Publications
Results
- Showing results for:
- Reset all filters
Search results
-
Journal articleMullish BH, Ghani R, McDonald J, et al., 2019,
Faecal microbiota transplant for eradication of multidrug-resistant Enterobacteriaceae: a lesson in applying best practice? Re: 'A five-day course of oral antibiotics followed by faecal transplantation to eradicate carriage of multidrug-resistant Enterobacteriaceae: A Randomized Clinical Trial'
, Clinical Microbiology and Infection, Vol: 25, Pages: 912-913, ISSN: 1198-743X -
Journal articleTosi T, Hoshiga F, Millership C, et al., 2019,
Inhibition of the Staphylococcus aureus c-di-AMP cyclase DacA by direct interaction with the phosphoglucosamine mutase GlmM
, PLoS Pathogens, Vol: 15, Pages: 1-28, ISSN: 1553-7366c-di-AMP is an important second messenger molecule that plays a pivotal role in regulating fundamental cellular processes, including osmotic and cell wall homeostasis in many Gram-positive organisms. In the opportunistic human pathogen Staphylococcus aureus, c-di-AMP is produced by the membrane-anchored DacA enzyme. Inactivation of this enzyme leads to a growth arrest under standard laboratory growth conditions and a re-sensitization of methicillin-resistant S. aureus (MRSA) strains to ß-lactam antibiotics. The gene coding for DacA is part of the conserved three-gene dacA/ybbR/glmM operon that also encodes the proposed DacA regulator YbbR and the essential phosphoglucosamine mutase GlmM, which is required for the production of glucosamine-1-phosphate, an early intermediate of peptidoglycan synthesis. These three proteins are thought to form a complex in vivo and, in this manner, help to fine-tune the cellular c-di-AMP levels. To further characterize this important regulatory complex, we conducted a comprehensive structural and functional analysis of the S. aureus DacA and GlmM enzymes by determining the structures of the S. aureus GlmM enzyme and the catalytic domain of DacA. Both proteins were found to be dimers in solution as well as in the crystal structures. Further site-directed mutagenesis, structural and enzymatic studies showed that multiple DacA dimers need to interact for enzymatic activity. We also show that DacA and GlmM form a stable complex in vitro and that S. aureus GlmM, but not Escherichia coli or Pseudomonas aeruginosa GlmM, acts as a strong inhibitor of DacA function without the requirement of any additional cellular factor. Based on Small Angle X-ray Scattering (SAXS) data, a model of the complex revealed that GlmM likely inhibits DacA by masking the active site of the cyclase and preventing higher oligomer formation. Together these results provide an important mechanistic insight into how c-di-AMP production can be regulated in the cell.
-
Journal articlePolo LM, Xu Y, Hornyak P, et al., 2019,
Efficient single-strand break repair requires binding to both poly(ADP-Ribose) and DNA by the central BRCT domain of XRCC1
, Cell Reports, Vol: 26, Pages: 573-581.e5, ISSN: 2211-1247XRCC1 accelerates repair of DNA single-strand breaks by acting as a scaffold protein for the recruitment of Polβ, LigIIIα, and end-processing factors, such as PNKP and APTX. XRCC1 itself is recruited to DNA damage through interaction of its central BRCT domain with poly(ADP-ribose) chains generated by PARP1 or PARP2. XRCC1 is believed to interact directly with DNA at sites of damage, but the molecular basis for this interaction within XRCC1 remains unclear. We now show that the central BRCT domain simultaneously mediates interaction of XRCC1 with poly(ADP-ribose) and DNA, through separate and non-overlapping binding sites on opposite faces of the domain. Mutation of residues within the DNA binding site, which includes the site of a common disease-associated human polymorphism, affects DNA binding of this XRCC1 domain in vitro and impairs XRCC1 recruitment and retention at DNA damage and repair of single-strand breaks in vivo.
