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Dutta A, Sharma P, Dass D, Yarlagadda V. Exploring the Darobactin Class of Antibiotics: A Comprehensive Review from Discovery to Recent Advancements. ACS Infect Dis 2024; 10:2584-2599. [PMID: 39028949 DOI: 10.1021/acsinfecdis.4c00412] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/21/2024]
Abstract
The prevalence of antimicrobial resistance in Gram-negative bacteria poses a greater challenge due to their intrinsic resistance to many antibiotics. Recently, darobactins have emerged as a novel class of antibiotics originating from previously unexplored Gram-negative bacterial species such as Photorhabdus, Vibrio, Pseudoalteromonas and Yersinia. Darobactins belong to the ribosomally synthesized and post-translationally modified peptide (RiPP) class of antibiotics, exhibiting selective activity against Gram-negative bacteria. They target the β-barrel assembly machinery (BAM), which is crucial for the maturation and insertion of outer membrane proteins in Gram-negative bacteria. The dar operon in the producer's genome encodes for the synthesis of darobactins, which are characterized by a fused ring system connected via an alkyl-aryl ether linkage (C-O-C) and a C-C cross-link. The enzyme DarE, using the radical S-adenosyl-l-methionine (rSAM), facilitates the formation of these bonds. Biosynthetic manipulation of the darobactin gene cluster, along with its expression in a surrogate host, has enabled access to diverse darobactin analogues with variable antibiotic activities. Recently, two independent research groups successfully achieved the total synthesis of darobactin, employing Larock heteroannulation to construct the bicyclic structure. This paper presents a comprehensive review of darobactins, encompassing their discovery through to the most recent advancements.
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Affiliation(s)
- Akash Dutta
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Peehu Sharma
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Dharam Dass
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India
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Bektas S, Kaptan E. Microbial lectins as a potential therapeutics for the prevention of certain human diseases. Life Sci 2024; 346:122643. [PMID: 38614308 DOI: 10.1016/j.lfs.2024.122643] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2024] [Revised: 03/20/2024] [Accepted: 04/10/2024] [Indexed: 04/15/2024]
Abstract
Lectins are protein or glycoprotein molecules with a specific ability to bind to carbohydrates. From viruses to mammals, they are found in various organisms and exhibit remarkable diverse structures and functions. They are significant contributors to defense mechanisms against microbial attacks in plants. They are also involved in functions such as controlling lymphocyte migration, regulating glycoprotein biosynthesis, cell-cell recognition, and embryonic development in animals. In addition, lectins serve as invaluable molecular tools in various biological and medical disciplines due to their reversible binding ability and enable the monitoring of cell membrane changes in physiological and pathological contexts. Microbial lectins, often referred to as adhesins, play an important role in microbial colonization, pathogenicity, and interactions among microorganisms. Viral lectins are located in the bilayered viral membrane, whereas bacterial lectins are found intracellularly and on the bacterial cell surface. Microfungal lectins are typically intracellular and have various functions in host-parasite interaction, and in fungal growth and morphogenesis. Although microbial lectin studies are less extensive than those of plants and animals, they provide insights into the infection mechanisms and potential interventions. Glycan specificity, essential functions in infectious diseases, and applications in the diagnosis and treatment of viral and bacterial infections are critical aspects of microbial lectin research. In this review, we will discuss the application and therapeutic potential of viral, bacterial and microfungal lectins.
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Affiliation(s)
- Suna Bektas
- Institute of Graduate Studies in Sciences, Istanbul University, Istanbul 34116, Turkey.
| | - Engin Kaptan
- Istanbul University, Faculty of Science Department of Biology, 34134 Vezneciler, Istanbul, Turkey.
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George A, Patil AG, Mahalakshmi R. ATP-independent assembly machinery of bacterial outer membranes: BAM complex structure and function set the stage for next-generation therapeutics. Protein Sci 2024; 33:e4896. [PMID: 38284489 PMCID: PMC10804688 DOI: 10.1002/pro.4896] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Revised: 12/28/2023] [Accepted: 12/31/2023] [Indexed: 01/30/2024]
Abstract
Diderm bacteria employ β-barrel outer membrane proteins (OMPs) as their first line of communication with their environment. These OMPs are assembled efficiently in the asymmetric outer membrane by the β-Barrel Assembly Machinery (BAM). The multi-subunit BAM complex comprises the transmembrane OMP BamA as its functional subunit, with associated lipoproteins (e.g., BamB/C/D/E/F, RmpM) varying across phyla and performing different regulatory roles. The ability of BAM complex to recognize and fold OM β-barrels of diverse sizes, and reproducibly execute their membrane insertion, is independent of electrochemical energy. Recent atomic structures, which captured BAM-substrate complexes, show the assembly function of BamA can be tailored, with different substrate types exhibiting different folding mechanisms. Here, we highlight common and unique features of its interactome. We discuss how this conserved protein complex has evolved the ability to effectively achieve the directed assembly of diverse OMPs of wide-ranging sizes (8-36 β-stranded monomers). Additionally, we discuss how darobactin-the first natural membrane protein inhibitor of Gram-negative bacteria identified in over five decades-selectively targets and specifically inhibits BamA. We conclude by deliberating how a detailed deduction of BAM complex-associated regulation of OMP biogenesis and OM remodeling will open avenues for the identification and development of effective next-generation therapeutics against Gram-negative pathogens.
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Affiliation(s)
- Anjana George
- Molecular Biophysics Laboratory, Department of Biological SciencesIndian Institute of Science Education and ResearchBhopalIndia
| | - Akanksha Gajanan Patil
- Molecular Biophysics Laboratory, Department of Biological SciencesIndian Institute of Science Education and ResearchBhopalIndia
| | - Radhakrishnan Mahalakshmi
- Molecular Biophysics Laboratory, Department of Biological SciencesIndian Institute of Science Education and ResearchBhopalIndia
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4
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Storek KM, Sun D, Rutherford ST. Inhibitors targeting BamA in gram-negative bacteria. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2024; 1871:119609. [PMID: 37852326 DOI: 10.1016/j.bbamcr.2023.119609] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Revised: 06/08/2023] [Accepted: 09/19/2023] [Indexed: 10/20/2023]
Abstract
Antibiotic resistance has led to an increase in the number of patient hospitalizations and deaths. The situation for gram-negative bacteria is especially dire as the last new class of antibiotics active against these bacteria was introduced to the clinic over 60 years ago, thus there is an immediate unmet need for new antibiotic classes able to overcome resistance. The outer membrane, a unique and essential structure in gram-negative bacteria, contains multiple potential antibacterial targets including BamA, an outer membrane protein that folds and inserts transmembrane β-barrel proteins. BamA is essential and conserved, and its outer membrane location eliminates a barrier that molecules must overcome to access this target. Recently, antibacterial small molecules, natural products, peptides, and antibodies that inhibit BamA activity have been reported, validating the druggability of this target and generating potential leads for antibiotic development. This review will describe these BamA inhibitors, highlight their key attributes, and identify challenges with this potential target.
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Affiliation(s)
- Kelly M Storek
- Department of Infectious Diseases, Genentech Inc., South San Francisco, CA, USA
| | - Dawei Sun
- Department of Structural Biology, Genentech Inc., South San Francisco, CA, USA
| | - Steven T Rutherford
- Department of Infectious Diseases, Genentech Inc., South San Francisco, CA, USA.
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5
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Theuretzbacher U, Blasco B, Duffey M, Piddock LJV. Unrealized targets in the discovery of antibiotics for Gram-negative bacterial infections. Nat Rev Drug Discov 2023; 22:957-975. [PMID: 37833553 DOI: 10.1038/s41573-023-00791-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/15/2023] [Indexed: 10/15/2023]
Abstract
Advances in areas that include genomics, systems biology, protein structure determination and artificial intelligence provide new opportunities for target-based antibacterial drug discovery. The selection of a 'good' new target for direct-acting antibacterial compounds is the first decision, for which multiple criteria must be explored, integrated and re-evaluated as drug discovery programmes progress. Criteria include essentiality of the target for bacterial survival, its conservation across different strains of the same species, bacterial species and growth conditions (which determines the spectrum of activity of a potential antibiotic) and the level of homology with human genes (which influences the potential for selective inhibition). Additionally, a bacterial target should have the potential to bind to drug-like molecules, and its subcellular location will govern the need for inhibitors to penetrate one or two bacterial membranes, which is a key challenge in targeting Gram-negative bacteria. The risk of the emergence of target-based drug resistance for drugs with single targets also requires consideration. This Review describes promising but as-yet-unrealized targets for antibacterial drugs against Gram-negative bacteria and examples of cognate inhibitors, and highlights lessons learned from past drug discovery programmes.
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Affiliation(s)
| | - Benjamin Blasco
- Global Antibiotic Research and Development Partnership (GARDP), Geneva, Switzerland
| | - Maëlle Duffey
- Global Antibiotic Research and Development Partnership (GARDP), Geneva, Switzerland
| | - Laura J V Piddock
- Global Antibiotic Research and Development Partnership (GARDP), Geneva, Switzerland.
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Gupta R, Singh M, Pathania R. Chemical genetic approaches for the discovery of bacterial cell wall inhibitors. RSC Med Chem 2023; 14:2125-2154. [PMID: 37974958 PMCID: PMC10650376 DOI: 10.1039/d3md00143a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2023] [Accepted: 08/10/2023] [Indexed: 11/19/2023] Open
Abstract
Antimicrobial resistance (AMR) in bacterial pathogens is a worldwide health issue. The innovation gap in discovering new antibiotics has remained a significant hurdle in combating the AMR problem. Currently, antibiotics target various vital components of the bacterial cell envelope, nucleic acid and protein biosynthesis machinery and metabolic pathways essential for bacterial survival. The critical role of the bacterial cell envelope in cell morphogenesis and integrity makes it an attractive drug target. While a significant number of in-clinic antibiotics target peptidoglycan biosynthesis, several components of the bacterial cell envelope have been overlooked. This review focuses on various antibacterial targets in the bacterial cell wall and the strategies employed to find their novel inhibitors. This review will further elaborate on combining forward and reverse chemical genetic approaches to discover antibacterials that target the bacterial cell envelope.
