23 November 2017
DNA-binding lipids protect bacteria
Published online 15 August 2017
Intracellular lipid droplets help protect bacteria under stress by stabilizing their DNA.
Lipid droplets have been found in the cells of almost all organisms and are known for their functions in lipid storage and metabolism, and intracellular molecular trafficking and signalling. Now, new research shows that they also bind to DNA, increasing the resistance of a bacterium when exposed to certain stressful conditions.
A team from China, with a researcher affiliated to King Abdulaziz University in Saudi Arabia, found that a protein, called microorganism lipid droplet small (MLDS) protein, along with its transcription factor, MLDS regulator (MLDSR), control and facilitate the binding of lipid droplets to DNA in the bacterium Rhodococcus jostii RHA1 (RHA1)1.
In their experiments, they compared DNA localization in lipid droplets between normal and mutant RHA1 in which MLDS and MLDSR were not functioning properly. They also put bacterial cells under stress by exposing them to low nitrogen levels and ultraviolet irradiation.
They found that stressful conditions increase the expression of MLDSR, which in turn regulates the expression of MLDS. Lipid droplets then bind to DNA through MLDS, which seems to protect it from stress-related breakages.
The survival and growth rates of bacterial strains with improperly functioning MDLSR were lower and their DNA-strand breaks were higher in extremely low nitrogen conditions compared to normal cells.
Strains with improperly functioning MDLSR were also more sensitive when exposed to ultraviolet irradiation and had more DNA-strand breaks than normal cells.
Lipid droplets present in cells are important for energy storage and nutrition and are vital to human health. Another role for lipid droplets in the human cell nucleus could be antibacterial acitivty. Bacterial lipid droplets are also being investigated for the development of biodiesel.
With such wide-ranging roles it is important to understand the functions of lipid droplets in various organisms.
The team of researchers next plans to investigate three more proteins in lipid droplets whose structures indicate they may also have DNA-binding potential.
- Zhang, C. et al. Bacterial lipid droplets bind to DNA via an intermediary protein that enhances survival under stress. Nat. Commun. http://dx.doi.org/10.1038/ncomms15979 (2017).