This study was conducted to analyze the genetic variability of Escherichia coli from domesticated animal wastes for microbial source tracking (MST) application in fecal contaminated shellfish growing waters of Xiangshan Bay, East China Sea. (GTG)₅ primer was used to generate 1363 fingerprints from E. coli isolated from feces of known 9 domesticated animal sources around this shellfish culture area. Jackknife analysis of the complete (GTG)₅-PCR DNA fingerprint library indicated that isolates were assigned to the correct source groups with an 84.28% average rate of correct classification. Based on one-year source tracking data, the dominant sources of E. coli were swine, chickens, ducks and cows in this water area. Moreover, annual and spatial changes of E. coli concentrations and host sources may affect the level and distribution of zoonotic pathogen species in waters. Our findings will further contribute to preventing fecal pollution in aquatic environments and quality control of shellfish.

Extensive production and application of γ-Fe₂O₃ magnetic nanoparticles (MNPs) has increased their potential risk on environment and human health. This report illustrates a genetic impact of γ-Fe₂O₃ magnetic nanoparticles (MNPs) on Escherichia coli (E. coli). After 3000-generation incubation with MNPs addition, obvious genomic variations were revealed by using repetitive extragenic palindromic PCR (rep-PCR) DNA fingerprint technique. The physicochemical interactions between MNPs and bacteria could be responsible for such genomic responses. It was revealed that Fe³⁺ concentration increased in the medium. Transmission electronic microscopy (TEM) and flow cytometry (FCM) analysis consistently demonstrated the occurrences of adsorption and membranes-internalization of MNPs outside and inside cells. Both increased Fe³⁺ ion and the uptake of MNPs facilitated Fe binding with proteins and DNA strands, resulting in enhancing the mutation frequency of E. coli. Our results would be of great help to assessing the potential impact of MNPs on human and environment.

The relationship between land use and microbial community structure at seven sites along the Lower Mekong River, between Thailand and the Loa People’s Democratic Republic, was investigated using Illumina next-generation sequencing of the V5–V6 hypervariable regions of the 16S rRNA gene. In total, 14,470 operational taxonomic units (OTUs) were observed. Community composition was significantly different between sampling years. Moraxellaceae and Comamonadaceae were the predominant bacterial families in upstream sites, which included agricultural and urban areas in the Loei and Nong Khai provinces of Thailand. Members of the family Comamonadaceae were prevalent in agricultural and urban sites in Bueng Kan Province, while Moraxellaceae and Burkholderiaceae were the major families in a site downstream of an urban area in the Nakhon Phanom Province of Thailand. The bacterial community observed from a forested area of Patam National Park in Thailand showed greatest diversity, and several major bacterial families including Comamonadaceae, Moraxellaceae, and Pseudomonadaceae were more dominant than other sites. The diversity of fecal indicator bacteria, determined by ERIC-PCR DNA fingerprinting, indicated the presence of 29 strains of Escherichia coli and 21 strains of Enterococcus, while TP-RAPD patterns represented six species of Enterococcus. Results of this study indicated that although the difference in the distribution of bacterial phyla and families was found among sampling sites, the bacterial community composition, based on the presence of OTUs, continuously retained its signature across approximately 758 km along the Lower Mekong River, regardless of the type of land use. Water parameters, including temperature, turbidity, DO, and air temperature, also differentially affected the abundance of bacterial families along the Mekong River.

