一株培菌白蚁后肠木聚糖降解细菌的分离与鉴定

Isolation and identification of xylan-degradation bacteria from hindgut of fungus-growing termite

【目的】从培菌白蚁——黄翅大白蚁肠道微生物菌群中分离能降解木聚糖的细菌。【方法】以木聚糖为唯一碳源,利用刚果红染色,根据透明圈大小进行筛选。通过显微形态,革兰氏染色及16S r RNA基因序列分析进行菌株鉴定。二硝基水杨酸(DNS)法测定细菌生长过程中木聚糖酶酶活变化,比较酶活与菌株生长状况的关系。【结果】从黄翅大白蚁肠道中筛选到一株具有较高木聚糖降解活性的革兰氏阳性菌Mb1,16S r RNA基因序列分析表明为类芽孢杆菌属细菌,命名为Paenibacillus sp.Mb1。该菌培养72 h后菌体浓度达到最高,木聚糖酶酶活主要存在于培养液上清中,酶活在对数期增长快,在培养96 h时达到最高值,之后趋于稳定。【结论】从黄翅大白蚁肠道中分离出一株具有较高木聚糖酶活的类芽孢杆菌,可作为产细菌木聚糖酶的潜在优良菌株。

[Objective] The study aims to isolate and identify xylan-degradation bacteria from the gut of a fungus-growing termite——Macrotermes barneyi. [Methods] Using an oligotrophic medium containing birchwood xylan as the only carbon source and Congo red activity staining method, we obtained a xylan-degradation bacteria based on the transparent zone around the clone and the bacteria was identified by microscope morphology, Gram-staining and 16 S r RNA gene sequence analysis. To learn the distribution of the xylanase, cell growth curve and xylanase assay of intercellular and extracellular activities were investigated using DNS method. [Results] The xylan-degradation strain, isolated from the gut of M. barneyi, was named as Paenibacillus sp. Mb1. The strain grew to a high level at 72 h. Paenibacillus sp. Mb1 secreted extracellular xylanase at a rapid rate in the exponential phase, and reached to the maximal xylanase production at 96 h, then kept steady until the end of Mb1 cultivation. [Conclusion] Paenibacillus sp. Mb1 with high xylanolytic activity have been isolated from the hindgut of M. barneyi. It might be a good candidate strain in studying termite xylan degradation and biomass conversion.