Researchers have described the 3D structure of the genome in the extremely small bacteria Mycoplasma pneumoniae. They discovered previously unknown arrangements of DNA within this tiny bacteria, which are also found in larger cells. Their findings suggest that this type of organization is a universal feature of living cells.
DNA contains the instructions for life, encoded within genes. Within all cells, DNA is organised into very long lengths known as chromosomes. In animal and plant cells these are double-ended, like pieces of string or shoelaces, but in bacteria they are circular. Whether stringy or circular, these long chromosomes must be organised and packaged inside a cell so that the genes can be switched on or off when they are required.
The scientists also used the Hi-C technique to study more detailed patterns of organisation within the Mycoplasma genome. In recent years, scientists all over the world have investigated the organisation of chromosomes inside cells from species ranging from larger bacteria to human. Next Generation Sequencing has allowed scientists to ‘read’ the DNA sequence of any genome, but this doesn’t reveal how genetic information is managed and organised in the crowded and bustling biological environment inside a cell. Now, new tools have revealed complex organisational structures within the genomes of larger organisms, with certain regions of chromosomes clustered together to form domains containing genes that are switched on or off together.
However, it was thought that these domains would not be found in Mycoplasma, because its genome is so small and it only makes around 20 different DNA binding proteins responsible for organising the chromosome, compared to the hundreds made by other 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.
Marie Trussart, the lead author on the paper, said: “Studying bacteria with such a small genome was a big technical challenge, especially because we were using super-resolution microscopy, and it took us five years to complete the project. We had suspected that the Mycoplasma genome might have a similar overall organisation to other bacteria, but we were completely surprised to find that it was also organised into domains, which can be considered as regulatory units of chromatin organisation and that we had identified a previously unknown layer of gene regulation. This research shows that the organisation and control of genes cannot be understood by just looking at the linear sequence of DNA in the genome. Indeed, to get the full picture of gene regulation we need to look at the three-dimensional organisation of the chromatin that also coordinates gene activity.” Paper. (public access) – 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. Defined chromosome structure in the genome-reduced bacterium Mycoplasma pneumoniae. Nature Communications, 2017; 8: 14665 DOI: 10.1038/ncomms14665 More.
These days, even simple bacteria have hidden structures. But it supposedly all just happened via Darwinism (natural selection acting on random mutation) even though we know full well it couldn’t have. No wonder the sea is boiling hot.
See also: Denis Noble’s new book calls for “fundamental revision” of neo-Darwinian theory Darwin apologists can probably convince the New York Times but these days that’s only a participation trophy.
Follow UD News at Twitter!