• Ocean and Polar Research
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• v.30 no.4
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• pp.509-518
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• 2008

Distribution of bacterial abundance and production was investigated in seawater around Saemangeum dike 7 times during March, $2007{\sim}July$, 2008. In the inner area of the dike, salinity variation was great due to river runoff from Mangyung and Dongjin Rivers and high chlorophyll a (chl a) concentrations up to $124.3{\mu}g\;l^{-1}$ was found. In the outer area of the dike, salinity was higher than in the inner area of the dike, and chl a was lower up to 10 times than in the inner area of the dike. Thus, the area of Saemangeum showed meso- to hypereutrophic conditions. Bacterial abundance and production ranged from 0.3 to $4.3{\times}10^9\;cells\;l^{-1}$ and from 5.2 to $570 pmol\;l^{-1}h^{-1}$ in outer area of the dike, respectively, while in the inner area of the dike bacterial abundance and production was 3 to 4 times higher ($0.4{\sim}12.7{\times}10^9\;cells\;l^{-1}$ and $12.3{\sim}1309\;pmol\;l^{-1}h^{-1}$, respectively) than those in the outer area. In both areas, bacterial abudance and production was highest in summer and lowest in winter. However, the variations of bacterial parameters was very large in each season. These large variations seemed to be related with the supply of organic matter. Bacterial abundance and production showed significant negative correlations with salinity in the inner area, suggesting that allochthonous organic matter input by river runoff could be an important factor in regulating the distribution of bacterial abundance and production. In addition, bacterial production also correlated positively with chl a in the inner area, suggesting that autochthonous substrate might be another regulating factor of bacterial growth in the area. These results suggest that the supply of both allochthonous organic substrates introduced by river runoff and autochthonous substrates produced by phytoplankon could be important in regulating bacterial growth and utilization of organic matter in the area. Thus, to manage water quality in the inner area of dike, it seems to be important to lower the load of both organic and inorganic nutrients from adjacent rivers.

• Journal of the korean society of oceanography
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• v.33 no.4
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• pp.205-211
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• 1998

Participating in a multi-disciplinary oceanography program in July 1997 in the vicinity of Tokdo, we studied the distributions of bacterial abundance and production along with those of phytoplankton and heterotrophic nanoflagellates. In the euphotic zone, chlorophyll a (chl a) concentrations ranged from 0.14 to 0.52 ${\mu}$g 1$^{-1}$. Bacterial abundance in the euphotic zone (0.12-0.21 ${\times}$ 10$^9$ cells 1$^{-1}$) in the study area was quite lower than that expected from the observed chi a concentration in the marine environment. The low bacterial abundance seemed to be due to active grazing pressure on bacteria. The fraction of primary production utilized by bacteria was also low(8-12%). Interestingly, surface water temperatures were love. at stations near islands compared to an offshore station located between Ulleungdo and Tokdo and the highest values of bacterial production and chi a were found at stations near islands, strongly indicating island mass effects.

• 한국해양학회지
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• v.27 no.2
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• pp.154-163
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• 1992

Bacterial abundance, production, and environmental parameters were investigated three times to study distribution of bacterial variables and to examine how estuarine mixing would influence the distribution of bacterial variables in the euphotic zone of the estuarine system of the Mankyung river and Dongjin river during a period of October, 1990-August, 1991. Although a limited number of investigations were made, bacterial abundance and production showed large variations from 0.4 to 5.8${\times}$10/SUP 9/ 1/SUP -1/ and from 0.1 to 22.2 ug C 1/SUP -1/ d/SUP -1/, respectively. The wide ranges of bacterial variables indicated very dynamic changes in conditions of bacterial growth in the estuary. Interestingly, bacterial abundance substantially increased with depth in most stations f shallow depth. but bacterial production remarkably decreased with depth. We propose that the observed distribution of bacterial abundance and production would be explained by estuarine mixing in the estuary. Analyses of mixing diagrams showed that estuarine mixing would mix conservatively bacteria and bacterial production. Further, estuarine mixing often seemed to cause an increase in bacterial abundance and reduction of bacterial production presumably due to resuspension of sediment. This suggests that roles of estuarine mixing would be significant in the distribution of bacterial abundance and production, and thus in biogeochemical cycles in the estuary.

• Journal of Microbiology and Biotechnology
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• v.29 no.2
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• pp.292-296
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• 2019

Soils amended for long-term with high levels of compost demonstrated greater abundance of bacterial members of the phylum Bacteroidetes whereas a decreasing trend in the relative abundance of phylum Acidobacteria was noted with increasing levels of compost. Metabolic profiles predicted by PICRUSt demonstrated differences in functional responses of the bacterial community according to the treatments. Soils amended with lower compost levels were characterized by abundance of genes encoding enzymes contributing to membrane transport and cell growth whereas genes encoding enzymes related to protein folding and transcription were enriched in soils amended with high levels of compost. Thus, the results of the current study provide extensive evidence of the influence of different compost levels on bacterial diversity and community structure in paddy soils.

