• Microbiology and Biotechnology Letters
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• v.49 no.1
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• pp.101-110
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• 2021

Interactions between microalgae and heterotrophic bacteria are common in natural environments. This study investigated the effect of heterotrophic bacteria on the activity of the photosynthetic eukaryotic alga Chlorella sp. MF1907 when cocultured. A total of 31 heterotrophic bacterial isolates belonging to different genera were cocultured with MF1907. Interactions of the alga with Agromyces, Rhodococcus, Sphingomonas, Hyphomicrobium, Rhizobium, and Pseudomonas were positive, while those with Burkholderia, Paraburkholderia, Micrococcus, Arthrobacter, Mycobacterium, Streptomyces, Pedobacter, Mucilaginibacter, Fictibacillus, Tumebacillus, Sphingopyxis, and Erythrobacter were negative (p < 0.05). A turnover experiment demonstrating a switch from heterotrophic to autotrophic activity of MF1907 was performed using 16 isolates exhibiting apparent effects (positive, negative, or neutral). Compared with the results of the coculture experiment, eight isolates exhibited the same outcomes, while the others did not. Consistently, Pseudomonas and Agromyces showed a remarkable positive effect on MF1907 activity, and Burkholderia, Streptomyces, and Erythrobacter had a marked negative effect. Our results suggest that it may be possible to use the isolates for controlling populations of microalgae in natural and engineered environments.

• Korean Journal of Microbiology
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• v.28 no.3
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• pp.204-209
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• 1990

The total and heterotrophic bacterial distributions, compositions and alkaline phosphatese actibities were analyzed in Lake Soyang from Sep. 1987 to Aug. 1988. The heterotrophic bacteria was small portion, 0.07-2.63% of total bacterial number which ranged from $3.2{\times}10^{5}$ to $3.2{\times}10^{6}$ cells/${\mu}\ell$. The composition of bacterial community was less diverse in summer and at the fish farm site and Peridinium blooming site. Pseudomonas and Flavo bacterium were the dominant genera in all sites. The highest proportion and activity of alkaline phsophatase was appeared in Flavobacterium, while Pseudomonas was the most predominant group.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.2
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• pp.205-212
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• 2008

This study aimed to investigate the biofilm formation, bacterial regrowth, and bacterial community structure in the granular-activated carbon (GAC) filter adsorbers (FAs) used in water treatment plants. In 2005 and 2006, raw water, settled water, GAC FA by depth, and filtered water were collected twice a year from water treatment plants (WTPs) B and S. The number of heterotrophic bacteria, including mesophilic and psychrophilic bacteria, in such collected waters was investigated along with the total number of coliforms therein. Heterotrophic bacteria were detected in most samples, mainly at the surface layers of the GAC FAs, and fewer such bacteria were found in the lower and bottom layers. An increase in the bacterial number, however, was observed in the samples from various depths of the GAC FAs in WTPs B and S compared with the surface layers. An increase in the bacterial number was also detected in the filtered water. This may indicate that there is a regrowth of the bacteria in the GAC FA. Considering, however, that heterotrophic bacteria were not found in the filtered water, it can be deduced that most bacteria are removed in the chlorination process. Coliforms were detected at the surface layer of the GAC FAs, but their regrowth was not observed. MicroLog systems were used to identify the bacteria community distribution. Eight genera and 14 species, including Pseudomonas spp., were detected in WTP B, and 8 genera and 9 species, including Aeromonas spp., in WTP S. Further studies are required to elucidate their role in the biofilms in water treatment processes.

• Korean Journal of Microbiology
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• v.26 no.4
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• pp.332-338
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• 1988

The density of heterotrophic bacterial population and heterotrophic activity were measured at monthly interval from March, 1986 to March, 1987 at four sites in the Sudong Stream, a tributary of North Han River. Total bacterial numbers and maximum uptake velocity ($V_{max}$) of glucose ranged as 0.8-$25.2\times 10^{5}$ cells/ml, 0.0006-24.39.$\mu$gC/1/hr, respectively. $V_{max}$ of glucose showed marked seasonal periodicity, with highest values in summer. But density of viable bacteria varied considerably, with no definite seasonal pattern. At the nucontaminated site which located in upstream, heterotrophic bacterial population and activities were relatively low, and small variations were observed downstream flowing except the site where animal originated sewage inputs occurred. And this large input of allochthonous materials and bacteria was an important factor for the stream condition.

