1Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Frederick, MD, USA.
2Center for Genome Sciences, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Frederick, MD, USA.
J Med Microbiol. 2019 Feb;68(2):263-278. doi: 10.1099/jmm.0.000908. Epub 2019 Jan 10.
Burkholderia pseudomallei, the tier 1 agent of melioidosis, is a saprophytic microbe that causes endemic infections in tropical regions such as South-East Asia and Northern Australia. It is globally distributed, challenging to diagnose and treat, infectious by several routes including inhalation, and has potential for adversarial use. B. pseudomallei strain MSHR5848 produces two colony variants, smooth (S) and rough (R), which exhibit a divergent range of morphological, biochemical and metabolic phenotypes, and differ in macrophage and animal infectivity. We aimed to characterize two major phenotypic differences, analyse gene expression and study the regulatory basis of the variation.
Phenotypic expression was characterized by DNA and RNA sequencing, microscopy, and differential bacteriology. Regulatory genes were identified by cloning and bioinformatics.Results/Key findings. Whereas S produced larger quantities of extracellular DNA, R was upregulated in the production of a unique chromosome 1-encoded Siphoviridae-like bacteriophage, φMSHR5848. Exploratory transcriptional analyses revealed significant differences in variant expression of genes encoding siderophores, pili assembly, type VI secretion system cluster 4 (T6SS-4) proteins, several exopolysaccharides and secondary metabolites. A single 3 base duplication in S was the only difference that separated the variants genetically. It occurred upstream of a cluster of bacteriophage-associated genes on chromosome 2 that were upregulated in S. The first two genes were involved in regulating expression of the multiple phenotypes distinguishing S and R.
Bacteriophage-associated proteins have a major role in the phenotypic expression of MSHR5848. The goals are to determine the regulatory basis of this phenotypic variation and its role in pathogenesis and environmental persistence of B. pseudomallei.
伯克霍尔德氏菌（Burkholderia pseudomallei）是类鼻疽病的一级病原体，是一种腐生微生物，在东南亚和澳大利亚北部等热带地区引起地方性感染。它在全球范围内分布，难以诊断和治疗，可通过吸入等多种途径感染，并且具有敌对用途的潜力。假鼻疽伯克霍尔德氏菌（Burkholderia pseudomallei）菌株 MSHR5848 产生两种菌落变体，光滑（S）和粗糙（R），它们表现出不同的形态、生化和代谢表型，并且在巨噬细胞和动物感染性方面存在差异。我们旨在表征两个主要的表型差异，分析基因表达并研究变异的调控基础。
通过 DNA 和 RNA 测序、显微镜和差异细菌学来描述表型表达。通过克隆和生物信息学鉴定调节基因。
结果/主要发现：S 产生大量的细胞外 DNA，而 R 在产生独特的染色体 1 编码的 Siphoviridae 样噬菌体φMSHR5848 方面被上调。探索性转录分析显示变体表达基因编码的差异显著，这些基因编码铁载体、菌毛组装、VI 型分泌系统簇 4（T6SS-4）蛋白、几种胞外多糖和次生代谢物。S 中仅有的 3 个碱基重复是将变体在遗传上分开的唯一区别。它发生在染色体 2 上噬菌体相关基因簇的上游，该基因簇在 S 中被上调。前两个基因参与调节区分 S 和 R 的多种表型的表达。
噬菌体相关蛋白在 MSHR5848 的表型表达中起主要作用。目标是确定这种表型变异的调控基础及其在假鼻疽伯克霍尔德氏菌（Burkholderia pseudomallei）发病机制和环境持久性中的作用。