The aim of the present study was to isolate several bacterial consortia from a soil sample and to establish if they could colonize zirconium-tin alloy, such as Zircaloy-4. Two bacterial consortia containing aerobic heterotrophic bacteria and anaerobic sulfate-reducing bacteria were isolated from a soil sample. The aerobic heterotrophic bacteria exhibited a higher capability to utilize different sole carbon sources, as compared with anaerobic sulfate-reducing bacteria. Based on a morphological, biochemical, and molecular analysis, bacterial isolates were identified as Pseudomonas putida IBBHA₁, Pseudomonas aeruginosa IBBHA₂, Achromobacter spanius IBBHA₃, Citrobacter freundii IBBSR₁, Citrobacter youngae IBBSR₂, and Citrobacter braakii IBBSR₃. Isolated bacterial consortia which possess distinct DNA fingerprints were able to form biofilms and colonize the surface of zirconium-tin alloy coupons, although the colonization of coupons by the aerobic heterotrophic bacteria or anaerobic sulfate-reducing bacteria alone was lower compared with that observed when the coupon was immersed in a mixture of both bacterial consortia. Coupons immersed in these bacterial consortia revealed changes in the surface characteristics, which can facilitate or accelerate zirconium-tin alloy corrosion. The accumulation of corrosion products on coupons surface was less significant when the coupons were immersed solely in aerobic heterotrophic bacteria or anaerobic sulfate-reducing bacteria, compared with that observed when the coupon was immersed in a mixture of both bacterial consortia.

The genotoxic effects of four heavy metal mixtures on Drosophila melanogaster were investigated with reference to gene expressions of heat shock proteins (HSP26, HSP60, HSP70 and HSP83), DNA profiles, and mitochondrial NADH dehydrogenase sequence. Adult D. melanogaster flies were treated with a mixture of four (Fe, Cu, Cd and Pb) heavy metals (HMs) in three different concentrations, which were selected based on one higher dose (HM3) and one lower dose (HM1) relative to the permitted limits (HM2) in drinking water at 1st, 5th and 10th days. It was determined that the amount of the accumulated heavy metals and the expressions of the HSP genes were changed with increasing exposure time. The accumulations of Cd and Pb were increased with increasing exposure time; additionally, the HSP expression patterns were determined as HSP70 > HSP60 > HSP26 > HSP83 HM1 (5th day), HM2 (5th day and 10th day), and HM3 (all exposure times). It was also determined that the application of the heavy metal mixture affected the random amplified polymorphic DNA (RAPD) profiles and the mitochondrial NADH dehydrogenase sequence of D. melanogaster. The highest base pair changes (9 bp) were determined at the HM2 concentration (permissible limits in drinking water) on the 1st day of treatment. Therefore, it was shown that mixture of four heavy metals caused a genotoxic effect and D. melanogaster is a useful model organism for heavy metal-induced genotoxicity studies.

The effects of a five-pesticide mixture on pesticide accumulation, phytohormone levels (indole-3-acetic acid, gibberellic acid, jasmonic acid, and salicylic acid), pigment contents (total chlorophyll and carotenoid), antioxidant enzyme (catalase and guaiacol peroxidase) activities, lipid peroxidation product (malondialdehyde), and DNA profiles were investigated in the leaves of Veronica beccabunga. Laboratory-acclimatized plants were treated with a mix of five pesticides (atrazine, disulfoton, chlorpyrifos, metalaxyl, and ethion) in doses of 50 ppt, 1 ppb, 100 ppb, and 1 ppm for 1, 3, and 6 days. The accumulation of each pesticide, from highest to lowest, was as follows: chlorpyrifos, atrazine, metalaxyl, disulfoton, and ethion. The amounts of total chlorophyll and protein decreased with increased pesticide concentration. Antioxidant enzyme activities and malondialdehyde amount increased linearly with increasing pesticide exposure. However, the highest pesticide concentration caused decreases in guaiacol peroxidase (POD) activity and malondialdehyde (MDA) content at all treatment times. Both jasmonic and salicylic acid levels increased with pesticide exposure and decreased gradually after. It was also determined that application of the pesticide mixture affected the DNA profiles of V. beccabunga. The most band changes were detected on the sixth day of treatment.

