Adaptation of intracytoplasmic membranes to altered light intensity in Rhodobacter sphaeroides
Adaptation of intracytoplasmic membranes to altered light intensity in Rhodobacter sphaeroides
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DOI：
10.1016/j.bbabio.2012.05.013
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发表时间：
2012-09-01
影响因子：
4.3
通讯作者：
Hunter, C. Neil
中科院分区：
文献类型：
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作者：
Adams, Peter G.;Hunter, C. Neil
光合细菌Rhodobacter sphaeroides利用嵌入球形胞质膜（ICM）中的细菌叶绿素（BChl）-蛋白质复合物网络来收集和利用太阳能。我们研究了高光照和低光照生长条件的影响，其中BChl水平从每个细胞1.6 x 10（6）到6.5 x 10（6）分子增加了大约四倍。这种额外的色素大部分被容纳在增殖的ICM系统中，该系统从每个细胞约274个囊泡增加到1468个囊泡。因此，16 x 10（6）nm（2）的专门膜表面积可用于收集和利用太阳能，而在高光条件下为3 x 10（6）nm（2）。使用原子力显微镜的膜映射揭示了紧密包装的二聚体和单体反应中心捕光1-PufX（RC-LH 1-PufX）复合物在高光ICM中，仅为小簇LH 2提供空间，而在适应低光期间形成广泛的LH 2-仅结构域，LH 2/RC比率增加了三倍。上色素带（UPB）位点的数量几乎没有变化，其中膜内陷开始; 704（5.8 × 10（5）BChls/细胞）和829（4.9 × 10（5）BChls/细胞）UPB位点每个细胞分别估计在高和低光条件下。因此，在高光细胞中较低的ICM含量是达到成熟的ICM内陷较少的结果。考虑到UPB膜中相对较差的LH 2-至-LH 1能量转移，可能高光细胞在能量捕获方面相对低效，但可以生长得足够好，而不需要将其光合膜从相对低效的UPB完全发育成高效的成熟ICM。(C)2012爱思唯尔有限公司版权所有。
The model photosynthetic bacterium Rhodobacter sphaeroides uses a network of bacteriochlorophyll (BChl)-protein complexes embedded in spherical intracytoplasmic membranes (ICM) to collect and utilise solar energy. We studied the effects of high- and low-light growth conditions, where BChl levels increased approximately fourfold from 1.6 x 10(6) to 6.5 x 10(6) molecules per cell. Most of this extra pigment is accommodated in the proliferating ICM system, which increases from approximately 274 to 1468 vesicles per cell. Thus, 16 x 10(6) nm(2) of specialised membrane surface area is made available for harvesting and utilising solar energy compared to 3 x 10(6) nm(2) under high-light conditions. Membrane mapping using atomic force microscopy revealed closely packed dimeric and monomeric reaction centre-light harvesting 1-PufX (RC-LH1-PufX) complexes in high-light ICM with room only for small clusters of LH2, whereas extensive LH2-only domains form during adaptation to low light, with the LH2/RC ratio increasing three-fold. The number of upper pigmented band (UPB) sites where membrane invagination is initiated hardly varied; 704 (5.8 x 10(5) BChls/cell) and 829 (4.9 x 10(5) BChls/cell) UPB sites per cell were estimated under high- and low-light conditions, respectively. Thus, the lower ICM content in high-light cells is a consequence of fewer ICM invaginations reaching maturity. Taking into account the relatively poor LH2-to-LH1 energy transfer in UPB membranes it is likely that high-light cells are relatively inefficient at energy trapping, but can grow well enough without the need to fully develop their photosynthetic membranes from the relatively inefficient UPB to highly efficient mature ICM. (C) 2012 Elsevier B.V. All rights reserved.