Browsing by Author "Ogun, Erdal"

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Arsenic Pollution and Anaerobic Arsenic Metabolizing Bacteria in Lake Van, the World's Largest Soda Lake
(Mdpi, 2022) Omeroglu, Esra Ersoy; Sudagidan, Mert; Ogun, Erdal
Arsenic is responsible for water pollution in many places around the world and presents a serious health risk for people. Lake Van is the world's largest soda lake, and there are no studies on seasonal arsenic pollution and arsenic-resistant bacteria. We aimed to determine the amount of arsenic in the lake water and sediment, to isolate arsenic-metabolizing anaerobic bacteria and their identification, and determination of arsenic metabolism. Sampling was done from 7.5 m to represent the four seasons. Metal contents were determined by using ICP-MS. Pure cultures were obtained using the Hungate technique. Growth characteristics of the strains were determined at different conditions as well as at arsenate and arsenite concentrations. Molecular studies were also carried out for various resistance genes. Our results showed that Lake Van's total arsenic amount changes seasonally. As a result of 16S rRNA sequencing, it was determined that the isolates were members of 8 genera with arsC resistance genes. In conclusion, to sustain water resources, it is necessary to prevent chemical and microorganism-based pollution. It is thought that the arsenic-resistant bacteria obtained as a result of this study will contribute to the solution of environmental arsenic pollution problems, as they are the first data and provide the necessary basic data for the bioremediation studies of arsenic from contaminated environmental habitats. At the same time, the first data that will contribute to the creation of the seasonal arsenic map of Lake Van are obtained.
Comprehensive Natural Radioactivity and Pollution Risk Assessments of Aquatic Media and Sediment in Lake Van (T?rkiye)
(Pergamon-elsevier Science Ltd, 2023) Zorer, Ozlem Selcuk; Yorgun, Nergiz Yildiz; Ozdemir, Omer Faruk; Ogun, Erdal; Aydin, Harun; Atici, Ataman Altug; Elp, Mahmut
This paper studies the radionuclide (137Cs, 226Ra, 232Th, 40K) activity concentrations and gross radioactivities in waters and sediments of Lake Van, which is the third largest closed lake (with no natural or artificial outlet) within the Earth. The physico-chemical parameters were measured and evaluated in the lake waters. The mean gross alpha activities in surface, middle and bottom waters are 0.04, 0.03 and 0.03 Bq/L, respectively, and in the same order, the mean gross beta activities are 0.30, 0.23 and 0.33 Bq/L, respectively. In sediment samples, the mean activity concentrations were measured as 1.98 Bq/g for gross-alpha, 3.46 Bq/g for gross-beta, 48.3 Bq/kg for 226Ra, 32.0 Bq/kg for 232Th, 540.1 Bq/kg for 40K and 25.9 Bq/kg for 137Cs. The radiation hazard parameters values based on the measured activities were calculated and Raeq values are lower than the world average value in all samples, while Dout and AED values are relatively high in some sediment samples.
Determination of Inorganic Phosphate-Solubilizing Bacteria in Sediment Samples Collected From Lake Van, Turkey
(Parlar Scientific Publications (p S P), 2020) Ogun, Erdal
In this study, it was aimed to determine the bacteria species of inorganic phosphate-solubilizing bacteria (IPSB) isolated from sediment samples collected from Lake Van, Turkey. The National Botanical Research Institute's phosphate (NBRIP)-bromophenol blue (BPB) growth medium was used to screen the IPSB. An alkalotolerant isolate was determined in the soluble tricalcium phosphate in the NBRIP-BPB medium. This isolate, called the S1 isolate, had a wide tolerance, ranging from pH 5.0 to 10.0. As a result of the spectrophotometric measurements, it was determined that the S1 isolate dissolved a maximum amount of PO4-3 (109.6 mg/L) at pH 6.0, 30 degrees C, and 120 h. In addition, phenotypic and molecular identification of the S1 isolate that dissolved in the inorganic phosphate was performed. Within the scope of molecular identification, the 16S ribosomal RNA region was amplified by polymerase chain reaction using appropriate universal primers. It was determined that this isolate belonged to the Bacillus pumilus species, based on the phylogenetic analysis of the 16S rRNA gene, using the maximum-likelihood method.
The Effect of Bacillus Sp Osu-142 Inoculation at Various Levels of Nitrogen Fertilization on Growth, Tuber Distribution and Yield of Potato (Solanum Tuberosum L.)
