Ribosomal modification genes effect on phenotype in Escherichia coli

Sammanfattning

Modifications of the ribosome in Escherichia coli are well documented for their direct impact on the ribosome. These modifications are controlled by genes that modify differing sections of the ribosome, mainly consisting of rlu and rlm genes. However, understanding of the gene’s direct impact on the cell’s fitness via growth rate and antibiotic resistance is relatively limited. The modifications of the ribosome are most present in the fifth domain of the 23S rRNA in E. coli, also known as the critical domain. This makes it of particular interest when it comes to understanding the modification’s impact on the strain. To understand the impact of individual genes, strains were constructed with different single deletions of genes. These include deletions of genes that modify the fifth domain of the large subunit of the ribosome as well as deletion of genes that modify the first domain (domain 0). Strains for larger combinations of deletions were created for domains zero, two, four and five. These strains were then used for antibiotic susceptibility tests as well as relative growth rate and relative final growth density tests. The tests indicate an increased antibiotic susceptibility when the gene rluC was deleted. Antibiotic susceptibility was also increased in some strains with larger deletions of multiple modification genes. The relative growth rate was seemingly mostly impacted by large complete domain deletions of the fifth domain. It was also, to a lesser degree, impacted by some single gene deletion strains, such as the rlmB deletion strain showing a decreased relative growth rate at 30 °C specifically. Multiple strains showed decreased relative final growth density values, mostly at 20 °C. In contrast, two strains with deletions of the rlmJ and rluE genes respectively showed increased relative final growth density. While some of these results are in accordance with previous studies, quite a few are not, signifying that further studies and tests need to be done to understand the ribosomal modification genes impact on fitness. However, if the results presented here can be replicated, it could alter our understanding of some of these genes, as it would imply that removing genes such as rlmJ and rluE could have a positive effect on the cell, at least when it comes to relative final growth density values.