Knockout of ribosomal genes bS22 and bL37 increases the sensitivity of mycobacteria to antibiotics / 生物工程学报

In recent years, two novel proteins in the ribosomes of mycobacteria have been discovered by cryo-electron microscopy. The protein bS22 is located near the decoding center of the 30S subunit, and the protein bL37 is located near the peptidyl transferase center of the 50S subunit. Since these two proteins bind to conserved regions of the ribosome targeted by antibiotics, it is speculated that they might affect the binding of related drugs to these targets. Therefore, we knocked out the genes encoding these two proteins in wild-type Mycolicibacterium smegmatis mc2155 through homologous recombination, and then determined the growth curves of these mutants and their sensitivity to related antibiotics. The results showed that compared with the wild-type strain, the growth rate of these two mutants did not change significantly. However, mutant ΔbS22 showed increased sensitivity to capreomycin, kanamycin, amikacin, streptomycin, gentamicin, paromomycin, and hygromycin B, while mutant ΔbL37 showed increased sensitivity to linezolid. These changes in antibiotics sensitivity were restored by gene complementation. This study hints at the possibility of using ribosomal proteins bS22 and bL37 as targets for drug design.

Mycobacterium genus and tRNA arrays

The presence of tRNA array, a region with high tRNA gene number and density, has been demonstrated in Mycobacterium genus. However, a recent phylogenomic study revealed the existence of five distinct monophyletic groups (genera) within this genus. Considering this new scenario, and based on in-silico analyses, we have identified and characterised the abundance and diversity of tRNA array units within Mycobacterium, Mycolicibacterium gen. nov., Mycolicibacillus gen. nov., and Mycobacteroides gen. nov. The occurrence and prevalence of tRNA arrays among the genera belonging to Actinobacteria indicate their possible role in the organismal fitness.