• Korean Journal of Microbiology
• /
• v.45 no.2
• /
• pp.140-147
• /
• 2009

In this study, anaerobic enrichment cultivation was performed with the sediments from the Gimpo and Inchon areas. Lactate as an electron donor and PCE as an electron acceptor was injected into the serum bottle with an anaerobic medium. After the incubation of 8 weeks, the reductive dechlorination of PCE was observed in 7 sites among 16 sites (43%). Three enrichment cultures showed completely dechlorination of PCE to ethene, while four enrichment culture showed transformation of PCE to cis-DCE. The bacterial community structure was analyzed by PCR-DGGE. Dechlorinating bacteria were detected by species-specific primers. The dominant species in seven anaerobic enrichments were found to belong to the genus of Dehalococcoides sp. and Geobacter sp., and Dehalobacter sp.

• Korean Journal of Microbiology
• /
• v.40 no.3
• /
• pp.248-253
• /
• 2004

To scrutinize the physiological diversity by BIOLOG microplate, the carbon source utilization patterns of 168 strains of oligotrophic bacteria and 132 strains of psychrotrophic bacteria isolated from Lake Baikal during 2000 and 2002 were investigated. Eighty-six percent (56 strains) of oxidase test positive group (GN-NENT group) and 89 % (92 strains) of oxidase test negative group (GN-ENT group) among oligotrophic bacteria, and 82% (85 strains) of oxidase test negative group among psychrotrophic bacteria were able to utilize $\alpha$-D-glucose as a sole-carbon-source, and 93% (26 strains) of oxidase test positive group among psychrotrophic bacteria were able to utilize bromosuccinic acid as a sole-carbon-source. However, most strains except few oligotrophic bacteria with oxidase test negative group were not able to utilize $\alpha$-D-lactose as a sole-carbon-source. Most dominant genus among 300 strains was Pseudomonas (49 strains). Other dominant genera belonged to Salmonella, Serratia, Buttiauxella, Pantoea, Yersinia, Brevundimonas, Hydrogenophaga, Photorhabdus, Sphingomonas, and Xenorhabdus. Our results by BIOLOG identification system were able to provide basic data to determine community-level carbon source utilization patterns and to accomplish the efficient and reliable identification for microbial community structure in Lake Baikal.

• Proceedings of the Microbiological Society of Korea Conference
• /
• 2008.05a
• /
• pp.42-44
• /
• 2008

Bacterial biofilms are analogous to multi-cellular organisms or to clonal communities of higher organisms. In this respect, it can be demonstrated that biofilms display the type of genetic variation associated with macroorganisms. The formation of genetic variants from biofilms is the result of internally produced and regulated signals and the appearance of these variants coincides with dispersal from the biofilm. Moreover, the generation of such variation, has similar outcomes for the bacterial community, where diversification of phenotypic traits ensures that the bacterial community optimizes its chances of success when dispersing or surviving when challenged with environmental stress. These observations increase the complexity with which we view bacteria and also suggest that microbial systems can serve as models for the testing of eukaryotic ecological theories.

• Research in Plant Disease
• /
• v.30 no.2
• /
• pp.165-175
• /
• 2024

The Korean fir tree (Abies koreana), an endemic species of South Korea, is experiencing a severe decline in population due to climate change. Studies on the conservation of Korean fir have been extensive, yet research regarding its correlation with rhizosphere bacterial communities remains scarce, warranting further investigation. In this study, metagenome amplicon sequencing targeting the 16S rRNA V4 region was conducted to examine the presence of specific bacterial communities in Korean fir and to investigate potential differences based on habitat types (rhizosphere of native or cultivated trees, soil of dead trees, and bulk soil) and seasonal variations (April, June, September, November). Here we show that although we could not identify specific taxa highly specifically with Korean fir, the rhizosphere bacterial community in native trees exhibited less variability in response to seasonal changes compared to that in bulk soils. Suggesting the establishment of relatively stable bacterial populations around the Korean fir natural habitat. Further research on other types of rhizosphere and/or microbes is necessary to investigate the distinct relationship of Korean fir with microbial communities.

