Nanopods: A New Bacterial Structure and Mechanism for Deployment of Outer Membrane Vesicles

Background: Bacterial outer membrane vesicles (OMV) are packets of periplasmic material that, via the proteins and other molecules they contain, project metabolic function into the environment. While OMV production is widespread in proteobacteria, they have been extensively studied only in pathogens, which inhabit fully hydrated environments. However, many (arguably most) bacterial habitats, such as soil, are only partially hydrated. In the latter, water is characteristically distributed as films on soil particles that are, on average thinner, than are typical OMV (ca. ≤10 nm water film vs. 20 to >200 nm OMV;). Methodology/Principal Findings: We have identified a new bacterial surface structure, termed a "nanopod", that is a conduit for projecting OMV significant distances (e.g., ≥6 µm) from the cell. Electron cryotomography was used to determine nanopod three-dimensional structure, which revealed chains of vesicles within an undulating, tubular element. By using immunoelectron microscopy, proteomics, heterologous expression and mutagenesis, the tubes were determined to be an assembly of a surface layer protein (NpdA), and the interior structures identified as OMV. Specific metabolic function(s) for nanopods produced by Delftia sp. Cs1-4 are not yet known. However, a connection with phenanthrene degradation is a possibility since nanopod formation was induced by growth on phenanthrene. Orthologs of NpdA were identified in three other genera of the Comamonadaceae family, and all were experimentally verified to form nanopods. Conclusions/Significance: Nanopods are new bacterial organelles, and establish a new paradigm in the mechanisms by which bacteria effect long-distance interactions with their environment. Specifically, they create a pathway through which cells can effectively deploy OMV, and the biological activity these transmit, in a diffusion-independent manner. Nanopods would thus allow environmental bacteria to expand their metabolic sphere of influence in a manner previously unknown for these organisms

Outer Membrane Vesicles of Porphyromonas gingivalis Elicit a Mucosal Immune Response

We previously reported that mutation of galE in Porphyromonas gingivalis has pleiotropic effects, including a truncated lipopolysaccharide (LPS) O-antigen and deglycosylation of the outer membrane protein OMP85 homolog. In the present study, further analysis of the galE mutant revealed that it produced little or no outer membrane vesicles (OMVs). Using three mouse antisera raised against whole cells of the P. gingivalis wild type strain, we performed ELISAs to examine the reactivity of these antisera with whole cells of the wild type or the galE mutant. All three antisera had significantly lower reactivity against the galE mutant compared to wild type. OMVs, but not LPS, retained the immunodominant determinant of P. gingivalis, as determined by ELISAs (with wild type LPS or OMVs as antigen) and absorption assays. In addition, we assessed the capacity of OMVs as a vaccine antigen by intranasal immunization to BALB/c mice. Synthetic double-stranded RNA polyriboinosinic polyribocytidylic acid [Poly (I∶C)], an agonist of Toll-like receptor 3 (TLR3), was used as the mucosal adjuvant. Vaccination with OMV elicited dramatically high levels of P. gingivalis-specific IgA in nasal washes and saliva, as well as serum IgG and IgA. In conclusion, the OMVs of P. gingivalis have an important role in mucosal immunogenicity as well as in antigenicity. We propose that P. gingivalis OMV is an intriguing immunogen for development of a periodontal disease vaccine

Membrane anchoring stabilizes and favors secretion of New Delhi metallo-β-lactamase

Carbapenems, 'last-resort' β-lactam antibiotics, are inactivated by zinc-dependent metallo-β-lactamases (MBLs). The host innate immune response withholds nutrient metal ions from microbial pathogens by releasing metal-chelating proteins such as calprotectin. We show that metal sequestration is detrimental for the accumulation of MBLs in the bacterial periplasm, because those enzymes are readily degraded in their nonmetallated form. However, the New Delhi metallo-β-lactamase (NDM-1) can persist under conditions of metal depletion. NDM-1 is a lipidated protein that anchors to the outer membrane of Gram-negative bacteria. Membrane anchoring contributes to the unusual stability of NDM-1 and favors secretion of this enzyme in outer-membrane vesicles (OMVs). OMVs containing NDM-1 can protect nearby populations of bacteria from otherwise lethal antibiotic levels, and OMVs from clinical pathogens expressing NDM-1 can carry this MBL and the bla[subscript NDM] gene. We show that protein export into OMVs can be targeted, providing possibilities of new antibacterial therapeutic strategies.Kinship Foundation. Searle Scholars ProgramMassachusetts Institute of Technology. Department of Chemistr