• Journal of Microbiology and Biotechnology
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• v.24 no.10
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• pp.1308-1318
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• 2014

The specific freshwater environment of reservoirs formed by streams has not been well studied. In this paper, the bacterioplankton community in such a reservoir, the Huangqian Reservoir in eastern China, was described using culture-independent molecular methods. We found that the most dominant bacterioplankton were affiliated with Cyanobacteria, followed by Betaproteobacteria, Bacteroidetes, Gammaproteobacteria, and Actinobacteria. Both bacterial abundance and diversity increased along the direction of water flow, and the 16S rRNA gene copy number in the water outlet was nearly an order of magnitude higher than that in the water inlet. Pearson correlation analyses indicated that nitrate had a significantly negative correlation with the bacterial abundance (p < 0.05) and that ammonium was positively correlated with bacterial abundance (p < 0.05). Interestingly, owing to a remarkably negative correlation (p < 0.01), the ratio of nitrate and ammonium might serve as a good pre dictor of the relative abundance of bacterioplankton. According to redundancy analysis, nitrate and dissolved oxygen were the major factors influencing the bacterial communities. In addition, we attempted to determine the reasons why such a reservoir could maintain good ecological balance for a period of decades, and we found that the environmental factors and bacterial communities both played critical roles. This research will benefit our understanding of bacterial communities and their surrounding environments in freshwater ecosystems.

• 한국해양학회지
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• v.30 no.5
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• pp.426-435
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• 1995

In order to assess the significance of ciliate grazing on bacterial population in carbon flow of the estuarine pelagic ecosystem of the Mankyung and Dongjin river (MD estuary), abundance and biomass of ciliates and grazing rate on bacteria of small (<40 um) ciliates were measured. Saplings were carried out four times from October 1993 to March 1995 in the estuarine system. Ciliates smaller than 40 um occupied more than 49.5% of total ciliates abundance. Clearance rate of small ciliates ranged from 18.0 to 16.3 nl cell/SUP -1/ h/SUP -1/. As bacterial abundance increased, ciliate's clearance rate decreased, suggesting that bacterial abundance effects on ciliate's grazing rate. Ciliate grazing rate was equal to 0.1 to 12.2% of bacterial productivity, and the ratio of ciliate ingestion over bacterial production increased exponentially with the increase of bacterial abundance (r$^2$=0.62, p$\leq$0.001). It seems that the effect of ciliate grazing on bacteria would be small in coastal waters and large in more eutrophic waters of high bacterial abundance. Carbon supplied by ciliate grazing on bacteria was avg. 3.1% of carbon amount required for the ciliate maximum productivity. Thus, the ecological role of ciliate in microbial loop was probably more important as a final consumer than as a direct consumer of bacteria.

• Asian-Australasian Journal of Animal Sciences
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• v.31 no.9
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• pp.1464-1473
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• 2018

Objective: To describe in-depth sequencing, the bacterial community diversity and its succession during ensiling of whole-plant maize and subsequent exposure to air. Methods: The microbial community dynamics of fermented whole-plant maize for 60 days (sampled on day 5, 10, 20, 40, 60) and subsequent aerobic exposure (sampled on day 63 after exposure to air for 3 days) were explored using Illumina Miseq sequence platform. Results: A total of 227,220 effective reads were obtained. At the genus level, there were 12 genera with relative abundance >1%, Lactobacillus, Klebsiella, Sporolactobacillus, Norank-c-cyanobacteria, Pantoea, Pediococcus, Rahnella, Sphingomonas, Serratia, Chryseobacterium, Sphingobacterium, and Lactococcus. Lactobacillus consistently dominated the bacterial communities with relative abundance from 49.56% to 64.17% during the ensiling process. Klebsiella was also an important succession bacterium with a decrease tendency from 15.20% to 6.41% during the ensiling process. The genus Sporolactobacillus appeared in late-ensiling stages with 7.70% abundance on day 40 and 5.32% on day 60. After aerobic exposure, the Lactobacillus decreased its abundance from 63.2% on day 60 to 45.03% on d 63, and Klebsiella from 5.51% to 5.64%, while Sporolactobacillus greatly increased its abundance to 28.15%. These bacterial genera belong to 5 phyla: Firmicutes (relative abundance: 56.38% to 78.43%) was dominant, others were Proteobacteria, Bacteroidetes, Cyanobacteria, and Actinobacteria. The bacterial communities clearly clustered into early-ensiling (d 5), medium-ensiling (d 10, d 20), late-ensiling (d 40, d 60), and aerobic exposure (d 63) clusters, with early- and late-ensiling communities more like each other than to the aerobic exposure communities. Conclusion: High-throughput sequencing based on 16S rRNA genes proved to be a useful method to explore bacterial communities of silage. The results indicated that the bacterial communities varied during fermentation and more dramatically during aerobic exposure. The study is valuable for understanding the mechanism of population change and the relationship between bacteria and ensilage characteristics.

