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Lost in transition

The impact of exoribonucleases enzymes in the shift between exponential and stationary growth phases

Escherichia coli is one of the most common bacteria in the human gut. Most strains are harmless and can even benefit their hosts by preventing colonization by pathogenic bacteria and producing vitamin K, others can provoke adverse reactions due to food poisoning. E. coli is one of the many organisms in which the team led by Cecilia Arraiano study the control of gene expression.

In their natural environment, bacteria constantly transitions between a rapid growth state (exponential phase) and a slow growth state (stationary phase) due to nutrient availability. This transition is essential to the survival of the bacteria and requires a massive readjustment of the expressed genes (transcriptome).

Exoribonucleases are key enzymes in the transition between the two growth phases since they control the degradation of the RNAs that are no longer necessary and at the same time contribute to the recycling of nucleotides. PNPase, RNase R and RNase II are the major degradative exoribonucleases in Escherichia coli. In their most recent paper, published today in Scientific Reports, ITQB NOVA researchers Vânia Pobre, Susana Barahona and Cecília Arraiano, in partnership with researchers from the Federal University of Paraná (UFPR), present the first global transcriptomic study comparing the roles of exoribonucleases in the transition between exponential and stationary phase.

“When the cells transition from exponential to stationary phase more than 1000 transcripts are affected”, explains Vânia Pobre, corresponding author of the paper. “However, only 491 transcripts are common to all exoribonucleases, suggesting that exoribonucleases affect the transition of the cells in different ways. For example, RNase R affects iron ion metabolism, while PNPase affects DNA replication demonstrating that each exoribonuclease influences the cells transition differently.”

The work provides a broader view of the bacterial adaptation to their environment and the role of exoribonucleases in that adaptation, leading to a better understanding of the development of E. coli.

Original paper

V. Pobre, S. Barahona, T. Dobrzanski, M. Steffens and C. M. Arraiano 

Defining the impact of exoribonucleases in the shift between exponential and stationary phases

Scientific Reports, DOI: 10.1038/s41598-019-52453-6

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