Marcos Pires

Nature Microbiology, Published online: 26 August 2019; doi:10.1038/s41564-019-0536-0

Metabolic state and ATP levels are better predictors of antibiotic lethality across diverse bacterial species than growth rate.

Nature Communications, Published online: 26 August 2019; doi:10.1038/s41467-019-11479-0

CRISPR activation strategies in bacteria are limited due to the reliance on σ70 promoters. Here the authors demonstrate eukaryote-like gene activation with high dynamic ranges using σ54- dependent promoters.

A new class of peptide whose ability to perturb cellular membranes is coupled to an enzyme‐mediated shift in the folding potential of the peptide into a membrane‐active conformation is reported by J. Shi and J. Schneider in their Communication on https://doi.org/10.1002/anie.201902470page 13706 ff. Folding potential is cell specific and depends on the amount of cell‐surface alkaline phosphatase present. Once folded, the concentration of the peptide determines whether it enters or lyses cells.

In their Communication (DOI: https://doi.org/10.1002/anie.20190651410.1002/anie.201906514), D. M. Perrin and co‐workers introduce fluorescent isoindole crosslink (FlICk) chemistry to produce cyclic peptides with a fluorescent twist. The reaction between ortho‐phthalaldehydes and amine‐ and thiol‐bearing side chains in peptides produces isoindole‐stapled, bioactive, mono‐ and bicyclic peptides with tunable photophysical properties, under mild, metal‐free conditions.

Nature Communications, Published online: 20 August 2019; doi:10.1038/s41467-019-11730-8

The limited efficacy of current immunotherapy suggests low antigen-specific T cells and immunosuppressive factors in tumor microenvironment (TME). Here, the authors develop a syringeable immunomodulatory multi-domain nanogel that can reprogram the TME and induce enhanced cancer immunotherapy.

Nature Biotechnology, Published online: 19 August 2019; doi:10.1038/s41587-019-0222-z

The authors designed stapled antimicrobial peptides that have potent antibacterial activity in mice and limited toxicity.

Nature Chemical Biology, Published online: 19 August 2019; doi:10.1038/s41589-019-0344-0

Inhibition of fatty acid synthase, FASN, blocks innate immune signaling through TLR/MyD88 in neutrophils by blocking palmitoylation of MyD88 by palmitoyltransferase zDHHC6 and improves outcomes in two mouse models of sepsis.

Nature Chemical Biology, Published online: 19 August 2019; doi:10.1038/s41589-019-0336-0

Buter et al. elucidated the biological function of the terpene nucleoside 1-TbAd, which is made abundantly by virulent but not avirulent Mycobacterium tuberculosis strains, and demonstrate that 1-TbAd regulates the pH and function of host macrophage endolysosomes.

Cohousing of laboratory mice with pet store animals changes the immune system and alters responsiveness to future challenges. Huggins et al. demonstrate that microbial exposure results in alterations to immune cells, serum cytokines, and microbiome composition. This study shows that cohousing alters the ability to detect pathogens through pattern-recognition receptors.

Nature Microbiology, Published online: 12 August 2019; doi:10.1038/s41564-019-0519-1

The cephamycin group of β-lactam antibiotics targets sporulation-associated penicillin-binding proteins across pathogens and can be repurposed as a cost-effective strategy to treat recurrent Clostridioides difficile infection.

Aminoglycoside efficacy is limited against non-respiring bacterial populations due to deficiencies in uptake. Radlinski et al. show that chemical induction of PMF-independent aminoglycoside uptake with rhamnolipids sensitizes non-respiring populations of S. aureus to aminoglycoside killing, expanding the utility of this important class of antibiotics.

