Stoker C R, Boston P J, Mancinelli R L, Segal W, Khare B N, Sagan C
NASA Ames Research Center, Moffett Field, California 94035, USA.
Icarus. 1990;85:241-56. doi: 10.1016/0019-1035(90)90114-o.
In this paper, we show that a wide variety of common soil bacteria are able to obtain their carbon and energy needs from tholin (a class of complex organic heteropolymers thought to be widely distributed through the solar system; in this case tholin was produced by passage of electrical discharge through a mixture of methane, ammonia, and water vapor). We have isolated aerobic, anaerobic, and facultatively anaerobic bacteria which are able to use tholin as a sole carbon source. Organisms which metabolize tholin represent a variety of bacterial genera including Clostridium, Pseudomonas, Bacillus, Acinetobacter, Paracoccus, Alcaligenes, Micrococcus, Corynebacterium, Aerobacter, Arthrobacter, Flavobacterium, and Actinomyces. Aerobic tholin-using bacteria were first isolated from soils containing unusual or sparse carbon sources. Some of these organisms were found to be facultatively anaerobic. Strictly anaerobic tholin-using bacteria were isolated from both carbon-rich and carbon-poor anaerobic lake muds. In addition, both aerobic and anaerobic tholin-using bacteria were isolated from common soil collected outside the laboratory building. Some, but not all, of the strains that were able to obtain carbon from tholin were also able to obtain their nitrogen requirements from tholin. Bacteria isolated from common soils were tested for their ability to obtain carbon from the water-soluble fraction, the ethanol-soluble fraction, and the water/ethanol-insoluble fraction of the tholin. Of the 3.5 x 10(7) bacteria isolated per gram of common soils, 1.7, 0.5, and 0.2%, respectively, were able to obtain their carbon requirements from the water-soluble fraction, the ethanol-soluble fraction and the water/ethanol-insoluble fraction of the tholin. The palatability of tholins to modern microbes may have implications for the early evolution of microbial life on Earth. Tholins may have formed the base of the food chain for an early heterotrophic biosphere before the evolution of autotrophy on the early Earth. Where tholins are present on other planets, they could possibly be metabolized by contaminant microorganisms transported to these bodies via spacecraft. Thus, the presence of tholins should be taken into account when evaluating the planetary quarantine requirements for probes to other planets.
在本文中，我们表明多种常见的土壤细菌能够从索林（一类被认为广泛分布于太阳系的复杂有机杂聚物；在此情况下，索林是通过对甲烷、氨和水蒸气的混合物进行放电产生的）中获取其碳和能量需求。我们已经分离出了能够将索林用作唯一碳源的需氧菌、厌氧菌和兼性厌氧菌。能够代谢索林的生物体代表了多种细菌属，包括梭菌属、假单胞菌属、芽孢杆菌属、不动杆菌属、副球菌属、产碱菌属、微球菌属、棒状杆菌属、气杆菌属、节杆菌属、黄杆菌属和放线菌属。利用索林的需氧菌最初是从含有不寻常或稀少碳源的土壤中分离出来的。其中一些生物体被发现是兼性厌氧的。严格厌氧的利用索林的细菌是从富碳和贫碳的厌氧湖泥中分离出来的。此外，利用索林的需氧菌和厌氧菌都是从实验室大楼外采集的普通土壤中分离出来的。一些（但不是全部）能够从索林中获取碳的菌株也能够从索林中获取其氮需求。对从普通土壤中分离出的细菌进行了测试，以确定它们从索林的水溶性部分、乙醇溶性部分和水/乙醇不溶性部分获取碳的能力。每克普通土壤中分离出的3.5×10⁷个细菌中，分别有1.7%、0.5%和0.2%能够从索林的水溶性部分、乙醇溶性部分和水/乙醇不溶性部分获取其碳需求。索林对现代微生物的适口性可能对地球上微生物生命的早期进化有影响。在早期地球自养作用进化之前，索林可能已经形成了早期异养生物圈食物链的基础。在其他行星上存在索林的地方，它们可能会被通过航天器运输到这些天体上的污染微生物代谢。因此，在评估前往其他行星的探测器的行星检疫要求时，应考虑索林的存在。