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Affiliation(s)
- Rinki Gupta
- Department of Biosciences and Bioengineering, Indian Institute of Technology Roorkee Roorkee - 247 667 Uttarakhand India
| | - Mangal Singh
- Department of Biosciences and Bioengineering, Indian Institute of Technology Roorkee Roorkee - 247 667 Uttarakhand India
| | - Ranjana Pathania
- Department of Biosciences and Bioengineering, Indian Institute of Technology Roorkee Roorkee - 247 667 Uttarakhand India
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MacNair CR, Tsai CN, Rutherford ST, Tan MW. Returning to Nature for the Next Generation of Antimicrobial Therapeutics. Antibiotics (Basel) 2023; 12:1267. [PMID: 37627687 PMCID: PMC10451936 DOI: 10.3390/antibiotics12081267] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2023] [Revised: 07/29/2023] [Accepted: 07/30/2023] [Indexed: 08/27/2023] Open
Abstract
Antibiotics found in and inspired by nature are life-saving cures for bacterial infections and have enabled modern medicine. However, the rise in resistance necessitates the discovery and development of novel antibiotics and alternative treatment strategies to prevent the return to a pre-antibiotic era. Once again, nature can serve as a source for new therapies in the form of natural product antibiotics and microbiota-based therapies. Screening of soil bacteria, particularly actinomycetes, identified most of the antibiotics used in the clinic today, but the rediscovery of existing molecules prompted a shift away from natural product discovery. Next-generation sequencing technologies and bioinformatics advances have revealed the untapped metabolic potential harbored within the genomes of environmental microbes. In this review, we first highlight current strategies for mining this untapped chemical space, including approaches to activate silent biosynthetic gene clusters and in situ culturing methods. Next, we describe how using live microbes in microbiota-based therapies can simultaneously leverage many of the diverse antimicrobial mechanisms found in nature to treat disease and the impressive efficacy of fecal microbiome transplantation and bacterial consortia on infection. Nature-provided antibiotics are some of the most important drugs in human history, and new technologies and approaches show that nature will continue to offer valuable inspiration for the next generation of antibacterial therapeutics.
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Affiliation(s)
- Craig R. MacNair
- Department of Infectious Diseases, Genentech Inc., South San Francisco, CA 94080, USA;
| | - Caressa N. Tsai
- School of Law, University of California, Berkeley, Berkeley, CA 94704, USA;
| | - Steven T. Rutherford
- Department of Infectious Diseases, Genentech Inc., South San Francisco, CA 94080, USA;
| | - Man-Wah Tan
- Department of Infectious Diseases, Genentech Inc., South San Francisco, CA 94080, USA;
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Xu Q, Guo M, Yu F. β-Barrel Assembly Machinery (BAM) Complex as Novel Antibacterial Drug Target. Molecules 2023; 28:molecules28093758. [PMID: 37175168 PMCID: PMC10180388 DOI: 10.3390/molecules28093758] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 03/05/2023] [Accepted: 03/08/2023] [Indexed: 05/15/2023] Open
Abstract
The outer membrane of Gram-negative bacteria is closely related to the pathogenicity and drug resistance of bacteria. Outer membrane proteins (OMPs) are a class of proteins with important biological functions on the outer membrane. The β-barrel assembly machinery (BAM) complex plays a key role in OMP biogenesis, which ensures that the OMP is inserted into the outer membrane in a correct folding manner and performs nutrient uptake, antibiotic resistance, cell adhesion, cell signaling, and maintenance of membrane stability and other functions. The BAM complex is highly conserved among Gram-negative bacteria. The abnormality of the BAM complex will lead to the obstruction of OMP folding, affect the function of the outer membrane, and eventually lead to bacterial death. In view of the important role of the BAM complex in OMP biogenesis, the BAM complex has become an attractive target for the development of new antibacterial drugs against Gram-negative bacteria. Here, we summarize the structure and function of the BAM complex and review the latest research progress of antibacterial drugs targeting BAM in order to provide a new perspective for the development of antibiotics.
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Affiliation(s)
- Qian Xu
- Laboratory of Molecular Pathology, Department of Pathology, Provincial Key Laboratory of Infectious Diseases and Molecular Immunopathology, Shantou University Medical College, Shantou 515041, China
| | - Min Guo
- Allergy Clinic, Zibo Central Hospital, Zibo 255000, China
| | - Feiyuan Yu
- Department of Cell Biology and Genetics, Shantou University Medical College, Shantou 515041, China
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Overly Cottom C, Stephenson R, Wilson L, Noinaj N. Targeting BAM for Novel Therapeutics against Pathogenic Gram-Negative Bacteria. Antibiotics (Basel) 2023; 12:679. [PMID: 37107041 PMCID: PMC10135246 DOI: 10.3390/antibiotics12040679] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 02/28/2023] [Accepted: 03/06/2023] [Indexed: 04/29/2023] Open
Abstract
The growing emergence of multidrug resistance in bacterial pathogens is an immediate threat to human health worldwide. Unfortunately, there has not been a matching increase in the discovery of new antibiotics to combat this alarming trend. Novel contemporary approaches aimed at antibiotic discovery against Gram-negative bacterial pathogens have expanded focus to also include essential surface-exposed receptors and protein complexes, which have classically been targeted for vaccine development. One surface-exposed protein complex that has gained recent attention is the β-barrel assembly machinery (BAM), which is conserved and essential across all Gram-negative bacteria. BAM is responsible for the biogenesis of β-barrel outer membrane proteins (β-OMPs) into the outer membrane. These β-OMPs serve essential roles for the cell including nutrient uptake, signaling, and adhesion, but can also serve as virulence factors mediating pathogenesis. The mechanism for how BAM mediates β-OMP biogenesis is known to be dynamic and complex, offering multiple modes for inhibition by small molecules and targeting by larger biologics. In this review, we introduce BAM and establish why it is a promising and exciting new therapeutic target and present recent studies reporting novel compounds and vaccines targeting BAM across various bacteria. These reports have fueled ongoing and future research on BAM and have boosted interest in BAM for its therapeutic promise in combatting multidrug resistance in Gram-negative bacterial pathogens.
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Affiliation(s)
- Claire Overly Cottom
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
| | - Robert Stephenson
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
| | - Lindsey Wilson
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
| | - Nicholas Noinaj
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
- Markey Center for Structural Biology, Purdue University, West Lafayette, IN 47907, USA
- Purdue Institute of Inflammation, Immunology and Infectious Disease, Purdue University, West Lafayette, IN 47907, USA
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10
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Bacteriocin Production Correlates with Epidemiological Prevalence of Phylotype I Sequevar 18 Ralstonia pseudosolanacearum in Madagascar. Appl Environ Microbiol 2023; 89:e0163222. [PMID: 36602304 PMCID: PMC9888187 DOI: 10.1128/aem.01632-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Bacterial wilt caused by the Ralstonia solanacearum species complex (RSSC) is a major threat to vegetable crops in Madagascar. For more effective disease management, surveys were carried out in the main vegetable production areas of the country, leading to the collection of 401 new RSSC isolates. Phylogenetic assignment of the isolates revealed a high prevalence of phylotype I sequevar 18. This result contrasts sharply with the epidemiological pattern of RSSC in neighboring islands, including Reunion Island, Comoros, Mayotte, Mauritius, Rodrigues, and the Seychelles, where phylotype I sequevar 31 is widespread. Molecular typing characterization of the Malagasy isolates allowed the identification of 96 haplotypes. Some are found in various plots located in different provinces, which suggests that they were probably disseminated via infected plant material. To find out a potential explanation for the observed epidemiological pattern, we examined the capacity of the Malagasy strains to produce bacteriocin. Interestingly, the highly prevalent genetic lineages I-18 produce bacteriocins that are active against all the genetic lineages present in the country. This work sheds light on the potential impact of bacteriocins in the epidemiology of Malagasy RSSC. IMPORTANCE Knowledge of the epidemiology of a plant pathogen is essential to develop effective control strategies. This study focuses on the epidemiological pattern of Ralstonia pseudosolanacearum phylotype I populations responsible for bacterial wilt in Madagascar. We identified, with the newly collected isolates in three provinces, four genetic lineages probably propagated via infected plant material in Madagascar. We revealed that the epidemiological situation in Madagascar contrasts with that of neighboring Indian Ocean islands. Interestingly, our study on the bacteriocin-producing capacity of Malagasy isolates revealed a correlation between the inhibitory activity of the producing strains and the observed epidemiology. These results suggested that the epidemiology of plant pathogens may be impacted by bacteriocin production.
