Role of outer membrane c-type cytochromes MtrC and OmcA in Shewanella oneidensis MR-1 cell production, accumulation, and detachment during respiration on hematite
Role of outer membrane c-type cytochromes MtrC and OmcA in Shewanella oneidensis MR-1 cell production, accumulation, and detachment during respiration on hematite
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DOI：
10.1111/j.1472-4669.2012.00321.x
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发表时间：
2012-07-01
期刊：
影响因子：
3.7
通讯作者：
Geesey, G. G.
中科院分区：
文献类型：
--
作者：
Mitchell, A. C.;Peterson, L.;Geesey, G. G.
铁还原细菌希瓦氏菌MR-1有能力在长期内通过呼吸结晶铁氧化物（如赤铁矿）来促进铁循环，当低结晶相耗尽时。MR-1的外膜细胞色素OmcA和MtrC与赤铁矿结合并将电子转移到赤铁矿的能力表明，当这种矿物被用作呼吸底物时，它们起着终端还原酶的作用。然而，它们的氧化还原行为和赤铁矿结合性质的差异表明它们在电子转移反应中起着不同的作用。在这里，我们研究了赤铁矿作为终端电子受体（TEA）时，细胞色素行为的这些差异如何影响生物膜的发育。在赤铁矿上附着后，野生型（WT）菌株的细胞以及a ？omcA突变体而不是a ？mtrC突变体在矿物表面复制积累。结果表明，当这种矿物作为TEA时，生长需要MtrC，而不需要OmcA。虽然在达到与WT细胞相当的最大表面细胞密度之前，缺乏OmcA不会阻碍赤铁矿上的细胞复制和积累，但一旦达到最大表面细胞密度，就需要OmcA来进行有效的电子转移和细胞附着到赤铁矿上。因此，OmcA可能在克服电子转移和细胞附着到赤铁矿上的障碍方面发挥作用，这些障碍是由与实现高表面细胞密度相关的细胞呼吸作用对矿物表面的还原性溶解造成的。
The iron-reducing bacterium Shewanella oneidensis MR-1 has the capacity to contribute to iron cycling over the long term by respiring on crystalline iron oxides such as hematite when poorly crystalline phases are depleted. The ability of outer membrane cytochromes OmcA and MtrC of MR-1 to bind to and transfer electrons to hematite has led to the suggestion that they function as terminal reductases when this mineral is used as a respiratory substrate. Differences in their redox behavior and hematite-binding properties, however, indicate that they play different roles in the electron transfer reaction. Here, we investigated how these differences in cytochrome behavior with respect to hematite affected biofilm development when the mineral served as terminal electron acceptor (TEA). Upon attachment to hematite, cells of the wild-type (WT) strain as well as those of a ?omcA mutant but not those of a ?mtrC mutant replicated and accumulated on the mineral surface. The results indicate that MtrC but not OmcA is required for growth when this mineral serves as TEA. While an OmcA deficiency did not impede cell replication and accumulation on hematite prior to achievement of a maximum surface cell density comparable to that established by WT cells, OmcA was required for efficient electron transfer and cell attachment to hematite once maximum surface cell density was achieved. OmcA may therefore play a role in overcoming barriers to electron transfer and cell attachment to hematite imposed by reductive dissolution of the mineral surface from cell respiration associated with achievement of high surface cell densities.