Working together with colleagues in Spain, Japan and Australia, researchers led by Luis Serrano, ICREA research professor and leader of the Design of Biological Systems laboratory at the CRG, focused their attention on the organisation of DNA within an organism with an extremely small genome – the pneumonia pathogen Mycoplasma pneumoniae.
Using a technique called Hi-C, which reveals the interactions between different pieces of DNA, the researchers created a three-dimensional ‘map’ of the Mycoplasma chromosome. They then used super-resolution microscopy to prove that this computer-generated map matched up with the real-life chromosome organisation inside bacterial cells.
Notably, the CRG team, discovered that Mycoplasma’s circular chromosome is consistently organised the same way in all the cells, with a region called the Origin (where DNA copying begins) at one end of the structure and the midpoint of the chromosome located at the opposite end. This is a similar arrangement to that seen in some other larger bacterial species. Intriguingly, the CRG team found that even the tiny Mycoplasma chromosome is organised into distinct structural domains, each containing genes that are also turned on or off in a co-ordinated way.
The discovery suggests that this level of organisation and genetic control is common to all living cells, from the largest to the smallest, and can be achieved with little more than a handful of DNA binding proteins and the structural properties of the DNA itself.
Trussart, M. et al. Defined chromosome structure in the genome-reduced bacterium Mycoplasma pneumoniae. Nat. Commun. 8, 14665 doi: 10.1038/ncomms14665 (2017).