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  1. Article ; Online: The divisome but not the elongasome organizes capsule synthesis in Streptococcus pneumoniae

    Rei Nakamoto / Sarp Bamyaci / Karin Blomqvist / Staffan Normark / Birgitta Henriques-Normark / Lok-To Sham

    Nature Communications, Vol 14, Iss 1, Pp 1-

    2023  Volume 13

    Abstract: Abstract The bacterial cell envelope consists of multiple layers, including the peptidoglycan cell wall, one or two membranes, and often an external layer composed of capsular polysaccharides (CPS) or other components. How the synthesis of all these ... ...

    Abstract Abstract The bacterial cell envelope consists of multiple layers, including the peptidoglycan cell wall, one or two membranes, and often an external layer composed of capsular polysaccharides (CPS) or other components. How the synthesis of all these layers is precisely coordinated remains unclear. Here, we identify a mechanism that coordinates the synthesis of CPS and peptidoglycan in Streptococcus pneumoniae. We show that CPS synthesis initiates from the division septum and propagates along the long axis of the cell, organized by the tyrosine kinase system CpsCD. CpsC and the rest of the CPS synthesis complex are recruited to the septum by proteins associated with the divisome (a complex involved in septal peptidoglycan synthesis) but not the elongasome (involved in peripheral peptidoglycan synthesis). Assembly of the CPS complex starts with CpsCD, then CpsA and CpsH, the glycosyltransferases, and finally CpsJ. Remarkably, targeting CpsC to the cell pole is sufficient to reposition CPS synthesis, leading to diplococci that lack CPS at the septum. We propose that septal CPS synthesis is important for chain formation and complement evasion, thereby promoting bacterial survival inside the host.
    Keywords Science ; Q
    Subject code 540
    Language English
    Publishing date 2023-06-01T00:00:00Z
    Publisher Nature Portfolio
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Article ; Online: Regulation of the cell division hydrolase RipC by the FtsEX system in Mycobacterium tuberculosis

    Jianwei Li / Xin Xu / Jian Shi / Juan A. Hermoso / Lok-To Sham / Min Luo

    Nature Communications, Vol 14, Iss 1, Pp 1-

    2023  Volume 15

    Abstract: Abstract The FtsEX complex regulates, directly or via a protein mediator depending on bacterial genera, peptidoglycan degradation for cell division. In mycobacteria and Gram-positive bacteria, the FtsEX system directly activates peptidoglycan-hydrolases ... ...

    Abstract Abstract The FtsEX complex regulates, directly or via a protein mediator depending on bacterial genera, peptidoglycan degradation for cell division. In mycobacteria and Gram-positive bacteria, the FtsEX system directly activates peptidoglycan-hydrolases by a mechanism that remains unclear. Here we report our investigation of Mycobacterium tuberculosis FtsEX as a non-canonical regulator with high basal ATPase activity. The cryo-EM structures of the FtsEX system alone and in complex with RipC, as well as the ATP-activated state, unveil detailed information on the signal transduction mechanism, leading to the activation of RipC. Our findings indicate that RipC is recognized through a “Match and Fit” mechanism, resulting in an asymmetric rearrangement of the extracellular domains of FtsX and a unique inclined binding mode of RipC. This study provides insights into the molecular mechanisms of FtsEX and RipC regulation in the context of a critical human pathogen, guiding the design of drugs targeting peptidoglycan remodeling.
    Keywords Science ; Q
    Subject code 572
    Language English
    Publishing date 2023-12-01T00:00:00Z
    Publisher Nature Portfolio
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  3. Article ; Online: SARS-CoV-2 Spike Protein and Mouse Coronavirus Inhibit Biofilm Formation by Streptococcus pneumoniae and Staphylococcus aureus

    Mun Fai Loke / Indresh Yadav / Teck Kwang Lim / Johan R. C. van der Maarel / Lok-To Sham / Vincent T. Chow

    International Journal of Molecular Sciences, Vol 23, Iss 3291, p

    2022  Volume 3291

    Abstract: The presence of co-infections or superinfections with bacterial pathogens in COVID-19 patients is associated with poor outcomes, including increased morbidity and mortality. We hypothesized that SARS-CoV-2 and its components interact with the biofilms ... ...

