Acinetobacter baumannii K106 and K112: Two Structurally and Genetically Related 6-Deoxy-l-talose-Containing Capsular Polysaccharides

Abstract

Whole genome sequences of two Acinetobacter baumannii clinical isolates, 48-1789 and MAR24, revealed that they carry the KL106 and KL112 capsular polysaccharide (CPS) biosynthesis gene clusters, respectively, at the chromosomal K locus. The KL106 and KL112 gene clusters are related to the previously described KL11 and KL83 gene clusters, sharing genes for the synthesis of l-rhamnose (l-Rhap) and 6-deoxy-l-talose (l-6dTalp). CPS material isolated from 48-1789 and MAR24 was studied by sugar analysis and Smith degradation along with one- and two-dimensional 1H and 13C NMR spectroscopy. The structures of K106 and K112 oligosaccharide repeats (K units) l-6dTalp-(1→3)-D-GlcpNAc tetrasaccharide fragment share the responsible genes in the respective gene clusters. The K106 and K83 CPSs also have the same linkage between K units. The KL112 cluster includes an additional glycosyltransferase gene, Gtr183, and the K112 unit includes α l-Rhap side chain that is not found in the K106 structure. K112 further differs in the linkage between K units formed by the Wzy polymerase, and a different wzy gene is found in KL112. However, though both KL106 and KL112 share the atr8 acetyltransferase gene with KL83, only K83 is acetylated.

Opportunities and Challenges of Bacterial Glycosylation for the Development of Novel Antibacterial Strategies

“…The repeating K units of A. baumannii CPS typically consist of 2-6 monosaccharide units and feature glucose, galactose, glucuronic acid, and nonulosonic acid, among others, also with acetyl or acyl modifications (K83 and K11; Figure 4B; Singh et al, 2019). Interestingly, several clinical isolates of A. baumannii (strains KL106, KL112, 48-1789, MAR24) were found to contain the bacterial monosaccharides 6-deoxy-l-talose and l-rhamnose (Kenyon et al, 2017;Kasimova et al, 2021). Importantly, dTDP-6-deoxy-l-talose is produced either from dTDP-l-Rha by the action of C4-epimerase or from dTDP-6-deoxy-l-lyxo-hexos-4-ulose by C4-reductase (Figure 4C; Kenyon et al, 2017).…”

A Nationwide Genomic Study of Clinical Klebsiella pneumoniae Carrying bla OXA-232 and rmtF in China

“…KL51 was reported from the United States, Sweden, the United Kingdom ( 33 ), Thailand ( 34 ), and Lebanon ( 35 ). KL112 has been reported from Russia ( 36 ). Understanding such vectors carrying the resistance genes could help improve strategies to control the spread of AMR ( 37 ).…”