• Journal of Animal Science and Technology
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• v.65 no.2
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• pp.387-400
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• 2023

Ruminal protozoa, especially entodiniomorphs, engulf other members of the rumen microbiome in large numbers; and they release oligopeptides and amino acids, which can be fermented to ammonia and volatile fatty acids (VFAs) by amino acid-fermenting bacteria (AAFB). Studies using defaunated (protozoa-free) sheep have demonstrated that ruminal protozoa considerably increase intraruminal nitrogen recycling but decrease nitrogen utilization efficiency in ruminants. However, direct interactions between ruminal protozoa and AAFB have not been demonstrated because of their inability to establish axenic cultures of any ruminal protozoan. Thus, this study was performed to evaluate the interaction between Entodinium caudatum, which is the most predominant rumen ciliate species, and an AAFB consortium in terms of feed degradation and ammonia production along with the microbial population shift of select bacterial species (Prevotella ruminicola, Clostridium aminophilum, and Peptostreptococcus anaerobius). From an Ent. caudatum culture that had been maintained by daily feeding and transfers every 3 or 4 days, the bacteria and methanogens loosely associated with Ent. caudatum cells were removed by filtration and washing. An AAFB consortium was established by repeated transfers and enrichment with casamino acids as the sole substrate. The cultures of Ent. caudatum alone (Ec) and AAFB alone (AAFB) and the co-culture of Ent. caudatum and AAFB (Ec + AAFB) were set up in three replicates and incubated at 39℃ for 72 h. The digestibility of dry matter (DM) and fiber (NDF), VFA profiles, ammonia concentrations, pH, and microscopic counts of Ent. caudatum were compared among the three cultures. The co-culture of AAFB and Ent. caudatum enhanced DM degradation, VFA production, and Ent. caudatum cell counts; conversely, it decreased acetate: propionate ratio although the total bacterial abundance was similar between Ec and the Ec + AAFB co-culture after 24 h incubation. The ammonia production and relative abundance of C. aminophilum and P. anaerobius did not differ between AAFB alone and the Ec + AAFB co-culture. Our results indicate that Ent. caudatum and AAFB could have a mutualistic interaction that benefited each other, but their interactions were complex and might not increase ammoniagenesis. Further research should examine how such interactions affect the population dynamics of AAFB.

• Journal of Microbiology and Biotechnology
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• v.22 no.6
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• pp.780-787
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• 2012

The maize pathogen Gibberella moniliformis produces fumonisins, a group of mycotoxins associated with several disorders in animals and humans, including cancer. The current focus of our research is to understand the regulatory mechanisms involved in fumonisin biosynthesis. In this study, we employed a proteomics approach to identify novel genes involved in the fumonisin biosynthesis under nitrogen stress. The combination of genome sequence, mutant strains, EST database, microarrays, and proteomics offers an opportunity to advance our understanding of this process. We investigated the response of the G. moniliformis proteome in limited nitrogen (N0, fumonisin-inducing) and excess nitrogen (N+, fumonisin-repressing) conditions by one- and two-dimensional electrophoresis. We selected 11 differentially expressed proteins, six from limited nitrogen conditions and five from excess nitrogen conditions, and determined the sequences by peptide mass fingerprinting and MS/MS spectrophotometry. Subsequently, we identified the EST sequences corresponding to the proteins and studied their expression profiles in different culture conditions. Through the comparative analysis of gene and protein expression data, we identified three candidate genes for functional analysis and our results provided valuable clues regarding the regulatory mechanisms of fumonisin biosynthesis.

• Journal of Microbiology and Biotechnology
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• v.30 no.8
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• pp.1169-1179
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• 2020

In this study, two soybean genotypes, i.e., aluminum-tolerant Baxi 10 (BX10) and aluminumsensitive Bendi 2 (BD2), were used as plant materials and acidic red soil was used as growth medium. The soil layers from the inside to the outside of the root are: rhizospheric soil after washing (WRH), rhizospheric soil after brushing (BRH) and rhizospheric soil at two sides (SRH), respectively. The rhizosphere bacterial communities were analyzed by high-throughput sequencing of V4 hypervariable regions of 16S rRNA gene amplicons via Illumina MiSeq. The results of alpha diversity analysis showed that the BRH and SRH of BX10 were significantly lower in community richness than that of BD2, while the WRH exhibited no significant difference between BX10 and BD2. Among the three sampling compartments of the same soybean genotype, WRH had the lowest community richness and diversity while showing the highest coverage. Beta diversity analysis results displayed no significant difference for any compartment between the two genotypes, or among the three different sampling compartments for any same soybean genotype. However, the relative abundance of major bacterial taxa, specifically nitrogen-fixing and/or aluminum-tolerant bacteria, was significantly different in the compartments of the BRH and/or SRH at phylum and genus levels, indicating genotype-dependent variations in rhizosphere bacterial communities. Strikingly, as compared with BRH and SRH, the WRH within the same genotype (BX10 or BD2) always had an enrichment effect on rhizosphere bacteria associated with nitrogen fixation.

