Ribosomal A site binding pattern differs between Arm methyltransferases from clinical pathogens and a natural producer of aminoglycosides.

The extensive use of aminoglycosides to treat bacterial infections has led to significant resistance, posing a global health threat. Recent clinical reports highlight high levels of aminoglycoside resistance due to Arm/Kam methyltransferases, which methylate specific nucleotides in 16S rRNA, preventing antibiotic binding to the ribosome. This study compared the ribosomal A site binding patterns of Arm methyltransferases from clinical pathogens (ArmA, RmtB, RmtC, and RmtD) with those of the Sgm methyltransferase from a natural aminoglycoside producer.

Structure of the SigE regulatory network in .

SigE is one of the main regulators of mycobacterial stress response and is characterized by a complex regulatory network based on two pathways, which have been partially characterized in conditions of surface stress. The first pathway is based on the induction of transcription by the two-component system MprAB, while the second is based on the degradation of SigE anti-sigma factor RseA by ClpC1P2, a protease whose structural genes are induced by ClgR. We characterized the dynamics of the SigE network activation in conditions of surface stress and low pH in .

Improvement of pBBR1MCS plasmids, a very useful series of broad-host-range cloning vectors.

pBBR1MCS vectors are small in size, contain unique cloning sites within the lacZα gene, and are mobilizable and compatible with various plasmid incompatibility groups. We cloned four genes for aminoglycoside resistance methyltransferases from the Arm and Kam families into pBBR1MCS-3 and expressed them in Escherichia coli. The activity of two of these enzymes was impaired because of the fusion with the first 20 amino acids of the β-galactosidase α-peptide derived from the pBBR1MCS-3 vector.

Structural basis for the methylation of A1408 in 16S rRNA by a panaminoglycoside resistance methyltransferase NpmA from a clinical isolate and analysis of the NpmA interactions with the 30S ribosomal subunit.

NpmA, a methyltransferase that confers resistance to aminoglycosides was identified in an Escherichia coli clinical isolate. It belongs to the kanamycin-apramycin methyltransferase (Kam) family and specifically methylates the 16S rRNA at the N1 position of A1408. We determined the structures of apo-NpmA and its complexes with S-adenosylmethionine (AdoMet) and S-adenosylhomocysteine (AdoHcy) at 2.

Tobramycin at subinhibitory concentration inhibits the RhlI/R quorum sensing system in a Pseudomonas aeruginosa environmental isolate.

Background: Antibiotics are not only small molecules with therapeutic activity in killing or inhibiting microbial growth, but can also act as signaling molecules affecting gene expression in bacterial communities. A few studies have demonstrated the effect of tobramycin as a signal molecule on gene expression at the transcriptional level and its effect on bacterial physiology and virulence. These have shown that subinhibitory concentrations (SICs) of tobramycin induce biofilm formation and enhance the capabilities of P.

The aminoglycoside resistance methyltransferase Sgm impedes RsmF methylation at an adjacent rRNA nucleotide in the ribosomal A site.

Ribosome-targeting antibiotics block protein synthesis by binding at functionally important regions of the bacterial rRNA. Resistance is often conferred by addition of a methyl group at the antibiotic binding site within an rRNA region that is already highly modified with several nucleotide methylations. In bacterial rRNA, each methylation requires its own specific methyltransferase enzyme, and this raises the question as to how an extra methyltransferase conferring antibiotic resistance can be accommodated and how it can gain access to its nucleotide target within a short and functionally crowded stretch of the rRNA sequence.