Rong Chengbo, Zhang Chan, Zhang Yiting, Qi Lei, Yang Jing, Guan Guohua, Li Ying, Li Jilun
State Key Laboratory of Agro-biotechnology and College of Biological Sciences, China Agricultural University, Beijing, People's Republic of China.
J Bacteriol. 2012 Aug;194(15):3972-6. doi: 10.1128/JB.00382-12. Epub 2012 May 25.
Magnetotactic bacteria (MTB) synthesize unique organelles, the magnetosomes, which are intracellular nanometer-sized, membrane-enveloped magnetite. The biomineralization of magnetosomes involves the uptake of large amounts of iron. However, the iron metabolism of MTB is not well understood. The genome of the magnetotactic bacterium Magnetospirillum gryphiswaldense strain MSR-1 contains two ferrous iron transport genes, feoB1 and feoB2. The FeoB1 protein was reported to be responsible mainly for the transport of ferrous iron and to play an accessory role in magnetosome formation. To determine the role of feoB2, we constructed an feoB2 deletion mutant (MSR-1 ΔfeoB2) and an feoB1 feoB2 double deletion mutant (MSR-1 NfeoB). The single feoB2 mutation did not affect magnetite crystal biomineralization. MSR-1 NfeoB had a significantly lower average magnetosome number per cell (∼65%) than MSR-1 ΔfeoB1, indicating that FeoB2 plays a role in magnetosome formation when the feoB1 gene is deleted. Our findings showed that FeoB1 has a greater ferrous iron transport ability than FeoB2 and revealed the differential roles of FeoB1 and FeoB2 in MSR-1 iron metabolism. Interestingly, compared to the wild type, the feoB mutants showed increased sensitivity to oxidative stress and lower activities of the enzymes superoxide dismutase and catalase, indicating that the FeoB proteins help protect bacterial cells from oxidative stress.
趋磁细菌（MTB）合成独特的细胞器——磁小体，磁小体是细胞内纳米大小、被膜包裹的磁铁矿。磁小体的生物矿化涉及大量铁的摄取。然而，趋磁细菌的铁代谢尚未得到充分了解。趋磁细菌嗜热栖热放线菌菌株MSR-1的基因组包含两个亚铁转运基因，feoB1和feoB2。据报道，FeoB1蛋白主要负责亚铁的转运，并在磁小体形成中起辅助作用。为了确定feoB2的作用，我们构建了一个feoB2缺失突变体（MSR-1ΔfeoB2）和一个feoB1 feoB2双缺失突变体（MSR-1 NfeoB）。单一的feoB2突变并不影响磁铁矿晶体的生物矿化。MSR-1 NfeoB每个细胞的平均磁小体数量比MSR-1ΔfeoB1显著降低（约65%），表明当feoB1基因缺失时，FeoB2在磁小体形成中发挥作用。我们的研究结果表明，FeoB1比FeoB2具有更强的亚铁转运能力，并揭示了FeoB1和FeoB2在MSR-1铁代谢中的不同作用。有趣的是，与野生型相比，feoB突变体对氧化应激的敏感性增加，超氧化物歧化酶和过氧化氢酶的活性降低，这表明FeoB蛋白有助于保护细菌细胞免受氧化应激。