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Recipient Cell Factors Influence Interbacterial Competition Mediated by Two Distinct Burkholderia dolosa Contact-Dependent Growth Inhibition Systems. J Bacteriol 2022; 204:e0054121. [PMID: 36000834 PMCID: PMC9487645 DOI: 10.1128/jb.00541-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Contact-dependent growth inhibition (CDI) systems mediate interbacterial antagonism between Gram-negative bacteria by delivering the toxic portion of a large surface protein (termed BcpA in Burkholderia species) to the cytoplasm of neighboring bacteria. Translocation of the antibacterial polypeptide into recipient cells requires specific recipient outer and inner membrane proteins, but the identity of these factors outside several model organisms is unknown. To identify genes involved in CDI susceptibility in the Burkholderia cepacia complex member Burkholderia dolosa, a transposon mutagenesis selection approach was used to enrich for mutants resistant to BcpA-1 or BcpA-2. Subsequent analysis showed that candidate regulatory genes contributed modestly to recipient cell susceptibility to B. dolosa CDI. However, most candidate deletion mutants did not show the same phenotypes as the corresponding transposon mutants. Whole-genome resequencing revealed that these transposon mutants also contained unique mutations within a three gene locus (wabO, BDAG_01006, and BDAG_01005) encoding predicted lipopolysaccharide (LPS) biosynthesis enzymes. B. dolosa wabO, BDAG_01006, or BDAG_01005 mutants were resistant to CDI and produced LPS with altered core oligosaccharide and O-antigen. Although BcpA-1 and BcpA-2 are dissimilar and expected to utilize different outer membrane receptors, intoxication by both proteins was similarly impacted by LPS changes. Together, these findings suggest that alterations in cellular regulation may indirectly impact the efficiency of CDI-mediated competition and demonstrate that LPS is required for intoxication by two distinct B. dolosa BcpA proteins. IMPORTANCEContact-dependent growth inhibition (CDI) system proteins, produced by many Gram-negative bacteria, are narrow spectrum antimicrobials that inhibit the growth of closely related neighboring bacteria. Here, we use the opportunistic pathogen Burkholderia dolosa to identify genes required for intoxication by two distinct CDI system proteins. Our findings suggest that B. dolosa recipient cells targeted by CDI systems are only intoxicated if they produce full-length lipopolysaccharide. Understanding the mechanisms underlying antagonistic interbacterial interactions may contribute to future therapeutic development.
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Biosynthesis of the Pseudomonas aeruginosa common polysaccharide antigen by D-Rhamnosyltransferases WbpX and WbpY. Glycoconj J 2022; 39:393-411. [PMID: 35166992 PMCID: PMC8853325 DOI: 10.1007/s10719-022-10040-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2021] [Revised: 11/28/2021] [Accepted: 01/12/2022] [Indexed: 12/28/2022]
Abstract
The Gram-negative bacterium Pseudomonas aeruginosa simultaneously expresses two O-antigenic glycoforms. While the O-specific antigen (OSA) is variable in composition, the common polysaccharide antigen (CPA) is highly conserved and is composed of a homopolymer of D-rhamnose (D-Rha) in trisaccharide repeating units [D-Rhaα1-2-D-Rhaα1-3-D-Rhaɑ1-3]n. We have previously reported that α3-D-Rha-transferase WbpZ transfers a D-Rha residue from GDP-D-Rha to D-GlcNAcα-O-PO3-PO3-(CH2)11-O-phenyl. Genes encoding two more D-Rha-transferases are found in the O antigen gene cluster (wbpX and wbpY). In this study we showed that WbpX and WbpY recombinantly expressed in E. coli differ in their donor and acceptor specificities and have properties of GT-B folded enzymes of the GT4 glycosyltransferase family. NMR spectroscopic analysis of the WbpY reaction product showed that WbpY transferred one D-Rha residue in α1-3 linkage to synthetic D-Rhaα1-3-D-GlcNAcα-O-PO3-PO3-(CH2)11-O-phenyl acceptor. WbpX synthesized several products that contained D-Rha in both α1-2 and α1-3 linkages. Mass spectrometry indicated that the mixture of WbpX and WbpY efficiently catalyzed the synthesis of D-Rha oligomers in a non-processive mechanism. Since O antigens are virulence factors, these findings open the door to advancing technology for antibacterial drug discovery and vaccine development.
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Antimicrobial Weapons of Pseudomonas aeruginosa. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2022; 1386:223-256. [DOI: 10.1007/978-3-031-08491-1_8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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14
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Snopková K, Dufková K, Chamrád I, Lenobel R, Čejková D, Kosina M, Hrala M, Holá V, Sedláček I, Šmajs D. Pyocin-mediated antagonistic interactions in Pseudomonas spp. isolated in James Ross Island, Antarctica. Environ Microbiol 2021; 24:1294-1307. [PMID: 34735036 DOI: 10.1111/1462-2920.15809] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 09/15/2021] [Accepted: 10/05/2021] [Indexed: 11/30/2022]
Abstract
Interactions within bacterial communities are frequently mediated by the production of antimicrobial agents. Despite the increasing interest in research of new antimicrobials, studies describing antagonistic interactions among cold-adapted microorganisms are still rare. Our study assessed the antimicrobial interactions of 36 Antarctic Pseudomonas spp. and described the genetic background of these interactions in selected strains. The overall bacteriocinogeny was greater compared to mesophilic Pseudomonas non-aeruginosa species. R-type tailocins were detected on transmission electron micrographs in 16 strains (44.4%); phylogenetic analysis of the corresponding gene clusters revealed that the P. prosekii CCM 8878 tailocin was related to the Rp3 group, whereas the tailocin in Pseudomonas sp. CCM 8880 to the Rp4 group. Soluble antimicrobials were produced by eight strains (22.-2%); gene mining found pyocin L homologues in the genomes of P. prosekii CCM 8881 and CCM 8879 and pyocin S9-like homologues in P. prosekii CCM 8881 and Pseudomonas sp. CCM 8880. Analysis of secretomes confirmed the production of all S- and L-type pyocin genes. Our results suggest that bacteriocin-based inhibition plays an important role in interactions among Antarctic soil bacteria, and these native, cold-adapted microorganisms could be a promising source of new antimicrobials.
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Affiliation(s)
- Kateřina Snopková
- Department of Biology, Faculty of Medicine, Masaryk University, Kamenice 753/5, Brno, 625 00, Czech Republic
| | - Kristýna Dufková
- Department of Biology, Faculty of Medicine, Masaryk University, Kamenice 753/5, Brno, 625 00, Czech Republic
| | - Ivo Chamrád
- Laboratory of Growth Regulators, Faculty of Science, Palacký University and Institute of Experimental Botany of the Czech Academy of Sciences, Šlechtitelů 241/27, Olomouc-Holice, 779 00, Czech Republic
| | - René Lenobel
- Laboratory of Growth Regulators, Faculty of Science, Palacký University and Institute of Experimental Botany of the Czech Academy of Sciences, Šlechtitelů 241/27, Olomouc-Holice, 779 00, Czech Republic
| | - Darina Čejková
- Veterinary Research Institute, Hudcova 296/70, Brno, 621 00, Czech Republic
| | - Marcel Kosina
- Department of Experimental Biology, Czech Collection of Microorganisms, Faculty of Science, Masaryk University, Kamenice 753/5, Brno, 625 00, Czech Republic
| | - Matěj Hrala
- Department of Biology, Faculty of Medicine, Masaryk University, Kamenice 753/5, Brno, 625 00, Czech Republic
| | - Veronika Holá
- Faculty of Medicine, Institute for Microbiology, Masaryk University and St. Anne's University Hospital Brno, Pekařská 664/53, Brno, 656 91, Czech Republic
| | - Ivo Sedláček
- Department of Experimental Biology, Czech Collection of Microorganisms, Faculty of Science, Masaryk University, Kamenice 753/5, Brno, 625 00, Czech Republic
| | - David Šmajs
- Department of Biology, Faculty of Medicine, Masaryk University, Kamenice 753/5, Brno, 625 00, Czech Republic
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Kathayat D, Helmy YA, Deblais L, Srivastava V, Closs G, Khupse R, Rajashekara G. Novel Small Molecule Growth Inhibitor Affecting Bacterial Outer Membrane Reduces Extraintestinal Pathogenic Escherichia coli (ExPEC) Infection in Avian Model. Microbiol Spectr 2021; 9:e0000621. [PMID: 34468186 PMCID: PMC8557866 DOI: 10.1128/spectrum.00006-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Accepted: 08/06/2021] [Indexed: 12/26/2022] Open
Abstract
Avian pathogenic Escherichia coli (APEC), a subgroup of extraintestinal pathogenic E. coli (ExPEC), causes colibacillosis in chickens and is reportedly implicated in urinary tract infections and meningitis in humans. A major limitation for the current ExPEC antibiotic therapy is the development of resistance, and antibacterial drugs that can circumvent this problem are critically needed. Here, we evaluated eight novel membrane-affecting anti-APEC small molecule growth inhibitors (GIs), identified in our previous study, against APEC infection in chickens. Among the GIs tested, GI-7 (the most effective), when administered orally (1 mg/kg of body weight), reduced the mortality (41.7%), severity of lesions (62.9%), and APEC load (2.6 log) in chickens. Furthermore, GI-7 administration at an optimized dose (60 mg/liter) in drinking water also reduced the mortality (14.7%), severity of lesions (29.5%), and APEC load (2.2 log) in chickens. The abundances of Lactobacillus and oleate were increased in the cecum and serum, respectively, of GI-7-treated chickens. Pharmacokinetic analysis revealed that GI-7 was readily absorbed with minimal accumulation in the tissues. Earlier, we showed that GI-7 induced membrane blebbing and increased membrane permeability in APEC, suggesting an effect on the APEC membrane. Consistent with this finding, the expression of genes essential for maintaining outer membrane (OM) integrity was downregulated in GI-7-treated APEC. Furthermore, decreased levels of lipopolysaccharide (LPS) transport (Lpt) proteins and LPS were observed in GI-7-treated APEC. However, the mechanism of action of GI-7 currently remains unknown and needs further investigation. Our studies suggest that GI-7 represents a promising novel lead compound that can be developed to treat APEC infection in chickens and related human ExPEC infections. IMPORTANCE APEC is a subgroup of ExPEC, and genetic similarities of APEC with human ExPECs, including uropathogenic E. coli (UPEC) and neonatal meningitis E. coli (NMEC), have been reported. Our study identified a novel small molecule growth inhibitor, GI-7, effective in reducing APEC infection in chickens with an efficacy similar to that of the currently used antibiotic sulfadimethoxine, notably with an 8-times-lower dose. GI-7 affects the OM integrity and decreases the Lpt protein and LPS levels in APEC, an antibacterial mechanism that can overcome the antibiotic resistance problem. Overall, GI-7 represents a promising lead molecule/scaffold for the development of novel antibacterial therapies that could have profound implications for treating APEC infections in chickens, as well as human infections caused by ExPECs and other related Gram-negative bacteria. Further elucidation of the mechanism of action of GI-7 and identification of its target(s) in APEC will benefit future novel antibacterial development efforts.
