Department of Microbiology, University of New Hampshire, Durham, New Hampshire 03824.
Appl Environ Microbiol. 1992 Apr;58(4):1102-9. doi: 10.1128/aem.58.4.1102-1109.1992.
Under anaerobic conditions and in the absence of alternative electron acceptors, growth of the magnetic bacterium Aquaspirillum magnetotacticum MSI was iron concentration dependent. Weak chelation of the iron (with quinate, oxalate, or 2,3-dihydroxybenzoate) enhanced growth, whereas strong chelation (with EDTA, citrate, or nitrilotriacetic acid) retarded the growth of strain MSI relative to that of controls lacking chelators. Growth was proportional to the percentage of unchelated iron in medium containing EDTA in various molar ratios to iron. Addition of the respiratory inhibitors antimycin A (5 muM), NaCN (10 mM), and NaN(3) (10 mM) inhibited growth with Fe(III) or NO(3) as the terminal electron acceptor. Growth with O(2) and NO(3) was inhibited by 2-heptyl-4-hydroxyquinolone-N-oxide (HOQNO) but not with 2 mM Fe(III). Under strongly reducing conditions, strain MS1 survived but grew poorly and became irreversibly nonmagnetic. Growth and iron reduction in anaerobic cultures were stimulated by the provision of small amounts of O(2) or H(2)O(2). Slow infusion of air to cultures which had reduced virtually all of the Fe(III) in the medium (2 mM) supported a high rate of iron reoxidation (relative to killed controls) and growth in proportion to the amount of iron reoxidized. Oxygen consumption by iron-reducing cultures was predominantly biological, since NaCN and HOQNO both inhibited consumption. Inhibition of oxygen consumption (and iron reoxidation) by the addition of ferrozine and the inhibition of iron oxidation (and oxygen consumption) by the addition of HOQNO suggest that iron oxidation by strain MS1 is an aerobic respiratory process, perhaps tied to energy conservation. Iron oxidation was also necessary for magnetite synthesis, since in microaerobic denitrifying cultures, sequestration of reduced iron by ferrozine present in 10-fold molar excess to the available iron resulted in loss of magnetism and a severe drop in the average magnetosome number of the cells.
在无氧条件下且不存在替代电子受体的情况下，磁性细菌 Aquaspirillum magnetotacticum MSI 的生长依赖于铁浓度。铁的弱螯合（与奎宁酸、草酸盐或 2,3-二羟基苯甲酸）会促进生长，而强螯合（与 EDTA、柠檬酸盐或氮三乙酸）则会使 MSI 菌株的生长相对于缺乏螯合剂的对照物减慢。生长与介质中 EDTA 与铁的各种摩尔比的未螯合铁的百分比成正比。在含有 EDTA 的介质中，添加呼吸抑制剂安密妥酸（5 μM）、NaCN（10 mM）和 NaN3（10 mM）会抑制以 Fe(III) 或 NO3-为末端电子受体的生长。以 O2 和 NO3-为电子受体的生长会被 2-庚基-4-羟基喹啉-N-氧化物（HOQNO）抑制，但不会被 2 mM Fe(III) 抑制。在强还原条件下，MS1 菌株存活但生长不良且变得不可逆地非磁性。在厌氧培养物中，少量 O2 或 H2O2 的提供会刺激生长和铁还原。向培养基中几乎还原了所有 Fe(III)（2 mM）的培养物中缓慢注入空气，支持铁的高再氧化速率（相对于死亡对照物），并与再氧化的铁量成正比。铁还原培养物的耗氧量主要是生物性的，因为 NaCN 和 HOQNO 都抑制了耗氧量。亚铁嗪的添加抑制了氧消耗（和铁再氧化），而 HOQNO 的添加抑制了铁氧化（和氧消耗），这表明 MS1 菌株的铁氧化是一种需氧呼吸过程，可能与能量守恒有关。铁氧化对于磁铁矿的合成也是必要的，因为在微需氧反硝化培养物中，存在于 10 倍摩尔过量的可用铁的亚铁嗪螯合还原铁会导致磁性丧失和细胞平均磁体数严重下降。
