Cross talk between DNA replication and LPS biosynthesis during cell growth

Bacteria are everywhere and their presence affects our daily life. They can be our friends, by helping us to digest inaccessible nutrients in our guts, producing the oxygen we breathe, degrading toxic materials or fermenting the foods we love. They can also be our foes by making us sick or spoiling our food.

Accepting that we will indefinitely share our planet with them, we think it best to understand in great detail how bacteria grow. This information will help us to get better at selectively destroying the bad bacteria around us, but may also enable us to engineer more efficient bacterial strains for biotechnological or medical applications.

The bacterial life cycle consists of several steps. First, cells need to grow in biomass, enlarge its shell, the bacterial envelope and copy its DNA. With all of this completed, the bacterial cells start a process we call cell division. During this process, the bacterium divides in half creating two individual cells that have all it takes to restart their growth cycle for the next generation.

These steps happen at the same time during growth, therefore they must be coordinated. However, exactly how bacterial cells coordinate DNA replication and growth of their cell envelopes is not yet known. Studying this question, our laboratory found that one of the master regulators of DNA replication, DiaA, might be the answer. We have shown that DiaA is genetically linked to envelope biogenesis and recognises a metabolite in envelope synthesis. With this proposal we want to better understand how DiaA communicates with envelope biogenesis to coordinate the two processes.

We think a detailed understanding of this process is important because knowing this could help us to make bacteria grow better if its desirable, or reduce their growth where it is not.

As bacteria grow they must enlarge the cell envelope, replicate their DNA and then segregate chromosomes between two daughter cells. Coordination of these processes ensures faithful transmission of genetic material to progeny and is thus essential to survival. These processes tend to be studied in isolation with determinants that coordinate them currently being unidentified. By using an unbiased genetic approach, we have uncovered an important genetic link between the processes of outer membrane (OM) protein biogenesis, lipopolysaccharide (LPS) biosynthesis and DNA replication in Escherichia coli. In addition, we have demonstrated that a key DNA replication control protein, DiaA, is able to bind an intermediate in the LPS biosynthesis pathway.
The possibility of cross-talk between OM biogenesis, LPS synthesis and DNA replication control is an exciting prospect that is well supported by our preliminary data. We propose to use structural biology, biochemistry and high-throughput genetic approaches to determine how initiation of DNA replication is coordinated with cell envelope synthesis for the first time.