Genomic and transcriptomic characteristics of type VI secretion system inKlebsiella pneumoniae

Abstract

AbstractThe Type VI secretion system (T6SS) serves as a crucial molecular weapon in interbacterial competition and significantly influences cell-cell interactions. Various bacterial species utilize their T6SSs to execute a multitude of functions, dictated by their ecological niche. However, the characteristics of T6SS in clinicalKlebsiella pneumoniae, a common opportunistic nosocomial pathogen, have not been fully elucidated. Here, we conducted a genomic analysis of 65 clinicalK. pneumoniaeisolates obtained from patients with varying infections. Genes encoding a T6SS cluster were present in all analyzed strains ofK. pneumoniae. Strains of identical sequence type (ST) carried structurally and numerically identical T6SS. Our study also highlights the importance of selecting conserved regions in key T6SS genes for effective primer design in PCR identification. We then utilized the predominant ST11K. pneumoniaeHS11286 to investigate the effect of knocking out T6SS marker geneshcporvgrG. Transcriptome analysis identified a total of 1,298 co-upregulated and 1,752 co-downregulated differentially expressed genes. Additionally, the absence ofhcporvgrGgene suppressed the expression of other T6SS-related genes within the locus I cluster. Pathway analysis showed that the Δhcpmutant exhibited alterations in transport, establishment of localization, localization and cell processes. Furthermore, interbacterial competition experiments showed thathcpandvgrGare essential for competitive ability of ST11K. pneumoniaeHS11286. This study furthers our understanding of the genomic characteristics of T6SS inK. pneumoniaeand suggested that the involvement of multiple genes in T6SS of strain HS11286.ImportanceGram-negative bacteria use T6SS to deliver effectors that interact with neighboring cells for niche advantage.K. pneumoniaeis an opportunistic nosocomial pathogen that often carriers multiple T6SS loci, the function of which has not yet been elucidated. We performed a genomic analysis of 65 clinicalK. pneumoniaestrains isolated from various sources, confirming that all strains contained T6SS. We then used transcriptomics to further study changes in gene expression and effect upon interbacterial competition following knockout of key T6SS genes in ST11K. pneumoniaeHS11286. Our findings revealed the distribution and genomic characteristics of T6SS in clinicalK. pneumoniae. This study also described the overall transcriptional changes in the predominant Chinese ST11 strain HS11286 upon deletion of crucial T6SS genes. Additionally, this work provides a reference for future research on the identification of T6SS in bacteria.