FORMALDEHYDE METABOLISM IN PURPLE NON SULPHUR BACTERIUM RHODOBACTER SPHAEROIDES

我们正在研究甲醛同化的途径， 紫色非硫细菌Rhodobacter sphaeroides 紫色 非硫细菌因其代谢多样性而众所周知， 使用各种各样的基质来满足碳和能源需求。 的 代谢这些底物中的一些，特别是甲基化 化合物，产生甲醛，必须进一步代谢或 会对细胞产生毒性 我们的数据显示甲醛 命运在R。球形细胞病取决于细胞是否生长在 存在或不存在氧气。 在厌氧条件下（光合作用） 生长条件、R. sphaeroides能够使用甲醇作为 唯一的碳源。 因为甲醛是 甲醇的氧化，它必须为R提供所有的碳骨架。 在光合生长条件下， 述通路中的 之前已经描述了甲醛同化， 微生物，粗提物中的酶测定表明，R.球形细胞 可以使用丝氨酸-异柠檬酸循环或卡尔文循环， 光合甲基营养生长 在有氧生长下 条件下，类似的酶试验表明，甲醛是 氧化成二氧化碳并释放到大气中， 从细胞中清除甲醛。 通过使用13 C标记的 酶试验中的底物，我们希望确认 这些细胞中的甲醛氧化产物。 通过表明 当特定的甲醛途径时， 将中间体添加到R中。sphaeroides提取物，我们将提供 直接证据来支持我们对甲醛 在存在和不存在氧的情况下的氧化。

We are investigating the pathway of formaldehyde assimilation in the purple non-sulphur bacterium Rhodobacter sphaeroides. Purple non-sulphur bacteria are well known for their metabolic diversity, using a wide variety of substrates for carbon and energy needs. The metabolism of some of these substrates, specifically methylated compounds, generates formaldehyde that must be further metabolized or would prove toxic to the cells. Our data suggest that formaldehyde's fate in R. sphaerodies is dependent on whether cells are grown in the presence or absence of oxygen. Under anaerobic (photosynthetic) growth conditions, R. sphaeroides is able to grow using methanol as a sole carbon source. Since formaldehyde is the immediate product of methanol oxidation, it must provide all the carbon skeletons for R. sphaeroides under photosynthetic growth conditions. Of the pathways that have previously been described for formaldehyde assimilation in microbes, enzyme assays in crude extracts suggest that R. sphaerodies may use either the Serine-Isocitrate cycle or the Calvin cycle for photosynthetic methylotrophic growth. Under aerobic growth conditions, similar enzyme assays suggest that formaldehyde is oxidized to carbon dioxide and released to the atmosphere thus detoxifiying formaldehyde form the cells. By using 13C-labeled substrates in enzyme assays, we hope to confirm the path(s) of formaldehyde oxidation products in these cells. By showing that the predicted products are formed when specific formaldehyde pathway intermediates are added to R. sphaeroides extracts, we will provide direct evidence to support our tentative pathway for formaldehyde oxidation in the presence and absence of oxygen.