Microbial Ecology, Department of Biology, Universität Konstanz, D-78465 Konstanz, Germany.
Microbiology (Reading). 2010 Aug;156(Pt 8):2428-2437. doi: 10.1099/mic.0.036004-0. Epub 2010 May 6.
In anaerobic enrichment cultures for phototrophic nitrite-oxidizing bacteria from different freshwater sites, two different cell types, i.e. non-motile cocci and motile, rod-shaped bacteria, always outnumbered all other bacteria. Most-probable-number (MPN) dilution series with samples from two freshwater sites yielded only low numbers (<or=3x10(3) cm(-3)) of phototrophic nitrite oxidizers. Slightly higher numbers (about 10(4) cm(-3)) were found in activated sewage sludge. Anaerobic phototrophic oxidation of nitrite was studied with two different isolates, the phototrophic sulfur bacterium strain KS1 and the purple nonsulfur bacterium strain LQ17, both of which were isolated from activated sludge collected from the municipal sewage treatment plant in Konstanz, Germany. Strain KS1 converted 1 mM nitrite stoichiometrically to nitrate with concomitant formation of cell matter within 2-3 days, whereas strain LQ17 oxidized only up to 60 % of the given nitrite to nitrate within several months with the concomitant formation of cell biomass. Nitrite oxidation to nitrate was strictly light-dependent and required the presence of molybdenum in the medium. Nitrite was oxidized in both the presence and absence of oxygen. Nitrite inhibited growth at concentrations higher than 2 mM. Hydroxylamine and hydrazine were found to be toxic to the phototrophs in the range 5-50 muM and did not stimulate phototrophic growth. Based on morphology, substrate-utilization pattern, in vivo absorption spectra, and 16S rRNA gene sequence similarity, strain KS1 was assigned to the genus Thiocapsa and strain LQ17 to the genus Rhodopseudomonas. Also, Thiocapsa roseopersicina strains DSM 217 and DSM 221 were found to oxidize nitrite to nitrate with concomitant growth. We conclude that the ability to use nitrite phototrophically as electron donor is widespread in nature, but low MPN counts indicate that its contribution to nitrite oxidation in the studied habitats is rather limited.
在来自不同淡水地点的光养亚硝酸盐氧化细菌的厌氧富集培养物中，两种不同的细胞类型，即非运动球菌和运动、杆状细菌，总是比所有其他细菌都多。来自两个淡水地点的最可能数（MPN）稀释系列样品仅产生低数量（<或=3x10(3)cm(-3))的光养亚硝酸盐氧化菌。在活性污水污泥中发现的数量略高（约 10(4)cm(-3))。使用两种不同的分离物研究了亚硝酸盐的厌氧光养氧化，即光养硫细菌菌株 KS1 和紫色非硫细菌菌株 LQ17，它们均从德国康斯坦茨市的城市污水处理厂的活性污泥中分离出来。KS1 菌株在 2-3 天内将 1mM 亚硝酸盐转化为硝酸盐，并同时形成细胞物质，而 LQ17 菌株则在数月内仅将给定的亚硝酸盐氧化至 60%的硝酸盐，并同时形成细胞生物质。亚硝酸盐氧化为硝酸盐严格依赖于光，并且需要培养基中存在钼。在有氧和无氧的情况下都可以氧化亚硝酸盐。亚硝酸盐在浓度高于 2mM 时会抑制生长。在 5-50μM 的范围内，发现羟胺和肼对光养生物有毒，并且不会刺激光养生长。基于形态、底物利用模式、体内吸收光谱和 16S rRNA 基因序列相似性，KS1 菌株被分配到 Thiocapsa 属，LQ17 菌株被分配到 Rhodopseudomonas 属。此外，还发现 Thiocapsa roseopersicina 菌株 DSM 217 和 DSM 221 能够将亚硝酸盐氧化为硝酸盐，并伴随着生长。我们得出结论，作为电子供体光养使用亚硝酸盐的能力在自然界中广泛存在，但低 MPN 计数表明，其对研究栖息地中亚硝酸盐氧化的贡献相当有限。