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Affiliation(s)
- Dipak Kathayat
- Center for Food Animal Health, Department of Animal Sciences, The Ohio State University, Wooster, Ohio, USA
| | - Yosra A. Helmy
- Center for Food Animal Health, Department of Animal Sciences, The Ohio State University, Wooster, Ohio, USA
| | - Loic Deblais
- Center for Food Animal Health, Department of Animal Sciences, The Ohio State University, Wooster, Ohio, USA
| | - Vishal Srivastava
- Center for Food Animal Health, Department of Animal Sciences, The Ohio State University, Wooster, Ohio, USA
| | - Gary Closs
- Center for Food Animal Health, Department of Animal Sciences, The Ohio State University, Wooster, Ohio, USA
| | - Rahul Khupse
- College of Pharmacy, University of Findlay, Findlay, Ohio, USA
| | - Gireesh Rajashekara
- Center for Food Animal Health, Department of Animal Sciences, The Ohio State University, Wooster, Ohio, USA
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16
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Bacteroidetocins Target the Essential Outer Membrane Protein BamA of Bacteroidales Symbionts and Pathogens. mBio 2021; 12:e0228521. [PMID: 34517753 PMCID: PMC8546649 DOI: 10.1128/mbio.02285-21] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Bacteroidetocins are a family of antibacterial peptide toxins that are produced by and target members of the phylum Bacteroidetes. To date, 19 bacteroidetocins have been identified, and four have been tested and shown to kill diverse Bacteroidales species (M. J. Coyne, N. Béchon, L. M. Matano, V. L. McEneany, et al., Nat Commun 10:3460, 2019, https://doi.org/10.1038/s41467-019-11494-1). Here, we identify the target and likely mechanism of action of the bacteroidetocins. We selected seven spontaneous mutants of four different genera, all resistant to bacteroidetocin A (Bd-A) and found that all contained mutations in a single gene, bamA. Construction of three of these bamA mutants in the wild-type (WT) strains confirmed they confer resistance to Bd-A as well as to other bacteroidetocins. We identified an aspartate residue of BamA at the beginning of exterior loop 3 (eL3) that, when altered, renders strains resistant to Bd-A. Analysis of a panel of diverse Bacteroidales strains showed a correlation between the presence of this aspartate residue and Bd-A sensitivity. Fluorescence microscopy and transmission electron microscopy (TEM) analysis of Bd-A-treated cells showed cellular morphological changes consistent with a BamA defect. Transcriptomic analysis of Bd-A-treated cells revealed gene expression changes indicative of cell envelope stress. Studies in mice revealed that bacteroidetocin-resistant mutants are outcompeted by their WT strain in vivo. Analyses of longitudinal human gut isolates showed that bamA mutations leading to bacteroidetocin resistance do not become fixed in the human gut, even in bacteroidetocin-producing strains and nonproducing coresident strains. Together, these data lend further support to the applicability of the bacteroidetocins as therapeutic peptides in the treatment of maladies involving Bacteroidales species.
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17
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Curley CL, Fedrigoni TP, Flaherty EM, Woodilla CJ, Hagan CL. Bacterial Contact-Dependent Inhibition Protein Binds near the Open Lateral Gate in BamA Prior to Toxin Translocation. Biochemistry 2021; 60:2956-2965. [PMID: 34541845 DOI: 10.1021/acs.biochem.1c00337] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Contact-dependent inhibition (CDI) is a mechanism of interbacterial competition in Gram-negative bacteria. The critical component of CDI systems is a large protein named CdiA; it forms a filament on the bacterial cell surface and contains a toxin domain at its C-terminal end. Upon binding to a receptor protein on the surface of a neighboring cell, CdiA delivers the toxin domain through the outer membrane of the neighboring bacterium. The mechanism of that delivery process is poorly understood. We have characterized how CdiA from E. coli EC93 binds to its receptor, BamA, to understand how this binding event might initiate the process of toxin delivery. BamA is an essential protein that assembles β-barrel proteins into the outer membranes of all Gram-negative bacteria; this assembly process depends on BamA's unique ability to open laterally in the lipid bilayer through a gate in its own membrane-embedded β-barrel. Through site-specific photo-cross-linking and mutational analysis, we demonstrate that the BamA-CdiA interaction depends on a small number of non-conserved amino acids on the extracellular surface of BamA, but the protein interface extends over a region near BamA's lateral gate. We further demonstrate that BamA's lateral gate can open without disrupting the interaction with CdiA. CdiA thus appears to initially engage BamA in a manner that could allow it to utilize BamA's lateral gate in subsequent steps in the toxin translocation process.
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Affiliation(s)
- Cameron L Curley
- Department of Chemistry, The College of the Holy Cross, Worcester, Massachusetts 01610, United States
| | - Thomas P Fedrigoni
- Department of Chemistry, The College of the Holy Cross, Worcester, Massachusetts 01610, United States
| | - Erin M Flaherty
- Department of Chemistry, The College of the Holy Cross, Worcester, Massachusetts 01610, United States
| | - Christopher J Woodilla
- Department of Chemistry, The College of the Holy Cross, Worcester, Massachusetts 01610, United States
| | - Christine L Hagan
- Department of Chemistry, The College of the Holy Cross, Worcester, Massachusetts 01610, United States
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18
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CESA-LUNA CATHERINE, ALATORRE-CRUZ JULIAMARÍA, CARREÑO-LÓPEZ RICARDO, QUINTERO-HERNÁNDEZ VERÓNICA, BAEZ ANTONINO. Emerging Applications of Bacteriocins as Antimicrobials, Anticancer Drugs, and Modulators of The Gastrointestinal Microbiota. Pol J Microbiol 2021; 70:143-159. [PMID: 34349808 PMCID: PMC8326989 DOI: 10.33073/pjm-2021-020] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Revised: 04/06/2021] [Accepted: 04/25/2021] [Indexed: 02/06/2023] Open
Abstract
The use of bacteriocins holds great promise in different areas such as health, food, nutrition, veterinary, nanotechnology, among others. Many research groups worldwide continue to advance the knowledge to unravel a novel range of therapeutic agents and food preservatives. This review addresses the advances of bacteriocins and their producer organisms as biocontrol agents for applications in the medical industry and agriculture. Furthermore, the bacteriocin mechanism of action and structural characteristics will be reviewed. Finally, the potential role of bacteriocins to modulate the signaling in host-associated microbial communities will be discussed.
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Affiliation(s)
- CATHERINE CESA-LUNA
- Centro de Investigaciones en Ciencias Microbiológicas (CICM), Instituto de Ciencias (IC), Benemérita Universidad Autónoma de Puebla (BUAP), Puebla, México
| | | | - RICARDO CARREÑO-LÓPEZ
- Centro de Investigaciones en Ciencias Microbiológicas (CICM), Instituto de Ciencias (IC), Benemérita Universidad Autónoma de Puebla (BUAP), Puebla, México
| | | | - ANTONINO BAEZ
- Centro de Investigaciones en Ciencias Microbiológicas (CICM), Instituto de Ciencias (IC), Benemérita Universidad Autónoma de Puebla (BUAP), Puebla, México
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19
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Page JE, Walker S. Natural products that target the cell envelope. Curr Opin Microbiol 2021; 61:16-24. [PMID: 33662818 PMCID: PMC8169544 DOI: 10.1016/j.mib.2021.02.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 01/22/2021] [Accepted: 02/03/2021] [Indexed: 02/07/2023]
Abstract
The inexorable spread of resistance to clinically used drugs demands that we maintain a full pipeline of antibiotic candidates. As organisms have struggled to survive and compete over evolutionary history, they have developed the capacity to make a remarkably diverse array of natural products that target the cell envelope. A few have been developed for use in the clinic but most have not, and there are still an enormous number of opportunities to investigate. Substrate-binding antibiotics for Gram-positive organisms, phage-derived lysins, and outer membrane protein-targeting agents for Gram-negative organisms represent promising avenues where nature's gifts may be repurposed for use in the clinic.
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Affiliation(s)
- Julia E Page
- Department of Microbiology, Harvard Medical School, HIM1013, 4 Blackfan Circle, Boston, MA, 02115, United States
| | - Suzanne Walker
- Department of Microbiology, Harvard Medical School, HIM1013, 4 Blackfan Circle, Boston, MA, 02115, United States.
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20
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Steenhuis M, van Ulsen P, Martin NI, Luirink J. A ban on BAM: an update on inhibitors of the β-barrel assembly machinery. FEMS Microbiol Lett 2021; 368:6287571. [PMID: 34048543 DOI: 10.1093/femsle/fnab059] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Accepted: 05/26/2021] [Indexed: 12/15/2022] Open
Abstract
Gram-negative pathogens are a rapidly increasing threat to human health worldwide due to high rates of antibiotic resistance and the lack of development of novel antibiotics. The protective cell envelope of gram-negative bacteria is a major permeability barrier that contributes to the problem by restricting the uptake of antibiotics. On the other hand, its unique architecture also makes it a suitable target for antibiotic interference. In particular, essential multiprotein machines that are required for biogenesis of the outer membrane have attracted attention in antibacterial design strategies. Recently, significant progress has been made in the development of inhibitors of the β-barrel assembly machine (BAM) complex. Here, we summarize the current state of drug development efforts targeting the BAM complex in pursuit of new antibiotics.
