Increased antibiotic susceptibility in Neisseria gonorrhoeae through adaptation to the cervical environment, bioRxiv, 2020-01-09
AbstractNeisseria gonorrhoeae is an urgent public health threat due to rapidly increasing incidence and antibiotic resistance. In contrast with the trend of increasing resistance, clinical isolates that have reverted to susceptibility regularly appear, prompting questions about which pressures compete with antibiotics to shape gonococcal evolution. Here, we used genome-wide association on the largest collection of N. gonorrhoeae isolates to date (n=4882) to identify loss-of-function (LOF) mutations in the efflux pump mtrCDE operon as a mechanism of increased antibiotic susceptibility and demonstrate that these mutations are overrepresented in cervical isolates relative to urethral isolates (odds ratio (OR) = 3.74, 95% CI [1.98-6.70]). In support of a model in which pump expression incurs a fitness cost in this niche, cervical isolates were also enriched relative to urethral isolates in LOF mutations in the mtrCDE activator mtrA (OR = 8.60, 95% CI [4.96-14.57]) and in farA, a subunit of the FarAB efflux pump (OR = 6.25, 95% CI [3.90-9.83]). In total, approximately 1 in 3 cervical isolates (36.4%) contained a LOF mutation in either the efflux pump components mtrC or farA or the activator mtrA. Our findings extend beyond N. gonorrhoeae to other Neisseria mtrC LOF mutations are rare (<1%) in the primarily nasopharyngeal-colonizing N. meningitidis in a collection of 14,798 genomes but enriched in a heterosexual urethritis-associated lineage (8.6%, p = 9.90×10-5), indicating that efflux pump downregulation contributes broadly to the adaptation of pathogenic Neisseria to the female urogenital tract. Overall, our findings highlight the impact of integrating microbial population genomics with host metadata and demonstrate how host environmental pressures can lead to increased antibiotic susceptibility.
biorxiv microbiology 0-100-users 2020Engineering E. coli for magnetic control and the spatial localization of functions, bioRxiv, 2020-01-07
AbstractThe fast-developing field of synthetic biology enables broad applications of programmed microorganisms including the development of whole-cell biosensors, delivery vehicles for therapeutics, or diagnostic agents. However, the lack of spatial control required for localizing microbial functions could limit their use and induce their dilution leading to ineffective action or dissemination. To overcome this limitation, the integration of magnetic properties into living systems enables a contact-less and orthogonal method for spatiotemporal control. Here, we generated a magnetic-sensing Escherichia coli by driving the formation of iron-rich bodies into bacteria. We found that these bacteria could be spatially controlled by magnetic forces and sustained cell growth and division, by transmitting asymmetrically their magnetic properties to one daughter cell. We combined the spatial control of bacteria with genetically encoded-adhesion properties to achieve the magnetic capture of specific target bacteria as well as the spatial modulation of human cell invasions.
biorxiv synthetic-biology 0-100-users 2020Probabilistic gene expression signatures identify cell-types from single cell RNA-seq data, bioRxiv, 2020-01-06
AbstractSingle-cell RNA sequencing (scRNA-seq) quantifies the gene expression of individual cells in a sample, which allows distinct cell-type populations to be identified and characterized. An important step in many scRNA-seq analysis pipelines is the classification of cells into known cell-types. While this can be achieved using experimental techniques, such as fluorescence-activated cell sorting, these approaches are impractical for large numbers of cells. This motivates the development of data-driven cell-type identification methods. We find limitations with current approaches due to the reliance on known marker genes and sensitivity to the quality of reference samples. Here we present a computationally light statistical approach, based on Naive Bayes, that leverages public datasets to combine information across thousands of genes and probabilistically assign cell-type identity. Using datasets ranging across species and tissue types, we demonstrate that our approach is robust to low-quality reference data and produces more accurate cell-type identification than current methods.
biorxiv genomics 0-100-users 2020Twelve Platinum-Standard Reference Genomes Sequences (PSRefSeq) that complete the full range of genetic diversity of Asian rice, bioRxiv, 2020-01-01
AbstractAs the human population grows from 7.8 billion to 10 billion over the next 30 years, breeders must do everything possible to create crops that are highly productive and nutritious, while simultaneously having less of an environmental footprint. Rice will play a critical role in meeting this demand and thus, knowledge of the full repertoire of genetic diversity that exists in germplasm banks across the globe is required. To meet this demand, we describe the generation, validation and preliminary analyses of transposable element and long-range structural variation content of 12 near-gap-free reference genome sequences (RefSeqs) from representatives of 12 of 15 subpopulations of cultivated rice. When combined with 4 existing RefSeqs, that represent the 3 remaining rice subpopulations and the largest admixed population, this collection of 16 Platinum Standard RefSeqs (PSRefSeq) can be used as a pan-genome template to map resequencing data to detect virtually all standing natural variation that exists in the pan-cultivated rice genome.
biorxiv genomics 0-100-users 2020Unconventional kinetochore kinases KKT2 and KKT3 have a unique zinc finger that promotes their kinetochore localization, bioRxiv, 2019-12-14
AbstractChromosome segregation in eukaryotes is driven by the kinetochore, a macromolecular protein complex that assembles onto centromeric DNA and binds spindle microtubules. Cells must tightly control the number and position of kinetochores so that all chromosomes assemble a single kinetochore. A central player in this process is the centromere-specific histone H3 variant CENP-A, which localizes specifically within centromeres and promotes kinetochore assembly. However, CENP-A is absent from several eukaryotic lineages including kinetoplastids, a group of evolutionarily divergent eukaryotes that have an unconventional set of kinetochore proteins. It remains unknown how kinetoplastids specify kinetochore positions or promote kinetochore assembly in the absence of CENP-A. Here we studied two homologous kinetoplastid kinases (KKT2 and KKT3) that localize constitutively at centromeres. KKT2 and KKT3 central domains were sufficient for centromere localization in Trypanosoma brucei. Crystal structures of the KKT2 central domain from two divergent kinetoplastids revealed a unique zinc finger domain, which promotes its kinetochore localization in T. brucei. Mutations in the equivalent zinc finger domain of KKT3 abolished its kinetochore localization and function. This study lays the foundation for understanding the mechanism of kinetochore specification and assembly in kinetoplastids.
biorxiv cell-biology 0-100-users 2019A Distinct Contractile Injection System Found in a Majority of Adult Human Microbiomes, bioRxiv, 2019-12-06
ABSTRACTAn imbalance of normal bacterial groups such as Bacteroidales within the human gut is correlated with diseases like obesity. A current grand challenge in the microbiome field is to identify factors produced by normal microbiome bacteria that cause these observed health and disease correlations. While identifying factors like a bacterial injection system could provide a missing explanation for why Bacteroidales correlates with host health, no such factor has been identified to date. The lack of knowledge about these factors is a significant barrier to improving therapies like fecal transplants that promote a healthy microbiome. Here we show that a previously ill-defined Contractile Injection System is carried in the gut microbiome of 99% of individuals from the United States and Europe. This type of Contractile Injection System, we name here Bacteroidales Injection System (BIS), is related to the contractile tails of bacteriophage (viruses of bacteria) and have been described to mediate interactions between bacteria and diverse eukaryotes like amoeba, insects and tubeworms. Our findings that BIS are ubiquitous within adult human microbiomes suggest that they shape host health by mediating interactions between Bacteroidales bacteria and the human host or its microbiome.
biorxiv microbiology 0-100-users 2019