粪产碱菌(Alcaligenes faecalis)吸收氢和同化CO_2的特性

H_2 Uptake and Carbon Dioxide Assimilation in Alcaligenes faecalis

应用同位素氚(T_2)和~13C(~13CO_2),证明了水稻联合固氮菌——粪产碱菌A—15是一种含有吸氢酶的兼性化能自养细菌,具有较强的吸氢能力,吸氨酶活性可达到13.11μmol H_2 ml^(-1) cultureh^(-1);同时,它还可利用H_2为能源同化CO_2营化能自养生活,其RuBPC活性为24.65 nmolCO_2 mg^(-1) protein min^(-1)。无论在自养还是异养条件下,H_2都支持、并促进固氮活性。粪产碱菌培养在N_2条件下比在NH_4^+条件下能积累更多的多聚-β羟基丁酸(PHB)。

By using T_2 tracer, it has been shown that the associative nitrogen-fixer Alcaligenes faecalis A--15 contains hydrogen uptake hydrogenase (Table 1). It could reduce TTC under a hy- drogen atmosphere. A. faecalis possesses rather high hydrogenase activity, and the maximum activity may reach 13.11 μmol H_2-uptake ml^(-1) culture h^(-1) (Fig. 1). A. faecalis could grow on N- and C-free culture medium supplied with CO_2. It utilizes and assimilates ^(13)CO^2 as the sole carbon source for its growth and fix dinitro- gen (Table. 2). A.faecalis contains RuBP car- boxylase when it grows under chemolithotrophic condition. The maximum activity of RuBP carboxylase is 24.65 nmol CO_2 fixed mg^(-1) pro- tein min^(-1) (Table. 3). Refractile lipoid (poly β-hydroxy butyrate, PHB) bodies occurred in the cells of A.faecalis. The content of PHB is higher in the N_2-grown cells than that in the NH_4^+ -grown cells (Fig. 2). The results also show that molecular hydrogen supports the nitrogen-fixing activity either in the presence or in the absence of carbon source is the culture medium (Table 4, 5). However the nitrogen- fixing rate supported by molecular hydrogen in the abscence of carbon source is higher than that in the presence of it. Nitrogenase activities decreased when the H_2 content was higher than 30% in the absence of carbon source and 25% in the presence of carbon source, respectively.