發(fā)布時間：2018-05-13 22:42

  本文選題：食物細菌 + 尿素�。� 參考：《云南大學(xué)》2015年博士論文

【摘要】：自然界中,食物細菌被認為是一類為線蟲提供食物的被動犧牲品。作為線蟲的食物,這類群細菌是如何生存并保持與捕食者相互動態(tài)平衡,進而維持自然生態(tài)系統(tǒng)中物種平衡的?這是微生物生態(tài)領(lǐng)域至今懸而未訣的重要科學(xué)問題。本研究揭示了這類細菌通過調(diào)控捕食線蟲真菌從腐生到寄生的生活史轉(zhuǎn)換-形成捕食器,幫助其捕殺線蟲,使線蟲從捕食者變?yōu)楸徊妒痴?從而達到細菌、真菌和線蟲三者動態(tài)平衡。 本研究發(fā)現(xiàn),高溫滅菌的牛糞對少孢節(jié)叢孢捕食器的誘導(dǎo)活性降低了6倍,推測牛糞細菌在誘導(dǎo)過程中可能起到關(guān)鍵作用。檢測牛糞中126株細菌,發(fā)現(xiàn)55株細菌能夠誘導(dǎo)捕食器形成,其中嗜麥寡養(yǎng)單胞菌是誘導(dǎo)捕食器形態(tài)建成最有效的菌株。隨后,結(jié)合柱層析、活性追蹤、質(zhì)譜等波譜方法確定尿素是嗜麥寡養(yǎng)單胞菌CD52誘導(dǎo)捕食器形成的活性化合物,且尿素對誘導(dǎo)捕食線蟲真菌形成不同類型的捕食器具有廣譜性。進一步檢測發(fā)現(xiàn),活性細菌都產(chǎn)生尿素,因此,尿素是調(diào)控捕食器形態(tài)建成的信號分子。 精氨酸反應(yīng)中,精氨酸酶裂解精氨酸生成鳥氨酸和尿素。RT-PCR分析顯示精氨酸酶在活性細菌中表達,且線蟲脅迫下表達量顯著提高。隨后,敲除CD52中精氨酸酶基因獲得突變體SmAarcA, LC-MS檢測SmAarcA完全不能產(chǎn)生尿素,并且誘導(dǎo)捕食器形成率降低了60%,證實細菌通過調(diào)節(jié)精氨酸酶的活性分泌尿素影響捕食器形態(tài)建成。 基因組序列分析顯示少孢節(jié)叢孢中存在尿素轉(zhuǎn)運蛋白和脲酶基因。同位素[13C,15N2]-urea追蹤發(fā)現(xiàn)：敲除轉(zhuǎn)運蛋白Utp79基因后,突變體Ao Autp79胞內(nèi)完全檢測不到同位素；但是,脲酶突變體AoΔure1胞內(nèi)同位素積累量顯著上升。與此同時,尿素完全不能誘導(dǎo)突變體AoΔutp79和AoΔure1產(chǎn)生捕食器。因此,尿素必須轉(zhuǎn)運進入真菌細胞內(nèi),經(jīng)過脲酶作用誘導(dǎo)捕食器的形成。尿素循環(huán)中,脲酶催化尿素生成氨和二氧化碳�；钚詼y定發(fā)現(xiàn),氨可以高效誘導(dǎo)捕食器的形成,而二氧化碳不能,所以,氨是誘導(dǎo)捕食器的下游信號分子。 通過研究細菌對線蟲的發(fā)育、后代、壽命和食物偏好的影響,確定了產(chǎn)尿素細菌對線蟲的生長發(fā)育沒有影響,這類細菌是線蟲的食物細菌。尿素作為地下信號分子可以在土壤中高效擴散,而且,與線蟲共同作用時,尿素顯著提高捕食器形成數(shù)量,暗示尿素與線蟲協(xié)同誘導(dǎo)捕食器形成。分析土壤中食物細菌、線蟲和捕食線蟲真菌三者之間的動態(tài)關(guān)系發(fā)現(xiàn),產(chǎn)尿素的食物細菌可以促使捕食線蟲真菌捕食器顯著增多,捕殺線蟲的起始時間提前8h。更重要的是,捕食線蟲真菌可以挽救食物細菌的群體數(shù)量,這些現(xiàn)象證實,食物細菌調(diào)控真菌產(chǎn)生更多捕食器殺死線蟲。 綜上所述,食物細菌可以產(chǎn)生尿素調(diào)控捕食線蟲真菌殺死其天敵線蟲,從而維持自身群體的穩(wěn)定,提示捕食與被捕食者之間的相互關(guān)系在維持自然界物種的平衡中起著重要的作用。
[Abstract]:In nature, food bacteria are considered as a passive victim of food for the nematode. As the food of the nematode, how does the group of bacteria survive and maintain dynamic balance with the predator, thus maintaining the balance of species in the natural ecosystem? This is an important scientific question suspended in the field of microbial ecology. The study reveals that these bacteria convert nematode fungi from saprophyte to parasitic life history - forming a predator, helping them to kill nematodes, making nematodes from predators to predators, thus achieving dynamic balance between the three species of bacteria, fungi and nematodes.
This study found that the induced activity of high temperature sterilized cow dung to oligospora trumpet predation was reduced by 6 times, and that cow dung bacteria could play a key role in the induction process. 126 strains of bacteria in cow dung were detected and 55 bacteria could induce the formation of predator. Subsequently, combined with column chromatography, activity tracing, mass spectrometry and other wave methods, urea was the active compound formed by the CD52 induced predator, and urea was broad-spectrum for different types of predatory fungi to induce nematode predatory fungi. A signal molecule morphogenetic in a food device.
