Gwinn M L, Stellwagen A E, Craig N L, Tomb J F, Smith H O
Department of Molecular Biology and Genetics, Johns Hopkins University, School of Medicine, Baltimore, Maryland 21205, USA.
J Bacteriol. 1997 Dec;179(23):7315-20. doi: 10.1128/jb.179.23.7315-7320.1997.
Haemophilus influenzae Rd is a gram-negative bacterium capable of natural DNA transformation. The competent state occurs naturally in late exponential growth or can be induced by a nutritional downshift or by transient anaerobiosis. The genes cya, crp, topA, and sxy (tfoX) are known to function in the regulation of competence development. The phosphoenolpyruvate:carbohydrate phosphotransferase system functions to maintain levels of cyclic AMP necessary for competence development but is not directly involved in regulation. The exact signal(s) for competence and the genes that mediate the signal(s) are still unknown. In an effort to find additional regulatory genes, H. influenzae Rd was mutated by using an in vitro Tn7 system and screened for mutants with a reduced ability to induce the competence-regulatory gene, comA. Insertions in atpA, a gene coding for the alpha subunit of the F1 cytoplasmic domain of the ATP synthase, reduce transformation frequencies about 20-fold and cause a significant reduction in expression of competence-regulatory genes, while the expression of constitutive competence genes is only minimally affected. In addition, we found that an insertion in atpB, which encodes the a subunit of the F0 membrane-spanning domain, has a similar effect on transformation frequencies.
流感嗜血杆菌Rd是一种能够进行自然DNA转化的革兰氏阴性细菌。感受态自然发生在指数生长后期，或者可以通过营养条件下调或短暂厌氧诱导产生。已知基因cya、crp、topA和sxy（tfoX）在感受态发育的调控中发挥作用。磷酸烯醇丙酮酸：碳水化合物磷酸转移酶系统的功能是维持感受态发育所需的环磷酸腺苷水平，但不直接参与调控。感受态的确切信号以及介导该信号的基因仍然未知。为了寻找其他调控基因，利用体外Tn7系统对流感嗜血杆菌Rd进行突变，并筛选诱导感受态调控基因comA能力降低的突变体。插入编码ATP合酶F1细胞质结构域α亚基的基因atpA，可使转化频率降低约20倍，并导致感受态调控基因的表达显著降低，而组成型感受态基因的表达仅受到轻微影响。此外，我们发现插入编码F0跨膜结构域a亚基的基因atpB对转化频率有类似影响。