ABSTRACT

Group B Streptococcus (GBS) infections constitute a major cause of invasive disease during the first three months of life and an unmet medical need that could be addressed by maternal vaccination. The GBS capsular polysaccharides (CPSs) have shown promise as vaccine targets in clinical studies. A highly specific serological assay to quantify maternal and neonatal anti-CPS antibody levels will be instrumental for GBS vaccine licensure. Here, we describe the development and comparison of two novel multiplex immunoassays (MIAs) based on the Luminex technology for the quantification of IgG antibodies recognizing the five most frequent GBS capsular variants (Ia, Ib, II, III, and V) out of the ten types identified. The first assay is based on the use of biotinylated CPSs coupled to streptavidin-derivatized magnetic microspheres (Biotin-CPS MIA), while the second is a sandwich assay with plain CPSs coupled to magnetic microspheres coated with polysaccharide-specific mouse monoclonal antibodies (Sandwich MIA). Both assays showed good specificity, linearity, and precision, although the Biotin-CPS MIA presented higher sensitivity and lower complexity than the Sandwich MIA. A panel of human sera representing a wide range of anti-CPS IgG concentrations was tested in parallel by the two assays, which resulted in comparable titers. Our data support the preservation of antigenic epitopes in the biotinylated polysaccharides and the suitability of the Biotin-CPS MIA for the precise determination of GBS anti-CPS IgG concentrations in human sera.

IMPORTANCE Group B streptococcal infections can cause death in neonates up to 3 months of age. Intrapartum antibiotic prophylaxis in GBS-colonized mothers has limited early infections but has no impact after the first week of life. The development of a maternal vaccine to address this unmet medical need has been identified as a priority by the World Health Organization, and the GBS CPSs are considered the best antigen targets. However, to date there are no accepted standardized assays to measure immune responses to the investigational vaccines and for establishment of serocorrelates of protection. Here, we describe the performance of two microsphere-based pentaplex immunoassays for the determination of antibodies recognizing the five most frequent GBS serotypes. Our data confirm that an assay based on biotinylated polysaccharides coupled to streptavidin microspheres would be suitable for the intended purpose.

ABSTRACT

Rod-shaped bacteria have two modes of peptidoglycan synthesis: lateral synthesis and synthesis at the cell division site. These two processes are controlled by two macromolecular protein complexes, the elongasome and divisome. Recently, it has been shown that the Bacillus subtilis RodA protein, which forms part of the elongasome, has peptidoglycan glycosyltransferase activity. The cell division-specific RodA homolog FtsW fulfils a similar role at the divisome. The human pathogen Listeria monocytogenes carries genes that encode up to six FtsW/RodA homologs; however, their functions have not yet been investigated. Analysis of deletion and depletion strains led to the identification of the essential cell division-specific FtsW protein, FtsW1. Interestingly, L. monocytogenes carries a gene that encodes a second FtsW protein, FtsW2, which can compensate for the lack of FtsW1, when expressed from an inducible promoter. L. monocytogenes also possesses three RodA homologs, RodA1, RodA2, and RodA3, and their combined absence is lethal. Cells of a rodA1 rodA3 double mutant are shorter and have increased antibiotic and lysozyme sensitivity, probably due to a weakened cell wall. Results from promoter activity assays revealed that expression of rodA3 and ftsW2 is induced in the presence of antibiotics targeting penicillin binding proteins. Consistent with this, a rodA3 mutant was more susceptible to the β-lactam antibiotic cefuroxime. Interestingly, overexpression of RodA3 also led to increased cefuroxime sensitivity. Our study highlights that L. monocytogenes genes encode a multitude of functional FtsW and RodA enzymes to produce its rigid cell wall and that their expression needs to be tightly regulated to maintain growth, cell division, and antibiotic resistance.

IMPORTANCE The human pathogen Listeria monocytogenes is usually treated with high doses of β-lactam antibiotics, often combined with gentamicin. However, these antibiotics only act bacteriostatically on L. monocytogenes, and the immune system is needed to clear the infection. Therefore, individuals with a compromised immune system are at risk to develop a severe form of Listeria infection, which can be fatal in up to 30% of cases. The development of new strategies to treat Listeria infections is necessary. Here we show that the expression of some of the FtsW and RodA enzymes of L. monocytogenes is induced by the presence of β-lactam antibiotics, and the combined absence of these enzymes makes bacteria more susceptible to this class of antibiotics. The development of antimicrobial agents that inhibit the activity or production of FtsW and RodA enzymes might therefore help to improve the treatment of Listeria infections and thereby lead to a reduction in mortality.

