Studies on alcohol tolerance of Zymomonas mobilis cell envelope

1. 从野竹的膜脂中分离到一种游离神经酰胺，其分子种类为n -2-棕榈酰-1,3-二羟基十六烷。2. 从紫霉中分离到一个PE n -甲基转移酶缺陷突变体，该突变体对PE、PMME和PDME的3种酶活性均完全缺陷。从该突变体获得的两个回复性菌株恢复了所有三种酶的活性，几乎达到了野生型菌株的水平，这表明在Z. mobilis中，该途径中的三步甲基化可能是由一种酶催化的。从Z. mobilis中分离到一个缺乏四羟基细菌藿烷（THBH）生物合成的突变体，为耐制氨抑素突变体。定量分析表明，四氢大麻酚含量降至亲本菌株的20%左右。该突变体表现出对高葡萄糖浓度敏感，但对高乙醇浓度耐受，这表明在Z. mobilis中，THBH可能是耐受前者的原因。从青霉中分离到THBH增加的突变株，其THBH含量增加到亲本株的3倍左右。在THBH缺陷突变体和THBH增加突变体中，对THBH、葡萄糖胺-THBH和碳环假葡糖-THBH的定量分析表明，这些类hopoid的侧链，四羟基戊烷、三羟基戊烯基葡萄糖胺和三羟基戊烯基碳环假葡糖，在类hopoid的生物合成中将被独立地纳入到hopane骨架中。

1. A free ceramide was isolated from membrane lipids of Z. mobilis and its molecular species was shown to be N-2-palmitoyl-1,3-dihydroxyhexadecane. 2. A PE N-methyltransferase-defective mutant was isolated from Z. mobilis, which was completely defective in all the three enzyme activities dependent on PE, PMME and PDME. Two revertants derived from the mutant recovered all the three enzyme activities to nearly the same levels of the wild type strain, suggesting that in Z. mobilis the three-step methylation in the pathway would be catalyzed by a single enzyme.3. A mutant deficient in tetrahydroxybacteriohopane (THBH) biosynthesis was isolated from Z. mobilis as a nystatin-resistant mutant. Quantitative analysis showed that the THBH content was reduced to about 20 % of that of the parent strain. The mutant exhibited to be sensitive to a high glucose concentration but tolerant to a high ethanol concentration, suggesting that in Z. mobilis the THBH might be responsible for tolerant to the former.4. A THBH-increased mutant was isolated from Z. mobiles, of which the THBH content was increased to about 3 times of that of the parent strain. Quantitative analysis of THBH, glucosamine-THBH and carbocyclic pseudopentose-THBH, in THBH-defective mutant and THBH-increased mutant suggests that the side-chains of those hopanoids, tetra- hydroxypentane, trihydroxypentenyl glucosamine and trihydroxypentenyl carbocyclic pseudopentose, would be independently incorporated into the hopane skeleton in hopanoid biosynthesis.