Anaerobic Respiration of Elemental Sulfur and Thiosulfate by Shewanella oneidensis MR-1 Requires psrA, a Homolog of the phsA Gene of Salmonella enterica Serovar Typhimurium LT2
Anaerobic Respiration of Elemental Sulfur and Thiosulfate by Shewanella oneidensis MR-1 Requires psrA, a Homolog of the phsA Gene of Salmonella enterica Serovar Typhimurium LT2
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DOI：
10.1128/aem.00888-09
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发表时间：
2009-08-15
影响因子：
4.4
通讯作者：
DiChristina, Thomas J.
中科院分区：
文献类型：
--
作者：
Burns, Justin L.;DiChristina, Thomas J.
同一希瓦氏菌MR-1是一种兼性厌氧γ变形菌，呼吸多种厌氧末端电子受体，包括无机硫化合物亚硫酸盐（SO32-）、硫代硫酸盐（S2O32-）、四硫酸盐（S4O62-）和单质硫（S-0）。然而，野刺草对无机硫化合物厌氧呼吸的分子机制尚不清楚。在本研究中，我们发现了一种三基因簇，其翻译产物与phsABC的产物具有59 - 73%的氨基酸相似性，phsABC是肠沙门氏菌血清型鼠伤寒杆菌LT2呼吸S-0和S2O32-所需的基因簇。在还原S-0和S2O32的Shewanella菌株的基因组中发现了phsA的同源物（注释为psrA），而在不能还原这些电子受体的Shewanella菌株的基因组中则缺失了phsA的同源物。构建了一种新的自杀载体，用于产生无标记的帧内缺失psrA，该基因编码硫代硫酸盐还原酶。psrA缺失突变体（PSRA1）保留下游基因psrB和psrC的表达，但不能呼吸S-0或S2O32-作为终端电子受体。基于这些结果，我们假设PsrA是S. oneidensis S2O32-末端还原酶的主要亚基，其最终产物（硫化物[HS-]或SO32-）参与驱动S-0呼吸的种内硫循环。
Shewanella oneidensis MR-1, a facultatively anaerobic gammaproteobacterium, respires a variety of anaerobic terminal electron acceptors, including the inorganic sulfur compounds sulfite (SO32-), thiosulfate (S2O32-), tetrathionate (S4O62-), and elemental sulfur (S-0). The molecular mechanism of anaerobic respiration of inorganic sulfur compounds by S. oneidensis, however, is poorly understood. In the present study, we identified a three-gene cluster in the S. oneidensis genome whose translated products displayed 59 to 73% amino acid similarity to the products of phsABC, a gene cluster required for S-0 and S2O32- respiration by Salmonella enterica serovar Typhimurium LT2. Homologs of phsA (annotated as psrA) were identified in the genomes of Shewanella strains that reduce S-0 and S2O32- yet were missing from the genomes of Shewanella strains unable to reduce these electron acceptors. A new suicide vector was constructed and used to generate a markerless, in-frame deletion of psrA, the gene encoding the putative thiosulfate reductase. The psrA deletion mutant (PSRA1) retained expression of downstream genes psrB and psrC but was unable to respire S-0 or S2O32- as the terminal electron acceptor. Based on these results, we postulate that PsrA functions as the main subunit of the S. oneidensis S2O32- terminal reductase whose end products (sulfide [HS-] or SO32-) participate in an intraspecies sulfur cycle that drives S-0 respiration.