RESUMEN
Despite the critical importance of essential genes, systems-level investigations of their contribution to antibiotic sensitivity have been limited. Using CRISPR Adaptation-mediated Library Manufacturing (CALM), we generated ultra-dense CRISPR interference (CRISPRi) libraries in methicillin-sensitive and -resistant strains of Staphylococcus aureus, which allowed us to quantify gene fitness on a global scale across ten clinically relevant antibiotics. This led to the identification of a comprehensive set of known and novel biological processes modulating bacterial fitness in the antibiotics. Notably, we found that essential genes from diverse processes dominated antibiotic-gene interactions, including a large number of synergistic interactions between bactericidal antibiotics and processes such as cell wall synthesis/cell division (CC), DNA replication/DNA recombination (DD), protein export, and coenzyme A biosynthesis. Simultaneous genetic perturbations of diverse CC and DD processes aggravated bacterial fitness, revealing a widespread synergy between the two highly coordinated processes. In contrast, perturbation of transcriptional, translational, and select energy processes antagonized the effects of bactericidal antibiotics. Finally, we show that small molecule inhibitors recapitulated synergistic antibiotic-gene interactions, providing a rational foundation for developing novel combinatorial antimicrobial therapies.
RESUMEN
Despite longstanding appreciation of gene expression heterogeneity in isogenic bacterial populations, affordable and scalable technologies for studying single bacterial cells have been limited. Although single-cell RNA sequencing (scRNA-seq) has revolutionized studies of transcriptional heterogeneity in diverse eukaryotic systems1-13, the application of scRNA-seq to prokaryotes has been hindered by their extremely low mRNA abundance14-16, lack of mRNA polyadenylation and thick cell walls17. Here, we present prokaryotic expression profiling by tagging RNA in situ and sequencing (PETRI-seq)-a low-cost, high-throughput prokaryotic scRNA-seq pipeline that overcomes these technical obstacles. PETRI-seq uses in situ combinatorial indexing11,12,18 to barcode transcripts from tens of thousands of cells in a single experiment. PETRI-seq captures single-cell transcriptomes of Gram-negative and Gram-positive bacteria with high purity and low bias, with median capture rates of more than 200 mRNAs per cell for exponentially growing Escherichia coli. These characteristics enable robust discrimination of cell states corresponding to different phases of growth. When applied to wild-type Staphylococcus aureus, PETRI-seq revealed a rare subpopulation of cells undergoing prophage induction. We anticipate that PETRI-seq will have broad utility in defining single-cell states and their dynamics in complex microbial communities.
Asunto(s)
Células Procariotas , ARN/genética , Análisis de Secuencia de ARN , Análisis de la Célula Individual , Biología Computacional/métodos , Perfilación de la Expresión Génica , Secuenciación de Nucleótidos de Alto Rendimiento , Células Procariotas/metabolismo , Análisis de la Célula Individual/métodos , TranscriptomaRESUMEN
The α7-nicotinic acetylcholine receptor (α7-nAChR) is a ligand-gated ion channel widely expressed in vertebrates and is associated with numerous physiological functions. As transmembrane ion channels, α7-nAChRs need to be expressed on the surface of the plasma membrane to function. The receptor has been reported to associate with proteins involved with receptor biogenesis, modulation of receptor properties, as well as intracellular signaling cascades and some of these associated proteins may affect surface expression of α7-nAChRs. The putative chaperone resistance to inhibitors of cholinesterase 3 (Ric-3) has been reported to interact with, and enhance the surface expression of, α7-nAChRs. In this study, we identified proteins that associate with α7-nAChRs when Ric-3 is expressed. Using α-bungarotoxin (α-bgtx), we isolated and compared α7-nAChR-associated proteins from two stably transfected, human tumor-derived cell lines: SH-EP1-hα7 expressing human α7-nAChRs and the same cell line further transfected to express Ric-3, SH-EP1-hα7-Ric-3. Mass spectrometric analysis of peptides identified thirty-nine proteins that are associated with α7-nAChRs only when Ric-3 was expressed. Significantly, and consistent with reports of Ric-3 function in the literature, several of the identified proteins are involved in biological processes that may affect nAChR surface expression such as post-translational processing of proteins, protein trafficking, and protein transport. Additionally, proteins affecting the cell cycle, the cytoskeleton, stress responses, as well as cyclic AMP- and inositol triphosphate-dependent signaling cascades were identified. These results illuminate how α-bgtx may be used to isolate and identify α7-nAChRs as well as how the expression of chaperones such as Ric-3 can influence proteins associating with α7-nAChRs. These associating proteins may alter activities of α7-nAChRs to expand their functionally-relevant repertoire as well as to affect biogenesis and membrane trafficking of α7-nAChRs.