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Affiliation(s)
- Maurice Steenhuis
- Department of Molecular Microbiology, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Vrije Universiteit, De Boelelaan 1085, 1081 HV, Amsterdam, The Netherlands
| | - Peter van Ulsen
- Department of Molecular Microbiology, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Vrije Universiteit, De Boelelaan 1085, 1081 HV, Amsterdam, The Netherlands
| | - Nathaniel I Martin
- Biological Chemistry Group, Institute of Biology Leiden, Leiden University, Nonnensteeg 3, 2311 VJ, Leiden, The Netherlands
| | - Joen Luirink
- Department of Molecular Microbiology, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Vrije Universiteit, De Boelelaan 1085, 1081 HV, Amsterdam, The Netherlands
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21
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Rooney WM, Chai R, Milner JJ, Walker D. Bacteriocins Targeting Gram-Negative Phytopathogenic Bacteria: Plantibiotics of the Future. Front Microbiol 2020; 11:575981. [PMID: 33042091 PMCID: PMC7530242 DOI: 10.3389/fmicb.2020.575981] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Accepted: 08/25/2020] [Indexed: 12/12/2022] Open
Abstract
Gram-negative phytopathogenic bacteria are a significant threat to food crops. These microbial invaders are responsible for a plethora of plant diseases and can be responsible for devastating losses in crops such as tomatoes, peppers, potatoes, olives, and rice. Current disease management strategies to mitigate yield losses involve the application of chemicals which are often harmful to both human health and the environment. Bacteriocins are small proteinaceous antibiotics produced by bacteria to kill closely related bacteria and thereby establish dominance within a niche. They potentially represent a safer alternative to chemicals when used in the field. Bacteriocins typically show a high degree of selectivity toward their targets with no off-target effects. This review outlines the current state of research on bacteriocins active against Gram-negative phytopathogenic bacteria. Furthermore, we will examine the feasibility of weaponizing bacteriocins for use as a treatment for bacterial plant diseases.
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Affiliation(s)
- William M. Rooney
- Plant Science Group, School of Life Sciences, Institute of Molecular, Cell and Systems Biology, University of Glasgow, Glasgow, United Kingdom
- College of Medical, Veterinary and Life Sciences, Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Ray Chai
- College of Medical, Veterinary and Life Sciences, Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Joel J. Milner
- Plant Science Group, School of Life Sciences, Institute of Molecular, Cell and Systems Biology, University of Glasgow, Glasgow, United Kingdom
| | - Daniel Walker
- College of Medical, Veterinary and Life Sciences, Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
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22
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Horne JE, Brockwell DJ, Radford SE. Role of the lipid bilayer in outer membrane protein folding in Gram-negative bacteria. J Biol Chem 2020; 295:10340-10367. [PMID: 32499369 PMCID: PMC7383365 DOI: 10.1074/jbc.rev120.011473] [Citation(s) in RCA: 77] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 06/03/2020] [Indexed: 01/09/2023] Open
Abstract
β-Barrel outer membrane proteins (OMPs) represent the major proteinaceous component of the outer membrane (OM) of Gram-negative bacteria. These proteins perform key roles in cell structure and morphology, nutrient acquisition, colonization and invasion, and protection against external toxic threats such as antibiotics. To become functional, OMPs must fold and insert into a crowded and asymmetric OM that lacks much freely accessible lipid. This feat is accomplished in the absence of an external energy source and is thought to be driven by the high thermodynamic stability of folded OMPs in the OM. With such a stable fold, the challenge that bacteria face in assembling OMPs into the OM is how to overcome the initial energy barrier of membrane insertion. In this review, we highlight the roles of the lipid environment and the OM in modulating the OMP-folding landscape and discuss the factors that guide folding in vitro and in vivo We particularly focus on the composition, architecture, and physical properties of the OM and how an understanding of the folding properties of OMPs in vitro can help explain the challenges they encounter during folding in vivo Current models of OMP biogenesis in the cellular environment are still in flux, but the stakes for improving the accuracy of these models are high. OMP folding is an essential process in all Gram-negative bacteria, and considering the looming crisis of widespread microbial drug resistance it is an attractive target. To bring down this vital OMP-supported barrier to antibiotics, we must first understand how bacterial cells build it.
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Affiliation(s)
- Jim E Horne
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - David J Brockwell
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Sheena E Radford
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
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23
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Vitale A, Pessi G, Urfer M, Locher HH, Zerbe K, Obrecht D, Robinson JA, Eberl L. Identification of Genes Required for Resistance to Peptidomimetic Antibiotics by Transposon Sequencing. Front Microbiol 2020; 11:1681. [PMID: 32793157 PMCID: PMC7390954 DOI: 10.3389/fmicb.2020.01681] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Accepted: 06/26/2020] [Indexed: 12/27/2022] Open
Abstract
Pseudomonas aeruginosa is an opportunistic human pathogen and a leading cause of nosocomial infections. Due to its high intrinsic and adaptive resistance to antibiotics, infections caused by this organism are difficult to treat and new therapeutic options are urgently needed. Novel peptidomimetic antibiotics that target outer membrane (OM) proteins have shown great promise for the treatment of P. aeruginosa infections. Here, we have performed genome-wide mutant fitness profiling using transposon sequencing (Tn-Seq) to identify resistance determinants against the recently described peptidomimetics L27-11, compounds 3 and 4, as well as polymyxin B2 (PMB) and colistin (COL). We identified a set of 13 core genes that affected resistance to all tested antibiotics, many of which encode enzymes involved in the modification of the lipopolysaccharide (LPS) or control their expression. We also identified fitness determinants that are specific for antibiotics with similar structures that may indicate differences in their modes of action. These results provide new insights into resistance mechanisms against these peptide antibiotics, which will be important for future clinical development and efforts to further improve their potency.
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Affiliation(s)
- Alessandra Vitale
- Department of Plant and Microbial Biology, University of Zurich, Zurich, Switzerland
| | - Gabriella Pessi
- Department of Plant and Microbial Biology, University of Zurich, Zurich, Switzerland
| | | | | | - Katja Zerbe
- Department of Chemistry, University of Zurich, Zurich, Switzerland
| | | | - John A Robinson
- Department of Chemistry, University of Zurich, Zurich, Switzerland
| | - Leo Eberl
- Department of Plant and Microbial Biology, University of Zurich, Zurich, Switzerland
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24
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Shotgun Proteomics of Ascidians Tunic Gives New Insights on Host-Microbe Interactions by Revealing Diverse Antimicrobial Peptides. Mar Drugs 2020; 18:md18070362. [PMID: 32668814 PMCID: PMC7401272 DOI: 10.3390/md18070362] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 07/09/2020] [Accepted: 07/10/2020] [Indexed: 12/26/2022] Open
Abstract
Ascidians are marine invertebrates associated with diverse microbial communities, embedded in their tunic, conferring special ecological and biotechnological relevance to these model organisms used in evolutionary and developmental studies. Next-generation sequencing tools have increased the knowledge of ascidians’ associated organisms and their products, but proteomic studies are still scarce. Hence, we explored the tunic of three ascidian species using a shotgun proteomics approach. Proteins extracted from the tunic of Ciona sp., Molgula sp., and Microcosmus sp. were processed using a nano LC-MS/MS system (Ultimate 3000 liquid chromatography system coupled to a Q-Exactive Hybrid Quadrupole-Orbitrap mass spectrometer). Raw data was searched against UniProtKB – the Universal Protein Resource Knowledgebase (Bacteria and Metazoa section) using Proteome Discoverer software. The resulting proteins were merged with a non-redundant Antimicrobial Peptides (AMPs) database and analysed with MaxQuant freeware. Overall, 337 metazoan and 106 bacterial proteins were identified being mainly involved in basal metabolism, cytoskeletal and catalytic functions. 37 AMPs were identified, most of them attributed to eukaryotic origin apart from bacteriocins. These results and the presence of “Biosynthesis of antibiotics” as one of the most highlighted pathways revealed the tunic as a very active tissue in terms of bioactive compounds production, giving insights on the interactions between host and associated organisms. Although the present work constitutes an exploratory study, the approach employed revealed high potential for high-throughput characterization and biodiscovery of the ascidians’ tunic and its microbiome.
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25
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Rooney WM, Grinter RW, Correia A, Parkhill J, Walker DC, Milner JJ. Engineering bacteriocin-mediated resistance against the plant pathogen Pseudomonas syringae. PLANT BIOTECHNOLOGY JOURNAL 2020; 18:1296-1306. [PMID: 31705720 PMCID: PMC7152609 DOI: 10.1111/pbi.13294] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Revised: 10/16/2019] [Accepted: 10/27/2019] [Indexed: 05/20/2023]
Abstract
The plant pathogen, Pseudomonas syringae (Ps), together with related Ps species, infects and attacks a wide range of agronomically important crops, including tomato, kiwifruit, pepper, olive and soybean, causing economic losses. Currently, chemicals and introduced resistance genes are used to protect plants against these pathogens but have limited success and may have adverse environmental impacts. Consequently, there is a pressing need to develop alternative strategies to combat bacterial disease in crops. One such strategy involves using narrow-spectrum protein antibiotics (so-called bacteriocins), which diverse bacteria use to compete against closely related species. Here, we demonstrate that one bacteriocin, putidacin L1 (PL1), can be expressed in an active form at high levels in Arabidopsis and in Nicotiana benthamiana in planta to provide effective resistance against diverse pathovars of Ps. Furthermore, we find that Ps strains that mutate to acquire tolerance to PL1 lose their O-antigen, exhibit reduced motility and still cannot induce disease symptoms in PL1-transgenic Arabidopsis. Our results provide proof-of-principle that the transgene-mediated expression of a bacteriocin in planta can provide effective disease resistance to bacterial pathogens. Thus, the expression of bacteriocins in crops might offer an effective strategy for managing bacterial disease, in the same way that the genetic modification of crops to express insecticidal proteins has proven to be an extremely successful strategy for pest management. Crucially, nearly all genera of bacteria, including many plant pathogenic species, produce bacteriocins, providing an extensive source of these antimicrobial agents.
