list of 50 genes that could be subject to regulation by this novel mechanism. We further investigated one such gene from the list, <i>sda</i>, which encodes a developmental checkpoint protein regulating both sporulation and biofilm formation. We showed that synonymously switching the TCN serine codons to AGC in <i>sda</i> led to delayed biofilm formation and sporulation. This engineered strain also outgrew strains with other synonymously substituted <i>sda</i> alleles (TCN) in competition assays for biofilm formation and sporulation. Finally, we showed that the AGC serine codon substitutions in <i>sda</i> elevated the Sda protein levels. This serine codon hierarchy-based novel signaling mechanism could be exploited by bacteria in adapting to stationary phase and regulating important biological processes.</p><p><strong>Importance: </strong>Genome-wide ribosome profiling in <i>Bacillus subtilis</i> shows that under serine limitation, ribosomes pause on the four TCN (N for A, C, G, and T), but not AGC/AGT serine codons, during translation at a global scale. This serine codon hierarchy (AGC/T vs TCN) differentially influences the translation efficiency of genes enriched in certain serine codons. In this study, we designed an algorithm to score all 4,000+ genes in the <i>B. subtilis</i> genome and generated a list of 50 genes that could be subject to this novel serine codon hierarchy-mediated regulation. We further investigated one such gene, <i>sda</i>, encoding a developmental checkpoint protein. We show that <i>sda</i> and cell developments controlled by Sda are also regulated by this novel mechanism.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0021024"},"PeriodicalIF":2.7,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11925247/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143390963","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":"Role of a TonB-dependent receptor and an oxygenase in iron-dependent copper resistance in <i>Caulobacter crescentus</i>.","authors":"Pauline Cherry, Hala Kasmo, Mauro Godelaine, Françoise Tilquin, Marc Dieu, Patsy Renard, Jean-Yves Matroule","doi":"10.1128/jb.00493-24","DOIUrl":"10.1128/jb.00493-24","url":null,"abstract":"<p><p>Copper (Cu) is potentially threatening for living organisms owing to its toxicity at high concentrations, requiring the onset of diverse detoxification strategies to maintain fitness. We previously showed that the environmental conditions modulate the response of the oligotrophic alphaproteobacterium <i>Caulobacter crescentus</i> to Cu excess. In the present study, we investigated the role of the Fe-importing TonB-dependent receptor (TBDR) CciT and its partner, CciO, a 2-oxoglutarate/Fe²⁺-dependent oxygenase, in Cu resistance. CciT is specifically involved in Cu resistance in both rich and poor media. Using inductively coupled plasma optical emission spectrometry, we found that under Cu stress, the cellular Cu content is reduced by overexpression of <i>cciT</i>, while the Fe content increases. Mutations of the three known Fe-importing TBDRs reveal that CciT is the primary Fe importer in these conditions and the only TBDR required for Cu resistance. In addition, the extracellular Fe concentration is positively correlated with the cellular Fe content and negatively correlated with the cellular Cu content, resulting in the protection of the cells against Cu excess. The operon organization of <i>cciT</i> and <i>cciO</i> is highly conserved across bacteria, indicating a functional link between the two proteins. Deletion of <i>cciT</i>, <i>cciO</i>, or both genes leads to similar Cu sensitivity. Catalytic mutations in CciT and CciO also result in Cu sensitivity. While CciO is not required for Cu and Fe transport, its precise function remains unknown. Overall, this study provides new insights into the role of Fe uptake in Cu resistance, emphasizing the critical influence of environmental conditions on bacterial physiology.IMPORTANCECopper is an essential metal for many living organisms, as it helps to drive crucial chemical reactions. However, when present in excess, copper turns toxic due to its high reactivity with biological molecules. Bacteria may encounter excess copper in various environments, such as polluted soils, agricultural copper treatments, and within the vacuoles of infected macrophages. In this study, we investigated the copper response in the environmental bacterium <i>Caulobacter crescentus</i>. Our findings reveal that environmental iron levels play a critical role in copper resistance, as increased iron prevents cellular copper accumulation and toxicity. We identified two essential proteins, CciT and CciO, that are involved in iron transport, providing protection against copper excess.