Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City 73104, OK, USA.
BMC Genomics. 2013 Dec 27;14:925. doi: 10.1186/1471-2164-14-925.
Haemophilus influenzae is a significant cause of childhood otitis media, and also has an absolute growth requirement for heme. Recent microarray studies using three H. influenzae isolates were used to propose a putative core of genes responsive to iron and heme levels. Included in the core modulon were thirty seven genes that are preferentially expressed under iron/heme limitation, most of which are directly involved with iron and or heme acquisition. In this report, the core iron/heme modulon was further refined following microarray analysis of two additional nontypeable H. influenzae isolates from patients with otitis media. The transcriptional status of the genes comprising the refined iron/heme core modulon was then assessed in vivo, in a chinchilla model of otitis media. These in vivo experiments were performed to address the hypothesis that iron and heme regulated genes are both highly expressed in vivo and important, during clinical infection.
Microarray analysis of two additional H. influenzae strains resulted in the definition of a core of iron/heme responsive genes. This core consisted of 35 genes maximally expressed under heme restriction and a further 20 genes maximally expressed in heme replete conditions. In vivo studies were performed with two nontypeable H. influenzae strains, 86-028NP and HI1722. The majority of operons identified as members of the core modulon by microarray were also actively upregulated in the chinchilla ear during otitis media. In 86-028NP, 70% of the operons were significantly upregulated while in HI1722 100% of the operons were upregulated in samples recovered from the chinchilla middle ear.
This study elucidates a conserved core of H. influenzae genes the transcription of which is altered by the availability of iron and heme in the growth environment, and further assesses transcription of these genes in vivo. Elucidation of this modulon allows for identification of genes with unrecognized roles in iron/heme acquisition or homeostasis and/or potential roles in virulence. Defining these core genes is also of potential importance in identifying targets for therapeutic and vaccine designs since products of these genes are likely to be preferentially expressed during growth in iron/heme restricted sites of the human body.
流感嗜血杆菌是儿童中耳炎的重要病因，并且绝对需要血红素才能生长。最近使用三种流感嗜血杆菌分离株的基因芯片研究提出了一个可能的与铁和血红素水平反应的核心基因模块。该核心模块包括 37 个在铁/血红素限制下优先表达的基因，其中大多数基因直接参与铁和/或血红素的获取。在本报告中，在对来自中耳炎患者的另外两种非典型流感嗜血杆菌分离株进行基因芯片分析后，进一步细化了核心铁/血红素模块。然后在中耳炎的南美栗鼠模型中评估了组成细化的铁/血红素核心模块的基因的转录状态。进行这些体内实验是为了验证这样一个假说，即铁和血红素调节的基因在体内都高度表达，并且在临床感染过程中很重要。
对另外两种流感嗜血杆菌菌株的基因芯片分析导致了铁/血红素反应基因核心的定义。该核心由 35 个在血红素限制下最大表达的基因和另外 20 个在血红素充足条件下最大表达的基因组成。使用两种非典型流感嗜血杆菌菌株 86-028NP 和 HI1722 进行体内研究。通过基因芯片鉴定为核心模块成员的大多数操纵子在中耳炎期间也在南美栗鼠耳中被积极上调。在 86-028NP 中，70%的操纵子显著上调，而在 HI1722 中，从南美栗鼠中耳回收的样本中 100%的操纵子上调。
本研究阐明了流感嗜血杆菌基因的一个保守核心，其转录受生长环境中铁和血红素的可用性的影响，并进一步评估了这些基因在体内的转录。阐明这个模块可以识别在铁/血红素获取或稳态中具有未知作用的基因，以及在毒力中具有潜在作用的基因。定义这些核心基因对于识别治疗和疫苗设计的靶标也很重要，因为这些基因的产物可能在人体中铁/血红素受限部位的生长过程中优先表达。