• Journal of Microbiology and Biotechnology
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• v.19 no.9
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• pp.858-868
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• 2009

The abundance, biomass, size distribution, and taxonomic composition of bacterial and protistan (heterotrophic and autotrophic nanoflagellates and ciliates) communities were investigated in six lakes of Masurian Lake District (north-eastern Poland) differing in trophic state. Samples were taken from the trophogenic water layer during summer stratification periods. Image analysis techniques with fluorescent in situ hybridization (FISH) as well as [$^3H$]-methyl-thymidine incorporation methods were applied to analyze differences in the composition and activity of bacterial communities. The greatest differences in trophic parameters were found between the humic lake and remaining non-humic ones. The same bacterial and heterotrophic nanoflagellate (HNF) cell size classes dominated in all the studied lakes. However, distinct increases in the contributions of large bacterial (>$1.0{\mu}m$) and HNF (>$10{\mu}m$) cells were observed in eutrophic lakes. The bacterial community was dominated by the ${\beta}$-Proteohacteria group, which accounted for 27% of total DAPI counts. Ciliate communities were largely composed of Oligotrichida. Positive correlations between bacteria and protists, as well as between nanoflagellates (both heterotrophic and autotrophic) and ciliates, suggest that concentrations of food sources may be important in determining the abundance of protists in the studied lakes.

• 한국해양학회지
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• v.29 no.2
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• pp.145-151
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• 1994

Investigations on distributions of bacterial abundance and production in the mideast part of the Yellow Sea were made in August and October, 1991 as a part of study of "The Exploitation Research of Marine Resources on the Yellow Sea". Here, we report spatial and temporal characteristics of distributions of bacteria in the mideast part of the Yellow Sea including data reported by Son (1989) for the same area. During the whole study period, bacterial abundance ranged from 0.5${\times}$10/SUP 8/ 1/SUP -1/ to 19${\times}$10/SUP 8/ 1/SUP -1/. Seasonal changes and the difference between two studies in bacterial abundance were less than 3.5 fold ar each station in the study area, except October, 1991. An interesting result was that bacterial abundances except October, 1991 were generally lower than those expected from the established relationship between chlorophyll and bacterial abundance in the oceans. For the bacterial abundance observed in October 1991, controlling factor(s) of bacteria might be different from the rest of study period. Bacterial production (0.1∼2.9ug C 1/SUP -1/ d/SUP -1/) comprised a small fraction (18${\pm}$11%) of primary production. Though data are limited, low bacterial abundances compared to chlorophyll concentration and low values of bacterial production to primary production seemed to occur in the mideast part of the Yellow Sea. Unravelling the causes of these phenomena would be necessary to understand the ecology of bacteria in the region.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.8 no.1
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• pp.44-57
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• 2003

Seasonal variations of bacterial abundance and production, heterotrophic nanoflagellate (HNF) abundance and HNF ingestion rates on bacteria using FLB together with environmental variables were investigated at intervals of a month in Kyeonggi Bay from December 1991 to November 1998. Bacterial abundance and production ranged from 0.38$\times$10$^{9}$ ~ 3.25$\times$10$^{9}$ cells 1$^{-1}$ (average 1.19$\pm$0.69$\times$10$^{9}$ cells 1$^{-1}$ ) and from 1.51 to 20.4 cells 1$^{-1}$ h$^{-1}$ (average 6.04$\pm$ 1.88$\times$10$^{6}$ cells 1$^{-1}$ h$^{-1}$ ), respectively. Bacterial abundance and production showed no differences at the high tide and low tide, and bacterial abundances were not different with depth, but bacterial production decreased with depth. Seasonal variation of bacterial abundance showed almost similar fluctuation pattern to those of DOC (dissolved organic carbon). HNF abundances ranged from 388 to 4,374 cells ml$^{-1}$ (average 1,344$\pm$130 cells ml$^{-1}$ ), were high in March, April, July and August. HNF abundance showed no difference between the high tide and low tide, and was not different with depth. The ingestion rates of HNF on bacteria were 1.0 to 6.3$\pm$10$^{6}$ bacteria 1$^{-1}$ h$^{-1}$ (average 3.12$\pm$0.55$\times$10$^{6}$ bacteria 1$^{-1}$ h$^{-1}$ ), resulting ingestion rates of HNF removed 19.4 to 141.4 %(average 62.3$\pm$12.0%) of bacterial production. Ingestion rates and grazing pressure of HNF on bacteria showed high correlation with HNF abundance. Although we cannot exactly discussion about seasonal variation of bacteria community in this study area where physical and chemical parameters were very complex, the results indicate that bacterial abundance and production were mainly controlled by resources supply as dissolved organic carbon and chlorophyll-a(bottom-up) except March which bacterial abundance and production uncoupled chlorophyll-a because of low dissolved organic carbon and low temperature, and were controlled by HNF grazing pressure(top-down) in the warm seasons except the winter.