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DNA microarray analysis for HepG2 cells exposed to wastewater effluents

ABSTRACT: The transcriptome analysis by the human DNA microarray was applied to evaluate the impacts of whole wastewater effluents from the membrane bioreactors (MBRs) and the activated sludge process (AS), on the biological processes of human hepatoma HepG2 cells. The three conventional bioassays (i.e., cytotoxicity tests and bioluminescence inhibition test) and chemical analysis of the domestic effluent standards were conducted in parallel since they are well-established methods with previous applications to wastewater. A significant variation of effluent quality was sdemonstrated among the tested effluents despite that all effluents met the 40 national effluent standards. The three conventional bioassays supported the result of the transcriptome analysis, indicating the comparable or even higher sensitivity of the new assay. The most superior effluent quality was found in the MBR operated at a relatively long sludge retention time (i.e., 40 days) and small membrane pore size (i.e., 0.03 μm). In addition, functional analysis of the differentially expressed genes revealed that the effluents made various impacts on the cellular functions, suggesting the transcriptome analysis by DNA microarray as more comprehensive, rapid and sensitive tool to detect multiple impacts of the whole effluents. Moreover, the potential genetic markers were proposed to quantitatively evaluate the treatability of the wastewater effluents.

ORGANISM(S): Homo sapiens

PROVIDER: GSE45605 | GEO | 2013/03/29

SECONDARY ACCESSION(S): PRJNA195381

REPOSITORIES: GEO

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Project description:Wastewater treatment plants use a variety of bioreactor types and configurations to remove organic matter and nutrients. Little is known regarding the effects of different configurations and within-plant immigration on microbial community dynamics. Previously, we found that the structure of ammonia-oxidizing bacterial (AOB) communities in a full-scale dispersed growth activated sludge bioreactor correlated strongly with levels of NO2- entering the reactor from an upstream trickling filter (Wells et al 2009). Here, to further examine this puzzling association, we profile within-plant microbial biogeography (spatial variation) and test the hypothesis that substantial microbial immigration occurs along a transect (raw influent, trickling filter biofilm, trickling filter effluent, and activated sludge) at the same full-scale wastewater treatment plant. AOB amoA gene abundance increased >30-fold between influent and trickling filter effluent concomitant with NO2- production, indicating unexpected growth and activity of AOB within the trickling filter. Nitrosomonas europaea was the dominant AOB phylotype in trickling filter biofilm and effluent, while a distinct ‘Nitrosomonas-like’ lineage dominated in activated sludge. Prior time series indicated that this ‘Nitrosomonas-like’ lineage was dominant when NO2- levels in the trickling filter effluent (i.e., activated sludge influent) were low, while N. europaea became dominant in the activated sludge when NO2- levels were high. This is consistent with the hypothesis that NO2- production may co-occur with biofilm sloughing, releasing N. europaea from the trickling filter into the activated sludge bioreactor. Phylogenetic microarray (PhyloChip) analyses revealed significant spatial variation in taxonomic diversity, including a large excess of methanogens in the trickling filter relative to activated sludge and attenuation of Enterobacteriaceae across the transect, and demonstrated transport of a highly diverse microbial community via the trickling filter effluent to the activated sludge bioreactor. Our results provide compelling evidence that substantial immigration between coupled process units occurs and may exert significant influence over microbial community dynamics within staged bioreactors.

Project description:Despite recent knowledge of the potential environmental impact that compounds present in municipal wastewater effluents, including contaminants of emerging concern (CECs), may have, the implications of fish exposure to this contaminant mixtures are not completely understood. The effects caused by effluent CECs may be subtle and diverse, thus the need for sensitive and comprehensive tools such as gene expression to detect such responses. In this study, we conducted laboratory exposures that examined plasma concentrations of vitellogenin (VTG), changes in secondary sexual characteristics and gene expression in sexually mature male fathead minnows (Pimephales promelas) exposed to environmentally realistic (0.5%) and higher (5%) concentrations of municipal wastewater effluents. Secondary and primary treated effluents were used. Several of the 32 CECs investigated were detected, including pharmaceuticals, personal care products, hormones, current use pesticides and industrial compounds. The percent of males with detectable levels of VTG was higher in fish exposed to effluent treatments. An increased number of males with changes in secondary sexual characteristics (e.g. development of ovipositors), was observed in fish exposed to 5% effluent treatments. Gene expression data indicated that overall expression patterns were characteristic to each effluent. Higher numbers of differentially expressed genes were observed in fish exposed to primary treated effluent when compared to controls. Differentially expressed genes belonged to several functional categories, including xenobiotic metabolism, estogenicity and energy/metabolism processes. Gene expression data provided information to understand some of the mechanisms behind the effects observed at higher biological levels. To investigate gene expression responses resulting from exposure to POTW effluents, two laboratory experiments were conducted using effluent from San Diego (Point Loma; SD) and Los Angeles (Hyperion; LA). The LA effluent received secondary treatment and the SD effluent received advanced primary treatment. Treatments used during exposures consisted of negative controls (moderately hard water), positive controls (E2), and 0.5% and 5% effluent concentrations. The 0.5% concentration of effluent represented an environmentally realistic exposure level. The 5% effluent concentration represented a higher level at which we expected biological responses. The exposures lasted 14 days. Treatments: EFFHa = 5% primary treated effluent EFFHb = 5% secondary treated effluent EFFLa = 0.5% primary treated effluent E2a = Estradiol, positive control for primary effluent E2b = Estradiol, positive control for secondary effluent CTRLa = Moderately hard water, negative control for primary effluent CTRLb = Moderately hard water, negative control for secondary effluent

Project description:Contaminants of emerging concern (CECs) in treated municipal effluents have the potential to adversely impact exposed organisms prompting elevated public concern. Using transcriptomic tools, we investigated changes in gene expression and cellular pathways in the liver of male fathead minnows (Pimephales promelas) exposed to 5% concentrations of full secondary-treated (HTP) or advanced primary-treated (PL) municipal wastewater effluents containing CECs. Gene expression changes were associated with apical endpoints (plasma vitellogenin and changes in secondary sexual characteristics). Of 32 effluent CECs analyzed, 28 were detected including pharmaceuticals, personal care products, hormones, and industrial compounds. Transcript patterns differed between effluents, however < 10% of these had agreement in the detected response (e.g. transcrips involved in xenobiotic detoxification, oxidative stress and apoptosis) in both effluents. Exposure to PL effluent caused changes in transcript levels of genes involved in metabolic pathways (e.g., lipid transport and steroid metabolism). Exposure to HTP effluent affected transcripts involved in signaling pathways (e.g., focal adhesion assembly and extracellular matrix). Exposure to both effluents produced significantly higher levels of plasma VTG and changes in secondary sexual characteristics (e.g., ovipositor development). Taken together the results suggest, a potential association between some transcriptomic changes and higher biological responses following effluent exposure; and a potential adverse outcome pathway following exposure to complex chemical mixtures containing CECs -. Furthermore, this study identified responses in key genes and pathways not previously implicated in exposure to CECS, , which could be consistent with effluent exposure (e.g., oxidative stress) in addition to other pathway responses specific to the effluent type. This may be useful for assessing the adverse health effects of fish by effluents exposure to CECs.

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DNA microarray analysis for HepG2 cells exposed to wastewater effluents

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