Study On Antimicrobial Activity Of Rhizosphere And Endophytic Actinomycetes From Peucedanum Praeruptorum Dunn And Identification Of Two New Species

Actinomycetes is a kind of microbial resources with extensive biological activity and its metabolites have diverse biological functions and chemical structures. The most commonly used antibiotics are producted by actinomycetes. In addition, the productions of actinomycetes have functions such as regulating plant growth, enzymatic activity, anti-tumor and so on. In recent years, the ratio that isolated new active substances from actinomycetes was declining. In order to increase the separation rate of new active metabolites, avoid repeated isolation of known compounds, researchers pay attention to the actinomycetes in special habitats, such as animals and plants endophytic actinomycetes and actinomycetes in extreme environments. This study aims to explore the plant endophytic and rhizosphere actinomycetes resources and find new actinomyces and biological active substances in medicinal plant and its rhizosphere.Traditional medicinal plant baihuaqianhu(Peucedanum praeruptorum Dunn) and its rhizosphere soil were collected as the source of separation. A total of 54 actinomycetes were isolated after repeated separation and purification. Oxford cup method and cross crossover method were applied to determine the antibacterial activity of the fermentation extract of 54 actinomycetes strains against two kinds of pathogenic bacteria and 14 kinds of pathogenic fungi respectively. Results showed that the bacteriostatic diameter of the fermentation extract of 3 actinomycetes strains against two kinds of bacteria reached 15 mm and the activity of 10 strains against pathogenic fungi were obvious. Among them, the bacteriostatic diameter of the fermentation extract of QH24, QH35 and QH36 against 2 kinds of pathogenic fungi could exceeded 15 mm. Hence, the three strains deserve further investigation.Strains NEAU-KD1 and NEAU-QHHV11 were chosen to perform 16 S r RNA gene sequence analysis after morphological features comparison and microscope analysis. The results of sequence alignment and phylogenetic tree construction showed that: strain NEAU-KD1 belongs to Mumia genera and NEAU-QHHV11 belongs to Streptomyces. Mumia flava NBRC 109973T(97.63 %) is highest similar to NEAU-KD1. While, Streptomyces graminilatus JL-6T(98.7%) and strain Streptomyces turgidiscabies ATCC 700248T(98.65%) have highest similarity to NEAU-QHHV11. Throughout the comparison with its similar strains in phenotypic characteristics, physiological and biochemical characteristics, chemical characteristics and the analysis of the molecular level, strain NEAU-KD1 and NEAU-QHHV11 respectively were in accordance with the basic characteristics of Mumia and Streptomyces. And it had obvious difference with other strains of the genus. Therefore, it could be concluded that the strain NEAU KD1 and NEAU QHHV11 were new spec ies of Mumia and Streptomyces, respectively. The strain NEAU-KD1 was named as Mumia xiangluensis. While, NEAU-QHHV11 was named as Streptomyces castaneus.