• Journal of Microbiology and Biotechnology
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• v.16 no.7
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• pp.1060-1067
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• 2006

This study was undertaken to determine the effect of reservoirs on water quality and the distribution of pathogenic and indicator bacteria in a drinking water distribution system (total length 14km). Raw water, disinfected water, and water samples from the distribution system were subjected to physicochemical and microbiological analyses. Most factors encountered at each season included residual chloride, nitrate, turbidity, and phosphorus for heterotrophic bacterial distribution, and hardness, heterotrophic bacteria, sampling site, and DOC (dissolved organic carbon) for bacteria on selective media. No Salmonella or Shigella spp. were detected, but many colonies of opportunistic pathogens were found. Comparing tap water samples taken at similar distances from the water treatment plant, samples that had passed through a reservoir had a higher concentration of heterotrophic bacteria, and a higher rate of colony formation with 10 times as many bacteria on selective media. Based on the results with m-Endo agar, the water in reservoirs appeared safe; however, coliforms and opportunistic pathogenic bacteria such as Pseudomonas aeruginosa were identified on other selective media. This study illustrates that storage reservoirs in the drinking water distribution system have low microbiological water quality by opportunistic pathogens, and therefore, water quality must be controlled.

• Ocean and Polar Research
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• v.24 no.1
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• pp.47-53
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• 2002

To evaluate the effect of reed population on the distribution and activities of microorganisms, vertical distribution of heterotrophic bacteria, degradation rate of cellulose, extracellular aminopeptidase activity (APA) and metabolic diversity based on GN2 Microlog plate were measured at two salt marsh stations in Hogok-ri, Namyang Bay, west coast of Korea. The number of heterotrophic bacteria at station 1 (reed population inhabited area) showed 2 to 6 times higher than that of station 2 (exposed area) with exception in the surface layer. Cellulose degradation rates in station 1 showed more than 50%. month-I and higher than that of station 2 (10.2 to 38.4%. $month^{-1}$). Yet the APA at two stations did not show difference except surface layer and suggested that APA might not be a significant factor in degrading marsh plant debris. Lipid class compounds, cell wall polymers and L-alanine were widely used by microorganisms. The number and activities of bacterial populations especially concerned in plant debris degradation seemed to be stimulated by the reed communities.

• Korean Journal of Microbiology
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• v.26 no.3
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• pp.256-261
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• 1988

Samples from Naktong Estuary had been taken for the characterization of heterotrophic bacterial communities and of the effects of environmental factors on their distribution in estuarine ecosystem. Bacterial communities isolated from seawater region were composed of more euryhalone groups than those from freshwater region, and the bacterial communities of summer were composed of more eurythermal groups than those of winter. Bacterial commnities became more diverse by the input of allochthonous bacteria from terrestrial and freshwater ecosystem, but less diverse by worse environmental conditions such as nutrient load, high salinity, low temperature, and so on.

• Journal of Korean Society on Water Environment
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• v.22 no.3
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• pp.527-533
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• 2006

Tetracycline is one of the mostly used antibiotics around the world. The purpose of this study was to evaluate the fate of two different types of tetracycline resistant bacteria in biological wastewater treatment plants. Tetracycline resistant enterics and heterotrophic bacteria were monitored under two different lab-scale experimental conditions. Tetracycline resistant enteric bacteria showed the lower percentages of total enteric bacteria and net specific growth rate in the monitored activated sludge system as compared to tetracycline resistant heterotrophic bacteria. Therefore, total enterics, potentially E.coli, might not be the best indicator microorganism for evaluating the antibiotic resistant bacteria in biological wastewater treatment plant.

• 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.29 no.5
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• pp.339-343
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• 1991

Heterotrophic activity, total bacteria and salinity were determined seasonally in the estuary of Naktong River over half tidal cycle. Heterotrophic activity was determined by the uptake of [U- $^{14}$ C]glucose. Heterotrophic activity fluctuated with the tides and was decreased as salinity increased. Teh great activity occurred near low ebb tide at all seasons except summer. The main environmental factor affecting hetreotrophic activity was the salinity rather than water temperature in the estuary of Naktong River. In order to estimate the effect of salt, salt was added to estuarine water. Vmax for glucose of salt-added water was 17% and 77% of original estuarine water at station 1 and 2 respectively and slight increase was observed at station 3. Respiration rate and Kt+Sn for glucose of salt-added sample increased at all 3 stations. The increase of the Kt value implies the reduced affinity of bacterial population for glucose. The effects of salinity on the heterotrophic activity were more extensive in the upper region of estuary than at the mouth.

