Amachi Seigo, Mishima Yukako, Shinoyama Hirofumi, Muramatsu Yasuyuki, Fujii Takaaki
Department of Bioresources Chemistry, Chiba University, 648 Matsudo, Matsudo-shi, Chiba 271-8510, Japan.
Appl Environ Microbiol. 2005 Feb;71(2):741-5. doi: 10.1128/AEM.71.2.741-745.2005.
Iodide (I(-))-accumulating bacteria were isolated from marine sediment by an autoradiographic method with radioactive (125)I(-). When they were grown in a liquid medium containing 0.1 microM iodide, 79 to 89% of the iodide was removed from the medium, and a corresponding amount of iodide was detected in the cells. Phylogenetic analysis based on 16S rRNA gene sequences indicated that iodide-accumulating bacteria were closely related to Flexibacter aggregans NBRC15975 and Arenibacter troitsensis, members of the family Flavobacteriaceae. When one of the strains, strain C-21, was cultured with 0.1 microM iodide, the maximum iodide content and the maximum concentration factor for iodide were 220 +/- 3.6 (mean +/- standard deviation) pmol of iodide per mg of dry cells and 5.5 x 10(3), respectively. In the presence of much higher concentrations of iodide (1 microM to 1 mM), increased iodide content but decreased concentration factor for iodide were observed. An iodide transport assay was carried out to monitor the uptake and accumulation of iodide in washed cell suspensions of iodide-accumulating bacteria. The uptake of iodide was observed only in the presence of glucose and showed substrate saturation kinetics, with an apparent affinity constant for transport and a maximum velocity of 0.073 muM and 0.55 pmol min(-1) mg of dry cells(-1), respectively. The other dominant species of iodine in terrestrial and marine environments, iodate (IO(3)(-)), was not transported.
采用放射性（125）I⁻放射自显影法从海洋沉积物中分离出了碘积累细菌。当它们在含有0.1微摩尔碘化物的液体培养基中生长时，79%至89%的碘化物从培养基中被去除，并且在细胞中检测到了相应量的碘化物。基于16S rRNA基因序列的系统发育分析表明，碘积累细菌与黄杆菌科的聚集弯曲杆菌NBRC15975和特罗伊茨海杆菌密切相关。当其中一个菌株C - 21在含有0.1微摩尔碘化物的培养基中培养时，碘化物的最大含量和最大浓缩系数分别为每毫克干细胞220±3.6（平均值±标准差）皮摩尔碘化物和5.5×10³。在碘化物浓度高得多（1微摩尔至1毫摩尔）的情况下，观察到碘化物含量增加但碘化物浓缩系数降低。进行了碘化物转运试验，以监测碘积累细菌洗涤后的细胞悬液中碘化物的摄取和积累。仅在葡萄糖存在下观察到碘化物的摄取，并且显示出底物饱和动力学，转运的表观亲和常数和最大速度分别为0.073微摩尔和0.55皮摩尔每分钟每毫克干细胞⁻¹。陆地和海洋环境中碘的其他主要形态，碘酸盐（IO₃⁻），未被转运。
