Draft whole-genome sequences of three Borrelia burgdorferi isolates from Western Canada

Whole-genome sequences are presented for three Borrelia burgdorferi, a causative agent of Lyme disease in North America, isolated from Ixodes pacificus ticks collected in British Columbia, Canada. Shotgun DNA libraries were prepared with Illumina DNA Prep and sequenced using the MiniSeq platform. Genome assemblies enabled multilocus sequence typing and ospC typing.

Complete genome sequences of bacteria isolated from cockroaches collected in a Bangladeshi hospital

We report the complete genome sequences of four bacterial strains that were isolated from Blattella germanica (German cockroaches) that were found in three wards of the Rajshahi Medical College Hospital. Multiple antibiotic resistance genes were identified in each genome, with one genome containing multiple plasmid-encoded resistance genes.

Emergence of Inducible Macrolide Resistance in Mycobacterium chelonae Due to Broad-Host-Range Plasmid and Chromosomal Variants of the Novel 23S rRNA Methylase Gene, erm(55)

Macrolides are a mainstay of therapy for infections due to nontuberculous mycobacteria (NTM). Among rapidly growing mycobacteria (RGM), inducible macrolide resistance is associated with four chromosomal 23S rRNA methylase (erm) genes. Beginning in 2018, we detected high-level inducible clarithromycin resistance (MICs of ≥16μg/mL) in clinical isolates of Mycobacterium chelonae, an RGM species not previously known to contain erm genes. Using whole-genome sequencing, we identified a novel plasmid-mediated erm gene. This gene, designated erm(55)P, exhibits <65% amino acid identity to previously described RGM erm genes. Two additional chromosomal erm(55) alleles, with sequence identities of 81% to 86% to erm(55)P, were also identified and designated erm(55)C and erm(55)T. The erm(55)T is part of a transposon. The erm(55)P allele variant is located on a putative 137-kb conjugative plasmid, pMchErm55. Evaluation of 133 consecutive isolates from 2020 to 2022 revealed 5 (3.8%) with erm(55). The erm(55)P gene was also identified in public data sets of two emerging pathogenic pigmented RGM species: Mycobacterium iranicum and Mycobacterium obuense, dating back to 2008. In both species, the gene appeared to be present on plasmids homologous to pMchErm55. Plasmid-mediated macrolide resistance, not described previously for any NTM species, appears to have spread to multiple RGM species. This has important implications for antimicrobial susceptibility guidelines and treatment of RGM infections. Further spread could present serious consequences for treatment of other macrolide-susceptible RGM. Additional studies are needed to determine the transmissibility of pMchErm55 and the distribution of erm(55) among other RGM species.

Structural Insights into the Inhibition of Undecaprenyl Pyrophosphate Synthase from Gram-Positive Bacteria

The polyprenyl lipid undecaprenyl phosphate (C₅₅P) is the universal carrier lipid for the biosynthesis of bacterial cell wall polymers. C₅₅P is synthesized in its pyrophosphate form by undecaprenyl pyrophosphate synthase (UppS), an essential cis-prenyltransferase that is an attractive target for antibiotic development. We previously identified a compound (MAC-0547630) that showed promise as a novel class of inhibitor and an ability to potentiate β-lactam antibiotics. Here, we provide a structural model for MAC-0547630's inhibition of UppS and a structural rationale for its enhanced effect on UppS from Bacillus subtilis versus Staphylococcus aureus. We also describe the synthesis of a MAC-0547630 derivative (JPD447), show that it too can potentiate β-lactam antibiotics, and provide a structural rationale for its improved potentiation. Finally, we present an improved structural model of clomiphene's inhibition of UppS. Taken together, our data provide a foundation for structure-guided drug design of more potent UppS inhibitors in the future.

A Slippery Scaffold: Synthesis and Recycling of the Bacterial Cell Wall Carrier Lipid

The biosynthesis of bacterial cell envelope polysaccharides such as peptidoglycan relies on the use of a dedicated carrier lipid both for the assembly of precursors at the cytoplasmic face of the plasma membrane and for the translocation of lipid linked oligosaccharides across the plasma membrane into the periplasmic space. This dedicated carrier lipid, undecaprenyl phosphate, results from the dephosphorylation of undecaprenyl pyrophosphate, which is generated de novo in the cytoplasm by undecaprenyl pyrophosphate synthase and released as a by-product when newly synthesized glycans are incorporated into the existing cell envelope. The de novo synthesis of undecaprenyl pyrophosphate has been thoroughly characterized from a structural and mechanistic standpoint; however, its dephosphorylation to the active carrier lipid form, both in the course of de novo synthesis and recycling, has only been begun to be studied in depth in recent years. This review provides an overview of bacterial carrier lipid synthesis and presents the current state of knowledge regarding bacterial carrier lipid recycling.

A Toxoplasma gondii locus required for the direct manipulation of host mitochondria has maintained multiple ancestral functions

The Toxoplasma gondii locus mitochondrial association factor 1 (MAF1) encodes multiple paralogs, some of which mediate host mitochondrial association (HMA). Previous work showed that HMA was a trait that arose in T. gondii through neofunctionalization of an ancestral MAF1 ortholog. Structural analysis of HMA-competent and incompetent MAF1 paralogs (MAF1b and MAF1a, respectively) revealed that both paralogs harbor an ADP ribose binding macro-domain, with comparatively low (micromolar) affinity for ADP ribose. Replacing the 16 C-terminal residues of MAF1b with those of MAF1a abrogated HMA, and we also show that only three residues in the C-terminal helix are required for MAF1-mediated HMA. Importantly these same three residues are also required for the in vivo growth advantage conferred by MAF1b, providing a definitive link between in vivo proliferation and manipulation of host mitochondria. Co-immunoprecipitation assays reveal that the ability to interact with the mitochondrial MICOS complex is shared by HMA-competent and incompetent MAF1 paralogs and mutants. The weak ADPr coordination and ability to interact with the MICOS complex shared between divergent paralogs may represent modular ancestral functions for this tandemly expanded and diversified T. gondii locus.

Purification, crystallization and X-ray diffraction analysis of Trypanosoma congolense insect-stage surface antigen (TcCISSA)

Trypanosoma congolense is a major contributor to the vast socioeconomic devastation in sub-Saharan Africa caused by animal African trypanosomiasis. These protozoan parasites are transmitted between mammalian hosts by tsetse-fly vectors. A lack of understanding of the molecular basis of tsetse-trypanosome interactions stands as a barrier to the development of improved control strategies. Recently, a stage-specific T. congolense protein, T. congolense insect-stage surface antigen (TcCISSA), was identified that shows considerable sequence identity (>60%) to a previously identified T. brucei insect-stage surface molecule that plays a role in the maturation of infections. TcCISSA has multiple di-amino-acid and tri-amino-acid repeats in its extracellular domain, making it an especially interesting structure-function target. The predicted mature extracellular domain of TcCISSA was produced by recombinant DNA techniques, purified from Escherichia coli, crystallized and subjected to X-ray diffraction analysis; the data were processed to 2.7 Å resolution.