• Journal of Environmental Science International
• /
• v.21 no.8
• /
• pp.989-996
• /
• 2012

Nitrate contamination of water environments can create serious problems such as eutrophication of rivers. Conventional biological processes for nitrate removal by heterotrophic denitrification often need additional organic substrates as carbon sources and electron donors. We tried to accelerate biological denitrification by using bioelectrochemical reactor (BER) in which electrode works as an electron donor. Denitrification activity of 8 environmental samples from various sediments, soils, groundwaters, and sludges were tested to establish an efficient enrichment culture for BER. The established enrichment culture from a soil sample showed stable denitrification activity without any nitrite accumulation. Microbial community analysis by using PCR-DGGE method revealed that dominant denitrifiers in the enrichment culture were Pantoea sp., Cronobacter sakazakii, and Castellaniella defragrans. Denitrification rate ($0.08kg/m^3{\cdot}day$) of the enrichment culture in BER with electrode poised at -0.5 V (vs Ag/AgCl) was higher than that ($2.1{\times}10^{-2}kg/m^3{\cdot}day$) of BER without any poised potential. This results suggested that biological denitrification would be improved by supplying potential throughout electrode in BER. Further research using BER without any organic substrate addition is needed to apply this system for bioremediation of water and wastewater contaminated by nitrate.

• Microbiology and Biotechnology Letters
• /
• v.39 no.1
• /
• pp.70-76
• /
• 2011

PCR-based Weissella species-specific detection method was developed to apply for the discrimination of Korean and Chinese kimchi by detecting a Weissella species only found in Korean or Chinese kimchi. PCR primers were designed from the species-specific sequence in the recN gene of each species. The primers allowed the species-specific detection and identification of nine species in the genera Weissella, and were successfully applied to the detection of W. cibaria, W. confusa, W. koreensis, and W. soli in kimchi with 20 ng template DNA. W. cibaria, W. confusa, and W. koreensis were detected from the Korean kimchi samples tested but W. soli was not detected. However, the four species were detected from Chinese kimchi samples. PCR-based W. soli-specific detection could not be perfectly applied as the Chinese kimchi discriminating method but has significance as an approach to evaluate the potential of scientific verification method based on the difference of microbial community.

• Asian-Australasian Journal of Animal Sciences
• /
• v.21 no.4
• /
• pp.603-615
• /
• 2008

Dietary fiber is an inevitable component in pig diets. In non-ruminants, it may influence many physiological processes in the gastrointestinal tract (GIT) such as transit time as well as nutrient digestion and absorption. Moreover, dietary fiber is also the main substrate of intestinal bacteria. The bacterial community structure is largely susceptible to changes in the fiber content of a pig's diet. Indeed, bacterial composition in the lower GIT will adapt to the supply of high levels of dietary fiber by increased growth of bacteria with cellulolytic, pectinolytic and hemicellulolytic activities such as Ruminococcus spp., Bacteroides spp. and Clostridium spp. Furthermore, there is growing evidence for growth promotion of beneficial bacteria, such as lactobacilli and bifidobacteria, by certain types of dietary fiber in the small intestine of pigs. Studies in rats have shown that both phosphorus (P) and calcium (Ca) play an important role in the fermentative activity and growth of the intestinal microbiota. This can be attributed to the significance of P for the bacterial cell metabolism and to the buffering functions of Ca-phosphate in intestinal digesta. Moreover, under P deficient conditions, ruminal NDF degradation as well as VFA and bacterial ATP production are reduced. Similar studies in pigs are scarce but there is some evidence that dietary fiber may influence the ileal and fecal P digestibility as well as P disappearance in the large intestine, probably due to microbial P requirement for fermentation. On the other hand, fermentation of dietary fiber may improve the availability of minerals such as P and Ca which can be subsequently absorbed and/or utilized by the microbiota of the pig's large intestine.

