Explore the vast range of titles available.

\"Barbara Winton and the rest of the Bright Sparks, Dr. Keegan Bright's team of young scientists, find themselves facing a challenge that will test all of their scientific skills and personal courage. They are competing in the first ever race to completely circle the Moon. The Sparks, and twenty-five other teams, have to count on one another as they face thousands of kilometers of unknown dangers, where even a simple accident can have fatal consequences. They form close friendships with racers from all over Earth, but also have to deal with former Spark, Pam, a mysterious and threatening figure whose departure from the Sparks program is shrouded in mystery\"-- Provided by publisher.

DNA methylation is pervasive across all domains of life. In bacteria, the presence of N6-methyladenosine (m6A) has been detected among diverse species, yet the contribution of m6A to the regulation of gene expression is unclear in many organisms. Here we investigated the impact of DNA methylation on gene expression and virulence within the human pathogen Streptococcus pyogenes, or Group A Streptococcus. Single Molecule Real-Time sequencing and subsequent methylation analysis identified 412 putative m6A sites throughout the 1.8 Mb genome. Deletion of the Restriction, Specificity, and Methylation gene subunits (ΔRSM strain) of a putative Type I restriction modification system lost all detectable m6A at the recognition sites and failed to prevent transformation with foreign-methylated DNA. RNA-sequencing identified 20 genes out of 1,895 predicted coding regions with significantly different gene expression. All of the differentially expressed genes were down regulated in the ΔRSM strain relative to the parent strain. Importantly, we found that the presence of m6A DNA modifications affected expression of Mga, a master transcriptional regulator for multiple virulence genes, surface adhesins, and immune-evasion factors in S. pyogenes. Using a murine subcutaneous infection model, mice infected with the ΔRSM strain exhibited an enhanced host immune response with larger skin lesions and increased levels of pro-inflammatory cytokines compared to mice infected with the parent or complemented mutant strains, suggesting alterations in m6A methylation influence virulence. Further, we found that the ΔRSM strain showed poor survival within human neutrophils and reduced adherence to human epithelial cells. These results demonstrate that, in addition to restriction of foreign DNA, gram-positive bacteria also use restriction modification systems to regulate the expression of gene networks important for virulence.

Catheter-associated urinary tract infections (CAUTIs), a common cause of healthcare-associated infections, are caused by a diverse array of pathogens that are increasingly becoming antibiotic resistant. We analyze the microbial occurrences in catheter and urine samples from 55 human long-term catheterized patients collected over one year. Although most of these patients were prescribed antibiotics over several collection periods, their catheter samples remain colonized by one or more bacterial species. Examination of a total of 366 catheter and urine samples identify 13 positive and 13 negative genus co-occurrences over 12 collection periods, representing associations that occur more or less frequently than expected by chance. We find that for many patients, the microbial species composition between collection periods is similar. In a subset of patients, we find that the most frequently sampled bacteria, Escherichia coli and Enterococcus faecalis , co-localize on catheter samples. Further, co-culture of paired isolates recovered from the same patients reveals that E. coli significantly augments E. faecalis growth in an artificial urine medium, where E. faecalis monoculture grows poorly. These findings suggest novel strategies to collapse polymicrobial CAUTI in long-term catheterized patients by targeting mechanisms that promote positive co-associations. The authors examine temporal polymicrobial community composition in patients with long-term urinary catheters to identify species co-occurrences and demonstrate uropathogenic Escherichia coli augments growth of a prevalent opportunistic uropathogen in urine.

Catheter-associated urinary tract infections (CAUTIs) contribute greatly to the burden of healthcare-associated infections. Acinetobacter baumannii is a Gram-negative bacterium with high levels of antibiotic resistance that is of increasing concern as a CAUTI pathogen. A. baumannii expresses fibrinogen-binding adhesins (Abp1D and Abp2D) that mediate biofilm formation on catheters, which become coated with fibrinogen upon insertion. Here we develop a protein subunit vaccine against the Abp1D and Abp2D receptor binding domains (RBD) and show that vaccination significantly reduces bacterial titers in a female mouse model of CAUTI. We further demonstrate that immunity to Abp2D RBD alone is sufficient for protection. Mechanistically, we define the B cell response to Abp2D RBD vaccination, demonstrate that passive immunization with Abp2D RBD -immune serum transfers immunity to naïve mice, and show that Abp2D RBD -immune serum inhibits bacterial binding to fibrinogen-coated catheters. This work represents an antibiotic-sparing strategy for the prevention of A. baumannii CAUTI which has an important role in the global fight against antimicrobial resistance. Acinetobacter baumannii is a multi-drug-resistant pathogen of urgent international concern. Here, the authors develop a protein subunit vaccine which prevents A. baumannii catheter-associated urinary tract infections in mice by inhibiting Abp2D, a key adhesive virulence factor.

