How a soil-living bacterium survives gene loss and starvation

A research team from the United Kingdom and Saudi Arabia has removed a gene regulating flagella production in a soil-living bacterium (Pseudomonas fluorescens) and exposed it to starvation in a culture plate. To their surprise, the bacteria grew flagella and moved fast to seek out nutrients elsewhere on the plate¹. 

To understand how the bacterium counters such gene loss and starvation, the researchers that included Abdullah Alsohim from the Qassim University, Saudi Arabia, deleted the flagella-regulating gene (fleQ) in two different strains of the bacterium. They then grew them in nutrient media.  

After four days, slow-spreading and fast-spreading bacteria with flagella evolved. By sequencing the bacterial genomes, they identified two point mutations in genes ntrB and ntrC, which are involved in nitrogen regulation, uptake and metabolism. The first mutation makes NtrB phosphorylate NtrC constitutively, which activates it, and the second confers dual regulatory flagellum production and nitrogen intake activity to NtrC. 

The ntrC gene and the deleted fleQ are in the same gene family with similar shapes and properties. The ntrC gene’s ability to take up the function of fleQ shows that genes can easily take over tasks from their family members. ‘This suggests that gene regulation possesses more ability to evolve than we suspected,” says co-author Louise J. Johnson from the University of Reading, UK. 

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