• Korean Journal of Microbiology
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• v.30 no.5
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• pp.366-370
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• 1992

Sediment samples were collected from the stations 0101-0921 located between N $32^{\circ}$30'~$34^{\circ}$30' and E $123^{\circ}$30'-$128^{\circ}$30' during July 31-August lO. 1988. The distributions of total heterotrophic bacteria, freshwater bacteria and hydrocarbon degrading bacteria were studied. Each bacterial distribution was in the range of $3{\times}10^{5}~9.2{\times}10^{6}CFU/cm^{3}$sediment, $3{\times}10^{3}~2.1{\times}10^{6}CFU/cm^{3}$ sediment and $2{\times}10^{4}~6.2{\times}10^{6}CFU/cm^{3}$ sediment. respectively. The percent of hydrocarbon degrading bacteria against total heterotrophic bacteria was 0.7-73,2 % which was much higher than other marine sediments reported. These values were statistically analyzed with the percent of freshwater bacteria against total heterotrophic bacteria. These two parameters were well correlated with the correlation coefficient r= 0.60058 (n=34) and P=0.OOO2. This means that the distributions of hydrocarbon degrading bacteria and freshwater bacteria in the research area were affected together by the fresh water discharge into the sea environment. Therefore it can be concluded that the distribution of hydrocarbon degrading bacteria in the sediment of South Sea was affected by petroleum hydrocarbon input from terrestrial region through rivers.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.4
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• pp.597-604
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• 2011

This study was performed to compare finished water quality among three different processes. A detailed assessment of performance was carried out during the five months of operation. Finished water quality was evaluated on the basis of parameters such as Dissolved organic carbon (DOC), $UV_{254}$ absorbance, haloacetic acid formation potential (HAAFP), geosmin, 2-methylisoborneol (2-MIB), heterotrophic bacteria and total coliform bacteria. The treatment processes were Process 1 (coagulation-flocculation-sedimentation-sand filtration-ozone-GAC), Process 2 (coagulation-flocculation-sedimentation -microfiltration-ozone-GAC), and Process 3 (coagulation-flocculation-sedimentation- sand filtration-GAC), compared side by side in the pilot testing. Process 2 was found to have better removal efficiency of DOC, $UV_{254}$ absorbance, HAAFP and heterotrophic bacteria in comparison with process 1 and process 3 under identical conditions. Geosmin, 2-MIB and total coliform bacteria were not detected in finished water from each process.

• Korean Journal of Environmental Biology
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• v.20 no.1
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• pp.85-90
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• 2002

In an artificial pH-gradient batch culture system, the author analyzed the effects of acidification on the species composition of heterotrophic bacteria. As the result of this study, it was found that the numbers of total bacteria were not affected by acidification and that the population size of heterotrophic bacteria decreased as pH became lower. The heterotrophic bacteria isolated from all of the pH gradient were 12 genera and 22 species, and among them, gram negative and gram positive bacteria were 04% and 30%, respectively. As pH decreased, the distribution rate of gram negative bacteria increased while that of gram positive bacteria decreased. Regarding to distribution rate of genuses in each pH gradient, 13 genuses appeared at pH 7 while only 5 genuses appeared at pH 3, which means that the diversity of genera decrease as pH decreased. The activities of extracellular enzyme showed the ranges of $0.008-0.292\;\mu{M}\ell^{-1}\;hr^{-1}$ in bioreactor system. The enzymatic activities decreased rapidly below pH 5 and then sustained 5-38% at the lower pH values.

• Environmental Engineering Research
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• v.22 no.1
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• pp.55-60
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• 2017

Provision of safe, accessible, and good water quality in the community is an important step towards reducing various waterborne illnesses. However, improving the quality of water should include spreading awareness to the public regarding the importance of cleaning their household water tanks. The aim of this study was to investigate the microbial quality of water of household water tanks in Dubai. The water samples from household water tanks were collected from forty houses, and a questionnaire was given to the residents to determine the history of the water tanks. The membrane filtration technique was used to quantify heterotrophic and total coliform bacteria on plate count agar and the violet red bile agar respectively. The overall results of this study have shown that 18 out of total 40 household water tanks contained different types of bacteria concentration level beyond local and widely accepted international standards. The overall results of this study indicated that there is a lack of awareness among residents regarding the importance of maintaining proper sanitation and hygiene of the household water tanks.

