Dabbs E R
Genetics Department, University of the Witwatersrand, Johannesburg, South Africa.
Antonie Van Leeuwenhoek. 1998 Jul-Oct;74(1-3):155-67. doi: 10.1023/a:1001728601321.
Generalised and specialised transduction systems were developed for Rhodococcus by means of bacteriophage Q4. The latter was used in conjunction with DNA from an unstable genetic element of R. rhodochrous to construct resistance plasmids which replicate in strains of R. equi, R. erythropolis and R. rhodochrous. One of the plasmids, pDA21, was joined with Erythropolis coli suicide vector pEcoR251 to obtain shuttle plasmids maintained in both rhodococci and E. coli. Conjugation between these rhodococcal strains demonstrated all were interfertile with each other and that some of the determinants for this were located on the unstable genetic element. Plasmids derived from this element, such as pDA21, carried the conjugative and self-incompatibility capacities; deletion analysis revealed that DNA necessary for self-incompatibility overlapped with that for arsenic resistance. Rifampicin is one of the principal chemotherapeutic agents used to treat infections by rhodococci and related organisms. The genes responsible for two types of inactivation have been cloned. The sequence of the R. equi DNA responsible for decomposition of the antibiotic strongly resembled those of monooxygenases acting upon phenolic compounds, consistent with the presence of a naphthalenyl moiety in the rifampicin molecule. Antibiotic resistance conferred by the gene was surprisingly specific to the semisynthetic compounds rifampicin (150-fold increase) and rifapentine (70-fold). Similar specificity was observed with the other inactivation gene cloned, which ribosylates rifampicin at the 23-hydroxyl position. A 60-bp sequence upstream of the monooxygenase and ribosylation genes is strikingly similar suggesting a shared pattern of regulation. Rhodococcal arsenic resistance and azo dye degradation genes have been cloned and characterised.
利用噬菌体Q4为红球菌开发了广义和专门的转导系统。后者与来自红平红球菌不稳定遗传元件的DNA结合使用，构建了在马红球菌、红串红球菌和红平红球菌菌株中复制的抗性质粒。其中一个质粒pDA21与红平红球菌自杀载体pEcoR251连接，获得了在红球菌和大肠杆菌中都能维持的穿梭质粒。这些红球菌菌株之间的接合表明它们彼此之间都能杂交，并且其中一些决定因素位于不稳定的遗传元件上。源自该元件的质粒，如pDA21，具有接合和自我不相容能力；缺失分析表明，自我不相容所需的DNA与抗砷所需的DNA重叠。利福平是用于治疗红球菌及相关生物感染的主要化疗药物之一。负责两种失活类型的基因已被克隆。负责抗生素分解的马红球菌DNA序列与作用于酚类化合物的单加氧酶的序列非常相似，这与利福平分子中存在萘基部分一致。该基因赋予的抗生素抗性令人惊讶地对半合成化合物利福平和利福喷丁具有特异性（分别增加150倍和70倍）。在另一个克隆的失活基因中也观察到了类似的特异性，该基因在利福平的23-羟基位置进行核糖基化。单加氧酶和核糖基化基因上游60bp的序列惊人地相似，表明存在共同的调控模式。红球菌的抗砷和偶氮染料降解基因已被克隆和表征。
