Project description:Rapidly growing antibiotic resistance among gastrointestinal pathogens, and the ability of antibiotics to induce the virulence of these pathogens makes it increasingly difficult to rely on antibiotics to treat gastrointestinal infections. The probiotic E. coli strain Nissle 1917 (EcN) is the active component of the pharmaceutical preparation Mutaflor® and has been successfully used in the treatment of gastrointestinal disorders. Gut bacteriophages are dominant players in maintaining the microbial homeostasis in the gut, however, their interaction with incoming probiotic bacteria remains to be at conception. The presence of bacteriophages in the gut makes it inevitable for any probiotic bacteria to be phage resistant, in order to survive and successfully colonize the gut. This study addresses the phage resistance of EcN, specifically against lytic T4 phage infection. From various experiments we could show that i) EcN is resistant towards T4 phage infection, ii) EcN’s K5 polysaccharide capsule plays a crucial role in T4 phage resistance and iii) EcN’s lipopolysaccharide (LPS) inactivates T4 phages and notably, treatment with the antibiotic polymyxin B which neutralizes the LPS destroyed the phage inactivation ability of isolated LPS from EcN. Our results further indicate that N-acetylglucosamine at the distal end of O6 antigen in EcN’s LPS could be the interacting partner with T4 phages. From our findings, we have reported for the first time, the role of EcN’s K5 capsule and LPS in its defense against T4 phages. In addition, by inactivating the T4 phages, EcN also protects E. coli K-12 strains from phage infection in tri-culture experiments. The combination of the identified properties is not found in other tested commensal E. coli strains. Furthermore, our research highlights phage resistance as an additional safety feature of EcN, a clinically successful probiotic E. coli strain.
Project description:To better understand host/phage interactions and the genetic bases of phage resistance in a model system relevant to potential phage therapy, we isolated several spontaneous mutants of the USA300 S. aureus clinical isolate NRS384 that were resistant to phage K. Six of these had a single missense mutation in the host rpoC gene, which encodes the RNA polymerase beta prime subunit. To examine the hypothesis that the mutations in the host RNA polymerase affect the transcription of phage genes, we performed RNA-seq analysis on total RNA samples collected from NRS384 wild-type (WT) and rpoC G17D mutant cultures infected with phage K, at different time points after infection. Infection of the WT host led to a steady increase of phage transcription relative to the host. Our analysis allowed us to define different early, middle, and late phage genes based on their temporal expression patterns and group them into transcriptional units. Predicted promoter sequences defined by conserved -35, -10, and in some cases extended -10 elements were found upstream of early and middle genes. However, sequences upstream of late genes did not contain clear, complete, canonical promoter sequences, suggesting that factors in addition to host RNA polymerase are required for their regulated expression. Infection of the rpoC G17D mutant host led to a transcriptional pattern that was similar to the WT at early time points. However, beginning at 20 minutes after infection, transcription of late genes (such as phage structural genes and host lysis genes) was severely reduced. Our data indicate that the rpoCG17D mutation prevents the expression of phage late genes, resulting in a failed infection cycle for phage K. In addition to illuminating the global transcriptional landscape of phage K throughout the infection cycle, these studies can inform our investigations into the bases of phage K’s control of its transcriptional program as well as mechanisms of phage resistance.
Project description:Display technologies, e.g., phage, ribosome, mRNA, bacterial, and yeast-display, combine high content peptide libraries with appropriate screening strategies to identify functional peptide sequences. Construction of large peptide library and display-screen system in intact mammalian cells will facilitate the development of peptide therapeutics targeting transmembrane proteins. Our previous work established linear-double-stranded DNAs (ldsDNAs) as innovative biological parts to implement AND gate genetic circuits in mammalian cell line. In the current study, we employ ldsDNA with terminal NNK degenerate codons as AND gate input to build highly diverse peptide library in mammalian cells. Only PCR reaction and cell transfection experiments are needed to construct the library. High-throughput sequencing (HTS) results reveal that our new strategy could generate peptide library with both amino acid sequence and peptide length diversities. Our work establishes ldsDNA as biological parts for building highly diverse peptide library in mammalian cells, which shows great application potential in developing therapeutic peptides targeting transmembrane proteins.
Project description:Pseudomonas syringae pv. phaseolicola (Pph) is a significant bacterial pathogen of agricultural crops, and phage Φ6 and other members of the dsRNA virus family Cystoviridae undergo lytic (virulent) infection of Pph, using the type IV pilus as the initial site of cellular attachment. Despite the popularity of Pph/phage Φ6 as a model system in evolutionary biology, Pph resistance to phage Φ6 remains poorly characterized. To investigate differences between phage Φ6 resistant Pseudomonas syringae pathovar phaseolicola strains, we performed expression analysis of super and non piliated strains of Pseudomonas syringae to determine the genetic cause of resistance to viral infection.
