土壤传染病与土壤疗效--土壤在治疗疾病方面远比在导致疾病方面发挥着更大的作用|阅读

导  读

土壤在治疗我们的疾病方面远比导致疾病发挥的作用更大！

来源：** 李保国  张宝贵  编译自第十五版/（美）雷· 韦尔（Ray R. Weil），尼尔· 布雷迪（Nyle C. Brady ）著,《The Nature and Properties of Soils》中专栏1.2内容。第十四版已有中文译版，《土壤学与生活》（美）布雷迪（Nyle C. Brady ），雷· 韦尔（Ray R. Weil）著；李保国，徐建明等译. 北京：科学出版社，2019.2。

土源传染病

在数百万土壤栖息的生物中，少数生物会给人类带来疾病甚至死亡。最臭名昭著的土壤致病细菌有引起破伤风的破伤风菌（Clostridium tetani）和导致炭疽病的炭疽杆菌（Bacillus anthracis），这些细菌的孢子可能在土壤中存活数十年。这些由土壤传播的传染性细菌疾病每年夺去数百万人，包括许多婴儿和在不卫生的条件下分娩的母亲。当土壤真菌（Blastomyces sp.）通过皮肤切口感染或被呼吸到肺部，就会导致一种罕见但仍能致命的土壤传播疾病。虽芽生菌病（Blastomycosis）在地理分布上通常与局地土壤条件相关，但因为其肺炎样肺部症状或皮肤溃疡症状有几个月的潜伏期，所以很难追踪，。隐球菌病是一种相当罕见的疾病，可以通过吸入一种土壤真菌- 隐球菌的孢子而感染，可引起脑损伤或肺炎样肺部症状。还有一些人类疾病是由微小的土壤动物引起的，如蛔虫、钩虫和原生动物，如隐孢子虫，会导致隐孢子虫病的广泛爆发。有时在一个城市中，如果含原生动物的土壤或农场粪便污染了饮用水，就会使数千人生病（但很少死亡）。还有一个常被忽视的健康危害，来自沙漠风刮起并传播到世界各地的细小粉尘。空气中的尘埃不仅会对肺组织造成物理刺激，从而导致癌症，而且还会携带病原性土壤微生物，这些微生物跨洲越洋后仍能存活并保持毒性。

土壤的疗效

上述讨论并不意味着我们什么时候在森林或花园里徒步旅行, 都应该戴上橡胶手套，（如果你手上有伤口，戴手套肯定是一个好的劝告）。相反，大多数土壤中，自然平衡压倒性地偏向有益生物，他们提供人类福利所必需的生态系统服务。例如，某些单细胞土壤动物如草履虫（Paramecium，如图），可吞噬前面提到的致病真菌隐球菌的孢子。事实上，土壤在治疗我们的疾病方面远比导致疾病发挥的作用更大！

图 土壤生态系统的自然平衡。草履虫，一种单细胞土壤动物（原生生物）吞噬和杀死致病真菌的孢子。箭头所指为草履虫体内的孢子; 白色刻度条 = 1μm。 Frager等提供微观图像（2010年）。

许多人没有意识到，生长在土壤中的植物是大多数药物（包括传统草药和现代药物）的来源，这些药物能够预防、缓解或治愈困扰并经常杀死我们祖先的许多疾病。Taxol（紫杉醇）的故事就是一个很好的例证。这种备受推崇的抗癌药物首次在俄勒冈州和华盛顿州太平洋沿岸土壤中生长的稀有紫杉树树皮中发现。在科学家研发出利用分子培养和转基因技术，从其他生物体制造出这种药物之前，对其需求已导致50万棵紫杉被砍伐。

土壤微生物本身是我们大多数拯救生命的抗生素的来源药物，如青霉素、环丙沙星和新霉素，它们来自某些土壤细菌（例如链球菌）和真菌（如青霉素），这些化合物是其针对竞争土壤微生物的防御策略的一部分。长期以来，用土壤黏土制成的膏药在传统医学中一直有效用于治疗皮肤状况和抵抗感染。一些研究甚至表明，只要与健康土壤密切接触（想一想勤劳的园丁），并呼吸它们产生的某些微生物或挥发性化合物，就可以通过与大脑化学的相互作用给人一种愉悦感。（脑细胞血清素的显著增加，是对土壤细菌和分枝杆菌作用的响应。多种多样的土壤微生物调节我们的免疫系统，提供人类福祉，是土壤提供的重要生态系统服务。 

有关土壤黏土（黏土上吸附的金属）具有愈合能力的研究，见奥托和海德尔（Otto and Haydel ,2013）。有关土壤（和其他环境）生物对人体免疫系统调节的综述，请参阅 Rook（2013）