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0049324"},"PeriodicalIF":2.7,"publicationDate":"2025-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143624851","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 co-conserved gene pair supports <i>Caulobacter</i> iron homeostasis during chelation stress.","authors":"Sergio Hernandez-Ortiz, Kiwon Ok, Thomas V O'Halloran, Aretha Fiebig, Sean Crosson","doi":"10.1128/jb.00484-24","DOIUrl":"10.1128/jb.00484-24","url":null,"abstract":"<p><p>Synthetic metal chelators are widely used in industrial, clinical, and agricultural settings, leading to their accumulation in the environment. We measured the growth of <i>Caulobacter crescentus</i>, a soil and aquatic bacterium, in the presence of the ubiquitous chelator ethylenediaminetetraacetic acid (EDTA) and found that it restricts growth by lowering intracellular iron levels. Using barcoded transposon sequencing, we identified an operonic gene pair, <i>cciT-cciO</i>, that is required to maintain iron homeostasis in laboratory media during EDTA challenge. <i>cciT</i> encodes one of four TonB-dependent transporters that are regulated by the ferric uptake repressor (Fur) and stands out among this group of genes in its ability to support <i>Caulobacter</i> growth across diverse media conditions. The function of CciT strictly requires <i>cciO</i>, which encodes a cytoplasmic Fe^II dioxygenase-family protein. Our results thus define a functional partnership between an outer membrane iron receptor and a cytoplasmic dioxygenase that are broadly co-conserved in Proteobacteria. We expanded our analysis to natural environments by examining the growth of mutant strains in freshwater from two lakes, each with biochemical and geochemical profiles that differ markedly from standard laboratory media. In lake water, <i>Caulobacter</i> growth did not require <i>cciT</i> or <i>cciO</i> and was less affected by EDTA treatment. This result aligns with our observation that EDTA toxicity is influenced by common forms of biologically chelated iron and the spectrum of free cations present in the medium. Our study defines a conserved iron acquisition system in Proteobacteria and bridges laboratory-based physiology studies with real-world conditions.IMPORTANCEMetal-chelating chemicals are widely used across industries, including as preservatives in the food sector, but their full impact on microbial physiology is not well understood. We identified two genes, <i>cciT</i> and <i>cciO</i>, that function together to support <i>Caulobacter crescentus</i> iron balance when cells are exposed to the common synthetic chelator, EDTA. CciT is an outer membrane transporter and CciO is a dioxygenase-family protein that are mutually conserved in many bacteria, including human pathogens where mutations in <i>cciT</i> homologs are linked to clinical resistance to the siderophore antibiotic cefiderocol. This study identifies a conserved genetic system that supports iron homeostasis during chelation stress and illuminates the iron acquisition versatility and stress resilience of <i>Caulobacter</i> in freshwater environments.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0048424"},"PeriodicalIF":2.7,"publicationDate":"2025-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143624846","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":"Identification of EcpK, a bacterial tyrosine pseudokinase important for exopolysaccharide biosynthesis in <i>Myxococcus xanthus</i>.","authors":"Luca Blöcher, Johannes Schwabe, Timo Glatter, Lotte Søgaard-Andersen","doi":"10.1128/jb.00499-24","DOIUrl":"https://doi.org/10.1128/jb.00499-24","url":null,"abstract":"<p><p>Bacteria synthesize chemically diverse capsular and secreted polysaccharides that function in many physiological processes and are widely used in industrial applications. In the ubiquitous Wzx/Wzy-dependent biosynthetic pathways for these polysaccharides, the polysaccharide co-polymerase (PCP) facilitates the polymerization of repeat units in the periplasm, and in Gram-negative bacteria, also polysaccharide translocation across the outer membrane. These PCPs belong to the PCP-2 family, are integral inner membrane proteins with extended periplasmic domains, and functionally depend on alternating between different oligomeric states. The oligomeric state is determined by a cognate cytoplasmic bacterial tyrosine kinase (BYK), which is either part of the PCP or a stand-alone protein. Interestingly, BYK-like proteins, which lack key catalytic residues and/or the phosphorylated Tyr residues, have been described. In <i>Myxococcus xanthu</i>s, the exopolysaccharide (EPS) is synthesized and exported <i>via</i> the Wzx/Wzy-dependent EPS pathway in which EpsV serves as the PCP. Here, we confirm that EpsV lacks the BYK domain. Using phylogenomics, experiments, and computational structural biology, we identify EcpK as important for EPS biosynthesis and show that it structurally resembles canonical BYKs but lacks residues important for catalysis and Tyr phosphorylation. Using proteomic analyses, two-hybrid assays, and structural modeling, we demonstrate that EcpK directly interacts with EpsV. Based on these findings, we suggest that EcpK is a BY pseudokinase and functions as a scaffold, which by direct protein-protein interactions, rather than by Tyr