STUDI JALUR PRODUKSI INDOLE-3-ACETIC ACID (IAA) PADA Serratia plymuthica UBCF_13

Liza Aulia, Yusfi (2025) STUDI JALUR PRODUKSI INDOLE-3-ACETIC ACID (IAA) PADA Serratia plymuthica UBCF_13. S3 thesis, Universitas Andalas.

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Abstract

SUMMARY Liza Aulia Yusfi. Indole-3-Acetic Acid (IAA) Producing Pathway Study on Serratia plymuthica UBCF_13. Supervised by Jamsari, Djong Hon Tjong, dan Irawati Chaniago. Serratia plymuthica UBCF_13 is a plant growth-promoting bacterial strain that can synthesize Indole-3-Acetic Acid (IAA). Studies related to the regulation of the IAA production pathway in bacteria can be analyzed using various methods including next generation sequencing (NGS), gene cloning, and gene knockout. However, these methods cannot be used simultaneously to determine the optimal conditions for IAA production. Therefore, this study combined the IAA production optimization process with transcriptomic and metabolomic analysis to obtain the best culture conditions for IAA production as well as to determine the IAA synthesis pathway in UBCF_13. The study was carried out from September 2021 to March 2023. The results of genome mining showed that the genes related to the IAA biosynthesis pathway in the UBCF_13 genome consisted of the tyrB, ipdC, puuC, DDC, oxdA, nthA, nthB, and amiE, which are thought to be involved in IPyA, TAM, IAOx/IAN and IAM pathway. The expression of these genes was then investigated based on the culture duration treatment. Additionally, indole compounds in extracts from various culture time treatments were identified and quantified by HPLC analysis. The results showed that the expression of puuC, nthA, nthB, DDC, amiE, and oxdA genes upregulated in 3 hours of culture duration treatment which was included in the lag phase. Furthermore, IAM metabolites were found in the extracts of culture duration treatments with the highest concentration obtained at 21 hours of incubation. Furthermore, the optimization of IAA production medium components (carbon, nitrogen, and mineral sources) was applied to investigate the expression of genes related to IAA biosynthesis in UBCF_13 as well as the identification and quantification of indole compounds. The expression of the tyrB, ipdC, puuC, oxdA, nthA, nthB, and amiE genes increased when sucrose was used as the carbon source. The expression levels of the ipdC, puuC, oxdA, nthB, and amiE genes also increased in the treatment with yeast extract as the nitrogen source. The tyrB, puuC, DDC, oxdA, nthA, nthB, and amiE genes were also upregulated in the culture medium with the addition of magnesium sulfate and calcium carbonate. The culture extract with this medium optimization treatment also produced IAM and IAA metabolites. Overall, the high expression levels of genes related to the IAM pathway (nthA, nthB, and amiE) and the findings of IAM compounds in the extracts of the optimized medium cultures support the hypothesis of the use of the IAM pathway for IAA synthesis by UBCF_13. Furthermore, elimination tests were carried out for each mineral component to obtain the optimal culture media composition. The test results showed that the optimal conditions and composition of the culture media for IAA production by UBCF_13 based on the combination of optimization processes consisted of sucrose, yeast extract, magnesium sulfate, and calcium carbonate in 21 hours of culture duration.

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