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[求助]
關(guān)于耐鉛細菌培養(yǎng)基的選擇:lb培養(yǎng)基和TMM培養(yǎng)基 已有1人參與
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求助各位大神,自從篩選耐鉛的細菌開始就一直被培養(yǎng)基的問題所困擾。。。 LB培養(yǎng)基因為營養(yǎng)成分復(fù)雜,加入鉛之后,液體中的鉛的有效濃度會低于其加入濃度(文獻中也多有討論),而且加入一點點的鉛也會有沉淀,呈渾濁的樣子。 后來就查了一些文獻,發(fā)現(xiàn)大家都用TMM培養(yǎng)基(tris buffer 培養(yǎng)基,原始文獻是Mergeay, 1985),后來又找了一篇文獻,也是引用的TMM培養(yǎng)基,寫的比較詳細。完全按照文獻中的方法配制(滅菌時沒有加葡萄糖碳源),加入1mM硝酸鉛,還是有沉淀。 關(guān)于附件方法中的tris-HCl 6.06g,我是參照了原始文獻說tris6.06g加的,然后沒有調(diào)PH(因為文獻里也沒有提出來),滅菌,發(fā)現(xiàn)PH約9.0,直接加鉛有沉淀;用鹽酸或者硝酸調(diào)ph=7之后,加鉛還是有沉淀。 對于絕大部分文獻都選用的這個培養(yǎng)基讓我折騰這么久還是不行,我也是要崩潰了。。。 跪求各位大神,幫我分析一下原因出在哪里呀。。。。 |
新蟲 (初入文壇)
轉(zhuǎn)貼,信息來自Eugeniusz Małkowski (University of Silesia in Katowice), 希望有幫助,![]() Lead is one of the most difficult metal to investigate in laboratory experiments, because it very easily precipitates or forms complex ions. I conducted a large number of experiments with Pb and observed many unique chemical properties of this metal. 1. Effect of pH I observed precipitation of Pb when pH of solutions was higher than 6.1-6.3. I observed this process even if I dissolved in the water only salt of Pb (PbCl2 or Pb(NO3)2, without any other chemical compounds. This precipitation is connected with Hydrolysis and can be easily overlooked if concentration of Pb is lower than 0.5-1.0 mM. Conclusion: If pH of your LB media was above 6.1-6.3. most of Pb could precipitate. If you want to conduct experiments with lead pH of nutrient solutions or any media has to be maximum 5.9-6,0 2. Effect of phosphates Lead very easy and quickly precipitates with phosphates and this reaction is observed irrespective of pH of solution. The product of this precipitation is not Pb3(PO4)2 but different types of pyromorphites, for example Pb5(PO4)3Cl. All pyromorphites are almost insoluble compounds. The formation of pyromorphites is connected with a large drop of pH of nutrient solution or media, which depends on the concentration of Pb salts (a higher concentration of Pb the higher drop of pH) and buffering capacity of solution. Plant physiologist use complete nutrient solutions to grow plants and for a treatment with Pb (one to several days) phosphates are removed from both control solutions and experimental (with Pb) solutions. Conclusion: Use of phosphate buffer in experiments with Pb is not acceptable, because even all Pb can be precipitated. However, it could be possible to use the standard media, but for the time of treatment with Pb phosphates have to be removed from the media. |
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