Abstract:

To provide excellent microbial agents for straw ripening and returning to the field in the cold and cool areas of Inner Mongolia, it is necessary to clarify the composition of low-temperature straw degradation complex strains. The compound strain-8, which can degrade corn straw under the laboratory condition of 15℃, was used as the material. A single strain was isolated from the selective medium-sodium carboxymethylcellulose solid medium, and identified by morphology, physiological and biochemical characteristics, 16S rRNA of bacteria, ITS rDNA of fungi and ß- ubulin gene sequence analysis. The results showed that fungus 8-F and bacterium 8-B were isolated from No. 8 strain with sodium carboxymethylcellulose solid medium. The morphological characteristics of 8-F colony were powdery white, felt-like and gram-negative. The hyphae were often twined into ropes. The conidial peduncle was tree-like or grape-spike branched, with a diameter of 1.5-2.0 μm. The conidia were terminal or intermediate, inverted pear-shaped, and (2.5-4.5)×(2.0-3.0) μm in size. The comparison of ITS rDNA sequence with the data system in GenBank database showed that it had 99% homology with Geomyces sp.. According to the above characteristics, it was identified as Geomyces pannorum. The cell of 8-B strain was rod-shaped, gram-negative, non-sporogenic, and its colony was light yellow and irregular in shape. It could produce 10 enzymes and use 37 carbon sources. Its 16S rDNA sequence had 99.71% homology with Stenotrophomonas humi, and was identified as Stenotrophomonas sp. according to the above characteristics. The dominant strains of the composite strains that could degrade corn straw under low temperature (15℃) laboratory conditions were Geomycos pannorum and Stenotrophomonas maltohilia.

Key words: enrichment, domestication, Geomyces pannorum, Stenotrophomonas maltophilia