Infectious diseases from soils 

Among the millions of soil-dwelling organisms, a few can bring disease and even death to humans. Among the more notorious soil pathogenic bacteria are Clostridium tetani, which causes tetanus and Bacillus anthracis, which causes anthrax and whose spores may survive in the soil for decades. Such soil-borne infectious bacterial diseases kill millions of people each year, including many babies and mothers who die during childbirth under unsanitary conditions. A less common, but still potentially fatal, soil-borne disease is caused when a soil fungus, Blastomyces sp, infects a cut in the skin or is breathed into the lungs. Blastomycosis is usually associated geographically with localized soil conditions, but it is hard to track down as its pneumonia-like lung symptoms or skin ulcerations may not appear for months after exposure. Cryptococcosis, a fairly rare disease causing brain damage or pneumonia-like lung symptoms, can be contracted by breathing in spores of Cryptococcus, another soil fungus. Still other human diseases are caused by microscopic soil animals, such round worms, hook worms, and protozoa. An example of the latter is Cryptosporidium sp., which cause widespread outbreaks of cryptosporidiosis, sometimes sickening (but rarely killing) thousands of people in a single city if the protozoa-containing soil or farm manure contaminates drinking water supplies. Another under-recognized health hazard comes from fine dust picked up by desert winds and carried halfway around the world (see Sections 2.2 and 17.2). Airborne dust not only poses a risk of physical irritation of lung tissues that results in cancer, but also carries pathogenic soil microorganisms that can remain alive and virulent during the intercontinental journey.

The curative powers of soils 

The aforementioned discussion does not mean that we should never hike in the forest or garden without rubber gloves (though gloves are a good idea if your hand has an open wound). To the contrary—the balance of nature in most soils is overwhelmingly in favor of organisms that provide ecosystem services essential to human welfare. For example, it was recently observed (Figure 1.9) that certain single-celled soil animals called Paramecium, voraciously eat the spores of the pathogenic fungus Cryptococcus just mentioned. In fact, soils play a far greater role in curing our diseases than in causing them! 

Many people are unaware that plants grown in the soil are the source of most of the medicines (both traditional herbals and modern pharmaceuticals) that prevent, alleviate or cure so many of the diseases and ailments that plagued and often killed our ancestors. The story of Taxol (paclitaxel) illustrates this role quite well. This highly prized anticancer drug was first discovered in the bark of a rare type of yew tree that grows in the Pacific coast soils of Oregon and Washington States. Demand for this drug resulted in the destruction of half a million of these yews before scientists learned to make it from other organisms using molecular culture and gene-transfer techniques.

Soil microorganisms themselves are the source of most of our life-saving antibiotics Drugs such as penicillin, ciprofloxacin, and neomycin originate from certain soil bacteria (e.g., Streptomyces) and fungi (e.g., Penicillium) that produce these compounds as part of their defensive strategies against competing soil microbes. See Chapter 11 for more on soil microbes and their antibiotics. Poultices made from soil clays have long been effectively used in traditional medicine to heal skin conditions and fight infections. Some research even suggests that just being in close contact with healthy soils (think avid gardeners) and breathing in certain microorganisms or volatile compounds they produce may give people a sense of well-being through interactions with their brain chemistry (the marked increase in brain cell serotonin in response to the soil bacterium, Mycobacterium vaccae, is well documented). Regulation of our immune systems and promotion of our well-being by diverse soil microbes should be considered among the ecosystem services that soils provide.

Figure 1.9 Balance of nature in the soil ecosystem. This Paramecium, a single celled soil animal (protista) ingests and kills spores of the human pathogenic fungus Cryptococcus. Arrow shows spores inside the paramecium; white scale bar = 1μm.  Microscopic image from Frager et al. 

(2010).

**Many scientific papers are available for further reading on soils and human health [see Alloway and Graham (2008); Frager et al. (2010); Griffin (2007); Liu and Khosla (2010); Stokes (2006)]. For research that illuminates why soil clays exhibit powers of healing (it’s the metals adsorbed to the clays!), see Otto and Haydel (2013). For a review of human immune system regulation by soil (and other environmental) organisms, see Rook (2013). 

Otto, C. C., and S. E. Haydel. 2013. “Exchangeable ions are responsible for the in vitro antibacterial properties of natural clay mixtures,” PLoS ONE, 8:e64068.

Rook, G. A. 2013. “Regulation of the immune system by biodiversity from the natural environment: An ecosystem service essential to health,” Proc Natl Acad Sci., 110:18360–18367.

荐  书

土壤家”近期文章推荐

“环境与健康观察”近期文章推荐

“土壤观察”近期文章推荐

我们是“土壤观察”（turangguancha），感谢您的阅读！

欢迎关注，欢迎分享到朋友圈或转发给好友,长按二维码，识别关注我们

联系我们请加13926117407微信号（或发邮件至[e-mail]）

如果觉得土壤观察干得不错，请转发朋友圈或点击“在看”