The synthesis of the ribosomal proteins of Escherichia coli during stationary growth phase

Abstract

The repression of cell growth as a response to starvation leads the bacterial culture to enter stationary growth phase. The cell needs to conserve the energy to survive the starvation. As a result, the metabolic processes of the cell slow down. The ribosome is one of the most energy-consuming organelles, as its main function is to carry out the protein synthesis. The ribosomal proteins have a profound effect on the correct functioning and assembly of the ribosome. To determine whether or not the ribosomal proteins of Escherichia coli are synthesised during stationary growth phase, the changes in the protein quantities over 14 days after the beginning of the growth were calculated. 24 out of 54 ribosomal proteins were found to be synthesised during stationary growth phase. Many of these proteins were found to have a positive effect on the cell during stationary growth phase, such as maintenance of the ribosome structural integrity, for instance, via protein exchange, and self-downregulation of the ribosomal protein synthesis. In estonian: Rakkude kasvu aeglustumisel stressitingimustel siseneb rakukultuuri statsionaarsesse kasvufaasi. Selle tulemusena aeglustub rakkude metabolism ning väheneb nende energiakasutus. Ribosoomid on ühed suurimatest energiatarbijatest rakkudes, viies läbi valkude sünteesi ehk translatsiooni. Ribosoomivalgud osalevad ribosoomi tertsiaalstruktuuri korrektses moodustumises ja funktsionaalsuse tagamises. Selleks, et detekteerida Escherichia coli ribosoomivalkude sünteesi statsionaarse kasvufaasi käigus, kasvatati rakke 14 päeva ning mõõdeti valkude koguse muutust rakukultuuris. Tulemused näitasid, et 24 r-valku 54st sünteesiti rakkudes statsionaarse kasvufaasi käigus. Sünteesitud r-valgud võivad omada positiivset efekti rakkudele, alustades ribosoomivalkude sünteesi repressiooniga ning lõpetades olemasolevate ribosoomide struktuuri terviklikkuse hoidmisega, läbi r-valkude vahetuse.