Antimicrobial peptides (AMPs) are small cationic molecules best known as mediators of the innate defence against microbial infection. While in vitro and ex vivo evidence suggest AMPs’ capacity to kill cancer cells, in vivo demonstration of an anti-tumour role of endogenous AMPs is lacking. Using a Drosophila model of tumourigenesis, we demonstrate a role for the AMP Defensin in the control of tumour progression. Our results reveal that Tumour Necrosis Factor mediates exposure of phosphatidylserine (PS), which makes tumour cells selectively sensitive to the action of Defensin remotely secreted from tracheal and fat tissues. Defensin binds tumour cells in PS-enriched areas, provoking cell death and tumour regression. Altogether, our results provide the first in vivo demonstration for a role of an endogenous AMP as an anti-cancer agent, as well as a mechanism that explains tumour cell sensitivity to the action of AMPs.

ABSTRACT

Despite antibiotics and sterile technique, postoperative infections remain a real and present danger to patients. Recent estimates suggest that 50% of the pathogens associated with postoperative infections have become resistant to the standard antibiotics used for prophylaxis. Risk factors identified in such cases include obesity and antibiotic exposure. To study the combined effect of obesity and antibiotic exposure on postoperative infection, mice were allowed to gain weight on an obesogenic Western-type diet (WD), administered antibiotics and then subjected to an otherwise recoverable sterile surgical injury (30% hepatectomy). The feeding of a WD alone resulted in a major imbalance of the cecal microbiota characterized by a decrease in diversity, loss of Bacteroidetes, a bloom in Proteobacteria, and the emergence of antibiotic-resistant organisms among the cecal microbiota. When WD-fed mice were administered antibiotics and subjected to 30% liver resection, lethal sepsis, characterized by multiple-organ damage, developed. Notable was the emergence and systemic dissemination of multidrug-resistant (MDR) pathobionts, including carbapenem-resistant, extended-spectrum β-lactamase-producing Serratia marcescens, which expressed a virulent and immunosuppressive phenotype. Analysis of the distribution of exact sequence variants belonging to the genus Serratia suggested that these strains originated from the cecal mucosa. No mortality or MDR pathogens were observed in identically treated mice fed a standard chow diet. Taken together, these results suggest that consumption of a Western diet and exposure to certain antibiotics may predispose to life-threating postoperative infection associated with MDR organisms present among the gut microbiota.

IMPORTANCE Obesity remains a prevalent and independent risk factor for life-threatening infection following major surgery. Here, we demonstrate that when mice are fed an obesogenic Western diet (WD), they become susceptible to lethal sepsis with multiple organ damage after exposure to antibiotics and an otherwise-recoverable surgical injury. Analysis of the gut microbiota in this model demonstrates that WD alone leads to loss of Bacteroidetes, a bloom of Proteobacteria, and evidence of antibiotic resistance development even before antibiotics are administered. After antibiotics and surgery, lethal sepsis with organ damage developed in in mice fed a WD with the appearance of multidrug-resistant pathogens in the liver, spleen, and blood. The importance of these findings lies in exposing how the selective pressures of diet, antibiotic exposure, and surgical injury can converge on the microbiome, resulting in lethal sepsis and organ damage without the introduction of an exogenous pathogen.

Treatment of Staphylococcus aureus infections is complicated by the development of antibiotic tolerance, a consequence of the ability of S. aureus to enter into a nongrowing, dormant state in which the organisms are referred to as persisters. We report that the clinically approved anthelmintic agent bithionol kills methicillin-resistant S. aureus...

