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All Journal HAYATI Journal of Biosciences
Maria Indah Purnamasari
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Agriculture, Biological Sciences & Forestry Earth & Planetary Sciences

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Effect of Synthetic Fertilizer on Diazotrophic Bacteria in Secondary Forest and Oil Palm Soils in Central Kalimantan Agustina, Delia; Purnamasari, Maria Indah; Karmawan, Listya Utami; Suwanto, Antonius
HAYATI Journal of Biosciences Vol. 32 No. 1 (2025): January 2025
Publisher : Bogor Agricultural University, Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.4308/hjb.32.1.106-116

Abstract

Soil microorganisms, especially diazotrophic bacteria, are vital for ecosystem sustainability, significantly contributing to nitrogen cycling and biodiversity conservation. Understanding the impact of different land-use practices on soil microorganisms, especially synthetic fertilizer addition, is essential for sustainable agriculture. This study compares soil properties, bacterial densities, and responses to fertilization in secondary forest soils and adjacent oil palm plantation soils located in PT Kerry Sawit Indonesia, Central Kalimantan. A greenhouse experiment was conducted using both secondary forest and oil palm plantation soils to evaluate the impacts of different synthetic fertilizers on nitrogen-fixing bacteria and soybean agronomic performance. Total soil bacteria and diazotrophic bacteria, essential for nitrogen fixation, were analyzed through microbiological assays and qPCR focusing on the nifH gene. Our findings show that oil palm plantation soils had higher levels of nitrogen, phosphate, and nitrate, while secondary forest soils had a higher abundance of diazotrophic bacteria. Furthermore, excessive nitrogen fertilization was found to reduce microbial density, negatively impacting plant sustainability, highlighting the importance of customized fertilizer management. The study highlights the intricate connections between land-use practices and microbial populations, providing valuable insights for balancing agricultural productivity with ecological sustainability.
Engineering of LysR-type Regulator DmlR in Burkholderia ubonensis CP01 to Enhance Its Antifungal Production against Ganoderma boninense Budinarta, Widyah; Purnamasari, Maria Indah; Hermosaningtyas, Anastasia Aliesa; Arifudin Rafif , Muhammad Ghildan; Prihatna , Cahya; Suwanto, Antonius
HAYATI Journal of Biosciences Vol. 33 No. 1 (2026): January 2026
Publisher : Bogor Agricultural University, Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.4308/hjb.33.1.28-43

Abstract

The utilization of an antifungal substance, occidiofungin and burkholdine, derived from Burkholderia ubonensis CP01 has displayed promising results in the management of basal stem rot caused by Ganoderma boninense. The study aims to further enhance the antifungal production of B. ubonensis CP01 through genetic modification. Through comparative genetic analysis, we identified the dmlR gene in B. ubonensis CP01, which is homologous to the scmR gene, a LysR-type transcriptional regulator (LTTR), in B. thailandensis. Deleting the dmlR gene in CP01 resulted in a complete loss of antifungal synthesis. In contrast, overexpression of this gene led to a substantial increase in antifungal production, as determined by an agar well diffusion assay. These findings suggest that dmlR acts as a positive regulator of antifungal gene expression in B. ubonensis CP01. RP-HPLC analysis revealed that the mutant strain overexpressing the dmlR gene (mutant WB12) produced a higher peak at the 24-25 minute elution time. Previous high-resolution mass spectrometry analysis by our group identified the compound at this peak as six analog compounds with monoisotopic masses similar to those of cyclic lipopeptides, including occidiofungin and burkholdine. The WB12 mutant exhibited approximately 15% higher concentrations of antifungal compounds than the wild type. Additionally, whole genome sequencing confirmed that the introduced dmlR gene had been integrated into the locus on chromosome 2 of B. ubonensis CP01. LTTRs play a pivotal role in regulating the production of antifungal agents in CP01. Furthermore, it highlights the potential for manipulating LTTRs to enhance the desirable characteristics of the Burkholderia genus in regard to the production of secondary metabolites.
Co-Authors Agustina, Delia Antonius Suwanto Arifudin Rafif , Muhammad Ghildan Budinarta, Widyah Hermosaningtyas, Anastasia Aliesa LISTYA UTAMI KARMAWAN Prihatna , Cahya