Defined chromosome structure in the genome-reduced bacterium Mycoplasma pneumoniae

Marie Trussart
Eva Yus
Sira Martinez
Davide Baù
Yuhei O. Tahara
Thomas Pengo
Michael Widjaja
Simon Kretschmer
Jim Swoger
Steven Djordjevic
Lynne Turnbull
Cynthia Whitchurch
Makoto Miyata
Marc A. Marti- Renom
Maria Lluch-Senar
Luís Serrano
Wednesday, March 8, 2017
Abstract: 
DNA-binding proteins are central regulators of chromosome organization; however, in genome-reduced bacteria their diversity is largely diminished. Whether the chromosomes of such bacteria adopt defined three-dimensional structures remains unexplored. Here we combine Hi-C and super-resolution microscopy to determine the structure of the Mycoplasma pneumoniae chromosome at a 10 kb resolution. We find a defined structure, with a global symmetry between two arms that connect opposite poles, one bearing the chromosomal Ori and the other the midpoint. Analysis of local structures at a 3 kb resolution indicates that the chromosome is organized into domains ranging from 15 to 33 kb. We provide evidence that genes within the same domain tend to be co-regulated, suggesting that chromosome organization influences transcriptional regulation, and that supercoiling regulates local organization. This study extends the current understanding of bacterial genome organization and demonstrates that a defined chromosomal structure is a universal feature of living systems.