ABSTRACT
Single-molecule techniques are ideally poised to characterize complex dynamics but are typically limited to investigating a small number of different samples. However, a large sequence or chemical space often needs to be explored to derive a comprehensive understanding of complex biological processes. Here we describe multiplexed single-molecule characterization at the library scale (MUSCLE), a method that combines single-molecule fluorescence microscopy with next-generation sequencing to enable highly multiplexed observations of complex dynamics. We comprehensively profiled the sequence dependence of DNA hairpin properties and Cas9-induced target DNA unwinding-rewinding dynamics. The ability to explore a large sequence space for Cas9 allowed us to identify a number of target sequences with unexpected behaviors. We envision that MUSCLE will enable the mechanistic exploration of many fundamental biological processes.
Subject(s)
DNA , High-Throughput Nucleotide Sequencing , Microscopy, Fluorescence , Single Molecule Imaging , High-Throughput Nucleotide Sequencing/methods , Single Molecule Imaging/methods , DNA/chemistry , DNA/genetics , Microscopy, Fluorescence/methods , CRISPR-Associated Protein 9 , Sequence Analysis, DNA/methods , Gene Library , CRISPR-Cas SystemsABSTRACT
In both prokaryotes and eukaryotes, the survival at temperatures considerably exceeding the optimum is supported by intense synthesis of the so-called heat shock proteins (HSPs), which act to overcome the adverse effects of heat stress. Among mycoplasmas (class Mollicutes), which have significantly reduced genomes, only some members of the Acholeplasmataceae family possess small HSPs of the α-crystallin type. Overproduction of a recombinant HSP IbpA (Hsp20) from the free-living mycoplasma Acholeplasma laidlawii was shown to increase the resistance of Escherichia coli to short-term heat shock. It has been long assumed that IbpA prevents protein aggregation and precipitation thereby increasing viability of E. coli cells. Several potential target proteins interacting with IbpA under heat stress were identified, including biosynthetic enzymes, enzymes of energy metabolism, and components of the protein synthesis machinery. Statistical analysis of physicochemical properties indicated that IbpA interaction partners significantly differ in molecular weight, charge, and isoelectric point from other members of the E. coli proteome. Upon shortterm exposure to increased temperature, IbpA was found to preferentially interact with high-molecular weight proteins having a pI of about 5.1, significantly lower than the typical values of E. coli proteins.
Subject(s)
Acholeplasma laidlawii/chemistry , Bacterial Proteins/chemistry , Escherichia coli/physiology , Heat-Shock Proteins, Small/chemistry , Hot Temperature , Recombinant Proteins/chemistry , Stress, PhysiologicalABSTRACT
SOS-response is an important tool of bacteria intended to protect their genome and thereby allow them to survive under adverse conditions. Recently SOS-response is considered to enhance mutagenesis and thus help bacteria acquire antibiotic resistance. Due to high significance of this phenomena it seems to be important to investigate processes that allow bacteria to survive after SOS-response activation. In current work the recovery of division process of Escherichia coli cells after division arrest due to expression of SOS-response protein SulA was studied. Data indicate that cells are able to rapidly restore normal division; also nucleoid occlusion seems to be the main septum positioning mechanism during the process. In the course of recovery FtsZ forms helix-like structures, which then transformate into Z-rings.
Subject(s)
Bacterial Proteins/metabolism , Cytokinesis/physiology , Cytoskeletal Proteins/metabolism , Escherichia coli Proteins/metabolism , Escherichia coli/metabolism , SOS Response, Genetics/physiology , Bacterial Proteins/genetics , Cytoskeletal Proteins/genetics , Escherichia coli/genetics , Escherichia coli Proteins/geneticsABSTRACT
FtsZ--a bacterial tubulin homolog--is one of the key bacterial division proteins, forming a contractile Z-ring at the midcell of dividing bacteria. In this work immunofluorescent labeling was used in conjunction with single-molecule localization microscopy (SMLM) to visualize native structures formed by FtsZ protein in Escherichia coli cells. This approach allowed the reorganization of FtsZ structures during cytokinesis to be visualized step-by-step. New data was obtained that support the hypothesis that the Z-ring is a spiral structure that constricts during division, assisting the formation of the septum between daughter cells.