Nature Microbiology, Published online: 29 July 2019; doi:10.1038/s41564-019-0512-8

Magnetotactic bacteria must assemble magnetosomes into a linear chain that orients the cell along magnetic fields, yet how spiral bacteria with highly curved surfaces accomplish this is unclear. Here, MamY is shown to assemble into linear structures that serve as a scaffold for magnetosomes in magnetotactic spirilla.

Bacillus cells faced with unfavorable environmental conditions undergo an asymmetric division process ultimately leading to the formation of the bacterial spore. In some instances the spore serves as an infectiou...

A blessing in disguise: Conjugating a diglycine (GG) to an antibiotic prodrug (chloramphenicol succinate) increases the rate of prodrug activation by increasing the rate of ester‐bond hydrolysis catalyzed by bacterial esterases. Dipeptide conjugation to antibiotic prodrugs can increase antibiotic efficacy and reduce adverse drug effects.

Abstract

Antimicrobial drug resistance demands novel approaches for improving the efficacy of antibiotics, especially against Gram‐negative bacteria. Herein, we report that conjugating a diglycine (GG) to an antibiotic prodrug drastically accelerates intrabacterial ester‐bond hydrolysis required for activating the antibiotic. Specifically, the attachment of GG to chloramphenicol succinate (CLsu) generates CLsuGG, which exhibits about an order of magnitude higher inhibitory efficacy than CLsu against Escherichia coli. Further studies reveal that CLsuGG undergoes rapid hydrolysis, catalyzed by intrabacterial esterases (e.g., BioH and YjfP), to generate chloramphenicol (CL) in E. coli. Importantly, the conjugate exhibits lower cytotoxicity to bone marrow stromal cells than CL. Structural analogues of CLsuGG indicate that the conjugation of GG to an antibiotic prodrug is an effective strategy for accelerating enzymatic prodrug hydrolysis and enhancing the antibacterial efficacy of antibiotics.

Nature Biotechnology, Published online: 22 July 2019; doi:10.1038/s41587-019-0192-1

BiTE-secreting CAR-T cells overcome antigen escape from EGFRvIII-targeted therapy for glioblastoma.

Enteric pathogens have developed mechanisms to disrupt tight junctions and increase gut permeability. Many studies have analysed the ability of live probiotics to protect intestinal epithelial cells against ti...

Nature Microbiology, Published online: 15 July 2019; doi:10.1038/s41564-019-0499-1

The use of nanobodies that inhibit the self-assembly of the S-layer protein Sap from B. anthracis enabled the elucidation of the structure of this protein. The nanobodies also trigger disintegration of assembled S-layers and attenuate both bacterial growth and anthrax pathology in animal models of infection.

Chimeric antigen receptor–T cell (CAR-T) therapy has been effective in the treatment of hematologic malignancies, but it has shown limited efficacy against solid tumors. Here we demonstrate an approach to enhancing CAR-T function in solid tumors by directly vaccine-boosting donor cells through their chimeric receptor in vivo. We designed amphiphile CAR-T ligands (amph-ligands) that, upon injection, trafficked to lymph nodes and decorated the surfaces of antigen-presenting cells, thereby priming CAR-Ts in the native lymph node microenvironment. Amph-ligand boosting triggered massive CAR-T expansion, increased donor cell polyfunctionality, and enhanced antitumor efficacy in multiple immunocompetent mouse tumor models. We demonstrate two approaches to generalizing this strategy to any chimeric antigen receptor, enabling this simple non–human leukocyte antigen–restricted approach to enhanced CAR-T functionality to be applied to existing CAR-T designs.

Nature Microbiology, Published online: 08 July 2019; doi:10.1038/s41564-019-0497-3

Genetic and β-lactam antibiotic-driven cell wall deficiency leads to increased glycolytic flux and the generation of reactive oxygen species, which inhibits bacterial L-form growth.

Staphylococcus aureus remains a medical challenge in the treatment of bacterial infections. It has acquired resistance to commonly used antibiotics, and to those considered to be the last weapons in treating stap...