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Thesis - University Access Only
Master of Science (MS)
Biology and Microbiology
Plants in nature associate with a diverse community of endophytic bacteria which can positively affect plant growth. A total of thirty-three putative endophytic bacteria were isolated from four different plants (Typha, Bromus tectorum, Festuca, and Nasturtium officinale) growing on stream banks in Hot Springs, SD. These isolated bacterial endophytes were identified and screened in vitro for Gram stain, Gram morphology, and colony morphology, (with 22 bacterial isolates being Gram positive and 11 being Gram negative). Bacterial isolates exhibiting a difference in morphological features were selected for molecular identification through partial 16S rRNA gene sequencing, which led to their identification as strains of Bacillus thuringienisis, B. cereus, B. atrophaeus, Pseudomonas sp., Cedecea davisae, Escherichia sp., Acinetobacter calcoaceticus, Lysinobacillus sp., Pantoea sp., and Citrobacter freundii. All 33 bacterial isolates were screened for different activities known to promote plant growth. Isolates identified as Pseudomonas sp., and Bacillus cereus were able to produce siderophore in vitro. Eleven isolates identified as Pseudomonas sp., Citrobacter freundii, Acinetobacter calcoaceticus, Pantoea sp., Cedecea davisae /Escherichia sp., and Bacillus thuringiensis solubilized insoluble phosphate in Pikovskya’s agar plates. The quantitative determination of the phytohoromones gibberellic acid (GA), and indole acetic acid (IAA) was done for all isolates by spectrophotometric xiii assay. The bacterial isolates produced gibberellic acid (GA) ranging from 0.09 to 0.35 mg/ml, and Indole acetic acid (IAA) ranging from 0.02 to 0.1 mg/ml. The 1-aminocyclopropane-1-carboxylate deaminase (ACC) activity produced by bacterial isolates was also assayed, twenty-two isolates were found to be positive for ACC deaminase activity, generated α-ketobutyrate from ACC ranging from 0.12 to 0.37 mM. Strains of Pseudomonas sp., Bacillus thuringienisis, B. cereus, B. atrophaeus, and Lysinbacillus sp. were antagonistic to mycelial growth of Fusarium graminearum. Moreover, Bacillus thuringienisis, B. cereus, and B. atrophaeus strains were able to produce chitinase to inhibit plant pathogens. Hence, the results indicate that the bacterial isolates may be used as promising microbial inoculants for plant growth and productivity.
Library of Congress Subject Headings
Includes bibliographical references (pages 101-110)
Number of Pages
South Dakota State University
In Copyright - Educational Use Permitted
Ashkan, Mada, "Identification and Screening of Putative Endophytic Bacteria for Plant Growth-Promoting Activity" (2015). Theses and Dissertations. 1760.