(Academic Journals, 2009) Ekin, Zehra; Oguz, Faruk; Erman, Murat; Ogun, Erdal
The objective of this study was to evaluate the yield response of potato to inoculation with Bacillus sp. OSU-142 at three levels of N fertilization (0, 120, and 240 kg ha(-1)) under field conditions in Ahlat District of Eastern Anatolia Region of Turkey in 2006 and 2007. Tuber inoculation with Bacillus sp. OSU-142 significantly affected yield and yield components in both years. Tuber yields and yield components were higher at all levels of nitrogen fertilizer in the inoculated plots as compared to the control. However, beneficial effect of Bacillus sp. OSU-142 on tuber yield was noted at 120 kg N ha-1, possibly indicating either more effective of inoculation in the low-N input agriculture or an interaction of Bacillus sp. OSU-142 with higher yielding seasonal conditions. In general, more response to inoculation was observed in the absence of major crop growth limitations, suggesting the complementary contribution of the Bacillus sp. OSU-142 treatment to more efficiently developing higher yielding potato.
Evolution of Slime Production by Coagulase-Negative Staphylococci and Enterotoxigenic Characteristics of Staphylococcus Aureus Strains Isolated From Various Human Clinical Specimens
(Soc General Microbiology, 2007) Boynukara, Banur; Gulhan, Timur; Gurturk, Kemal; Alisarli, Mustafa; Ogun, Erdal
The present study was designed to determine the slime production of coag u lase- negative staphylococci (CoNS) and the enterotoxigenic properties of Staphylococcus aureus strains, and to evaluate the clinical importance of slime-producing CoNS and enterotoxigenic S. aureus strains isolated from various human clinical specimens. For this purpose, a total of 120 Staphylococcus strains were isolated and identified, and further characterized for their slime production and enterotoxigenicity. Of the clinical isolates, 55 (45.8 %) were found to be S. aureus, and the others (54.2 %) were identified as CoNS. Of the CoNS, 20 (116.7 %) were further identified as Staphylococcus hominis, 18 (15 %) as Staphylococcus epidermidis, six (5 %) as Staphylococcus xylosus, six (5 %) as Staphylococcus warneri, five (4.2 as Staphylococcus sciuri, four (3.3 %) as Staphylococcus haemolyticus, and two each (1. 7 as Staphylococcus simulans, Staphylococcus capitis and Staphylococcus saprophyticus, respectively. Thirty-nine (60%) of 65 CoNS were found to be slime producers. Slime production was observed in all CoNS, except S. capitis, mostly from blood (38.5 %), tracheal aspiration (20.5 %) and urine (112.8 %) specimens. In addition, of the 55 S. aureus isolates, 46 (83.6 %) were found to be enterotoxigenic, and of these S. aureus strains, 39 (84.7 %) were positive for staphylococcal enterotoxin (SE)A. The results of this study showed that the slime-producing CoNS were mostly found in clinical specimens of blood, tracheal aspirate and urine. SEA was the predominant enterotoxin type detected in S. aureus strains from human clinical specimens.
Optimization of Uricase Enzyme Produced by Moderately Haloalkalitolerant Halomonas Sp. F1 Isolate Characterized and Isolated From Lake Van, Turkey
(Parlar Scientific Publications (p S P), 2019) Esen, Firdevs; Ogun, Erdal
In this study, isolates were isolated from Lake Van, a soda lake, and tested for their ability to produce the enzyme uricase. M9 minimal salt medium was used for the primary screening studies. The activity of the enzyme was then determined in different media compositions by analyzing the activity of the crude enzyme solution. In the presence of yeast extract (436.58 U/ml), used as a source of organic nitrogen, the highest activity was determined. In addition, phenotypic and molecular identification of the uricase-positive isolate was performed. Within the scope of molecular identification, the 16S ribosomal RNA region was amplified by polymerase chain reaction using the appropriate universal primers. This isolate was determined by the phylogenetic analysis of the 16S rRNA gene, based on the neighboring joining method, in the genus Halomonas.
Synthesis of Novel Tetra-Substituted Pyrazole Derivatives From 2,3-Furandione
(Bentham Science Publ Ltd, 2019) Genc, Hasan; Tasdemir, Volkan; Tozlu, Israfil; Ogun, Erdal
Synthesis of pyrazole-3-carboxylic acid was progressed via two different protocols, one of which is solid state. Pyrazole-3-carboxylic acid was converted into different derivatives such as ester, urea, amide and nitrile. The amide compound was converted to nitrile using SOCl2 and DMF. Solid state heating of carboxylic acid gave decarboxylated product. Cyclization of tetra-substituted pyrazole with hydrazines resulted in pyrazolopyridazinones. The antimicrobial activities of the synthesized pyrazole derivatives against Bacillus cereus, Escherichia coli, Micrococcus luteus, Staphylococcus aureus, and Saccharomyces cerevisiae were evaluated. One of the pyrazole derivatives which possess nitro group showed antimicrobial activity in only B. cereus, a Gram-positive bacteria, with an MIC of 128 mu g/mL.