• Journal of Marine Bioscience and Biotechnology
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• v.13 no.1
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• pp.10-19
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• 2021

This study investigated how ozone treatment can successfully inactivate pathogenic bacteria in both artificial seawater and effluents discharged from the fishery quarantine station in Pyeongtaek Port, Korea. Vibrio sp. and Streptococcus sp. were initially inoculated into the artificial seawater. All microbes were almost completely inactivated within 10 min and 30 min by injecting 6.4 mg/min and 2.0 mg/min of ozone, respectively. It was discovered that the water storing Pleuronichthys, Pelteobagrus, and Cyprinus imported from China contained the indicator bacteria, Vibrio sp., Enterococcus sp., total coliforms, and heterotrophic microorganisms. Compared to the control, three indicator bacteria were detected at two to six times higher concentrations. The water samples displayed a diverse microbial community, comprising the following four phyla: Bacteroidetes, Proteobacteria, Firmicutes, and Actinobacteria. Almost all indicator bacteria were inactivated in 5 min at 2.0 mg/min of ozonation; comparatively, 92.9%-98.2% of the less heterotrophic microorganisms were deactivated within the same time period. By increasing the dosage to 6.4 mg/min, 100% deactivation was achieved after 10 min. Despite the almost complete inactivation of most indicator bacteria at high doses after 10 min, several bacterial strains belonging to the Proteobacteria have still been found to be resistant under the given operational conditions.

• 한국해양학회지
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• v.30 no.5
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• pp.413-425
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• 1995

Abundances and bacterivory of heterotrophic and mixotrophic nanoflagellates were investigated fourtimes between October 1993 and March 1995 in an estuarine system of the Mankyung and Dongjin rivers to understand distributions of nanoflagellates and ecological significance of bacterivory of nanoflagellates. Bacterivory of nanoflagellates were measured with fluorescently labeled bacteria (FLB). Heterotrophic and autotrophic flagellates showed a rage of 438-4,159 cells ml/SUP -1/ (mean of 2,145 cells ml/SUP -1/, n=20) and 971- 4,935 cells ml/SUP -1/ (mean of 2,2226 cells ml/SUP -1/, n-20), respectively. These two groups of nanoflagellates generally showed similar distributions of abundance. Abundances of heterotrophic nanoflagellates, known as major grazers of bacteria, and those of autotrophic nanoflagellates with chloroplasts showed statistically significant correlations with bacterial abundance (respectively, r$^2$=0.51 and r $^2$=0.47, p>0.05). Mixotrophic nanoflagellates seemed to comprise at least 4-23% of autotrophic nanoflagellate populations. Individual predation rates of heterotrophic nanoflagellates ranged from 2.2 to 14.2 bacteria flagellate/SUP -1/ h/SUP -1/ (mean of 4.9 bacteria flagellate/SUP -1/h/SUP -1/, n=16), and those of mixotrophic nanoflagellates from 1.6 to 9.7 bacteria flagellate/SUP -1/ h/SUP-1/ (mean of 3.7 bacteria flagellate /SUP -1/ h/SUP -1/, n=16). Bacterivory by mixotrophic nanoflagellates comprised from 30 to 69% of total nanoflagellates grazing on bacteria, indicating the significant role of mixotrophic nanoflagellates as grazers on bacteria in the study area. The ratios of grazing rates on bacteria to bacterial secondary production ranged widely from 0.06 to 1.23. In June, when abundances of total nanoflagellates were low, removal of bacteria by bacterivory of nanoflagellates was also a small fraction (0.08${\pm}$ 0.01, n=4) of bacterial production. In other seasons, nanoflagellates usually grazed on bacteria in significant fraction (0.06${\pm}$0.37, n=9) of bacterial production. Both heterotrophic and mixotrophic nanoflagellates appear to be major grazers on bacteria, and might transfer bacterial secondary production to higher trophic level in an estuarine system of the Mankyung and Dongjin rivers.