Dopson Mark, Baker-Austin Craig, Bond Philip L
School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK.
Centre for Ecology, Evolution and Conservation, University of East Anglia, Norwich NR4 7TJ, UK.
Microbiology (Reading). 2005 Dec;151(Pt 12):4127-4137. doi: 10.1099/mic.0.28362-0.
To investigate the metabolic biochemistry of iron-oxidizing extreme acidophiles, a proteomic analysis of chemomixotrophic and chemo-organotrophic growth, as well as protein expression in the absence of organic carbon, was carried out in Ferroplasma species. Electron transport chain inhibitor studies, spectrophotometric analysis and proteomic results suggest that oxidation of ferrous iron may be mediated by the blue copper-haem protein sulfocyanin and the derived electron passes to a cbb3 terminal electron acceptor. Despite previous suggestions of a putative carbon dioxide fixation pathway, no up-regulation of proteins typically associated with carbon dioxide fixation was evident during incubation in the absence of organic carbon. Although a lack of known carbon dioxide fixation proteins does not constitute proof, the results suggest that these strains are not autotrophic. Proteins putatively involved in central metabolic pathways, a probable sugar permease and flavoproteins were up-regulated during chemo-organotrophic growth in comparison to the protein complement during chemomixotrophic growth. These results reflect a higher energy demand to be derived from the organic carbon during chemo-organotrophic growth. Proteins with suggested function as central metabolic enzymes were expressed at higher levels during chemomixotrophic growth by Ferroplasma acidiphilum Y(T) compared to 'Ferroplasma acidarmanus' Fer1. This study addresses some of the biochemical and bioenergetic questions fundamental for survival of these organisms in extreme acid-leaching environments.
为了研究铁氧化嗜酸嗜极菌的代谢生物化学，对嗜铁菌属进行了化学混合营养生长和化学有机营养生长的蛋白质组分析，以及在无有机碳条件下的蛋白质表达分析。电子传递链抑制剂研究、分光光度分析和蛋白质组学结果表明，亚铁的氧化可能由蓝铜-血红素蛋白硫氰酸酶介导，衍生电子传递至cbb3末端电子受体。尽管之前有关于假定的二氧化碳固定途径的推测，但在无有机碳培养期间，通常与二氧化碳固定相关的蛋白质并未明显上调。虽然缺乏已知的二氧化碳固定蛋白并不构成证据，但结果表明这些菌株不是自养型。与化学混合营养生长期间的蛋白质组相比，在化学有机营养生长期间，假定参与中心代谢途径的蛋白质、一种可能的糖通透酶和黄素蛋白上调。这些结果反映出在化学有机营养生长期间，需要从有机碳中获取更高的能量。与“嗜酸嗜铁菌”Fer1相比，嗜酸嗜铁菌Y(T)在化学混合营养生长期间，具有中心代谢酶功能的蛋白质表达水平更高。本研究解决了这些生物体在极端酸浸环境中生存所必需的一些生化和生物能量学问题。