• Journal of Microbiology and Biotechnology
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• v.20 no.5
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• pp.862-870
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• 2010

Cyperus rotundus L. is a perennial herb that was found to be dominating an area in northeast Brazil previously contaminated with petroleum. In order to increase our knowledge of microorganism-plant interactions in phytoremediation, the bacterial community present in the rhizosphere and roots of C. rotundus was evaluated by culture-dependent and molecular approaches. PCR-DGGE analysis based on the 16S rRNA gene showed that the bacterial community in bulk soil, rhizosphere, and root samples had a high degree of similarity. A complex population of alkane-utilizing bacteria and a variable nitrogen-fixing population were observed via PCR-DGGE analysis of alkB and nifH genes, respectively. In addition, two clone libraries were generated from alkB fragments obtained by PCR of bulk and rhizosphere soil DNA samples. Statistical analyses of these libraries showed that the compositions of their respective populations were different in terms of alkB gene sequences. Using culturedependent techniques, 209 bacterial strains were isolated from the rhizosphere and rhizoplane/roots of C. rotundus. Dot-blot analysis showed that 17 strains contained both alkB and nifH gene sequences. Partial 16S rRNA gene sequencing revealed that these strains are affiliated with the genera Bosea, Cupriavidus, Enterobacter, Gordonia, Mycoplana, Pandoraea, Pseudomonas, Rhizobium, and Rhodococcus. These isolates can be considered to have great potential for the phytoremediation of soil with C. rotundus in this tropical soil area.

• Journal of Korean Society on Water Environment
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• v.39 no.1
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• pp.61-75
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• 2023

Denitrifying bacteria convert nitrate to nitrogen gas using an external carbon source as an electron donor. The external carbon source affects the denitrification performance and bacterial community structure. Although methanol is a cheap and effective external carbon source, the addition of diverse carbon sources may improve the total nitrogen removal rate and biomass characteristics, such as settleability. In this study, denitrifying reactions were performed using solely methanol and mixed carbon sources of methanol, glucose, and acetate in a sequencing batch reactor. The denitrifying reactor using methanol resulted in a total nitrogen removal rate of 0.39 ± 0.025 kg-N/m³-day while the suspended biomass transformed into dark brown granules. Methyloversatilis discipulorum had the highest predominance at 43.84%. The individual denitrifying biomasses, which were separately enriched with methanol, glucose, and acetate, showed the same total nitrogen removal performance of 0.39 ± 0.016 kg-N/m³-day. However, the addition of mixed carbon sources showed an improved total nitrogen removal rate of 0.42 ± 0.043 kg-N/m³-day, with the domination of Candidatus Saccaribacteria at 25.61%. The denitrifying granules turned pale yellow color. Influent COD/NO₃^--N ratios of 3.5, 5, and 7.5 exhibited COD/NO₃^--N consumptions of 4.3 ± 0.4, 4.4 ± 0.8, and 5.2 ± 0.7, and the consistent predominance of Candidatus Saccharibacteria.

• Journal of Environmental Science International
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• v.17 no.4
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• pp.469-477
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• 2008

The aerobic photosynthetic bacterium, which produces bacterial carotenoids was isolated and identified from coastal marine environments. This bacterium was identified by 16S rDNA sequencing and designated as Erythrobacter longus SY-46. E. longus SY-46 was Gram negative and rod shape, and the optimal culture conditions were $25^{\circ}C$, pH 7.0, and 3.0% NaCl concentration, respectively. The carbon and nitrogen sources required for the optimal growth were lactose and tryptone, respectively. Fatty acid compositions of E. longus SY-46 were $C_{18:1}$(78.32%), v-linolenic acid($C_{18:3n9.12.15c}:3.83%$), margaric acid($C_{17:0}$: 3.38%), palmitic acid($C_{16:0}$: 3.07%), and docosahexaenoic acid($C_{22:6n3}$: 2.21%). In addition, E. longus SY-46 showed the characteristic absorption peaks of bacterial carotenoids(in the region of 450 to 480 nm) and bacteriochlorophyll(770 to 772 nm). Major carotenoids of E. longus SY-46 were polyhydroxylated xanthophylls such as fucoxanthin and zeaxanthin.

