ABSTRACT Excessive input of nitrogen fertilizer causes nitrogen pollution in aquatic environments. Utilizing microbial inoculants seems to be effective in decreasing the extent of nitrogen fertilizer application. Genome sequencing analysis of Azoarcus sp. strain KH32C, which was isolated from a paddy-upland rotation paddy field in Japan, showed that the strain may interact with plants. In this study, we examined the effect of inoculation of rice seeds with strain KH32C as a bacterial inoculant in paddy fields without nitrogen fertilization. Rice of three cultivars inoculated with strain KH32C were cultivated in paddy fields with different soil carbon and nitrogen levels. We investigated the growth rate of rice plants and the elemental composition of brown rice. In addition, the bacterial community structures in the rice root-associated soil were examined using molecular genetic analysis. KH32C inoculation resulted in an increase in the rice plant growth rate in the early growth phase with cultivar Nipponbare. Elemental composition analysis showed that the zinc concentration in brown rice of Nipponbare was increased by KH32C inoculation. KH32C inoculation affected the bacterial community in Nipponbare root-associated soil. The community of potential plant growth-promoting bacteria, the majority of which were in the class Alphaproteobacteria, had relatively high abundance in the early growth stage after KH32C inoculation. Our results indicated that strain KH32C can be utilized as a bacterial inoculant with the effect of promoting rice growth and enhancing the zinc content of rice grains in low nitrogen input paddy fields.

中文翻译：

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固氮弧菌 KH32C菌株影响低氮输入稻田水稻植株生长和根系相关土壤细菌群落

摘要 氮肥的过量投入导致水生环境中的氮污染。使用微生物接种剂似乎可以有效减少氮肥的施用量。Azoarcus sp. 基因组测序分析。菌株 KH32C 是从日本的旱田轮作稻田中分离出来的，表明该菌株可能与植物相互作用。在这项研究中，我们研究了在不施氮肥的稻田中用菌株 KH32C 作为细菌接种剂接种水稻种子的效果。在不同土壤碳和氮水平的稻田中种植了接种 KH32C 菌株的三个品种的水稻。我们调查了水稻植株的生长速度和糙米的元素组成。此外，使用分子遗传分析检查水稻根系相关土壤中的细菌群落结构。KH32C 接种导致水稻生长早期与栽培品种 Nipponbare 的生长速率增加。元素组成分析表明，接种KH32C可提高日本晴糙米中锌的含量。KH32C 接种影响了日本晴根相关土壤中的细菌群落。潜在的植物促生长菌群落在接种 KH32C 后的早期生长阶段具有相对较高的丰度，其中大部分属于 Alphaproteobacteria 类。