• Journal of Animal Science and Technology
• /
• v.62 no.5
• /
• pp.638-647
• /
• 2020

This study determined the substitution effects of rice for corn as the main grain source in a total mixed ration (TMR). In vitro rumen fermentation characteristics and microbes were assessed using two experimental diets. Diets included 33% dry matter (DM) of either corn (Corn TMR) or rice grains (Rice TMR). In a 48-h in vitro incubation, DM digestibility (IVDMD), neutral detergent fiber degradability (IVNDFD), crude protein digestibility (IVCPD), volatile fatty acids (VFAs), pH and ammonia nitrogen (NH₃-N) were estimated. Gas production has been calculated at 3, 6, 12, 24 and 48 h. Our results indicate that the gas production, VFAs, IVDMD, and IVNDFD of Rice TMR were higher than those of Corn TMR (p < 0.05). Ruminal pH and total fungi were significantly higher in Corn TMR (p < 0.05) than in Rice TMR; however, NH₃-N and IVCPD were not affected by treatment type. In conclusion, substituting rice for corn at 33% DM in TMR appears to have no negative effects on in vitro rumen fermentation characteristics. Therefore, rice grains are an appropriate alternative energy source in early fattening stage diets of beef cattle.

• Journal of Microbiology and Biotechnology
• /
• v.28 no.1
• /
• pp.105-108
• /
• 2018

Beef was dry aged for 40-60 days under controlled environmental conditions in a refrigerated room with a relative humidity of 75%-80% and air-flow. To date, there is little information on the microbial diversity and characteristics of dry aged beef. In this study, we explored the effect of change in meat microorganisms on dry aged beef. Initially, the total bacteria and LAB were significantly increased for 50 days during all dry aging periods. There was an absence of representative foodborne pathogens as well as coliforms. Interestingly, fungi including yeast and mold that possess specific features were observed during the dry aging period. The 5.8S rRNA sequencing results showed that potentially harmful yeasts/molds (Candida sp., Cladosporium sp., Rhodotorula sp.) were present at the initial point of dry aging and they disappeared with increasing dry aging time. Interestingly, Penicillium camemberti and Debaryomyces hansenii used for cheese manufacturing were observed with an increase in the dry aging period. Taken together, our results showed that the change in microorganisms exerts an influence on the quality and safety of dry aged beef, and our study identified that fungi may play an important role in the palatability and flavor development of dry aged beef.

• ALGAE
• /
• v.29 no.4
• /
• pp.249-265
• /
• 2014

As with land crops, cultivated algae are affected by various diseases ranging from large outbreaks of a disease to chronic epiphytes, which may downgrade the value of the final product. The recent development of intensive and dense mariculture practices has enabled some new diseases to spread much faster than before. A new disease is reported almost every year, and the impact of diseases is expected to increase with environmental change, such as global warming. We observed the incidence of diseases in two Pyropia sea farms in Korea from 2011 to 2014, and estimated the economic loss caused by each disease. Serious damage is caused by the oomycete pathogens, Pythium porphyrae and Olpidiopsis spp., which decreased the productivity of the Pyropia sea farms. In Seocheon sea farms, an outbreak of Olpidiopsis spp. disease resulted in approximately US $1.6 million in loss, representing approximately 24.5% of total sales during the 2012-2013 season. The damage caused by green-spot disease was almost as serious as oomycete diseases. An outbreak of green-spot disease in the Seocheon sea farms resulted in approximately US $1.1 million in loss, representing 10.7% of total sales in the 2013-2014 season in this area. However, the causative agent of green-spot disease is still not confirmed. "Diatom felt" is regarded as a minor nuisance that does not cause serious damage in Pyropia; however, our case study showed that the economic loss caused by "diatom felt" might be as serious as that of oomycete diseases. Bacteria and cyanobacteria are indigenous members of epiphytic microbial community on Pyropia blades, but can become opportunistic pathogens under suitable environmental conditions, especially when Pyropia suffers from other diseases. A regular acid wash of the Pyropia cultivation nets is the most common treatment for all of the above mentioned diseases, and represents approximately 30% of the total cost in Pyropia sea farming. However, the acid wash is ineffective for some diseases, especially for Olpidiopsis and bacterial diseases.