phosphorylation, facilitates EpsV function. EcpK and EpsV homologs are present in other bacteria, suggesting broad conservation of this mechanism and establishing a phosphorylation-independent PCP-2 subfamily.IMPORTANCEBacteria produce a variety of polysaccharides with important biological functions. In Wzx/Wzy-dependent pathways for the biosynthesis of secreted and capsular polysaccharides in Gram-negative bacteria, the polysaccharide co-polymerase (PCP) is a key protein that facilitates repeat unit polymerization and polysaccharide translocation across the outer membrane. PCP function depends on assembly/disassembly cycles that are determined by the phosphorylation/dephosphorylation cycles of an associated bacterial tyrosine kinase (BYK). Here, we identify the BY pseudokinase EcpK as essential for exopolysaccharide biosynthesis in <i>Myxococcus xanthus</i>. Based on experiments and computational structural biology, we suggest that EcpK is a scaffold protein, guiding the assembly/disassembly cycles of the partner PCP <i>via</i> binding/unbinding cycles independently of Tyr phosphorylation/dephosphorylation cycles. We suggest that this novel mechanism is broadly conserved.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0049924"},"PeriodicalIF":2.7,"publicationDate":"2025-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143604928","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 geranylgeranyl reductase homolog required for cholesterol production in Myxococcota.","authors":"Alysha K Lee, Paula V Welander","doi":"10.1128/jb.00495-24","DOIUrl":"https://doi.org/10.1128/jb.00495-24","url":null,"abstract":"<p><p>Myxococcota is a phylum of sterol-producing bacteria. They exhibit a clade depth for sterol biosynthesis unparalleled in the bacterial domain and produce sterols of a biosynthetic complexity that rivals eukaryotes. Additionally, the sterol biosynthesis pathways found in this phylum have been proposed as a potential source for sterol biosynthesis in the last eukaryotic common ancestor, lending evolutionary importance to our understanding of this pathway in Myxococcota. However, sterol production has only been characterized in a few species, and outstanding questions about the evolutionary history of this pathway remain. Here, we identify two myxobacteria, <i>Minicystis rosea</i> and <i>Sandaracinus amylolyticus</i>, capable of cholesterol biosynthesis. These two myxobacteria possess a cholesterol biosynthesis pathway that differs in both the ordering and enzymes involved in biosynthesis compared with <i>Enhygromyxa salina</i>, a myxobacterium previously demonstrated to produce cholesterol, as well as the canonical pathways found in eukaryotes. We characterize an alternative bacterial reductase responsible for performing C-24 reduction, further delineating bacterial cholesterol production from eukaryotes. Finally, we examine the distribution and phylogenetic relationships of sterol biosynthesis proteins across both cultured and uncultured Myxococcota species, providing evidence for multiple acquisition events and instances of both horizontal and vertical transfer at the family level. Altogether, this work further demonstrates the capacity of myxobacteria to synthesize eukaryotic sterols but with an underlying diversity in the biochemical reactions that govern sterol synthesis, suggesting a complex evolutionary history and refining our understanding of how myxobacterial cholesterol production relates to their eukaryotic counterparts.</p><p><strong>Importance: </strong>Sterols are essential and ubiquitous lipids in eukaryotes, but their significance in bacteria is less understood. Sterol production in Myxococcota, a phylum of developmentally complex predatory bacteria, has provided insight into novel sterol biochemistry and prompted discussion regarding the evolution of this pathway within both the eukaryotic and bacterial domains. Here, we characterize cholesterol biosynthesis in two myxobacteria, providing evidence for distinct pathway organization and identifying a unique protein responsible for C-24 reduction. We couple these results with the phylogenomic analysis of sterol biosynthesis within Myxococcota, revealing a complicated evolutionary history marked by vertical and horizontal transfer. This suggests a mosaic acquisition of this pathway in Myxococcota and highlights the complex role myxobacteria may have had in sterol transfer to eukaryotes.