-
Journal articleAndreasen M, Meisl G, Taylor JD, et al., 2019,
Physical determinants of amyloid assembly in biofilm formation
, mBio, Vol: 10, ISSN: 2150-7511A wide range of bacterial pathogens have been shown to form biofilms, which significantly increase their resistance to environmental stresses, such as antibiotics, and are thus of central importance in the context of bacterial diseases. One of the major structural components of these bacterial biofilms are amyloid fibrils, yet the mechanism of fibril assembly and its importance for biofilm formation are currently not fully understood. By studying fibril formation in vitro, in a model system of two common but unrelated biofilm-forming proteins, FapC from Pseudomonas fluorescens and CsgA from Escherichia coli, we found that the two proteins have a common aggregation mechanism. In both systems, fibril formation proceeds via nucleated growth of linear fibrils exhibiting similar measured rates of elongation, with negligible fibril self-replication. These similarities between two unrelated systems suggest that convergent evolution plays a key role in tuning the assembly kinetics of functional amyloid fibrils and indicates that only a narrow window of mechanisms and assembly rates allows for successful biofilm formation. Thus, the amyloid assembly reaction is likely to represent a means for controlling biofilm formation, both by the organism and by possible inhibitory drugs.IMPORTANCE Biofilms are generated by bacteria, embedded in the formed extracellular matrix. The biofilm's function is to improve the survival of a bacterial colony through, for example, increased resistance to antibiotics or other environmental stresses. Proteins secreted by the bacteria act as a major structural component of this extracellular matrix, as they self-assemble into highly stable amyloid fibrils, making the biofilm very difficult to degrade by physical and chemical means once formed. By studying the self-assembly mechanism of the fibrils from their monomeric precursors in two unrelated bacteria, our experimental and theoretical approaches shed light on the mechanism of functional amyloid as
-
Journal articleArthur PK, Amarh V, Cramer P, et al., 2019,
Characterization of two new multidrug-resistant strains of mycobacterium smegmatis: tools for routine in vitro screening of novel anti-mycobacterial agents
, Antibiotics, Vol: 8, ISSN: 2079-6382Mycobacterium tuberculosis is a pathogen of global public health concern. This threat is exacerbated by the emergence of multidrug-resistant and extremely-drug-resistant strains of the pathogen. We have obtained two distinct clones of multidrug-resistant Mycobacterium smegmatis after gradual exposure of Mycobacterium smegmatis mc² 155 to increasing concentrations of erythromycin. The resulting resistant strains of Mycobacterium smegmatis exhibited robust viability in the presence of high concentrations of erythromycin and were found to be resistant to a wide range of other antimicrobials. They also displayed a unique growth phenotype in comparison to the parental drug-susceptible Mycobacterium smegmatis mc² 155, and a distinct colony morphology in the presence of cholesterol. We propose that these two multidrug-resistant clones of Mycobacterium smegmatis could be used as model organisms at the inceptive phase of routine in vitro screening of novel antimicrobial agents targeted against multidrug-resistant Mycobacterial tuberculosis.
-
Journal articleBotella H, Vaubourgeix J, 2019,
Building walls: Work that never ends
, Trends in Microbiology, Vol: 27, Pages: 4-7, ISSN: 0966-842XFluorescent amino acid analogs have proven to be useful tools for studying the dynamics of peptidoglycan metabolism. García-Heredia and colleagues showed that their route of incorporation differs depending on the adjunct fluorophore and applied this property to investigate mycobacterial peptidoglycan synthesis and remodeling with heightened granularity.
-
Book chapterHaag AF, Ross Fitzgerald J, Penadés JR, 2019,
Staphylococcus aureus in animals
, Gram-Positive Pathogens, Pages: 731-746The genus Staphylococcus currently comprises 81 species and subspecies (https://www.dsmz.de/bacterial-diversity/prokaryotic-nomenclature-up-to-date/prokaryotic-nomenclature-up-to-date.html), and most members of the genus are mammalian commensals or opportunistic pathogens that colonize niches such as skin, nares, and diverse mucosal membranes. Several species are of significant medical or veterinary importance. Staphylococcus pseudintermedius (1) is a leading cause of pyoderma in dogs and is considered to be a significant reservoir of antimicrobial resistance factors for the genus (2, 3). S. pseudintermedius is very similar to Staphylococcus intermedius and can be distinguished from other coagulase-positive staphylococci by positive arginine dihydrolase and acid production from β-gentiobiose and d-mannitol (4) or by using a multiplex-PCR approach targeting the nuclease gene nuc (5). Staphylococcus saprophyticus is the second leading cause of uncomplicated urinary tract infections (6). While Staphylococcus epidermidis is a normal component of the epidermal microbiota, it is a leading cause of biofilm contamination of medical devices (7). The most promiscuous and most significant human pathogenic staphylococcal species is Staphylococcus aureus, which is the causal agent of a variety of disease symptoms that can range from cosmetic to lethal manifestations. S. aureus is distinguished from most members of the genus by its abundant production of secreted coagulase, an enzyme which converts serum fibrinogen to fibrin and promotes clotting. However, the S. intermedius group and some strains of Staphylococcus lugdunensis have coagulase activity (5, 8, 9).
