Fadime Yilmaz

Challenging tin toxicity by a novel strain isolated from freshwaters

AbstractThe first major challenge for the bioremediation field is to select the most promising types of biomass. Hence, the objective of this study was to isolate and identify a novel species which has the potential to remediate tin in freshwaters. For this reason, a bacterium designated as Sn11, with 59 μg ml−1 maximum tolerable concentration of tin was isolated selectively from the freshwater samples collected along the river Kirikkale-Kizilirmak, Turkey. Identification of the isolate was done using biochemical tests, fatty acid methyl ester analysis, and 16S rRNA sequencing. Fatty acids produced by the isolate investigated were assumed as typical for the genus Pantoea. Pantoea were highly homogeneous by dominant C16:0 and C16:1 cis 9 fatty acids. 16S rRNA sequence analysis also confirmed that the isolate Sn11 had 98% homology with Pantoea agglomerans. The complete sorption of 59 μg ml−1 tin by P. agglomerans was recorded at about 20 h incubation. Due to higher affinity toward tin sorption, P. agglomera...

vanA Gene Harboring Enterococcal and Non-enterococcal Isolates Expressing High Level Vancomycin and Teicoplanin Resistance Reservoired in Surface Waters

Untreated wastewaters and treated effluents even after final disinfection contain antibiotic resistant bacteria and resistance genes before they are released into surface waters. A correlation between resistant bacteria and antibiotics in surface waters has been found, as have antibiotic resistance genes. Of particular interest are vancomycin-resistant enterococci harboring vanA gene that confers high level of resistance to glycopeptide antibiotics including teicoplanin. Therefore, in this study, river water samples were analysed to investigate vancomycin- and teicoplanin-resistant bacterial isolates harboring vanA gene. Out of 290, 15 surface water isolates displayed resistance to both antibiotics. These glycopeptide resistant enterococcal and non-enterococcal isolates, identified by 16S rRNA sequencing, were found to harbor vanA gene with sequence similarities of 50 % to 100 %. The presence of d-alanine-d-lactate ligase encoded by vanA gene was also shown for all vancomycin- and teicoplanin-resistant isolates through western blot analysis. Due to reuse of treated wastewater and release of untreated wastewaters to water bodies, antibiotic resistant bacteria and resistance genes are being introduced into surface waters and present human health risks. Therefore, surface waters are not only hot spots for vanA harboring enterococcal isolates but also non-enterococcal isolates due to gene dissemination and require special scientific consideration.

Biosorption of Strontium from Aqueous Solutions by Micrococcus luteus Sr02

ABSTRACT Although strontium (Sr2+) is found in soils, sediments and surface waters, there is limited evidence about its biosorption. In this study, a surface water strain being highly tolerant to Sr2+ was isolated and identified as Micrococcus luteus Sr02 by using 16S rRNA sequencing. Biosorption behavior and mechanisms of Sr2+ by M. luteus Sr02 were investigated through batch experiments, zeta potential measurements, Fourier transform infrared spectroscopy and scanning electron microscopy. The results showed that M. luteus Sr02 have potential to sorb Sr2+ and can be used efficiently for the removal of Sr2+ from aqueous solutions.

Higher alkyl sulfatase activity required by microbial inhabitants to remove anionic surfactants in the contaminated surface waters

Biodegradation of anionic surfactants, like sodium dodecyl sulfate (SDS) are challenged by some bacteria through the function of the enzyme alkyl sulfatases. Therefore, identifying and characterizing bacteria capable of degrading SDS with high alkyl sulfatase enzyme activity are pivotal. In this study, bacteria isolated from surfactant contaminated river water were screened for their potential to degrade SDS. Primary screening carried out by the conventional enrichment culture technique and assessment of SDS-degrading ability through methylene blue active substance assay revealed 12, out of 290, SDS-degrading surface water bacteria with maximum SDS degrading abilities of 46-94% in 24-54 h. The isolates exhibited optimum growth at SDS concentration of 1 g/L, but tolerated up to 15-75 g/L. Eleven isolates were identified as the species of Pseudomonas and one isolate was identified as Aeromonas through 16S rRNA sequencing. Proteolytic activity of alkyl sulfatases in the identified isolates was shown by using native-PAGE analysis. The determined enzyme activities changed in between 1.32 and 2.90 U/mg in the crude extracts. Preliminary experiments showed that the isolates with the alkyl sulfatase enzyme activities ≥2.50 U/mg were strong gratuitous degraders. However, their relative importance in soil, sewage, and wastewater treatment plants remains to be assessed.

Use of cadA-Specific Primers and DNA Probes as Tools to Select Cadmium Biosorbents with Potential in Remediation Strategies

Biosorption, using cadmium-resistant bacterial isolates, is often regarded as a relatively inexpensive and efficient way of cleaning up wastes, sediments, or soils polluted with cadmium. Therefore, many efforts have been devoted to the isolation of cadmium-resistant isolates for the efficient management of cadmium remediation processes. However, isolation, identification and in situ screening of efficient cadmium-resistant isolates are primary challenges. To overcome these challanges, in this study, cadA, cadmium resistance coding gene, specific primers and DNA probes were used to identify and screen cadmium-resistant bacteria in the cadmium-polluted river waters through polymerase chain reaction (PCR) and fluorescein in situ hybridization (FISH). PCR amplification of the cadA amplicon coupled with 16S rRNA sequencing revealed various gram-positive and -negative bacterial isolates harboring cadA. Accordingly, a cadA-mediated DNA probe was prepared and used for in situ screening of cadmium-resistant isolates from water samples collected from cadmium-polluted river waters. The FISH analyses of cadA probe showed highly specific and efficient hybridization with cadA harboring isolates. The use of primers and DNA probes specific for cadA gene seems to be very helpful tools for the selection and screening of cadmium biosorbents with potential to be used in the remediation of cadmium-polluted sites.