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Affiliation(s)
- William M. Rooney
- Plant Science GroupInstitute of Molecular, Cell and Systems Biology & School of Life SciencesUniversity of GlasgowGlasgowUK
- Institute of Infection, Immunity & InflammationCollege of Medical, Veterinary & Life SciencesUniversity of GlasgowGlasgowUK
| | - Rhys W. Grinter
- Institute of Infection, Immunity & InflammationCollege of Medical, Veterinary & Life SciencesUniversity of GlasgowGlasgowUK
- Present address:
School of Biological SciencesCentre for Geometric BiologyMonash UniversityClaytonVictoria3800Australia
| | - Annapaula Correia
- Wellcome Trust Sanger InstituteWellcome Trust Genome CampusHinxtonUK
- Present address:
Department of ZoologyUniversity of OxfordSouth Parks RoadOxfordOX1 3PSUK
| | - Julian Parkhill
- Wellcome Trust Sanger InstituteWellcome Trust Genome CampusHinxtonUK
- Present address:
Department of Veterinary MedicineUniversity of CambridgeMadingley RoadCambridgeCB3 0ESUK
| | - Daniel C. Walker
- Institute of Infection, Immunity & InflammationCollege of Medical, Veterinary & Life SciencesUniversity of GlasgowGlasgowUK
| | - Joel J. Milner
- Plant Science GroupInstitute of Molecular, Cell and Systems Biology & School of Life SciencesUniversity of GlasgowGlasgowUK
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26
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The Role of Pseudomonas aeruginosa Lipopolysaccharide in Bacterial Pathogenesis and Physiology. Pathogens 2019; 9:pathogens9010006. [PMID: 31861540 PMCID: PMC7168646 DOI: 10.3390/pathogens9010006] [Citation(s) in RCA: 89] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Revised: 12/15/2019] [Accepted: 12/17/2019] [Indexed: 12/13/2022] Open
Abstract
The major constituent of the outer membrane of Gram-negative bacteria is lipopolysaccharide (LPS), which is comprised of lipid A, core oligosaccharide, and O antigen, which is a long polysaccharide chain extending into the extracellular environment. Due to the localization of LPS, it is a key molecule on the bacterial cell wall that is recognized by the host to deploy an immune defence in order to neutralize invading pathogens. However, LPS also promotes bacterial survival in a host environment by protecting the bacteria from these threats. This review explores the relationship between the different LPS glycoforms of the opportunistic pathogen Pseudomonas aeruginosa and the ability of this organism to cause persistent infections, especially in the genetic disease cystic fibrosis. We also discuss the role of LPS in facilitating biofilm formation, antibiotic resistance, and how LPS may be targeted by new antimicrobial therapies.
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27
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MacNair CR, Tsai CN, Brown ED. Creative targeting of the Gram-negative outer membrane in antibiotic discovery. Ann N Y Acad Sci 2019; 1459:69-85. [PMID: 31762048 DOI: 10.1111/nyas.14280] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 10/30/2019] [Accepted: 10/31/2019] [Indexed: 12/13/2022]
Abstract
The rising threat of multidrug-resistant Gram-negative bacteria is exacerbated by the scarcity of new antibiotics in the development pipeline. Permeability through the outer membrane remains one of the leading hurdles in discovery efforts. However, the essentiality of a robust outer membrane makes itself an intriguing antimicrobial target. Herein, we review drug discovery efforts targeting the outer membrane and the prospective antimicrobial leads identified.
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Affiliation(s)
- Craig R MacNair
- Michael G. DeGroote Institute for Infectious Disease Research, Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
| | - Caressa N Tsai
- Michael G. DeGroote Institute for Infectious Disease Research, Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
| | - Eric D Brown
- Michael G. DeGroote Institute for Infectious Disease Research, Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
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28
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Imai Y, Meyer KJ, Iinishi A, Favre-Godal Q, Green R, Manuse S, Caboni M, Mori M, Niles S, Ghiglieri M, Honrao C, Ma X, Guo JJ, Makriyannis A, Linares-Otoya L, Böhringer N, Wuisan ZG, Kaur H, Wu R, Mateus A, Typas A, Savitski MM, Espinoza JL, O'Rourke A, Nelson KE, Hiller S, Noinaj N, Schäberle TF, D'Onofrio A, Lewis K. A new antibiotic selectively kills Gram-negative pathogens. Nature 2019; 576:459-464. [PMID: 31747680 PMCID: PMC7188312 DOI: 10.1038/s41586-019-1791-1] [Citation(s) in RCA: 402] [Impact Index Per Article: 80.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Accepted: 11/08/2019] [Indexed: 11/16/2022]
Abstract
The current need for novel antibiotics is especially acute for
drug-resistant Gram-negative pathogens1,2. These
microorganisms have a highly restrictive permeability barrier, which limits
penetration of most compounds3,4. As a result, the last class of
antibiotics acting against Gram-negative bacteria was developed in the
60s2. We reason that
useful compounds can be found in bacteria that share similar requirements for
antibiotics with humans, and focus on Photorhabdus symbionts of
entomopathogenic nematode microbiomes. Here we report a new antibiotic that we
name darobactin, from a screen of Photorhabdus isolates.
Darobactin is coded by a silent operon with little production under laboratory
conditions, and is ribosomally synthesized. Darobactin has an unusual structure
with two fused rings that form post-translationally. The compound is active
against important Gram-negative pathogens both in vitro and in
animal models of infection. Mutants resistant to darobactin map to BamA, an
essential chaperone and translocator that folds outer membrane proteins. Our
study suggests that bacterial symbionts of animals harbor antibiotics that are
particularly suitable for development into therapeutics.
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Affiliation(s)
- Yu Imai
- Antimicrobial Discovery Center, Department of Biology, Northeastern University, Boston, MA, USA
| | - Kirsten J Meyer
- Antimicrobial Discovery Center, Department of Biology, Northeastern University, Boston, MA, USA
| | - Akira Iinishi
- Antimicrobial Discovery Center, Department of Biology, Northeastern University, Boston, MA, USA
| | - Quentin Favre-Godal
- Antimicrobial Discovery Center, Department of Biology, Northeastern University, Boston, MA, USA
| | - Robert Green
- Antimicrobial Discovery Center, Department of Biology, Northeastern University, Boston, MA, USA
| | - Sylvie Manuse
- Antimicrobial Discovery Center, Department of Biology, Northeastern University, Boston, MA, USA
| | - Mariaelena Caboni
- Antimicrobial Discovery Center, Department of Biology, Northeastern University, Boston, MA, USA
| | - Miho Mori
- Antimicrobial Discovery Center, Department of Biology, Northeastern University, Boston, MA, USA
| | - Samantha Niles
- Antimicrobial Discovery Center, Department of Biology, Northeastern University, Boston, MA, USA
| | - Meghan Ghiglieri
- Antimicrobial Discovery Center, Department of Biology, Northeastern University, Boston, MA, USA
| | - Chandrashekhar Honrao
- Center for Drug Discovery, Department of Pharmaceutical Sciences, Northeastern University, Boston, MA, USA
| | - Xiaoyu Ma
- Center for Drug Discovery, Department of Pharmaceutical Sciences, Northeastern University, Boston, MA, USA
| | - Jason J Guo
- Center for Drug Discovery, Department of Pharmaceutical Sciences, Northeastern University, Boston, MA, USA.,Barnett Institute for Chemical and Biological Analysis, Department of Chemistry and Chemical Biology, Northeastern University, Boston, MA, USA
| | - Alexandros Makriyannis
- Center for Drug Discovery, Department of Pharmaceutical Sciences, Northeastern University, Boston, MA, USA
| | - Luis Linares-Otoya
- Institute for Insect Biotechnology, Justus-Liebig-University of Giessen, Giessen, Germany
| | - Nils Böhringer
- Institute for Insect Biotechnology, Justus-Liebig-University of Giessen, Giessen, Germany
| | - Zerlina G Wuisan
- Institute for Insect Biotechnology, Justus-Liebig-University of Giessen, Giessen, Germany
| | - Hundeep Kaur
- Biozentrum, University of Basel, Basel, Switzerland
| | - Runrun Wu
- Purdue Institute of Inflammation, Immunology and Infectious Disease, Purdue University, West Lafayette, IN, USA.,Markey Center for Structural Biology, Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
| | - André Mateus
- Genome Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Athanasios Typas
- Genome Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Mikhail M Savitski
- Genome Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Josh L Espinoza
- Department of Human Biology, J. Craig Venter Institute, La Jolla, CA, USA.,Department of Genomic Medicine, J. Craig Venter Institute, La Jolla, CA, USA
| | - Aubrie O'Rourke
- Department of Human Biology, J. Craig Venter Institute, La Jolla, CA, USA.,Department of Genomic Medicine, J. Craig Venter Institute, La Jolla, CA, USA
| | - Karen E Nelson
- Department of Human Biology, J. Craig Venter Institute, La Jolla, CA, USA.,Department of Genomic Medicine, J. Craig Venter Institute, La Jolla, CA, USA.,Department of Human Biology, J. Craig Venter Institute, Rockville, MD, USA.,Department of Genomic Medicine, J. Craig Venter Institute, Rockville, MD, USA
| | | | - Nicholas Noinaj
- Purdue Institute of Inflammation, Immunology and Infectious Disease, Purdue University, West Lafayette, IN, USA.,Markey Center for Structural Biology, Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
| | - Till F Schäberle
- Institute for Insect Biotechnology, Justus-Liebig-University of Giessen, Giessen, Germany.,Department of Bioresources, Fraunhofer Institute for Molecular Biology and Applied Ecology, Giessen, Germany.,German Center for Infection Research (DZIF), Partner Site Giessen-Marburg-Langen, Giessen, Germany
| | - Anthony D'Onofrio
- Antimicrobial Discovery Center, Department of Biology, Northeastern University, Boston, MA, USA
| | - Kim Lewis
- Antimicrobial Discovery Center, Department of Biology, Northeastern University, Boston, MA, USA.
