Department of Biological Sciences , Auburn University , Auburn , Alabama 36849 , United States.
National Center for Natural Products Research, Research Institute of Pharmaceutical Sciences, School of Pharmacy , The University of Mississippi , University , Mississippi 38677 , United States.
J Nat Prod. 2018 Jun 22;81(6):1321-1332. doi: 10.1021/acs.jnatprod.7b00903. Epub 2018 Jun 13.
A functional metagenomic approach identified novel and diverse soil-derived DNAs encoding inhibitors to methicillin-resistant Staphylococcus aureus (MRSA). A metagenomic DNA soil library containing 19 200 recombinant Escherichia coli BAC clones with 100 Kb average insert size was screened for antibiotic activity. Twenty-seven clones inhibited MRSA, seven of which were found by LC-MS to possess modified chloramphenicol ( Cm) derivatives, including three new compounds whose structures were established as 1-acetyl-3-propanoylchloramphenicol, 1-acetyl-3-butanoylchloramphenicol, and 3-butanoyl-1-propanoylchloramphenicol. Cm was used as the selectable antibiotic for cloning, suggesting that heterologously expressed enzymes resulted in derivatization of Cm into new chemical entities with biological activity. An esterase was found to be responsible for the enzymatic regeneration of Cm, and the gene trfA responsible for plasmid copy induction was found to be responsible for inducing antibacterial activity in some clones. Six additional acylchloramphenicols were synthesized for structure and antibacterial activity relationship studies, with 1- p-nitrobenzoylchloramphenicol the most active against Mycobacterium intracellulare and Mycobacterium tuberculosis, with MICs of 12.5 and 50.0 μg/mL, respectively.
一种功能宏基因组学方法鉴定了新型和多样化的来源于土壤的 DNA，这些 DNA 编码了对耐甲氧西林金黄色葡萄球菌（MRSA）的抑制剂。对一个包含 19200 个平均插入大小为 100 Kb 的重组大肠杆菌 BAC 克隆的宏基因组 DNA 土壤文库进行了抗生素活性筛选。有 27 个克隆抑制了 MRSA，其中 7 个通过 LC-MS 被发现含有修饰的氯霉素（Cm）衍生物，包括三种新化合物，其结构被确定为 1-乙酰基-3-丙酰基氯霉素、1-乙酰基-3-丁酰基氯霉素和 3-丁酰基-1-丙酰基氯霉素。Cm 被用作克隆的选择抗生素，这表明异源表达的酶将 Cm 衍生化为具有生物活性的新化学实体。发现一种酯酶负责 Cm 的酶促再生，而负责诱导质粒拷贝的 trfA 基因被发现负责诱导一些克隆中的抗菌活性。另外合成了 6 种酰基氯霉素进行结构和抗菌活性关系研究，其中 1-对硝基苯甲酰基氯霉素对胞内分枝杆菌和结核分枝杆菌最有效，MIC 分别为 12.5 和 50.0 μg/mL。
