Discovered a new adaptation strategy in marine bacteria

 Cell membranes are made up of lipids that contain phosphorus. Until recently it was thought that these molecules, the phospholipids, were essential for the functioning of the cell. An investigation directed by the Higher Council for Scientific Research (CSIC) has revealed that, in the absence of phosphorus, marine bacteria are capable of rebuilding their membranes with lipids without this component. The work has been published in the journal of the International Society for Microbial Ecology .

“The study reveals that, in response to the scarcity of phosphorus, the marine bacterial communities of the Mediterranean Sea, one of the poorest systems in phosphorus on the planet, remodel their membranes and replace up to 80% of lipids. This allows them to reuse and recycle the phosphorus that is contained in their membranes, formed before the shortage of phosphorus, and use it for the synthesis of other molecules essential for life, such as DNA (which cannot do without phosphorus) ”, explains the CSIC researcher Marta Sebastián, from the Institute of Marine Sciences.

Scientists have carried out experiments with evolutionarily very different bacteria, although morphologically almost the same under the microscope, and have been able to see that, in the absence of phosphorus, bacteria synthesize different lipids without phosphorus to rebuild their cell membranes. The process, which is explained in the publication, is reversible: when phosphorus is added to their growth medium, the bacteria synthesize phospholipids again.

The 'plcP' gene is the key

Phospholipids are made up of two fatty acids attached to a glycerol molecule, which in turn is attached to the phosphorous molecule. Through genetic manipulation, the authors have confirmed that the plcP gene is responsible for breaking down phospholipids so that phosphorus can be reused by the cell. The study has shown that another gene, called agt, is responsible for adding a sugar to glycerol, thus forming lipids that have sugar instead of phosphorus (glycolipids).

"The results of this work indicate that at times of the year when there is a shortage of phosphorus, bacteria build their membranes with glycolipids and others that contain sulfur and nitrogen instead of phosphorus," adds Sebastián. The study, which analyzes the global marine metagenomic databases of the Tara Oceans and Global Ocean Survey oceanographic campaigns, finds that between 60 and 100% of bacteria that inhabit phosphorus-poor areas of the ocean possess the plcP gene, which allows this adaptation.

“In other words, most of the bacteria in these areas are capable of replacing their membrane phospholipids and it gives us an idea of ​​the ecological relevance of this process. Our work is an example of how much we have to discover about the adaptation of microorganisms to variations in environmental conditions. Knowing it is crucial to predict how ecosystems will change in the future since marine microorganisms are the basis of the marine food chain and the engines of biogeochemical cycles ”, concludes the researcher.