• KSBB Journal
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• 제28권2호
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• pp.146-150
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• 2013

In this study, we investigated the effects of longterm exposure to ionic liquid (IL) on Shewanella oneidensis MR-1 (MR-1). MR1 was acclimated through repeated exposure to IL. The acclimated strain was named as S. oneidensis SH-1 (SH-1) and compared with MR-1 in various aspects including morphology, cell surface hydrophobicity (CSH), motility, and fatty acid. Compared to the MR-1, SH-1 showed elongated cell shape on scanning electron microscopy. Upon exposure to IL, hydrophobicity of SH-1 (28.2%) was higher that of MR-1 (3.3%). In contrast, motility of SH-1 (7 mm) was lower than that also of MR-1 (22 mm), and branched chain fatty acid of SH-1 was lower than that of MR-1, 27.6% and 41.1%, respectively.

• Biotechnology and Bioprocess Engineering:BBE
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• 제11권2호
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• pp.127-133
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• 2006

Shewanella oneidensis MR-1 has the ability to inhale certain metals and chemical compounds and exhale these materials in an altered state; as a result, this microorganism has been widely applied in bioremediation protocols. However, the relevant characteristics of cell growth and biosynthesis of PuFAs have yet to be thoroughly investigated. Therefore, in this study, we have attempted to characterize the growth and fatty acid profiles of S. oneidensis MR-1 under a variety of temperature conditions. The fastest growth of S. oneidensis MR-1 was observed at $30^{\circ}C$, with a specific growth rate and doubling time of $0.6885h^{-1}\;and\;1.007 h$. The maximum cell mass of this microorganism was elicited at a temperature of $4^{\circ}C$. The eicosapentaenoic acid (EPA) synthesis of S. oneidensis MR-1 was evaluated under these different culture temperatures. S. oneidensis MR-1 was found not to synthesize EPA at temperatures in excess of $30^{\circ}C$, but was shown to synthesize EPA at temperatures below $30^{\circ}C$. The EPA content was found to increase with decreases in temperature. We then evaluated the EPA biosynthetic pathway, using a phylogenetic tree predicted on 16s rRNA sequences, and the homology of ORFs between S. oneidensis MR-1 and Shewanella putrefaciens SCRC-2738, which is known to harbor a polyketide synthase (PKS)-like module. The phylogenetic tree revealed that MR-1 was very closely related to both Moritella sp., which is known to synthesize DHA via a PKS-like pathway, and S. putrefaciens, which has been reported to synthesize EPA via an identical pathway. The homology between the PKS-like module of S. putrefaciens SCRC-2738 and the entire genome of S. oneidensis MR-1 was also analyzed, in order to mine the genes associated with the PKS-like pathway in S. oneidensis MR-1. A putative PKS-like module for EPA biosynthesis was verified by this analysis, and was also corroborated by the experimental finding that S. oneidensis MR-1 was able to synthesize EPA without the expression of $dihomo-{\gamma}-linoleic$ acid (DGLA) and arachidonic acid (AA) formed during EPA synthesis via the FAS pathway.

• Journal of Microbiology and Biotechnology
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• 제33권5호
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• pp.687-697
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• 2023

Identification of novel, electricity-producing bacteria has garnered remarkable interest because of the various applications of electricigens in microbial fuel cell and bioelectrochemical systems. Shewanella marisflavi BBL25, an electricity-generating microorganism, uses various carbon sources and shows broader sugar utilization than the better-known S. oneidensis MR-1. To determine the sugar-utilizing genes and electricity production and transfer system in S. marisflavi BBL25, we performed an in-depth analysis using whole-genome sequencing. We identified various genes associated with carbon source utilization and the electron transfer system, similar to those of S. oneidensis MR-1. In addition, we identified genes related to hydrogen production systems in S. marisflavi BBL25, which were different from those in S. oneidensis MR-1. When we cultured S. marisflavi BBL25 under anaerobic conditions, the strain produced 427.58 ± 5.85 µl of biohydrogen from pyruvate and 877.43 ± 28.53 µl from xylose. As S. oneidensis MR-1 could not utilize glucose well, we introduced the glk gene from S. marisflavi BBL25 into S. oneidensis MR-1, resulting in a 117.35% increase in growth and a 17.64% increase in glucose consumption. The results of S. marisflavi BBL25 genome sequencing aided in the understanding of sugar utilization, electron transfer systems, and hydrogen production systems in other Shewanella species.

