The discovery of aminoglycoside 66-40C, a novel dimeric, unsaturated imine produced by Micromonospora inyoensis, afforded a versatile intermediate for the synthesis of a variety of sisomicin analogues modified at the 6' position. The conversion of 66-40C into sisomicin, antibiotic G-52, and a series of novel 6'-substituted analogues of sisomicin is described, and the biological activity of the products is discussed.

As transmission intensity has declined in Senegal, so has the genetic complexity of circulating Plasmodium falciparum parasites, resulting in specific genotypes emerging and persisting over years. We address whether changes in parasite genetic signatures can alter the immune repertoire to variant surface antigens, and whether such responses can influence the expansion or contraction of specific parasite genotypes in the population. We characterize parasites within genotypic clusters, defined as identical by a 24-SNP molecular barcode and a haplotype identifier for other highly polymorphic loci; we measure expression of variant surface antigens (VSA) such as PfEMP-1 by transcript expression typing and expressed var DBL1α sequencing in ex vivo and short-term adapted RNA samples; and we measure IgG responses against VSAs from short-term adapted parasites. We find that parasites within genotypic clusters are genetically identical at other highly polymorphic loci. These parasites express similar Ups var classes and largely the same dominant var DBL1α sequences ex vivo. These parasites are recognized similarly by anti-VSA antibodies after short-term adaptation to culture; however, antibody responses do not correlate with genotype frequencies over time. Both genotype-specific and multiple genotype-reactive surface IgG responses are observed in this population. Parasites with identical genomes are extremely similar in their expression and host antibody recognition of VSAs. Monitoring changes in population-level parasite genomics and transmission dynamics is critical, as fluctuations will influence the breadth of resulting host immune responses to circulating parasite genotypes. These findings suggest shared immune recognition of genetically similar parasites, which has implications for both our understanding of immunity and vaccine development strategies in malaria elimination settings.

7We present the first method for efficient recovery of complete, closed genomes directly 8 from microbiomes using nanopore long-read sequencing and assembly. We apply our approach 9 to three healthy human gut communities and compare results to short read and read cloud 10 approaches. We obtain nine finished genomes including the first reported closed genome of 11Prevotella copri, an organism with highly repetitive genome structure prevalent in non-western 12 human gut microbiomes. longstanding goal of microbiome research. Although current reference-based methods are able 16 to detect known organisms and genes in metagenomes, only de novo approaches are able to 17 characterize novel genome sequences, or accurately place mobile or transferred elements in 18 new genomic contexts. The tremendous diversity and plasticity of bacterial genomes, as well as 19 the difficulty of bacterial isolation and culture, demand effective culture-free methods for 20 producing genomes directly from metagenomes. 21 Current metagenomic sequencing and assembly methods do not typically yield finished 22 bacterial genomes, although previous efforts have achieved single closed genomes in simple 23 communities 1 , or multiple genomes with skilled manual assembly and scaffolding 2 . 24Consequently, genome drafts are formed by grouping (i.e. binning) similar contigs within 25 fragmentary assemblies 3,4 . This is an imperfect process, often compromising the purity or the 26 completeness of the genome reconstruction. As assembly contiguity increases, the sensitivity 27 and specificity of genome binning are improved as fewer, larger contigs need to be grouped to 28 form each genome. Indeed, at the point when genomes are assembled in single contigs, binning 29 becomes unnecessary. Nanopore long read assembly has yielded complete genomes in 30 cultured bacterial isolates 5-8 , suggesting potential for effective assembly in more complex 31 microbial communities. However, the performance of nanopore and other long read approaches 32 in metagenomic sequencing and assembly has been limited by the lack of effective and efficient 33 methods to maximize molecular weight, mass yield and purity of DNA extracted from these 34 samples. 35We present a workflow consisting of stool DNA extraction, nanopore sequencing, 36 assembly and post-processing steps capable of producing multiple complete, circular bacterial 37 genomes directly from metagenomes. Our extraction approach produces microgram quantities 38 of pure, high molecular weight (HMW) DNA suitable for long read sequencing from as little as 39 300 milligrams (mg) of stool. Our computational workflow, consisting of assembly and post-40 processing, does not involve manual intervention in assembly, scaffolding, bacterial isolation, or 41 existing reference coverage of the target metagenome. Thus, this workflow is the first to provide 42 a rapid, simple, cost-effective, automated approach to close high numbers of bacterial genomes 43 directly from metagenomic samples. 44 Short read and read cloud data and ass...

A series of tylosins and acyl derivatives of 23-O-demycinosyltylosin (DMT) were initially tested for in vitro antibacterial activity and serum levels in squirrel monkeys (po) and mice (iv). Overall, the DMT compoundswere moreactive in vitro than the tylosins. Twotetraacylated DMTs,Sch 37644 and Sch 38646, were selected from the initial studies for further evaluation and compared to erythromycin and A-56268 (6-O-methyl erythromycin). Sch 37644 and Sch 38646 were 2 to 8-fold less potent in vitro against Gram-positive bacteria than erythromycin and A-56268. In squirrel monkeys, Sch 37644 (AUC, 19.7 fig-hour/ml) and A-56268 (21.6//g-hour/ml) had similar serum levels following po administration of 20 mg/kg, while Sch 38646 (1 1.8 fig à" hour/ml) and erythromycin (1.5 ,ug-hour/ml) had lower levels. In mice administered 200mg/kg orally, Sch 37644 (AUC, 19.4 fig-hour/ml) and Sch 38646 (15.4 fig-hour/ml) had higher serum levels than erythromycin (5.7 fighour/ml). A-56268 was the most active po macrolide in mouse protection studies (PD50s) against Staphylococci and Streptococci, while Sch 37644 and Sch 38646 were similar to erythromycin. 1131 Erythromycin, the most commonlyprescribed macrolide antibiotic for urinary tract and respiratory infections, has the disadvantage of being poorly absorbed after po administration. Therefore, a new series of macrolide antibiotics were prepared from tylosin and tested for improved po pharmacokinetics, as well as the retention of the good efficacy of erythromycin against Gram-positive infections. The derivatives were tested for in vitro antimicrobial activity, and pharmacokinetics in squirrel monkeys (po) and mice (iv). On the basis of initial results, two compounds were selected for further studies, 3,23,2'-triO -acetyl-23-0demycinosyl-4//^-/so-valeryltylosin (Sch 37644) and its 12,13-epoxy derivative (Sch 38646). These compoundswere compared to erythromycin and a new orally active erythromycin derivative, A-56268 (Abbott Laboratories, Abbott Park, IL). The data were presented in part at the 27th Interscience Conference on Antimicrobial Agents and Chemotherapy0. Materials and Methods Antibiotics A series of tylosin derivatives were synthesized by Dr. Mallams in our laboratories2'3*. These derivatives consisted of two structurally related groups of compounds: Tylosin and 23-O-demycinosyltylosin (DMT) and their acyl, hydrazone, and 12,13-epoxy derivatives. The structures of the two selected derivatives, Sch 37644 and Sch 38646, are shown in Fig. 1.