In the reaction of arginine, arginase lysis of arginine produced ornithine and urea.RT-PCR analysis showed that arginine was expressed in active bacteria, and the expression amount was significantly increased under nematode stress. Then, the mutant SmAarcA was obtained by knockout of the arginase gene in CD52, and LC-MS detected that SmAarcA completely failed to produce urea and induced the formation of a predator. The rate is reduced by 60%, which confirms that bacteria regulate the formation of the preys by regulating the activity of arginase and excreting urea.
Genomic sequence analysis showed the presence of urea transporter and urease gene in the small sporospora. Isotopic [13C, 15N2]-urea traced: after knockout of transporter Utp79 gene, the mutant Ao Autp79 was completely undetected in the cytoplasm of Ao Autp79; however, the accumulation of intracellular isotopes in the urease mutant Ao Delta ure1 increased significantly. The mutants Ao Delta utp79 and Ao Delta ure1 can not be induced to produce a predator. Therefore, urea must be transported into the fungal cells to induce the formation of a predator through urease action. Urease catalyzes urea to produce ammonia and carbon dioxide in the urea cycle. Ammonia is a downstream signal molecule that induces a predator.
By studying the effects of bacteria on the development, offspring, life and food preference of nematodes, it is determined that urea producing bacteria have no effect on the growth and development of nematodes. These bacteria are the food bacteria of the nematode. Urea can spread efficiently in the soil as an underground signal molecule, and when the nematode is combined with the nematode, urea can significantly increase the formation of the predator. The dynamic relationship between the food bacteria in the soil, the nematode and the nematode trapping fungi in the soil, the dynamic relationship between the three groups of nematode and nematode fungi found that the food bacteria producing urea could increase the predation of the nematode predatory fungi. The predation of the nematode early 8h. was more important than that of the nematode predatory fungi. The number of bacteria saved in food helps to confirm that food bacteria control fungi produce more predators to kill nematodes.
In summary, food bacteria can produce urea to regulate the nematode predatory fungi to kill their natural enemy nematodes, thus maintaining the stability of their own populations, suggesting that the relationship between predators and predators plays an important role in maintaining the balance of natural species.

【學(xué)位授予單位】：云南大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：S432.45;S476.1

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相關(guān)期刊論文 前1條

1 董世娟,楊曉野,楊蓮茹,劉珍蓮;捕食線蟲性真菌——梨形指環(huán)菌的分離與鑒定[J];廣西農(nóng)業(yè)生物科學(xué);2004年01期

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本文編號：1885175