• Biotechnology and Bioprocess Engineering:BBE
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• 제11권6호
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• pp.510-515
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• 2006

The putative EPA synthesis gene cluster was mined from the entire genome sequence of Shewanella oneidensis MR-1. The gene cluster encodes a PKS-like pathway that consists of six open reading frames (ORFs): ORFSO1602 (multi-domain beta-ketoacyl synthase, KS-MAT-4ACPs-KR), ORFSO1600 (acyl transferase, AT), ORFSO1599 (multi-domain beta-ketoacyl synthase, KS-CLF-DH-DH), ORFSO1597 (enoyl reductase, ER), ORFSO1604 (phosphopentetheine transferase, PPT), and ORFSO1603 (transcriptional regulator). In order to prove involvement of the PKS-like machinery in EPA synthesis, a 20.195-kb DNA fragment containing the genes was amplified from S. oneidensis MR-1 by the long-PCR method. Its identity was confirmed by the methods of restriction enzyme site mapping and nested PCR of internal genes orfSO1597 and orfSO1604. The DNA fragment was cloned into Escherichia coli using cosmid vector SuperCos1 to form pCosEPA. Synthesis of EPA was observed in four E. coli clones harboring pCosEPA, of which the maximum yield was 0.689% of the total fatty acids in a clone designated 9704-23. The production yield of EPA in the E. coli clone was affected by cultivation temperature, showing maximum yield at $20^{\circ}C$ and no production at $30^{\circ}C$ or higher. In addition, production yield was inversely proportional to glucose concentration of the cultivation medium. From the above results, it was concluded that the PKS-like modules catalyze the synthesis of EPA. The synthetic process appears to be subject to regulatory mechanisms triggered by various environmental factors. This most likely occurs via the control of gene expression, protein stability, or enzyme activity.

• 한국환경농학회지
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• 제40권3호
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• pp.194-202
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• 2021

BACKGROUND: Towards achievement of sustainable agriculture, using microbial inoculants may present promising alternatives without adverse environmental effects; however, there are challenging issues that should be addressed in terms of effectiveness and ecology. Viability and stability of the bacterial inoculants would be one of the major issues in effectiveness of microbial pesticide uses, and the changes within the indigenous microbial communities by the inoculants would be an important factor influencing soil ecology. Here we investigated the stability of the introduced bacterial strains in the soils planted with barley and its effect on the diversity shifts of the rhizosphere soil bacteria. METHODS AND RESULTS: Two different types of bacterial strains of Bacillus thuringiensis and Shewanella oneidensis MR-1 were inoculated to the soils planted with barley. To monitor the stability of the inoculated bacterial strains, genes specific to the strains (XRE and mtrA) were quantified by qPCR. In addition, bacterial community analyses were performed using v3-v4 regions of 16S rRNA gene sequences from the barley rhizosphere soils, which were analyzed using Illumina MiSeq system and Mothur. Alpha- and beta-diversity analyses indicated that the inoculated rhizosphere soils were grouped apart from the uninoculated soil, and plant growth also may have affected the soil bacterial diversity. CONCLUSION: Regardless of the survival of the introduced non-native microbes, non-indigenous bacteria may influence the soil microbial community and diversity.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2005년도 생물공학의 동향(XVI)
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• pp.400-400
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• 2005

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2005년도 생물공학의 동향(XVII)
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• pp.371-372
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• 2005

• Geomechanics and Engineering
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• 제12권5호
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• pp.863-870
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• 2017

With the increasing interest in using bacterial biofilms in geo-engineering practices, such as soil improvement, sealing leakage in earth structures, and hydraulic barrier installation, understanding of the contribution of bacterial biofilm formation to mechanical and hydraulic behavior of soils is important. While mechanical properties of soft gel-like biofilms need to be identified for appropriate modeling and prediction of behaviors of biofilm-associated soils, elastic properties of biofilms remain poorly understood. Therefore, this study investigated the microscale Young's modulus of biofilms produced by Shewanella oneidensis MR-1 in a liquid phase. The indentation test was performed on a biofilm sample using the atomic force microscopy (AFM) with a spherical indentor, and the force-indentation responses were obtained during approach and retraction traces. Young's modulus of biofilms was estimated to be ~33-38 kPa from these force-indentation curves and Hertzian contact theory. It appears that the AFM indentation result captures the microscale local characteristics of biofilms and its stiffness is relatively large compared to the other methods, including rheometer and hydrodynamic shear tests, which reflect the average macro-scale behaviors. While modeling of mechanical behaviors of biofilm-associated soils requires the properties of each component, the obtained results provide information on the mechanical properties of biofilms that can be considered as cementing, gluing, or filling materials in soils.