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Continuous exposure of pesticides in an aquifer changes microbial biomass, diversity and degradation potential
Published in Poul L. Bjerg, Peter Engesgaard, Thomas D. Krom, Groundwater 2000, 2020
J.R. de Lipthay, K. Johnsen, J. Aamand, N. Tuxen, H.-J. Albrechtsen, P.L. Bjerg
Sediment and groundwater samples were collected along (A1, A2, B2) as well as outside (K1) the contaminant plume at Vejen. Batch experiments were set up to investigate whether the different history of exposure to pesticides in the Vejen aquifer had affected the potential of degradation of these chemicals. The batch experiments included the same pesticides as used in the injection field study as well as the herbicide 2,4-D. Impact on bacterial biomass was determined by direct counting of DAPI stained cells and by enumeration of culturable bacteria using selective (Gould’s S1) as well as less selective (water agar) media. Enumeration of phenoxyalcanoic acid degraders was performed by a MPN technique. Effect on bacterial diversity was determined by three different methods: (i) phenotypic diversity by description of colony morphology, (ii) functional diversity by community substrate usage, inoculating samples into Eco Microplates, and (iii) genetic diversity by performance of Denaturing Gradient Gel Electrophoresis of PCR amplified 16S rDNA. Furthermore, a number of chemical and physical analyses were performed, e.g. pH, oxygen, concentrations of anions and cations, sediment type, content of organic carbon.
In Vivo Studies
Published in Alexandra C. Miller, Depleted Uranium, 2006
David E. McClain, Alexandra C. Miller
The earliest studies on DU effects involved using cellular model systems and were conducted in the mid-1990s at the U.S Armed Forces Radiobiology Research Institute. A strategic research approach involving the progression from cellular studies to animal model and finally to human epidemiology considerations was the approach used by Dr. Miller and colleagues (Figure 1.1). This research group used an immortalized human cell line to study neoplastic transformation, genomic instability, genotoxicity, and radiation-induced damage. The neoplastic transformation model approach was used to evaluate carcinogenic potential of DU (Figure 1.2). In this approach, human cells are exposed to the test material and then plated for colony formation. An evaluation of the colony morphology is used to define the state of transformation of the exposed cells. These were the first studies to demonstrate that DU could transform human cells into the malignant phenotype. Miller et al. (1998b) observed transformation of human osteoblast (HOS) cells to a tumorigenic phenotype after exposure to uranyl chloride, a soluble DU compound. DU-treated cells also demonstrated anchorage-independent growth, increased levels of the k-ras oncogene, and decreased levels of Rb tumor suppressor protein. The latter changes are associated with the malignant phenotype in other heavy metal treated cells. A comparison to insoluble DU (uranium dioxide), and other nonradioactive heavy metals was done to enable a comparison of DU-induced effects to those of better known carcinogenic heavy metals like nickel. Transformation rates of DU-exposed cells were 9.6 times that of untreated controls, and transformed cells formed tumors in nude mice. The results from all these transformation studies are compiled in Table 1.2. A comparison of the transformation values indicates that DU can neoplastically transform human cells similar to other better-known heavy metals and at a similar magnitude. These results were the first indication that DU could be carcinogenic; however, as is the case for any determination of carcinogenicity, in vivo studies would be necessary to more fully understand DUs potential as a carcinogen. The studies done to assess DU carcinogenicity in vivo are discussed in detail in a later chapter. Not only was the human cell model excellent as a means to study DU, but the same model was used to evaluate additional carcinogenic, mutagenic, and genotoxic endpoints.
Removal of lindane in liquid culture using soil bacteria and toxicity assessment in human skin fibroblast and HCT116 cell lines
Published in Environmental Technology, 2023
Banishree Sahoo, Surabhi Chaudhuri
Initially, the isolate NITDBS9 was characterized based on various morphological, biochemical and physiological properties. Morphological characterization included microscopic and macroscopic examination such as colony morphology, shape, gram-staining, pigmentation, etc. Biochemical characterization included enzyme activities such as catalase, oxidase, lipase and urease tests, starch and casein hydrolysis, Voges–Proskauer test, methyl red test, utilization of different carbon sources, ability to produce hydrogen sulphide, citrate utilization, and mannitol salt agar tests. All these characterizations were performed following the methods described by Cappuccino and Sherman [20]. 16S rRNA gene sequencing was used for the molecular characterization of NITDBS9. For this, the genomic DNA of NITDBS9 was isolated, purified and checked for quality in 1.2% agarose gel [21]. Amplification and sequencing of 16S rRNA gene were done following the method discussed in a previous study [19]. BLAST analysis was done for the resulting nucleotide sequence using the NCBI online tool [22]. The sequences were aligned using the ClustalW program, evolutionary distances were calculated and the phylogenetic tree was constructed using the MEGAX software (version 10.1.7). Finally, the sequence was submitted to NCBI, and an accession number was generated.
Waste frying oil hydrolysis and lipase production by cold-adapted Pseudomonas yamanorum LP2 under non-sterile culture conditions
Published in Environmental Technology, 2021
Senba Komesli, Sumeyya Akbulut, Nazli Pinar Arslan, Ahmet Adiguzel, Mesut Taskin
To determine the extent of possible contamination in non-sterile media, 0.1 mL sample withdrawn from the culture was spread on Petri dishes containing TSA medium after diluted with sterile saline water. The inoculated Petri dishes were then left to the incubation at 15°C for 48 h. Colony morphology (shape, texture, colour and size) of bacteria developing on TSA was examined. In order to determine whether bacterial colonies were different from each other, a sample taken from each colony was spread on a glass slide, and then the slides were examined under a microscope to determine the shape, size and motility of bacterial cells. Briefly, the presence of different bacteria (unwanted bacterial contamination) during optimization studies was determined by colony morphology and microscopic examination. On the other hand, in the last step (optimization of the incubation period) the presence of possible contamination was also investigated by using 16S RNA sequence analysis. For this purpose, 16S RNA sequence analysis of each bacterial colony on TSA was performed, as described in materials and methods section 2.5. In the end, colonies were counted, and the degree of contamination was expressed by the symbols −, +, ++ and +++. No contamination (−), less contamination (+), moderate contamination (++) and high contamination (+++).
Domestic wastewater treatment efficiency of the pilot-scale trickling biofilter system with variable flow rates and hydraulic retention times
Published in Environmental Technology, 2021
Abdul Rehman, Haris Ali, Iffat Naz, Devendra P. Saroj, Safia Ahmed
Bacteriological assessment of biofilm developed on pebbles and gravels filter media were performed according to their standard procedure as described in Bergey’s Manual of Determinative Bacteriology (9th Edition). Colony morphology (size, pigmentation, form, opacity, margin and elevation of colonies) appeared over the surface of growth media was observed by naked eye and then standard Gram staining procedure was used for microscopy of bacterial isolates. After microscopy, different biochemical tests were performed to identify bacterial isolates.