Discovery, structure and function of plasmid mediated shufflon / 生物工程学报

Antimicrobial resistance has become a major public health issue of global concern. Conjugation is an important way for fast spreading drug-resistant plasmids, during which the type Ⅳ pili plays an important role. Type Ⅳ pili can adhere on the surfaces of host cell and other medium, facilitating formation of bacterial biofilms, bacterial aggregations and microcolonies, and is also a critical factor in liquid conjugation. PilV is an adhesin-type protein found on the tip of type Ⅳ pili encoded by plasmid R64, and can recognize the lipopolysaccharid (LPS) molecules that locate on bacterial membrane. The shufflon is a clustered inversion region that diversifies the PilV protein, which consequently affects the recipient recognition and conjugation frequency in liquid mating. The shufflon was firstly discovered on an IncI1 plasmid R64 and has been identified subsequently in plasmids IncI2, IncK and IncZ, as well as the pathogenicity island of Salmonella typhi. The shufflon consists of four segments including A, B, C, and D, and a specific recombination site named sfx. The shufflon is regulated by its downstream-located recombinase-encoding gene rci, and different rearrangements of the shufflon region in different plasmids were observed. Mobile colistin resistance gene mcr-1, which has attracted substantial attentions recently, is mainly located in IncI2 plasmid. The shufflon may be one of the contributors to fast spread of mcr-1. Herein, we reviewed the discovery, structure, function and prevalence of plasmid mediated shufflon, aiming to provide a theoretical basis on transmission mechanism and control strategy of drug-resistant plasmids.

Application of whole genome sequencing technology and bioinformatics analysis in antimicrobial resistance researches / 生物工程学报

The emergence and spread of antimicrobial resistance has become a serious global issue. Bacterial characteristics, such as antimicrobial resistance genes, virulence-associated genes, plasmid types, and phylogenetic relationship among different strains, are the keys to unravel the occurrence and dissemination of antimicrobial resistance. However, the accuracy and efficiency of the traditional techniques, such as polymerase chain reaction and pulsed field gel electrophoresis is insufficient to underlying the mystery of antimicrobial resistance. Recently, the whole genome sequencing and high-throughput bioinformatics analysis have been successfully used in antimicrobial resistance studies, helping scientists to obtain the nature of antimicrobial resistance bacteria quickly, and more precisely to paint the evolutionary relationship among different strains. Therefore, in this study, we aim to systematically introduce the recent development of whole genome sequencing analysis, including different methods and corresponding characteristics of library preparation, platform sequencing, data analysis, and the latest application of the technology in the antimicrobial resistance research. We hope that this review can provide more comprehensive knowledge about whole genome sequencing and bioinformatic analysis for antimicrobial resistance research.

Classification and phylogenetic analysis of the genus Mobiluncus based on matrix-assisted laser de-sorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and whole genome sequen-cing / 中华微生物学和免疫学杂志

Objective To identify Mobiluncus species with matrix-assisted laser desorption/ioniza-tion time-of-flight mass spectrometry (MALDI-TOF MS) and 16S rRNA gene sequencing and to analyze anti-biotic resistance genes and phylogenetic relationships among Mobiluncus species with whole genome sequen-cing. Methods Twenty-five Mobiluncus strains were isolated after anaerobic culture of 65 vaginal secretion samples of patients with bacterial vaginosis (BV) and identified to species level by MALDI-TOF MS and 16S rRNA gene sequencing. The whole genome DNA of each strain was extracted for next-generation sequencing. SPAdes was used to assembly genomes. Resistance genes were searched in ARGD database. The core ge-nome of all isolates was analyzed by Harvest to construct phylogenetic tree. Results MALDI-TOF MS could only identify Mobiluncus curtisii, while 16S rRNA gene sequencing could identify both Mobiluncus mulieris and Mobiluncus curtisii. Results of the whole genome sequencing showed that tetracycline resistance gene tet ( o) and macrolides resistance gene erm(x) were the two predominant acquired resistance genes of Mobilun-cus with a positive rate of 84. 7% and 61. 5% respectively. Intra-species relationships of the two Mobiluncus species were close, but a distant phylogenetic relationship was found between the two species. Conclusion This study shows that MALDI-TOF MS can't be used to identify Mobiluncus mulieris at present. Mobiluncus strains have potential resistance to tetracycline and macrolides. Intra-species evolution of Mobiluncus is slow, which indicates that there is no growing trend towards new species for the time being.