Acetate Assimilation by Nitrobacter agilis in Relation to Its “Obligate Autotrophy”
Acetate Assimilation by Nitrobacter agilis in Relation to Its “Obligate Autotrophy”
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DOI：
10.1128/jb.95.3.844-855.1968
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发表时间：
1968-03
影响因子：
3.2
通讯作者：
A. Smith;D. S. Hoare
中科院分区：
文献类型：
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作者：
A. Smith;D. S. Hoare
乙酸盐（1至10毫米）对亚硝酸盐氧化率或敏捷硝化杆菌的指数生长没有影响。然而，乙酸-1-14 C和-2-14 C都被生长的培养物同化，乙酸碳贡献了新合成的细胞碳的33%至39%。来自乙酸的碳被掺入所有主要细胞成分中，包括细胞蛋白质和聚-β-羟基丁酸酯（PHB）的大多数氨基酸。在醋酸盐存在下生长的培养物显示出浑浊度显着增加，部分原因是蛋白质合成和“指数后阶段”（亚硝酸盐供应完全耗尽时）中PHB的积累。细胞悬液; Agilis在不存在碳酸氢盐甚至不存在亚硝酸盐的情况下同化乙酸盐。然而，亚硝酸盐的加入增加了乙酸同化率的细胞悬浮液。14 C-乙酸酯的分布纳入细胞悬浮液定性发现与生长的文化。N. Agilis缓慢地将乙酸盐氧化成CO2。此外，亚硝酸盐抑制CO2生产乙酸，但增加了同化的乙酸碳到细胞材料。N. Agilis含有三羧酸循环的所有酶。N.的生长在乙酸盐存在下的Agilis没有显著影响三羧酸循环的酶的水平，但确实导致异柠檬酸酶的比活性增加100倍。相反，羧基歧化酶被部分抑制。N. Agilis在含有乙酸盐和酪蛋白水解产物的培养基上通过七次转移进行异养生长。亚硝酸盐的添加增加了异养生长的速率。异养生长的生物体仍然保留了与亚硝酸盐一起自养生长的能力。然而，这些生物氧化亚硝酸盐的速度较慢。分析了来自自养和异养培养物的微生物，以确定其脱氧核糖核酸的平均鸟嘌呤加胞嘧啶含量;在两种情况下，平均值均为61.2 ± 1%。我们的结论是N. Agilis不是专性自养生物;它似乎是兼性自养生物，与新的兼性自养生物中间硫杆菌（Thiobacillusintermedius）非常相似。
Acetate (1 to 10 mm) had no effect on the rate of nitrite oxidation or exponential growth by Nitrobacter agilis. However, acetate-1-14C and -2-14C were both assimilated by growing cultures, and acetate carbon contributed 33 to 39% of newly synthesized cell carbon. Carbon from acetate was incorporated into all of the major cell constituents, including most of the amino acids of cell protein and poly-β-hydroxybutyrate (PHB). Cultures grown in the presence of acetate showed a significant increase in turbidity, attributable in part to protein synthesis and the accumulation of PHB in the “post-exponential phase,” when the supply of nitrite was completely exhausted. Cell suspensons of N. agilis assimilated acetate in the absence of bicarbonate and even in the absence of nitrite. However, the addition of nitrite increased the rate of acetate assimilation by cell suspensions. The distribution of 14C-acetate incorporated by cell suspensions was qualitatively similar to that found with growing cultures. Cell suspensions of N. agilis slowly oxidized acetate to CO2. Addition of nitrite suppressed CO2 production from acetate but increased the assimilation of acetate carbon into cell material. N. agilis contained all the enzymes of the tricarboxylic acid cycle. Growth of N. agilis in the presence of acetate did not significantly affect the levels of the enzymes of the tricarboxylic acid cycle, but did result in a 100-fold increase in the specific activity of isocitratase. In contrast, carboxydismutase was partially repressed. N. agilis was grown heterotrophically through seven transfers on a medium containing acetate and casein hydrolysate. The addition of nitrite increased the rate of heterotrophic growth. Heterotrophically grown organisms still retained their ability to grow autotrophically with nitrite. However, these organisms oxidized nitrite at a slower rate. Organisms from autotrophic and heterotrophic cultures were analyzed to determine the mean guanine plus cytosine content of their deoxyribonucleic acid; in both cases this mean was 61.2 ± 1%. We concluded that N. agilis is not an obligate autotroph; it appears to be a facultative autotroph which resembles the novel facultative autotroph, Thiobacillus intermedius, very closely.