Research On Cellulolytic Bacteria In Songnen Leymus Chinensis Grassland

We have isolated 48 cellulolytic strains from soil sample with Leymus chinensis litter which can make use of sodium carboxymethyl cellulose to grow well. We obtain 14 cellulose degradation bacteria strains initially after removal of the similarity and the same strain to do the further research.1. Nine isolates were confirmed as the species of Streptomyces, and one as the species of Ochrobactrum,one of genus Enterobacter,one of genus Agrobacterium,one of genus Stenotrophomonas and one of genus Pseudomonas. The 16 SrDNA nucleic acid sequences were submitted to genbank,we have obtained the strains sequence accession numbers: KJ716528-KJ716541.Almost all the isolated strains can grow well on the culture medium with maltose, xylose, mannitol, lactose,sucrose, glucose, dextrin as carbon source.Most strains were able to produce extracellular amylase to utilizate starch and produce significant hydrolysis circle. All strains can grow well on the medium with 4% NaCl and pH 10.5 conditions, showing some of the saline alkaline tolerance. Some strains showed positive reaction in the fermentation of sugar, methyl red test, V.P test with acid production trend.2. The CMC cellulase activity of 14 isolates was analyzed in this experiment. CMCase production properties of the isolates suggest that most of the strains were able to produce CMCase. When they make use of the straw fiber as substrate, approximately 1.5 to 2.0 times when they decompose CMC substrates. The strains which were isolated from soil samples in August showed higher cellulose activity, such as Sn-1,Sn-7,Sn-8,Sn-9,Sn-10; Streptomyces is most likely the dominant cellulolytic strains in the Songnen Leymus chinensis grassland, showing higher enzyme activity.3. Xylanase activities were observed in all the 14 isolates moreover most of the xylanase activities in the isolates were even higher than those of cellulose, Streptomyces Sn-9 xylanase was the highest about 0.67 IU/mL.4. All the bacteria strains were capable of growing on nitrogen-free CMC cellulose media and means that all the strains were cellulolytic nitrogen fixing bacteria. Acetylene reduction method was used in strains nitrogenase activities analyses, the strains nitrogenase activity were 2.20~4.44 nmol nmolC2H4 h-1mL-1. We added 0.2% NaCl 1.2% NaCl in liquid fermentation experiments, nitrogenase activities were measured. Different concentrations of NaCl also have a certain effect on the nitrogenase activity. Streptomyces Sn-13 was identified the highest nitrogenase activity about 3.04nmolC2H4h-1mL-1 on ashby culture with 0.2% NaCl and 3.14 nmolC2H4 h-1mL-1 on ashby culture with 1.2% NaCl.5. In addition, the growth promoting effect of isolates was studied.All the isolated strains were capable of producing IAA which would stimulate plants growth,Sn-6 was identified the strongest capacity of producing IAA, almost up to 66.67mg/L; comparison of the different strains on producing IAA capacity suggest that Streptomyces can be measured higher yield of IAA. Some of isolates such as Sn-5 and Sn-6 exhibited phosphate-solubilizing activities with forming clear rings around colonies on GY agar plates and Siderophore production capacity. All strains were not detected significant production of ACC deaminase activity.Determination of the antibacterial activity showed that the antibacterial activity of Streptomyces fermentation liquid were better on E.coli. than Staphylococcus. Sn-5 and Sn-9 have good antibacterial activity on both E.coli. and Staphylococcus aureus, the antibacterial circle is more obvious than other strains.6. We applied the Indigenous strain Sn-5 and the exogenous alkaline bacterial to Leymus chinensis grassland to analyze the growth-promoting effect and compare the differences between two treatments. ANOVA analysis shows no significant difference between Leymus chinensis dry weight and wet weight. After experimental treatment, plant height were significantly higher than the control group, Sn-5 was significantly higher than alkaline bacteria, and two kinds of treatment were significantly higher than control. There are no significant difference after treatment on Leymus chinensis branch number.