Department of Microbiology and Immunology and Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, Maryland, USA.
Infect Immun. 2012 Mar;80(3):1232-42. doi: 10.1128/IAI.06138-11. Epub 2012 Jan 3.
Enterotoxigenic Escherichia coli (ETEC) is an important pathogenic variant (pathovar) of E. coli in developing countries from a human health perspective, causing significant morbidity and mortality. Previous studies have examined specific regulatory networks in ETEC, although little is known about the global effects of inter- and intrakingdom signaling on the expression of virulence and colonization factors in ETEC. In this study, an E. coli/Shigella pan-genome microarray, combined with quantitative reverse transcriptase PCR (qRT-PCR) and RNA sequencing (RNA-seq), was used to quantify the expression of ETEC virulence and colonization factors. Biologically relevant chemical signals were combined with ETEC isolate E24377A during growth in either Luria broth (LB) or Dulbecco's modified Eagle medium (DMEM), and transcription was examined during different phases of the growth cycle; chemical signals examined included glucose, bile salts, and preconditioned media from E. coli/Shigella isolates. The results demonstrate that the presence of bile salts, which are found in the intestine and thought to be bactericidal, upregulates the expression of many ETEC virulence factors, including heat-stable (estA) and heat-labile (eltA) enterotoxin genes. In contrast, the ETEC colonization factors CS1 and CS3 were downregulated in the presence of bile, consistent with findings in studies of other enteric pathogens. RNA-seq analysis demonstrated that one of the most differentially expressed genes in the presence of bile is a unique plasmid-encoded AraC-like transcriptional regulator (peaR); other previously unknown genetic elements were found as well. These results provide transcriptional targets and putative mechanisms that should help improve understanding of the global regulatory networks and virulence expression in this important human pathogen.
肠产毒性大肠杆菌（ETEC）是发展中国家人类健康方面重要的致病性变体（血清型），可导致发病率和死亡率显著上升。先前的研究已经研究了 ETEC 中的特定调控网络，但对于种间和种内信号对 ETEC 毒力和定植因子表达的全局影响知之甚少。在这项研究中，使用大肠杆菌/志贺氏菌泛基因组微阵列结合定量逆转录 PCR（qRT-PCR）和 RNA 测序（RNA-seq）来量化 ETEC 毒力和定植因子的表达。将生物相关的化学信号与 ETEC 分离株 E24377A 结合，在 Luria 肉汤（LB）或 Dulbecco 修改的 Eagle 培养基（DMEM）中生长，并在生长周期的不同阶段检查转录；检查的化学信号包括葡萄糖、胆汁盐和大肠杆菌/志贺氏菌分离株的预培养介质。结果表明，存在于肠道中且被认为具有杀菌作用的胆汁盐上调了许多 ETEC 毒力因子的表达，包括耐热（estA）和不耐热（eltA）肠毒素基因。相比之下，CS1 和 CS3 定植因子在存在胆汁时下调，这与其他肠病原体研究的结果一致。RNA-seq 分析表明，在存在胆汁的情况下表达最不同的基因之一是一种独特的质粒编码的 AraC 样转录调节因子（peaR）；还发现了其他以前未知的遗传元件。这些结果提供了转录靶标和潜在的机制，应该有助于提高对该重要人类病原体中全局调控网络和毒力表达的理解。