• Journal of Microbiology and Biotechnology
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• v.26 no.2
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• pp.373-384
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• 2016

The membrane-aerated biofilm reactor (MABR) is a promising municipal wastewater treatment process. In this study, two cross-flow MABRs were constructed to explore the carbon and nitrogen removal performance and bacterial succession, along with changes of influent loading shock comprising flow velocity, COD, and NH₄-N concentrations. Redundancy analysis revealed that the function of high flow velocity was mainly embodied in facilitating contaminants diffusion and biosorption rather than the success of overall bacterial populations (p > 0.05). In contrast, the influent NH₄-N concentration contributed most to the variance of reactor efficiency and community structure (p < 0.05). Pyrosequencing results showed that Anaerolineae, and Beta- and Alphaproteobacteria were the dominant groups in biofilms for COD and NH₄-N removal. Among the identified genera, Nitrosomonas and Nitrospira were the main nitrifiers, and Hyphomicrobium, Hydrogenophaga, and Rhodobacter were the key denitrifiers. Meanwhile, principal component analysis indicated that bacterial shift in MABR was probably the combination of stochastic and deterministic processes.

• ALGAE
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• v.19 no.2
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• pp.145-148
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• 2004

As a result of the 2-year monthly monitoring of the phytoplankton community at 3 stations in Mankyeong Estuary, Korea, we learned that cyan bacterial species of the genus Anabaena occurred at most sampling points with huge salinity differences (0.1-32.5 psu). We isolated several clones of Anabaena spp. from the monitoring stations, and screen out two euryhaline and nitrogen-fixing Anabaena clones, CB-MAL21 and CB-MAL22. The two clones were grown under various environmental gradients such as temperature (20, 30, 35 and 40$^{\circ}C$), salinity (0, 2, 5, 15 and 30psu), and $PO_4^{3-}$-P concentration (0, 1.6, 8.0, 40 and 200 ${\mu}M$M). Growth of CB-MAL21 and CB-MAL22 was measured by daily monitoring of chlorophyll fluorescence from each experimental culture for more than three serial transfers. Both the two experimental clones did not grow at 0psu. Maximal growth rates of the two clones were markedly reduced at lower $PO_4^{3-}$-P concentrations showing negligible growth at 0 and 1.6 ${\mu}M$M. However, growth of CB-MAL21 was not affected by low $NO_3^--$ concentration in culture media, showing the nitrogen-fixing ability. Maximum biomass yields of the two clones decreased dramatically at 35 and 40$^{\circ}C$. Optimal growth conditions for the two experimental clones were determined to be 20-30$^{\circ}C$, 40 ${\mu}M$M $PO_4^{3-}$-P, and wide salinity range from 5.0 to over 30psu. Best growth of CB-MAL21 was shown at (20$^{\circ}C$-15psu), which is less saline and cooler condition than those (i.e., 30$^{\circ}C$-30psu) for the best growth of CB-MAL22. The euryhaline and nitrogen-fixing CB-MAL21 strain thus can be a candidate laboratory culture for the future cyan bacterial marine biotechnology in temperate coastal waters.

• Journal of the Korean Society of Tobacco Science
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• v.9 no.2
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• pp.11-24
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• 1987

Lines were developed from the two crosses, BY4 X NC 82 and BY 4 X BY 104, by bulk, backcross and anther-derived dihaploid methods of breeding , and their variations in major agronomic, chemical characters, heritability, and response to selection were compared. 1. The anther-derived dihaploid lines showed a greater genetic variability and heritability in characters investigated than the lines developed by the other two methods of breeding . However, those were Inferior In agronomic characters and yielded 15.4% less leaf tobacco than the lines developed by the bulk method. 2. The lines developed by bulk method were higher In the frequency of lines resistant to bacterial wilt and in the yield, but Its lines appeared later flowering. inferior leaf Quality, and higher total nitrogen contents than those developed by the backcross method of breeding. 3. In the population of the lines developed by the backcross method, bacterial wilt resistant lines were less frequent, but the lines with a good leaf quality were more frequent.

• Korean Journal of Medicinal Crop Science
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• v.28 no.3
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• pp.183-194
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• 2020

Background: This study investigated the effect of soil properties and soil bacterial community on early growth characteristics of wild-simulated ginseng (Panax ginseng C. A. Meyer) in coniferous and mixed forest experimental fields. Methods and Results: The soil bacterial community was analyzed using a high throughput sequencing technique (Illumina MiSeq sequencing). The relationship between the soil bacterial community, soil properties, and growth characteristics of wild-simulated ginseng were analyzed using principal coordinate analysis (PCoA) and the Pearson's correlation analysis. Soil properties and soil bacterial community showed significant difference with forest physiognomy. Results of Pearson's correlation analysis and PCoA showed that the soil properties (soil pH, organic matter, total nitrogen, and cation exchange capacity) and soil bacterial community had significant correlation with tree species ratio and early growth characteristics of wild-simulated ginseng. Conclusions: This study clearly demonstrated the effect of soil properties and soil bacterial community on early growth characteristics of wild-simulated ginseng in coniferous and mixed forest. Moreover, these results will help in the selection of suitable cultivation sites for wild-simulated ginseng.