    Abstract The presence of co-infections or superinfections with bacterial pathogens in COVID-19 patients is associated with poor outcomes, including increased morbidity and mortality. We hypothesized that SARS-CoV-2 and its components interact with the biofilms generated by commensal bacteria, which may contribute to co-infections. This study employed crystal violet staining and particle-tracking microrheology to characterize the formation of biofilms by Streptococcus pneumoniae and Staphylococcus aureus that commonly cause secondary bacterial pneumonia. Microrheology analyses suggested that these biofilms were inhomogeneous soft solids, consistent with their dynamic characteristics. Biofilm formation by both bacteria was significantly inhibited by co-incubation with recombinant SARS-CoV-2 spike S1 subunit and both S1 + S2 subunits, but not with S2 extracellular domain nor nucleocapsid protein. Addition of spike S1 and S2 antibodies to spike protein could partially restore bacterial biofilm production. Furthermore, biofilm formation in vitro was also compromised by live murine hepatitis virus, a related beta-coronavirus. Supporting data from LC-MS-based proteomics of spike–biofilm interactions revealed differential expression of proteins involved in quorum sensing and biofilm maturation, such as the AI-2E family transporter and LuxS, a key enzyme for AI-2 biosynthesis. Our findings suggest that these opportunistic pathogens may egress from biofilms to resume a more virulent planktonic lifestyle during coronavirus infections. The dispersion of pathogens from biofilms may culminate in potentially severe secondary infections with poor prognosis. Further detailed investigations are warranted to establish bacterial biofilms as risk factors for secondary pneumonia in COVID-19 patients.
    Keywords Streptococcus pneumoniae ; Staphylococcus aureus ; biofilm ; COVID-19 ; SARS-CoV-2 ; coronavirus ; Biology (General) ; QH301-705.5 ; Chemistry ; QD1-999
    Subject code 572
    Language English
    Publishing date 2022-03-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  4. Article ; Online: Structural basis of peptide secretion for Quorum sensing by ComA

    Lin Yu / Xin Xu / Wan-Zhen Chua / Hao Feng / Zheng Ser / Kai Shao / Jian Shi / Yumei Wang / Zongli Li / Radoslaw M. Sobota / Lok-To Sham / Min Luo

    Nature Communications, Vol 14, Iss 1, Pp 1-

    2023  Volume 17

    Abstract: Abstract Quorum sensing (QS) is a crucial regulatory mechanism controlling bacterial signalling and holds promise for novel therapies against antimicrobial resistance. In Gram-positive bacteria, such as Streptococcus pneumoniae, ComA is a conserved ... ...

    Abstract Abstract Quorum sensing (QS) is a crucial regulatory mechanism controlling bacterial signalling and holds promise for novel therapies against antimicrobial resistance. In Gram-positive bacteria, such as Streptococcus pneumoniae, ComA is a conserved efflux pump responsible for the maturation and secretion of peptide signals, including the competence-stimulating peptide (CSP), yet its structure and function remain unclear. Here, we functionally characterize ComA as an ABC transporter with high ATP affinity and determined its cryo-EM structures in the presence or absence of CSP or nucleotides. Our findings reveal a network of strong electrostatic interactions unique to ComA at the intracellular gate, a putative binding pocket for two CSP molecules, and negatively charged residues facilitating CSP translocation. Mutations of these residues affect ComA’s peptidase activity in-vitro and prevent CSP export in-vivo. We demonstrate that ATP-Mg2+ triggers the outward-facing conformation of ComA for CSP release, rather than ATP alone. Our study provides molecular insights into the QS signal peptide secretion, highlighting potential targets for QS-targeting drugs.
    Keywords Science ; Q
    Subject code 570
    Language English
    Publishing date 2023-11-01T00:00:00Z
    Publisher Nature Portfolio
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  5. Article ; Online: RNA thermosensors facilitate Streptococcus pneumoniae and Haemophilus influenzae immune evasion.