• Korean Journal of Microbiology
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• v.29 no.5
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• pp.329-338
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• 1991

From July 1985 to December 1986, 28 variables of phycal-chemical factors, bacteria and heterotrophic activity were investigated 17 times at 3 stations in the estuary of Naktong River and the influences of environmental factors to bacterial population and heterotrophic activity were analyzed through multiple regression. The results of multiple regression were as follows. At station 1, total bacteria and heterotrophic bacteria(Z-25) could explain 57% of the variation of maximum uptake velocity for glucose and 54% of turnover time for glucose was explained by total coliform bacteria and MBOD, Sixty four percent of the variation of Kt+SN was accounted for salinity, MBOD-N and inorganic phosphate. Turnover rate for acetate was also accounted for the change of MBOD-P by 56%. At station 2 maximum uptake velocity for glucose depends on MBOD-N by 81%; turnover time on bacteria by 50%; Kt+Sn on avilable nutrient by 61%. More than 50% of maximum uptake velocity and turnover time for glucose were influenced by bacteria and that of Kt+Sn by the change of nutrient in the surface water of station 3. In the bottom water of station 3, the change of maximumuptake velocity, turnover time and Kt+Sn for glucose was controlled by total bacteria and available nutrient, bacteria, the change of nutrient salts respectively. On the whole, more than 50% of maximum uptake velocity and turnover time for glucose could be due to the change in the number of bacetria and the value of Kt+Sn was affected by the change of nutrient salts. Turnover rate for acetate was controlled by available phosphate at station 1 and by bacteria at station 2 and 3, which showed a distinct difference between the environmental factors which govern the rate of glucose and acetate uptake in the Naktong esturine ecosystem. And bacterial communities were controlled by available nutrients at station 1, by nutrient salts and salinity at station 2 and in the surface water of station 3 and by salinity in the bottom water of station 3.

• Journal of Environmental Science International
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• v.16 no.7
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• pp.855-863
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• 2007

In order to understand the temporal distribution of pico- and nanoplankton and factors controlling its distribution at a station in Okkye Bay of Masan Bay located in the southern part of Korea, this study was conducted on two weeks interval from April 2005 to April 2006, and several abiotic and biotic factors were measured. During the study, picoplankton consisted of picoflagellates, cyanobacteria and heterotrophic bacteria, and nanoplankton consisted of nanoflagellates excluding dinoflagellates. The concentration of chlorophyll-a (chl-a) was a mean of $4.33\;{\mu}g/L$, and the nanoplanktonic ($<20\;{\mu}m$) chl-a size fraction was a mean of 39.5 % and significantly correlated with water temperature. The abundances of cyanobacteria and photosynthetic flagellates (PF) were means of $24.4{\times}10^{3}\;cells/mL\;and\;2.87{\times}10^{3}\;cells/mL$, respectively. The contribution of picoflagellates to the PF abundance varied among the sampling occasions and was a mean of 29 %, but to the PF carbon biomass was 2.6 % only. The PF abundance had significant relationships with water temperature, and silicate and TIN concentrations, suggesting that the PF abundance seemed to be primarily bottom-up regulated. The abundance of heterotrophic bacteria was a mean of $3.18{\times}10^{6}\;cells/mL$ and unlike other ecosystems it did not have relationships with chl-a and heterotrophic flagellates (HF), suggesting that bacterial abundance did not seem to be bottom-up or top-down regulated. HF mostly consisted of cells less than $5{\mu}m$ and its abundance was a mean of $2.71{\times}10^{3}\;cells/mL$. Of the HF abundance, picoflagellates occupied about 31 %, and occupied about 9 % of the HF carbon biomass. HF grazing activity on heterotrophic bacteria was relatively low and removed about 10 % of bacterial abundance, suggesting that HF might not be major consumers of bacteria and there seems to be other consumers in Okkye Bay. These results suggest that Okkye Bay may have a unique microbial ecosystem.

• 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.

• Journal of the korean society of oceanography
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• v.37 no.2
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• pp.58-65
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• 2002

The study of microbial communities in sediments is impaired by the lack of reliable extraction methods. This study reports on the efficiency of recovery of a method for extracting bacteria, protists and diatoms from sandy sediments using a modified decant/fix method. The best extractions were achieved after fixation with a microtubule stabilising fixative and subsequent sonication for 80 seconds. We estimate that the efficiencies of recovery of bacteria and mixed heterotrophic flagellates were $96.4{\pm}3.5\%$ and $96.9{\pm}4.6\%$, respectively. Diatoms were recovered with an efficiency of 38-83% and varied considerably from species to species. This study suggests that the decant/fix method is effective in extracting small cells such as bacteria and heterotrophic flagellates, and that the efficiency of recovery of the method varies due to cell length and different types of organisms. When microbial carbon biomass had been underestimated by up to 32%, with much of that relating to larger cells such as microalgae and ciliates. We note that the corrected abundances may be still a subset of the total numbers present.