Oxygen-dependent autoaggregation in Shewanella oneidensis MR-1
Oxygen-dependent autoaggregation in Shewanella oneidensis MR-1
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DOI：
10.1111/j.1462-2920.2008.01608.x
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发表时间：
2008-07-01
影响因子：
5.1
通讯作者：
Beliaev, A. S.
中科院分区：
文献类型：
--
作者：
McLean, J. S.;Pinchuk, G. E.;Beliaev, A. S.
在需氧恒化器培养物中，维持在50%溶解氧（2）张力（3.5 mg l（-1）溶解氧（2）），希瓦氏菌oneidensis菌株MR-1在加入0.68 mM CaCl（2）后迅速聚集，并在高稀释率下保持这种多细胞表型。有助于聚集体结构稳定性的细胞外基质材料的共聚焦显微镜分析揭示了细胞外DNA、蛋白质和糖缀合物的存在。然而，在O（2）限制性生长（溶解的O（2）低于检测）开始时，MR-1菌株的补充Ca（2+）的恒化器培养物迅速分解并作为运动的分散细胞生长。全球转录组分析比较有氧聚集O（2）-有限的非聚集细胞识别基因编码细胞与细胞和细胞表面粘附因子，其转录增加暴露于增加O（2）浓度。好氧聚集的细胞还显示了假定的厌氧电子转移和金属还原基因的同源物的表达增加，包括mtrD（SO 1782）、mtrE（SO 1781）和mtrF（SO 1780）。我们的数据表明，MR-1的自聚集机制依赖于pilD基因的功能，该基因编码一个假定的prepilin肽酶。S.缺乏PilD和相关途径（包括IV型和Msh皮利生物发生）的oneidensis菌株MR-1显示出对H（2）O（2）的敏感性中度增加。综上所述，我们的证据表明，在S。oneidensis MR-1可以作为生化解毒的替代或补充，以减少有氧代谢期间与活性氧物质产生相关的氧化应激，同时促进聚集体内部缺氧条件的发展。
In aerobic chemostat cultures maintained at 50% dissolved O(2) tension (3.5 mg l(-1) dissolved O(2)), Shewanella oneidensis strain MR-1 rapidly aggregated upon addition of 0.68 mM CaCl(2) and retained this multicellular phenotype at high dilution rates. Confocal microscopy analysis of the extracellular matrix material contributing to the stability of the aggregate structures revealed the presence of extracellular DNA, protein and glycoconjugates. Upon onset of O(2)-limited growth (dissolved O(2) below detection) however, the Ca(2+)-supplemented chemostat cultures of strain MR-1 rapidly disaggregated and grew as motile dispersed cells. Global transcriptome analysis comparing aerobic aggregated to O(2)-limited unaggregated cells identified genes encoding cell-to-cell and cell-to-surface adhesion factors whose transcription increased upon exposure to increased O(2) concentrations. The aerobic aggregated cells also revealed increased expression of putative anaerobic electron transfer and homologues of metal reduction genes, including mtrD (SO1782), mtrE (SO1781) and mtrF (SO1780). Our data indicate that mechanisms involved in autoaggregation of MR-1 are dependent on the function of pilD gene which encodes a putative prepilin peptidase. Mutants of S. oneidensis strain MR-1 deficient in PilD and associated pathways, including type IV and Msh pili biogenesis, displayed a moderate increase in sensitivity to H(2)O(2). Taken together, our evidence indicates that aggregate formation in S. oneidensis MR-1 may serve as an alternative or an addition to biochemical detoxification to reduce the oxidative stress associated with production of reactive oxygen species during aerobic metabolism while facilitating the development of hypoxic conditions within the aggregate interior.