Department of Civil and Environmental Engineering, University of Wisconsin at Madison, Madison, WI 53706, USA.
Environ Microbiol. 2010 May;12(5):1205-17. doi: 10.1111/j.1462-2920.2010.02163.x. Epub 2010 Feb 9.
Here we report the first metatranscriptomic analysis of gene expression and regulation of 'Candidatus Accumulibacter'-enriched lab-scale sludge during enhanced biological phosphorus removal (EBPR). Medium density oligonucleotide microarrays were generated with probes targeting most predicted genes hypothesized to be important for the EBPR phenotype. RNA samples were collected at the early stage of anaerobic and aerobic phases (15 min after acetate addition and switching to aeration respectively). We detected the expression of a number of genes involved in the carbon and phosphate metabolisms, as proposed by EBPR models (e.g. polyhydroxyalkanoate synthesis, a split TCA cycle through methylmalonyl-CoA pathway, and polyphosphate formation), as well as novel genes discovered through metagenomic analysis. The comparison between the early stage anaerobic and aerobic gene expression profiles showed that expression levels of most genes were not significantly different between the two stages. The majority of upregulated genes in the aerobic sample are predicted to encode functions such as transcription, translation and protein translocation, reflecting the rapid growth phase of Accumulibacter shortly after being switched to aerobic conditions. Components of the TCA cycle and machinery involved in ATP synthesis were also upregulated during the early aerobic phase. These findings support the predictions of EBPR metabolic models that the oxidation of intracellularly stored carbon polymers through the TCA cycle provides ATP for cell growth when oxygen becomes available. Nitrous oxide reductase was among the very few Accumulibacter genes upregulated in the anaerobic sample, suggesting that its expression is likely induced by the deprivation of oxygen.
在这里，我们报告了第一个富 'Candidatus Accumulibacter' 的实验室规模污泥的基因表达和调控的宏转录组分析，该污泥是在增强生物除磷（EBPR）过程中富集得到的。使用针对大多数假设对 EBPR 表型重要的预测基因的探针生成了中密度寡核苷酸微阵列。在厌氧和有氧阶段的早期（分别在添加乙酸盐后 15 分钟和切换到曝气时）收集 RNA 样品。我们检测了许多与碳和磷酸盐代谢有关的基因的表达，这些基因如 EBPR 模型所提出的（例如，聚羟基烷酸酯的合成、通过甲基丙二酰辅酶 A 途径的分裂三羧酸循环和多磷酸盐的形成），以及通过宏基因组分析发现的新基因。早期厌氧和有氧基因表达谱之间的比较表明，两个阶段的大多数基因的表达水平没有显著差异。有氧样品中上调的大多数基因预计编码转录、翻译和蛋白质易位等功能，这反映了 Accumulibacter 在被切换到有氧条件后不久的快速生长阶段。TCA 循环的组件和涉及 ATP 合成的机械也在早期有氧阶段被上调。这些发现支持了 EBPR 代谢模型的预测，即当氧气可用时，通过 TCA 循环氧化细胞内储存的碳聚合物为细胞生长提供 ATP。在厌氧样品中，少数几种被上调的 Accumulibacter 基因之一是亚硝酸盐还原酶，这表明其表达可能是由于缺氧而诱导的。