    Hannes Eichner / Jens Karlsson / Laura Spelmink / Anuj Pathak / Lok-To Sham / Birgitta Henriques-Normark / Edmund Loh

    PLoS Pathogens, Vol 17, Iss 4, p e

    2021  Volume 1009513

    Abstract: Bacterial meningitis is a major cause of death and disability in children worldwide. Two human restricted respiratory pathogens, Streptococcus pneumoniae and Haemophilus influenzae, are the major causative agents of bacterial meningitis, attributing to ... ...

    Abstract Bacterial meningitis is a major cause of death and disability in children worldwide. Two human restricted respiratory pathogens, Streptococcus pneumoniae and Haemophilus influenzae, are the major causative agents of bacterial meningitis, attributing to 200,000 deaths annually. These pathogens are often part of the nasopharyngeal microflora of healthy carriers. However, what factors elicit them to disseminate and cause invasive diseases, remain unknown. Elevated temperature and fever are hallmarks of inflammation triggered by infections and can act as warning signals to pathogens. Here, we investigate whether these respiratory pathogens can sense environmental temperature to evade host complement-mediated killing. We show that productions of two vital virulence factors and vaccine components, the polysaccharide capsules and factor H binding proteins, are temperature dependent, thus influencing serum/opsonophagocytic killing of the bacteria. We identify and characterise four novel RNA thermosensors in S. pneumoniae and H. influenzae, responsible for capsular biosynthesis and production of factor H binding proteins. Our data suggest that these bacteria might have independently co-evolved thermosensing abilities with different RNA sequences but distinct secondary structures to evade the immune system.
    Keywords Immunologic diseases. Allergy ; RC581-607 ; Biology (General) ; QH301-705.5
    Subject code 572
    Language English
    Publishing date 2021-04-01T00:00:00Z
    Publisher Public Library of Science (PLoS)
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  6. Article ; Online: Maturing Mycobacterium smegmatis peptidoglycan requires non-canonical crosslinks to maintain shape

    Catherine Baranowski / Michael A Welsh / Lok-To Sham / Haig A Eskandarian / Hoong Chuin Lim / Karen J Kieser / Jeffrey C Wagner / John D McKinney / Georg E Fantner / Thomas R Ioerger / Suzanne Walker / Thomas G Bernhardt / Eric J Rubin / E Hesper Rego

    eLife, Vol

    2018  Volume 7

    Abstract: In most well-studied rod-shaped bacteria, peptidoglycan is primarily crosslinked by penicillin-binding proteins (PBPs). However, in mycobacteria, crosslinks formed by L,D-transpeptidases (LDTs) are highly abundant. To elucidate the role of these unusual ... ...

    Abstract In most well-studied rod-shaped bacteria, peptidoglycan is primarily crosslinked by penicillin-binding proteins (PBPs). However, in mycobacteria, crosslinks formed by L,D-transpeptidases (LDTs) are highly abundant. To elucidate the role of these unusual crosslinks, we characterized Mycobacterium smegmatis cells lacking all LDTs. We find that crosslinks generate by LDTs are required for rod shape maintenance specifically at sites of aging cell wall, a byproduct of polar elongation. Asymmetric polar growth leads to a non-uniform distribution of these two types of crosslinks in a single cell. Consequently, in the absence of LDT-mediated crosslinks, PBP-catalyzed crosslinks become more important. Because of this, Mycobacterium tuberculosis (Mtb) is more rapidly killed using a combination of drugs capable of PBP- and LDT- inhibition. Thus, knowledge about the spatial and genetic relationship between drug targets can be exploited to more effectively treat this pathogen.
    Keywords Mycobacterium tuberculosis ; Mycobacterium smegmatis ; peptidoglycan ; polar growth ; rod shape maintenance ; Medicine ; R ; Science ; Q ; Biology (General) ; QH301-705.5
    Language English
    Publishing date 2018-10-01T00:00:00Z
    Publisher eLife Sciences Publications Ltd
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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