-
Journal articleO'Connor G, Krishnan N, Fagan-Murphy A, et al., 2019,
Inhalable poly(lactic-co-glycolic acid) (PLGA) microparticles encapsulating all-trans-Retinoic acid (ATRA) as a host-directed, adjunctive treatment for Mycobacterium tuberculosis infection
, European Journal of Pharmaceutics and Biopharmaceutics, Vol: 134, Pages: 153-165, ISSN: 0939-6411Ending the tuberculosis (TB) epidemic by 2030 was recently listed in the United Nations (UN) Sustainable Development Goals alongside HIV/AIDS and malaria as it continues to be a major cause of death worldwide. With a significant proportion of TB cases caused by resistant strains of Mycobacterium tuberculosis (Mtb), there is an urgent need to develop new and innovative approaches to treatment. Since 1989, researchers have been assessing the anti-bacterial effects of the active metabolite of vitamin A, all trans-Retinoic acid (ATRA) solution, in Mtb models. More recently the antibacterial effect of ATRA has been shown to regulate the immune response to infection via critical gene expression, monocyte activation and the induction of autophagy leading to its application as a host-directed therapy (HDT). Inhalation is an attractive route for targeted treatment of TB, and therefore we have developed ATRA-loaded microparticles (ATRA-MP) within the inhalable size range (2.07 ± 0.5 µm) offering targeted delivery of the encapsulated cargo (70.5 ± 2.3%) to the site of action within the alveolar macrophage, which was confirmed by confocal microscopy. Efficient cellular delivery of ATRA was followed by a reduction in Mtb growth (H37Ra) in THP-1 derived macrophages evaluated by both the BACT/ALERT® system and enumeration of colony forming units (CFU). The antibacterial effect of ATRA-MP treatment was further assessed in BALB/c mice infected with the virulent strain of Mtb (H37Rv). ATRA-MP treatments significantly decreased the bacterial burden in the lungs alongside a reduction in pulmonary pathology following just three doses administered intratracheally. The immunomodulatory effects of targeted ATRA treatment in the lungs indicate a distinct yet effective mechanism of action amongst the formulations. This is the first study to-date of a controlled release ATRA treatment for TB suitable for inhalation that offers improved targeting of a HDT, retains antib
-
Journal articleGodlee C, Cerny O, durkin C, et al., 2019,
SrcA is a chaperone for the Salmonella SPI-2 type three secretion system effector SteD
, Microbiology, Vol: 165, Pages: 15-25, ISSN: 1350-0872Effector proteins of type three secretion systems (T3SS) often require cytosolic chaperones for their stabilization, to interact with the secretion machinery and to enable effector delivery into host cells. We found that deletion of srcA, previously shown to encode a chaperone for the Salmonella pathogenicity island 2 (SPI-2) T3SS effectors SseL and PipB2, prevented the reduction of mature Major Histocompatibility Complex class II (mMHCII) from the surface of antigen-presenting cells during Salmonella infection. This activity was shown previously to be caused by the SPI-2 T3SS effector SteD. Since srcA and steD are located in the same operon on the Salmonella chromosome, this suggested that the srcA phenotype might be due to an indirect effect on SteD. We found that SrcA is not translocated by the SPI-2 T3SS but interacts directly and forms a stable complex with SteD in bacteria with a 2 : 1 stoichiometry. We found that SrcA was not required for SPI-2 T3SS-dependent, neutral pH-induced secretion of either SseL or PipB2 but was essential for secretion of SteD. SrcA therefore functions as a chaperone for SteD, explaining its requirement for the reduction in surface levels of mMHCII.
-
Journal articleGollan B, Grabe G, Michaux C, et al., 2019,
Bacterial Persisters and Infection: Past, Present, and Progressing
, ANNUAL REVIEW OF MICROBIOLOGY, VOL 73, Vol: 73, Pages: 359-385, ISSN: 0066-4227- Author Web Link
- Cite
- Citations: 130
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.