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0049524"},"PeriodicalIF":2.7,"publicationDate":"2025-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143604926","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":"Metabolic characterization of alkane monooxygenases and the growth phenotypes of <i>Pseudomonas aeruginosa</i> ATCC 33988 on hydrocarbons.","authors":"Thusitha S Gunasekera, Loryn L Bowen, Jhoanna C Alger","doi":"10.1128/jb.00508-24","DOIUrl":"https://doi.org/10.1128/jb.00508-24","url":null,"abstract":"<p><p>There is a demand and widespread interest in evaluating microbial community structures and metabolic processes in hydrocarbon environments. The current work aims to detect microbial subgroups (phenotypic subsets) and their metabolic processes, such as substrate specificity and expression of niche-associated genes. In this study, we were able to discriminate different cell types in real time from a complex sample matrix to allow the detection of live, dead, and injured cell populations in jet fuels. We found that the expression of <i>alkB1</i> and <i>alkB2</i> genes is induced in a growth-dependent manner and <i>alkB2</i> induction started before <i>alkB1</i>. This indicates that as an early response of <i>Pseudomonas aeruginosa</i> cells' exposure to alkanes, cells activate <i>alkB2</i> gene induction. Deletion of <i>alkB1</i> and <i>alkB2</i> genes completely inhibited <i>P. aeruginosa</i> ATCC 33988 growth in jet fuel, suggesting that two alkane monooxygenases are responsible for the degradation of alkanes and jet fuel. Interestingly, the AlkB2 has a broader (<i>n</i>-C8<i>-n</i>-C16) substrate range compared to AlkB1 (<i>n</i>-C12-<i>n</i>-C16). The data indicate that two alkane utilization pathways can coexist in <i>P. aeruginosa</i> ATCC 33988, and they are differentially expressed in response to <i>n</i>-C6<i>-n-</i>C16 alkanes found in jet fuel. This study provided additional information on the heterogeneity and phenotypic diversity within the same species after exposure to hydrocarbons. This work advances our understanding of microbial community structures and provides new insight into the alkane metabolism of <i>P. aeruginosa</i>.IMPORTANCEAlkane degradation allows for the natural breakdown of hydrocarbons found in crude oil, which can significantly contribute to environmental remediation. The metabolic process of microbes to hydrocarbons and the expression of niche-associated genes are not well understood. <i>Pseudomonas aeruginosa</i> ATCC 33988, originally isolated from a jet fuel tank, degrades hydrocarbons effectively and outcompetes the type strain <i>Pseudomonas aeruginosa</i> PAO1. In this study, we found differential expression of <i>alkB1</i> and <i>alkB2</i> alkane monooxygenase genes and the relative importance of these genes in alkane degradation. We found different phenotypic subsets within the same genotype, which are influenced by hydrocarbon stress. Overall, the research conducted in this study significantly contributes to our knowledge about microbial processes and community structure in hydrocarbon environments.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0050824"},"PeriodicalIF":2.7,"publicationDate":"2025-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143604863","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":"Recent insights into Wzy polymerases and lipopolysaccharide O-antigen biosynthesis.","authors":"Alice Ascari, Renato Morona","doi":"10.1128/jb.00417-24","DOIUrl":"https://doi.org/10.1128/jb.00417-24","url":null,"abstract":"<p><p>Bacteria synthesize a plethora of complex surface-associated polysaccharides which enable them to persist and thrive in distinct niches. These glycans serve an array of purposes pertaining to virulence, colonization, antimicrobial resistance, stealth, and biofilm formation. The Wzx/Wzy-dependent pathway is universally the predominant system for bacterial polysaccharide synthesis. This system is responsible for the production of lipopolysaccharide (LPS) O-antigen (Oag), enterobacterial common antigen, capsule, and exopolysaccharides, with orthologs present in both Gram-negative and Gram-positive microbes. Studies focusing principally on <i>Pseudomonas</i>, <i>Shigella</i>, and <i>Salmonella</i> LPS Oag synthesis have provided much of the framework underpinning the biochemical and molecular mechanism behind polysaccharide synthesis via this pathway. LPS Oag production via the Wzx/Wzy-dependent pathway occurs through the stepwise activity of multiple key biosynthetic enzymes, including primarily the polymerase, Wzy, which is responsible for the Oag assembly, and the polysaccharide co-polymerase, Wzz, which effectively modulates the length of the glycan produced. In this review, we provide a comprehensive summary of the latest genetic, structural, and mechanistic data for the main protein candidates of the Wzx/Wzy-dependent pathway, in addition to an examination of their substrate specificities. Furthermore, we have reviewed recent insights pertaining to the dynamics/kinetics of glycan synthesis by this mechanism, including the interplay of the key proteins among themselves and in complex with their substrate. Lastly, we outline key gaps in the literature and suggest future research avenues, with the aim to stimulate ongoing research into this critical pathway responsible for the production of key virulence factors for numerous debilitating and lethal pathogens.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0041724"},"PeriodicalIF":2.7,"publicationDate":"2025-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143604869","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}