Bacterial chromosome organization
Organisation of the circular chromosome in E.coli
Although the physical properties of chromosomes, including their morphology, mechanics, and dynamics are crucial for their biological function, many basic questions remain unresolved.
In this project, we directly image the circular chromosome in live E. coli with a broadened cell shape. We find that it exhibits a torus topology with, on average, a lower-density origin of replication and an ultrathin flexible string of DNA at the terminus of replication. At the single-cell level, the torus is strikingly heterogeneous, with blob-like Mbp-size domains that undergo major dynamic rearrangements, splitting and merging at a minute timescale. Our findings provide an architectural basis for the understanding of the dynamic spatial organization of bacterial genomes in live cells.
Cell Boundary Confinement Sets the Size and Position of
In this project, we show in Escherichia coli that spatial confinement plays a dominant role in determining both the chromosome size and it’s position. In E.coli cells with lengths up to 10 times the normal size, single chromosomes are observed to expand only ~4-fold in size. Chromosomes show pronounced internal dynamics but exhibit a robust positioning where single nucleoids reside robustly at mid-cell, whereas two nucleoids self-organize at 1/4 and 3/4 positions. The cell-size-dependent expansion of the nucleoid is only modestly influenced by deletions of nucleoid-associated proteins, whereas osmotic manipulation experiments reveal a prominent role of molecular crowding.
Influence of antibiotics on bacterial chromosomes
Diseases caused by various bacteria constitute one of the biggest public health problems worldwide, causing ~15 million deaths per year. Therefore improving our understanding of the antibiotic function as well as bacterial resistance mechanism is of paramount importance.
In our lab, we developed a novel method to manipulate bacterial cell shapes and by doing so we investigate the finer structure of E.coli chromosome. In the current framework we plan study the influence of antibiotics on the chromosomes of live bacteria, by using fluorescence microscopy and quantitative data analysis (Fig.3).