ArnS, a kinase involved in starvation-induced archaellum expression

Organisms have evolved motility organelles that allow them to move to favorable habitats. Cells integrate environmental stimuli into intracellular signals to motility machineries to direct this migration. Many motility organelles are complex surface appendages that have evolved a tight, hierarchical regulation of expression. In the crenearchaeon Sulfolobus acidocaldarius, biosynthesis of the archaellum is regulated by regulatory network proteins that control expression of archaellum components in a phosphorylation-dependent manner. A major trigger for archaellum expression is nutrient starvation, but although some components are known, the regulatory cascade triggered by starvation is poorly understood. In this work, we identify the starvation-induced Ser/Thr protein kinase ArnS (Saci_1181) which is located proximally to the archaellum operon. Deletion of arnS results in reduced motility, though the archaellum is properly assembled. Therefore, our experimental and modelling results indicate that ArnS plays an essential role in the precisely controlled expression of archaellum components during starvation-induced motility in Sulfolobus acidocaldarius. Furthermore we combine in vivo experiments and mathematical models to describe for the first time in archaea the dynamics of key regulators of archaellum expression

Flux et perte d'azote dans un ecosysteme : contribution a l'etude de la denitrification

CNRS RP 185 (1802) / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

Whimsical (Waldenstrom's Macroglobulinemia Study Involving CArt-wheeL): A Global Patient-Derived Data Registry Capturing Treatment, Quality of Life and COVID-19 Data

Introduction: Patient-derived data can increase breadth of knowledge in rare cancers like Waldenström's Macroglobulinemia (WM), including patient-reported outcomes (PROs). WhiMSICAL (Waldenström's Macroglobulinemia Study Involving CArt-wheeL) is the only global registry capturing patient-derived data for hypothesis generation in WM. Rapidly adaptable, it has been amended to capture Coronavirus Disease 2019 (COVID-19) data. Methods: An ethically-approved WM-specific extension to www.cart-wheel.org, an online rare cancer database for patient-derived data, was developed by clinician and patient investigators. Participants complete consent, and enter symptom, pathology, treatment and PRO (EORTC-QLQ-C30, Impact of Event Scale-6) data online. Recruitment strategies utilizing social media tools are driven by the International Waldenström's Macroglobulinemia Foundation investigators. A validation study compared patient-entered data with data-manager-entered data in the Australia & New Zealand Lymphoma & Related Diseases Registry (LaRDR). To capture the impact of COVID-19, additional questions on COVID-19 testing, symptoms and therapy, as well as effect on WM management in those without COVID-19, were included in April 2020. Results: 453 patients from 19 countries have been recruited, predominantly from USA (46%) and Australia (25%), with male predominance (62%). At diagnosis, median age was 61 (range 24-83), median IgM 2620 mg/dL (IQR 1320-3850 mg/dL, n=175) and median hemoglobin 11.4 g/dL (IQR 9.5-12.9 g/dL, n=181). Of the 365 (81%) patients providing symptoms at diagnosis, fatigue/muscle weakness was most common (46%) and 30% were asymptomatic. Using the Impact of Event Scale for symptoms of post-traumatic stress disorder (PTSD) resulting from a cancer diagnosis, the mean score among 387 patients was 5.9 (no stress=0, maximal stress=24), with 39/387 (10%) scoring >13 (PPV 94% for PTSD, Thoresen et al, 2010). This proportion did not increase for scores entered after March 1st, 2020 - 12/123 (10%) - when the COVID-19 pandemic became a global crisis. Marked treatment variation was noted, with 47 different first-line therapeutic combinations documented by 302 patients. Median time from diagnosis to first treatment for USA patients was 48 days (IQR 13-404, n=133) vs Rest of World (ROW) 176 days (IQR 20-885, n=163), (p=0.01). At median follow up of 38.5 months, first-line bendamustine rituximab had superior time to next treatment outcomes compared to other first-line therapies: rituximab monotherapy, dexamethasone-rituximab-cyclophosphamide and Bruton tyrosine kinase inhibitors (BTKi, Figure 1). 51 patients exposed to BTKi had a trend to higher EORTC QLQ-C30 global scales, mean 78.6±17.7, compared to 148 not exposed: mean 73.4±22.6 (p=0.13), despite higher treatment burden: median lines of treatment 2 (IQR 1-4) and 1 (IQR 1-2), respectively (p83%. 188/453 (42%) participants responded to the impact of COVID-19 questions; 75/188 (40%) had reduced face-to-face reviews, 4/188 (2%) had delays to starting treatment and 57/188 (30%) documented no impact. Of the 188 respondents, 23 (12%) had COVID-19 testing, with two returning a positive result and neither requiring hospitalization. Conclusion: WhiMSICAL is a robust, rapidly adaptable, global patient-derived data platform, providing insight into patient symptoms, real-world therapies and PROs. It is a scientific, ethically-approved portal for contributing the patients' voice in this rare lymphoma