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29
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Hews CL, Cho T, Rowley G, Raivio TL. Maintaining Integrity Under Stress: Envelope Stress Response Regulation of Pathogenesis in Gram-Negative Bacteria. Front Cell Infect Microbiol 2019; 9:313. [PMID: 31552196 PMCID: PMC6737893 DOI: 10.3389/fcimb.2019.00313] [Citation(s) in RCA: 77] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Accepted: 08/19/2019] [Indexed: 12/20/2022] Open
Abstract
The Gram-negative bacterial envelope is an essential interface between the intracellular and harsh extracellular environment. Envelope stress responses (ESRs) are crucial to the maintenance of this barrier and function to detect and respond to perturbations in the envelope, caused by environmental stresses. Pathogenic bacteria are exposed to an array of challenging and stressful conditions during their lifecycle and, in particular, during infection of a host. As such, maintenance of envelope homeostasis is essential to their ability to successfully cause infection. This review will discuss our current understanding of the σE- and Cpx-regulated ESRs, with a specific focus on their role in the virulence of a number of model pathogens.
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Affiliation(s)
- Claire L Hews
- School of Biological Sciences, University of East Anglia, Norwich, United Kingdom
| | - Timothy Cho
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
| | - Gary Rowley
- School of Biological Sciences, University of East Anglia, Norwich, United Kingdom
| | - Tracy L Raivio
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
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30
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Diversity of Contact-Dependent Growth Inhibition Systems of Pseudomonas aeruginosa. J Bacteriol 2019; 201:JB.00776-18. [PMID: 31036723 DOI: 10.1128/jb.00776-18] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Contact-dependent growth inhibition (CDI) systems are used in bacterial competition to hinder the growth of neighboring microbes. These systems utilize a two-partner secretion mechanism to display the CdiA exoprotein at the bacterial cell surface. CdiA forms a long filamentous stalk that facilitates binding to a target cell and delivery of a C-terminal toxin (CT) domain. This CT domain is processed and delivered into the cytoplasm of a target cell upon contact. CDI systems also encode a cognate immunity protein (CdiI) that protects siblings and resistant targeted cells from intoxication by high-affinity binding to the CT. CdiA CT domains vary among strains within a species, and many alleles encode enzymatic functions that target nucleic acids. This variation is thought to help drive diversity and adaptation within a species. CdiA diversity is well studied in Escherichia coli and several other bacteria, but little is known about the extent of this diversity in Pseudomonas aeruginosa. The purpose of this review is to highlight the variability that exists in CDI systems of P. aeruginosa. We show that this diversity is apparent even among strains isolated from a single geographical region, suggesting that CDI systems play an important role in the ecology of P. aeruginosa.
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31
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Ghequire MGK, De Mot R. LlpB represents a second subclass of lectin-like bacteriocins. Microb Biotechnol 2019; 12:567-573. [PMID: 30702207 PMCID: PMC6465234 DOI: 10.1111/1751-7915.13373] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Revised: 01/14/2019] [Accepted: 01/15/2019] [Indexed: 12/11/2022] Open
Abstract
Bacteriocins are secreted bacterial proteins that selectively kill related strains. Lectin-like bacteriocins are atypical bacteriocins not requiring a cognate immunity factor and have been primarily studied in Pseudomonas. These so-called LlpAs are composed of a tandem of B-lectin domains. One domain interacts with d-rhamnose residues in the common polysaccharide antigen of Pseudomonas lipopolysaccharide (LPS). The other lectin domain is crucial for interference with the outer membrane protein assembly machinery by interacting with surface-exposed loops of its central component BamA. Via genome mining, we identified a second subclass of Pseudomonas lectin-like proteins, termed LlpB, consisting of a single B-lectin domain. We show that these proteins also display bactericidal activity. Among LlpB-resistant transposon mutants of an LlpB-susceptible Pseudomonas strain, a major subset was hit in an acyltransferase gene, predicted to be involved in LPS core modification, hereby suggesting that LlpBs equally attach to LPS for surface anchoring. This indicates that LPS binding and target strain specificity are condensed in a single B-lectin domain. The identification of this second subclass of lectin-like bacteriocins further expands the toolbox of antibacterial warfare deployed by bacteria and holds potential for their integration in biotechnological applications.
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Affiliation(s)
- Maarten G. K. Ghequire
- Centre of Microbial and Plant GeneticsKU LeuvenKasteelpark Arenberg 20 bus 24603001HeverleeBelgium
| | - René De Mot
- Centre of Microbial and Plant GeneticsKU LeuvenKasteelpark Arenberg 20 bus 24603001HeverleeBelgium
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32
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Robinson JA. Folded Synthetic Peptides and Other Molecules Targeting Outer Membrane Protein Complexes in Gram-Negative Bacteria. Front Chem 2019; 7:45. [PMID: 30788339 PMCID: PMC6372539 DOI: 10.3389/fchem.2019.00045] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Accepted: 01/17/2019] [Indexed: 02/06/2023] Open
Abstract
Conformationally constrained peptidomimetics have been developed to mimic interfacial epitopes and target a wide selection of protein-protein interactions. ß-Hairpin mimetics based on constrained macrocyclic peptides have provided access to excellent structural mimics of ß-hairpin epitopes and found applications as interaction inhibitors in many areas of biology and medicinal chemistry. Recently, ß-hairpin peptidomimetics and naturally occurring ß-hairpin-shaped peptides have also been discovered with potent antimicrobial activity and novel mechanisms of action, targeting essential outer membrane protein (OMP) complexes in Gram-negative bacteria. This includes the Lpt complex, required for transporting LPS to the cell surface during OM biogenesis and the BAM complex that folds OMPs and inserts them into the OM bilayer. The Lpt complex is a macromolecular superstructure comprising seven different proteins (LptA-LptG) that spans the entire bacterial cell envelope, whereas the BAM complex is a folding machine comprising a ß-barrel OMP (BamA) and four different lipoproteins (BamB-BamE). Folded synthetic and natural ß-hairpin-shaped peptides appear well-suited for interacting with proteins within the Lpt and BAM complexes that are rich in ß-structure. Recent progress in identifying antibiotics targeting these complexes are reviewed here. Already a clinical candidate has been developed (murepavadin) that targets LptD, with potent antimicrobial activity specifically against pseudmonads. The ability of folded synthetic ß-hairpin epitope mimetics to interact with ß-barrel and ß-jellyroll domains in the Lpt and Bam complexes represent new avenues for antibiotic discovery, which may lead to the development of much needed new antimicrobials to combat the rise of drug-resistant pathogenic Gram-negative bacteria.
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Affiliation(s)
- John A Robinson
- Department of Chemistry, University of Zurich, Zurich, Switzerland
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33
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Salazar AJ, Sherekar M, Tsai J, Sacchettini JC. R pyocin tail fiber structure reveals a receptor-binding domain with a lectin fold. PLoS One 2019; 14:e0211432. [PMID: 30721244 PMCID: PMC6363177 DOI: 10.1371/journal.pone.0211432] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Accepted: 01/14/2019] [Indexed: 01/07/2023] Open
Abstract
R pyocins are ɸCTX-like myophage tailocins of Pseudomonas sp. Adsorption of R pyocins to target strains occurs by the interaction of tail fiber proteins with core lipopolysaccharide (LPS). Here, we demonstrate that N-terminally truncated R pyocin tail fibers corresponding to a region of variation between R-subtypes are sufficient to bind target strains according to R-subtype. We also report the crystal structures of these tail fiber proteins and show that they form an elongated helical trimer composed of three domains arranged linearly from N- to C-terminus: a baseplate proximal head, medial shaft, and distal foot. The head and shaft domains contain novel structural motifs. The foot domain, however, is composed of a conserved jellyroll fold and shares high structural similarity to the tail fiber of myophage AP22, podophage tailspike C-terminal domains (LKA-1 and ɸ297), and several eukaryotic adhesins (discoidin I/II, agglutinin, and octocoral lectin). Many of these proteins bind polysaccharides by means of their distal loop network, a series of highly variable loops at one end of the conserved jellyroll fold backbone. Our structures reveal that the majority of R-subtype specific polymorphisms cluster in patches covering a cleft formed at the oligomeric interface of the head domain and in a large patch covering much of the foot domain, including the distal loop network. Based on the structural variation in distal loops within the foot region, we propose that the foot is the primary sugar-binding domain of R pyocins and R-subtype specific structural differences in the foot domain distal loop network are responsible for binding target strains in an R-subtype dependent manner.
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Affiliation(s)
- Adam J. Salazar
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, United States of America
| | - Mukul Sherekar
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, United States of America
| | - Jennifer Tsai
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, United States of America
| | - James C. Sacchettini
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, United States of America
- * E-mail:
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34
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Raabis S, Li W, Cersosimo L. Effects and immune responses of probiotic treatment in ruminants. Vet Immunol Immunopathol 2019; 208:58-66. [PMID: 30712793 PMCID: PMC6526955 DOI: 10.1016/j.vetimm.2018.12.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Revised: 10/25/2018] [Accepted: 12/30/2018] [Indexed: 02/07/2023]
Abstract
Gut microbial colonization and establishment are vital to ruminant health and production. This review article focuses on current knowledge and methods used to understand and manipulate the gut microbial community in ruminant animals, with a special focus on probiotics treatment. This review highlights the most promising of studies in this area, including gut microbial colonization and establishment, effect of gastrointestinal tract microbial community on host mucosal innate immune function, impact of feeding strategies on gut microbial community, current probiotic treatments in ruminants, methods to manipulate the gut microbiota and associated antimicrobial compounds, and models and cell lines used in understanding the host immune response to probiotic treatments. As a lot of work in this area was done in humans and mice, this review article also includes up-to-date knowledge from relevant studies in human and mouse models. This review is a useful resource for scientists working in the areas of ruminant nutrition and health, and to researchers investigating the microbial ecology and its relation to animal health.
