Yale University, Department of Molecular, Cellular, and Developmental Biology, P.O. Box 208103, New Haven, CT 06520-8103, USA.
Appl Environ Microbiol. 2010 Jul;76(13):4396-401. doi: 10.1128/AEM.01763-09. Epub 2010 May 7.
To gain insight into the diversity and origins of antibiotic resistance genes, we identified resistance genes in the soil in an apple orchard using functional metagenomics, which involves inserting large fragments of foreign DNA into Escherichia coli and assaying the resulting clones for expressed functions. Among 13 antibiotic-resistant clones, we found two genes that encode bifunctional proteins. One predicted bifunctional protein confers resistance to ceftazidime and contains a natural fusion between a predicted transcriptional regulator and a beta-lactamase. Sequence analysis of the entire metagenomic clone encoding the predicted bifunctional beta-lactamase revealed a gene potentially involved in chloramphenicol resistance as well as a predicted transposase. A second clone that encodes a predicted bifunctional protein confers resistance to kanamycin and contains an aminoglycoside acetyltransferase domain fused to a second acetyltransferase domain that, based on nucleotide sequence, was predicted not to be involved in antibiotic resistance. This is the first report of a transcriptional regulator fused to a beta-lactamase and of an aminoglycoside acetyltransferase fused to an acetyltransferase not involved in antibiotic resistance.
为了深入了解抗生素耐药基因的多样性和起源，我们采用功能宏基因组学的方法，在一个苹果园中对土壤中的耐药基因进行了鉴定。功能宏基因组学包括将大量的外源 DNA 片段插入到大肠杆菌中，并检测所得克隆中表达的功能。在 13 个抗生素耐药的克隆中，我们发现了两个编码双功能蛋白的基因。其中一个预测的双功能蛋白赋予头孢他啶耐药性，并在一个预测的转录调节因子和一个β-内酰胺酶之间存在天然融合。对编码预测的双功能β-内酰胺酶的整个宏基因组克隆的序列分析揭示了一个可能与氯霉素耐药有关的基因，以及一个预测的转座酶。另一个编码预测的双功能蛋白的克隆对卡那霉素具有耐药性，并含有一个氨基糖苷乙酰转移酶结构域，与第二个乙酰转移酶结构域融合，根据核苷酸序列预测，该结构域不参与抗生素耐药性。这是首次报道转录调节因子与β-内酰胺酶融合，以及氨基糖苷乙酰转移酶与不参与抗生素耐药性的乙酰转移酶融合的情况。