Project description:Whole-genome sequencing is an important way to understand the genetic information, gene function, biological characteristics, and living mechanisms of organisms. There is no difficulty to have mega-level genomes sequenced at present. However, we encountered a hard-to-sequence genome of Pseudomonas aeruginosa phage PaP1. The shotgun sequencing method failed to dissect this genome. After insisting for 10 years and going over 3 generations of sequencing techniques, we successfully dissected the PaP1 genome with 91,715 bp in length. Single-molecule sequencing revealed that this genome contains lots of modified bases, including 51 N6-methyladenines (m6A) and 152 N4-methylcytosines (m4C). At the same time, further investigations revealed a novel immune mechanism of bacteria, by which the host bacteria can recognize and repel the modified bases containing inserts in large scale, and this led to the failure of the shotgun method in PaP1 genome sequencing. Strategy of resolving this problem is use of non-library dependent sequencing techniques or use of the nfi- mutant of E. coli DH5M-NM-1 as the host bacteria to construct the shotgun library. In conclusion, we unlock the mystery of phage PaP1 genome hard to be sequenced, and discover a new mechanism of bacterial immunity in present study. Methylation profiling of Pseudomonas aeruginosa phage PaP1 using kinetic data generated by single-molecule, real-time (SMRT) sequencing on the PacBio RS.
Project description:Single cell multi-omic readouts of both the cellular transcriptome and proteome have significantly enhanced our ability to comprehensively characterize cellular states. Most approaches in this area rely on oligonucleotide barcode-conjugated antibodies that target cell surface epitopes of interest, enabling their concomitant detection with the transcriptome. However, a similar high-throughput measurement of other cellular modalities such as the epigenome in concert with protein levels have not been described. Moreover, detection of epitopes is limited to antigens for which a specific antibody is available. Here, we introduce PHAGE-ATAC, an approach that enables the scalable and simultaneous detection of protein levels and chromatin accessibility data in single cells using the assay of transposase-accessible chromatin with sequencing (ATAC-seq). Quantitative detection of proteins by PHAGE-ATAC is accomplished through the use of engineerable nanobody-displaying phages that are genetically barcoded within the nanobody-encoding phagemids. We demonstrate the utility of PHAGE-ATAC for multimodal single cell genomic analysis in both cell lines and primary human cells. Analogous to phage display approaches, we further establish a synthetic high-complexity library of nanobody-displaying phages and demonstrate its utility to select novel antigen-specific nanobodies for PHAGE-ATAC.
Project description:Single cell multi-omic readouts of both the cellular transcriptome and proteome have significantly enhanced our ability to comprehensively characterize cellular states. Most approaches in this area rely on oligonucleotide barcode-conjugated antibodies that target cell surface epitopes of interest, enabling their concomitant detection with the transcriptome. However, a similar high-throughput measurement of other cellular modalities such as the epigenome in concert with protein levels have not been described. Moreover, detection of epitopes is limited to antigens for which a specific antibody is available. Here, we introduce PHAGE-ATAC, an approach that enables the scalable and simultaneous detection of protein levels and chromatin accessibility data in single cells using the assay of transposase-accessible chromatin with sequencing (ATAC-seq). Quantitative detection of proteins by PHAGE-ATAC is accomplished through the use of engineerable nanobody-displaying phages that are genetically barcoded within the nanobody-encoding phagemids. We demonstrate the utility of PHAGE-ATAC for multimodal single cell genomic analysis in both cell lines and primary human cells. Analogous to phage display approaches, we further establish a synthetic high-complexity library of nanobody-displaying phages and demonstrate its utility to select novel antigen-specific nanobodies for PHAGE-ATAC.
Project description:Single cell multi-omic readouts of both the cellular transcriptome and proteome have significantly enhanced our ability to comprehensively characterize cellular states. Most approaches in this area rely on oligonucleotide barcode-conjugated antibodies that target cell surface epitopes of interest, enabling their concomitant detection with the transcriptome. However, a similar high-throughput measurement of other cellular modalities such as the epigenome in concert with protein levels have not been described. Moreover, detection of epitopes is limited to antigens for which a specific antibody is available. Here, we introduce PHAGE-ATAC, an approach that enables the scalable and simultaneous detection of protein levels and chromatin accessibility data in single cells using the assay of transposase-accessible chromatin with sequencing (ATAC-seq). Quantitative detection of proteins by PHAGE-ATAC is accomplished through the use of engineerable nanobody-displaying phages that are genetically barcoded within the nanobody-encoding phagemids. We demonstrate the utility of PHAGE-ATAC for multimodal single cell genomic analysis in both cell lines and primary human cells. Analogous to phage display approaches, we further establish a synthetic high-complexity library of nanobody-displaying phages and demonstrate its utility to select novel antigen-specific nanobodies for PHAGE-ATAC.