Ohkawa H, Price G D, Badger M R, Ogawa T
Bioscience Center, Nagoya University, Chikusa, Nagoya 464-8601, Japan.
J Bacteriol. 2000 May;182(9):2591-6. doi: 10.1128/JB.182.9.2591-2596.2000.
Six mutants (B1 to B6) that grew poorly in air on BG11 agar plates buffered at pH 8.0 were rescued after mutations were introduced into ndhB of wild-type (WT) Synechocystis sp. strain PCC 6803. In these mutants and a mutant (M55) lacking ndhB, CO(2) uptake was much more strongly inhibited than HCO(3)(-) uptake, i.e., the activities of CO(2) and HCO(3)(-) uptake in B1 were 9 and 85% of those in the WT, respectively. Most of the mutants grew very slowly or did not grow at all at pH 6.5 or 7.0 in air, and their ability to grow under these conditions was correlated with CO(2) uptake capacity. Detailed studies of B1 and M55 indicated that the mutants grew as fast as the WT in liquid at pH 8.0 under air, although they grew poorly on agar plates. The contribution of CO(2) uptake appears to be larger on solid medium. Five mutants were constructed by inactivating each of the five ndhD genes in Synechocystis sp. strain PCC 6803. The mutant lacking ndhD3 grew much more slowly than the WT at pH 6.5 under 50 ppm CO(2), although other ndhD mutants grew like the WT under these conditions and showed low affinity for CO(2) uptake. These results indicated the presence of multiple NAD(P)H dehydrogenase type I complexes with specific roles.
在BG11琼脂平板（pH 8.0缓冲）上于空气中生长不良的六个突变体（B1至B6），在将突变引入野生型（WT）集胞藻PCC 6803菌株的ndhB后得到挽救。在这些突变体以及一个缺失ndhB的突变体（M55）中，CO₂吸收比HCO₃⁻吸收受到的抑制要强得多，即B1中CO₂和HCO₃⁻吸收活性分别是野生型中的9%和85%。大多数突变体在空气中pH 6.5或7.0时生长非常缓慢或根本不生长，它们在这些条件下的生长能力与CO₂吸收能力相关。对B1和M55的详细研究表明，尽管这些突变体在琼脂平板上生长不良，但在空气中pH 8.0的液体培养基中它们的生长速度与野生型一样快。在固体培养基上，CO₂吸收的贡献似乎更大。通过使集胞藻PCC 6803菌株中的五个ndhD基因分别失活构建了五个突变体。在50 ppm CO₂条件下，pH 6.5时，缺失ndhD3的突变体生长比野生型慢得多，尽管其他ndhD突变体在这些条件下生长与野生型相似，并且对CO₂吸收表现出低亲和力。这些结果表明存在具有特定作用的多种I型NAD(P)H脱氢酶复合物。
