不同红树林地区老鼠簕内生放线菌的分离及其环境适应性

Isolation and environmental adaptation of endophytic Actinomycetes in Acanthus ilicifolius of different mangrove

【目的】比较不同红树林地区的老鼠簕内生放线菌的地理分布,了解内生放线菌与其所处环境的相关性。【方法】分别从5个不同地点的红树林采集老鼠簕全株植物,采用9种分离培养基,从植株不同部位分离内生放线菌,用16S rRNA基因序列分析鉴定到属,用添加不同NaCl浓度的ISP 2液体培养基进行耐盐度测试,用无氮基础培养基进行固氮活性测试。【结果】共分离得到内生放线菌52株,其中从叶、茎和根部分别获得5株、2株和45株,花和果中未分离到。52株内生放线菌分别属于小单孢菌属(47株),链霉菌属(3株),疣孢菌属(1株)和继生菌属(1株)。48株菌表现出耐盐或嗜盐特征,其中18株最高耐盐度20%,4株不能在无盐条件下生长,12株菌可在含有3.3%NaCl的培养基上生长良好。4株菌可在无氮培养基下生长。【结论】对47株内生小单孢菌的地理分布分析表明,老鼠簕内生小单孢菌的类群因不同地理位置有很大差异。耐盐和固氮活性测试结果表明了老鼠簕内生放线菌对环境的适应性。

[Objective] To investigate geographical distribution of Acanthus ilicifolius endophytic actinomycetes of different mangrove regions, and their environmental adaptation. [Methods] Endophytic actinomycete strains were isolated from different part of Acanthus ilicifolius plant collected from 5 mangrove sites using 9 different selective isolation media. Isolates were identificated to genus level using 16S rRNA gene sequence analysis. NaCl tolerance was tested using ISP 2 liquid medium supplement with different NaCl concentrations. Potential of nitrogen-fixation isolates were surveyed using nitrogen-free medium. [Results] A total of 52 endophytic actinomycete strains were successfully isolated from Acanthus ilicifolius plant, among which 5 isolates were from surface- sterilized leaves, 2 isolates from stems and the re-maining 45 isolates were from roots. Analysis of 16S rRNA gene sequences of these isolates showed that they belonged to members of the genera Jishengella （1 isolate）, Micromonospora （47 isolates）, Streptomycetes （3 isolates） and Verrucosispora （1 isolate）. Forty eight isolates were halo-tolerant or halophilic, including 18 isolates exhibited highest tolerance come up to 20% NaCl, 4 isolates can’t grow in salt-free medium, and 12 isolates exhibited good growth in presence of 3.3% NaCl. Meanwhile, 4 strains can grow on nitrogen-free medium that showed potential of nitrogen-fixation. [Conclusion] Analysis of 47 Micromonospora isolates from 5 mangrove locations indicated that there were different endophytic Micromonospora groups of Acanthus ilicifolius among different geographical sites. The results obtained revealed the en-vironmental adaptation of the Acanthus ilicifolius endophytic actinomycetes.