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Affiliation(s)
- Sarah Raabis
- School of Veterinary Medicine, University of Wisconsin-Madison, United States
| | - Wenli Li
- Dairy Forage Research Center, Agricultural Research Service, USDA, 1925 Linden Drive, Madison, WI, 53706, United States.
| | - Laura Cersosimo
- University of Florida, Department of Animal Sciences, Gainesville, FL, United States
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35
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Biessy A, Novinscak A, Blom J, Léger G, Thomashow LS, Cazorla FM, Josic D, Filion M. Diversity of phytobeneficial traits revealed by whole-genome analysis of worldwide-isolated phenazine-producing Pseudomonas spp. Environ Microbiol 2018; 21:437-455. [PMID: 30421490 DOI: 10.1111/1462-2920.14476] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Revised: 11/02/2018] [Accepted: 11/06/2018] [Indexed: 12/24/2022]
Abstract
Plant-beneficial Pseudomonas spp. competitively colonize the rhizosphere and display plant-growth promotion and/or disease-suppression activities. Some strains within the P. fluorescens species complex produce phenazine derivatives, such as phenazine-1-carboxylic acid. These antimicrobial compounds are broadly inhibitory to numerous soil-dwelling plant pathogens and play a role in the ecological competence of phenazine-producing Pseudomonas spp. We assembled a collection encompassing 63 strains representative of the worldwide diversity of plant-beneficial phenazine-producing Pseudomonas spp. In this study, we report the sequencing of 58 complete genomes using PacBio RS II sequencing technology. Distributed among four subgroups within the P. fluorescens species complex, the diversity of our collection is reflected by the large pangenome which accounts for 25 413 protein-coding genes. We identified genes and clusters encoding for numerous phytobeneficial traits, including antibiotics, siderophores and cyclic lipopeptides biosynthesis, some of which were previously unknown in these microorganisms. Finally, we gained insight into the evolutionary history of the phenazine biosynthetic operon. Given its diverse genomic context, it is likely that this operon was relocated several times during Pseudomonas evolution. Our findings acknowledge the tremendous diversity of plant-beneficial phenazine-producing Pseudomonas spp., paving the way for comparative analyses to identify new genetic determinants involved in biocontrol, plant-growth promotion and rhizosphere competence.
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Affiliation(s)
- Adrien Biessy
- Department of Biology, Université de Moncton, Moncton, NB, Canada
| | - Amy Novinscak
- Department of Biology, Université de Moncton, Moncton, NB, Canada
| | - Jochen Blom
- Bioinformatics and Systems Biology, Justus-Liebig-Universität Giessen, Giessen, Germany
| | - Geneviève Léger
- Department of Biology, Université de Moncton, Moncton, NB, Canada
| | - Linda S Thomashow
- United States Department of Agriculture - Agricultural Research Service, Pullman, WA, USA
| | - Francisco M Cazorla
- Instituto de Hortofruticultura Subtropical y Mediterránea "La Mayora", Universidad de Málaga, Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Departamento de Microbiología, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain
| | - Dragana Josic
- Department of Microbiology, Institute of Soil Science, Belgrade, Serbia
| | - Martin Filion
- Department of Biology, Université de Moncton, Moncton, NB, Canada
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36
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Ghequire MGK, Öztürk B, De Mot R. Lectin-Like Bacteriocins. Front Microbiol 2018; 9:2706. [PMID: 30483232 PMCID: PMC6240691 DOI: 10.3389/fmicb.2018.02706] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Accepted: 10/23/2018] [Indexed: 12/22/2022] Open
Abstract
Bacteria produce a diverse array of antagonistic compounds to restrict growth of microbial rivals. Contributing to this warfare are bacteriocins: secreted antibacterial peptides, proteins and multi-protein complexes. These compounds typically eliminate competitors closely related to the producer. Lectin-like bacteriocins (LlpAs) constitute a distinct class of such proteins, produced by Pseudomonas as well as some other proteobacterial genera. LlpAs share a common architecture consisting of two B-lectin domains, followed by a short carboxy-terminal extension. Two surface-exposed moieties on susceptible Pseudomonas cells are targeted by the respective lectin modules. The carboxy-terminal domain binds D-rhamnose residues present in the lipopolysaccharide layer, whereas the amino-terminal domain interacts with a polymorphic external loop of the outer-membrane protein insertase BamA, hence determining selectivity. The absence of a toxin-immunity module as found in modular bacteriocins and other polymorphic toxin systems, hints toward a novel mode of killing initiated at the cellular surface, not requiring bacteriocin import. Despite significant progress in understanding the function of LlpAs, outstanding questions include the secretion machinery recruited by lectin-like bacteriocins for their release, as well as a better understanding of the environmental signals initiating their expression.
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Affiliation(s)
| | - Başak Öztürk
- Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen, Braunschweig, Germany
| | - René De Mot
- Centre of Microbial and Plant Genetics, KU Leuven, Leuven, Belgium
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37
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Ghequire MGK, Öztürk B. A Colicin M-Type Bacteriocin from Pseudomonas aeruginosa Targeting the HxuC Heme Receptor Requires a Novel Immunity Partner. Appl Environ Microbiol 2018; 84:e00716-18. [PMID: 29980560 PMCID: PMC6121995 DOI: 10.1128/aem.00716-18] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Accepted: 06/28/2018] [Indexed: 12/16/2022] Open
Abstract
Pyocins are bacteriocins secreted by Pseudomonas aeruginosa, and they assist in the colonization of different niches. A major subset of these antibacterial proteins adopt a modular organization characteristic of polymorphic toxins. They include a receptor-binding domain, a segment enabling membrane passage, and a toxin module at the carboxy terminus, which eventually kills the target cells. To protect themselves from their own products, bacteriocin-producing strains express an immunity gene concomitantly with the bacteriocin. We show here that a pyocin equipped with a phylogenetically distinct ColM toxin domain, PaeM4, mediates antagonism against a large set of P. aeruginosa isolates. Immunity to PaeM4 is provided by the inner membrane protein PmiC, which is equipped with a transmembrane topology not previously described for the ColM family. Given that strains lacking a pmiC gene are killed by PaeM4, the presence of such an immunity partner likely is a key criterion for escaping cellular death mediated by PaeM4. The presence of a TonB box in PaeM4 and enhanced bacteriocin activity under iron-poor conditions strongly suggested the targeting of a TonB-dependent receptor. Evaluation of PaeM4 activities against TonB-dependent receptor knockout mutants in P. aeruginosa PAO1 revealed that the heme receptor HxuC (PA1302) serves as a PaeM4 target at the cellular surface. Because other ColM-type pyocins may target the ferrichrome receptor FiuA, our results illustrate the versatility in target recognition conferred by the polymorphic nature of ColM-type bacteriocins.IMPORTANCE The antimicrobial armamentarium of a bacterium is a major asset for colonizing competitive environments. Bacteriocins comprise a subset of these compounds. Pyocins are an example of such antibacterial proteins produced by Pseudomonas aeruginosa, killing other P. aeruginosa strains. A large group of these molecules show a modular protein architecture that includes a receptor-binding domain for initial target cell attachment and a killer domain. In this study, we have shown that a novel modular pyocin (PaeM4) that kills target bacteria via interference with peptidoglycan assembly takes advantage of the HxuC heme receptor. Cells can protect themselves from killing by the presence of a dedicated immunity partner, an integral inner membrane protein that adopts a transmembrane topology distinct from that of proteins currently known to provide immunity against such toxin activity. Understanding the receptors with which pyocins interact and how immunity to pyocins is achieved is a pivotal step toward the rational design of bacteriocin cocktails for the treatment of P. aeruginosa infections.
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Affiliation(s)
| | - Başak Öztürk
- Leibniz Institut DSMZ-German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany
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38
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Pseudomonas chlororaphis Produces Multiple R-Tailocin Particles That Broaden the Killing Spectrum and Contribute to Persistence in Rhizosphere Communities. Appl Environ Microbiol 2018; 84:AEM.01230-18. [PMID: 30030224 DOI: 10.1128/aem.01230-18] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Accepted: 07/10/2018] [Indexed: 12/18/2022] Open
Abstract
R-tailocins are high-molecular-weight bacteriocins resembling bacteriophage tails. Pseudomonas chlororaphis 30-84 is a plant growth-promoting rhizobacterial (PGPR) strain that produces two distinct R-tailocin particles with different killing spectra. The two R-tailocins have different evolutionary histories but are released by the same lysis cassette. A previous study showed that both tailocins are important for pairwise competition with susceptible rhizosphere-colonizing strains; however, the broader role of tailocins in competition with the native rhizosphere microbiome was not tested. Genomic analysis of the P. chlororaphis 30-84 R-tailocin gene cluster uncovered the presence of three tail fiber genes in the tailocin 2 genetic module that could potentially result in tailocin 2 particles having different tail fibers and thus a wider killing spectrum. In this study, the tail fibers were found to incorporate onto different tailocin 2 particles, each with a distinct killing spectrum. A loss of production of one or both tailocins resulted in decreased P. chlororaphis 30-84 persistence within the wheat rhizosphere when in competition with the native microflora but not bulk soil. The capacity to produce three different versions of a single tailocin, each having one of three different types of tail fibers, is a previously unreported mechanism that leads to a broader R-tailocin killing spectrum. This study also provides evidence for the function of R-tailocins in competition with rhizosphere microbiome communities but not in bulk soil.IMPORTANCE Although R-tailocin gene clusters typically encode one tail fiber protein, three tail fiber-resembling genes were identified in association with one of the two sets of R-tailocin genes within the tailocin cluster of P. chlororaphis 30-84 and other sequenced P. chlororaphis strain genomes. This study confirmed that P. chlororaphis 30-84 not only produces two distinct tailocins, but that one of them is produced with three different types of tail fibers. This is a previously unreported strategy to increase the breadth of strains targeted by an R-tailocin. Our finding that R-tailocins produced by a PGPR Pseudomonas strain enhanced its persistence within the wheat rhizosphere microbiome confirms that R-tailocin production contributes to the population dynamics of rhizobacterial communities.
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