DNA methyltransferases (MTases) influence gene expression, cell cycle control, and host defense through DNA modification. Predicted MTases are pervasive across bacterial genomes, but the vast majority remain uncharacterized. Bacterial DNA methyltransferases (MTases) function in restriction modification systems, cell cycle control, and the regulation of gene expression. DnmA is a recently described DNA MTase that forms N6-methyladenosine at nonpalindromic 5′- GACG A G -3′ sites in Bacillus subtilis , yet how DnmA activity is regulated is unknown. To address DnmA regulation, we tested substrate binding in vitro and found that DnmA binds poorly to methylated DNA and to an RNA-DNA hybrid with the DNA recognition sequence. Further, DnmA variants with amino acid substitutions that disrupt cognate sequence recognition or catalysis also bind poorly to DNA. Using superresolution fluorescence microscopy and single-molecule tracking of DnmA-PAmCherry, we characterized the subcellular DnmA diffusion and detected its preferential localization to the replisome region and the nucleoid. Under conditions where the chromosome is highly methylated, upon RNA-DNA hybrid accumulation, or with a DnmA variant with severely limited DNA binding activity, DnmA is excluded from the nucleoid, demonstrating that prior methylation or accumulation of RNA-DNA hybrids regulates the association of DnmA with the chromosome in vivo . Furthermore, despite the high percentage of methylated recognition sites and the proximity to putative endonuclease genes conserved across bacterial species, we find that DnmA fails to protect B. subtilis against phage predation, suggesting that DnmA is functionally an orphan MTase involved in regulating gene expression. Our work explores the regulation of a bacterial DNA MTase and identifies prior methylation and RNA-DNA hybrids as regulators of MTase localization. These MTase regulatory features could be common across biology. IMPORTANCE DNA methyltransferases (MTases) influence gene expression, cell cycle control, and host defense through DNA modification. Predicted MTases are pervasive across bacterial genomes, but the vast majority remain uncharacterized. Here, we show that in the soil microorganism Bacillus subtilis , the DNA MTase dnmA and neighboring genes are remnants of a phage defense system that no longer protects against phage predation. This result suggests that portions of the bacterial methylome may originate from inactive restriction modification systems that have maintained methylation activity. Analysis of DnmA movement in vivo shows that active DnmA localizes in the nucleoid, suggesting that DnmA can search for recognition sequences throughout the nucleoid region with some preference for the replisome. Our results further show that prior DNA methylation and RNA-DNA hybrids regulate DnmA dynamics and nucleoid localization, providing new insight into how DNA methylation is coordinated within the cellular environment.

The alarming rise of multidrug-resistant Gram-positive bacteria has precipitated a healthcare crisis, necessitating the development of new antimicrobial therapies. Here we describe a new class of antibiotics based on a ring-fused 2-pyridone backbone, which are active against vancomycin-resistant enterococci (VRE), a serious threat as classified by the Centers for Disease Control and Prevention, and other multidrug-resistant Gram-positive bacteria. Ring-fused 2-pyridone antibiotics have bacteriostatic activity against actively dividing exponential phase enterococcal cells and bactericidal activity against nondividing stationary phase enterococcal cells. The molecular mechanism of drug-induced killing of stationary phase cells mimics aspects of fratricide observed in enterococcal biofilms, where both are mediated by the Atn autolysin and the GelE protease. In addition, combinations of sublethal concentrations of ring-fused 2-pyridones and standard-of-care antibiotics, such as vancomycin, were found to synergize to kill clinical strains of VRE. Furthermore, a broad range of antibiotic resistant Gram-positive pathogens, including those responsible for the increasing incidence of antibiotic resistant healthcare-associated infections, are susceptible to this new class of 2-pyridone antibiotics. Given the broad antibacterial activities of ring-fused 2-pyridone compounds against Gram-positive (GmP) bacteria we term these compounds GmPcides, which hold promise in combating the rising tide of antibiotic resistant Gram-positive pathogens.

ABSTRACT Bacillus subtilis is a Gram-positive bacterium that serves as an important experimental system. B. subtilis NCIB 3610 is an undomesticated strain that exhibits phenotypes lost from the more common domesticated laboratory strains. Here, we announce the complete genome sequence of DK1042, a genetically competent derivative of NCIB 3610.

We have developed GmPcides from a peptidomimetic dihydrothiazolo ring-fused 2-pyridone scaffold that have antimicrobial activities against a broad-spectrum of Gram-positive pathogens. Here we examine the treatment efficacy of GmPcides using skin and soft tissue infection (SSTI) and biofilm formation models by . Screening our compound library for minimal inhibitory (MIC) and minimal bactericidal (MBC) concentrations identified GmPcide PS757 as highly active against . Treatment of biofilm with PS757 revealed robust efficacy against all phases of biofilm formation by preventing initial biofilm development, ceasing biofilm maturation and eradicating mature biofilm. In a murine model of SSTI, subcutaneous delivery of PS757 resulted in reduced levels of tissue damage, decreased bacterial burdens and accelerated rates of wound-healing, which were associated with down-regulation of key virulence factors, including M protein and the SpeB cysteine protease. These data demonstrate that GmPcides show considerable promise for treating infections.

Ribosomal RNA (rRNA) is methylated in organisms ranging from bacteria to metazoans. Despite the pervasiveness of rRNA methylation in biology, the function of rRNA methylation on ribosome function is poorly understood. In this work, we identify a biological function for the rRNA 2'-O-methylcytidine methyltransferase TlyA, conserved between and . The deletion in confers a cold sensitive phenotype and resistance to aminoglycoside antibiotics that target the 16S rRNA. We show that Δ cells have ribosome assembly defects characterized by accumulation of the 50S subunit. Using a genetic approach and based on sequence alignments with other rRNA methyltransferases we tested the importance of potential catalytic residues and S-adenosyl-L-methionine (SAM) cofactor binding sites. We show that TlyA shares the common rRNA methyltransferase catalytic triad KDK and a SAM binding motif GxSxG which differs from TlyA. Together our work demonstrates that is critical for ribosome assembly and we identify key residues for TlyA function . Since lacks TlyA or a functional equivalent, our work highlights key differences in ribosome maturation between , and more divergent Gram-negative bacteria providing new insight into translation and antibiotic resistance mechanisms.