光合细菌Rhodobacter sphaeroides的醋酸代谢

Acetic Acid Metabolism Of Photosynthetic Bacteria (PSB) Rhodobacter sphaeroides

利用PSB处理高浓度有机废水是一项十分诱人的废水处理新技术和废水资源化途径。本文就R.sphaeroides对醋酸的利用性,共存有机酸对醋酸代谢的影响进行了试验研究,并对它醋酸代谢的可能途径作了探讨。 R.sphaeroides生长的最适醋酸浓度为25 mmnol.dm^(-3),醋酸浓度增至200mmol.dm^(-3)时,虽然R.sphaeroides迟缓期长达24小时以上,但仍能缓慢地生长。共存的琥珀酸对R.sphaeroides的醋酸代谢有明显影响。当TCA循环中的α-酮戊二酸脱氢酶被抑制时,R.sphae-roides的生长几乎完全受阻,当乌头酸酶被抑制时,醋酸仍能被利用。R.sphaeroides中有苹果酸合成酶活性,没检测到异柠檬酸裂介酶和高柠檬酸合成酶的活性。因而R.sphaeroides可能既不通过TCA循环右半部分和乙醛酸循环生成乙醛酸,也不通过高柠檬酸循环生成乙醛酸,进而由苹果酸的合成而生成草酰乙酸。

Utilization of ace acetic acid by R. sphaeroides, influence of organic acids presented on acetic acid metabolism and most probable pathway of acetic acid metabolism are examined. The most optimal growth concentration of acetic acid for R. sphaeroides is 25 mmmol.din^(-3), but it also can growth slowly with increacing acetic acid concentration until 200 mmol·dm^(-3), in this condition lag phase is more than 24 hours. When a-ketoglutarate dehydrogenase in the TCA circle is repressed, the growth of R. sphaeroides will be almost obstructed completely. When aconitase is repressed, acetate can be still utlized. As there is malate synthase activity among R. sphaeroides, we find neither isocitrate lyase activity nor homocitrate synthase activity. Therefore, it is possible that R. sphaeroides will metabolize acetate and grow glyoxylate without passing by the right part of TCA circle and the glyoxylate circle and homocitrste circle, and finally get oxaloacetate by synthesis of malate.