Applying an integrated approach using the Comet, micronucleus (MN), and random amplified polymorphic DNA (RAPD) assays, occurrence of erythrocytic nuclear abnormalities (ENAs) and the liver activity of antioxidants enzymes (catalase and glutathione-S-transferase (GST)) was carried out to evaluate the effects of acute (6, 24, and 96 h) and subchronic (15 days) exposures to aluminum on fish Prochilodus lineatus. The Comet assay showed that fish erythrocytes exhibited significantly higher DNA damage after 6 and 96 h of Al exposure. MN frequencies were very low and did not increase significantly after Al exposures, while ENAs frequency increased significantly after all exposure periods. RAPD profiles obtained with DNA from fish fins collected before the toxicity tests were compared to the profiles with DNA from gills and liver of the same fish sampled after Al exposures. Alterations in RAPD profiles, including appearance and disappearance of bands, after 6 h, 24 h, and 15 days of Al exposure were detected. Fish exposed to Al for 6 and 24 h also showed significant increases in GST and catalase activities. These results indicated that Al exposure was genotoxic to P. lineatus, inducing DNA damage in peripheral erythrocytes. The induction of antioxidant enzymes might be an indication that Al causes oxidative damage to DNA, while the very low frequency of MN suggests that Al does not produce clastogenic or aneugenic effects. Genotoxic effects after 15 days of Al exposure was revealed only by RAPD, showing that this assay represents a sensitive method to detect genotoxic damage, occasionally not detected by other genotoxic tests used in toxicological genetics studies.

In Mexican waters, there is no a formal and well-established monitoring program of harmful algal blooms (HAB) events. Until now, most of the work has been focused on the characterization of organisms present in certain communities. Therefore, the development of new techniques for the rapid detection of HAB species is necessary. Capillary electrophoresis finger print technique (CE-SSCP) is a fingerprinting technique based on the identification of different conformers dependent of its base composition. This technique, coupled with capillary electrophoresis, has been used to compare and identify different conformers. The aim of this study was to determine if CE-SSCP analysis of ribosomal RNA (rRNA) gene fragments could be used for a rapid identification of toxic and harmful HAB species to improve monitoring activities along the coasts of Baja California Sur, Mexico.Three different highly variable regions of the 18S and 28S rRNA genes were chosen and their suitability for the discrimination of different dinoflagellate species was assessed by CE-SSCP.The CE-SSCP results obtained for the LSU D7 fragment has demonstrated that this technique with this gene region could be useful for the identification of the ten dinoflagellates species of different genera.We have shown that this method can be used to discriminate species and the next step will be to apply it to natural samples to achieve our goal of molecular monitoring for toxic algae in Mexican waters. This strategy will offer an option to improve an early warning system of HAB events for coastal BCS, allowing the possible implementation of mitigation strategies. A monitoring program of HAB species using molecular methods will permit the analysis of several samples in a short period of time, without the pressure of counting with a taxonomic expert in phytoplankton taxonomy.

Spatial increases and temporal shifts in outbreaks of gelatinous plankton have been observed over the past several decades in many estuarine and coastal ecosystems. The effects of these blooms on marine ecosystem functioning and particularly on the dynamics of the heterotrophic bacteria are still unclear. The response of the bacterial community from a Mediterranean coastal lagoon to the addition of dissolved organic matter (DOM) from the jellyfish Aurelia aurita, corresponding to an enrichment of dissolved organic carbon (DOC) by 1.4, was assessed for 22 days in microcosms (8 l). The high bioavailability of this material led to (i) a rapid mineralization of the DOC and dissolved organic nitrogen from the jellyfish and (ii) the accumulation of high concentrations of ammonium and orthophosphate in the water column. DOM from jellyfish greatly stimulated heterotrophic prokaryotic production and respiration rates during the first 2 days; then, these activities showed a continuous decay until reaching those measured in the control microcosms (lagoon water only) at the end of the experiment. Bacterial growth efficiency remained below 20 %, indicating that most of the DOM was respired and a minor part was channeled to biomass production. Changes in bacterial diversity were assessed by tag pyrosequencing of partial bacterial 16S rRNA genes, DNA fingerprints, and a cultivation approach. While bacterial diversity in control microcosms showed little changes during the experiment, the addition of DOM from the jellyfish induced a rapid growth of Pseudoalteromonas and Vibrio species that were isolated. After 9 days, the bacterial community was dominated by Bacteroidetes, which appeared more adapted to metabolize high-molecular-weight DOM. At the end of the experiment, the bacterial community shifted toward a higher proportion of Alphaproteobacteria. Resilience of the bacterial community after the addition of DOM from the jellyfish was higher for metabolic functions than diversity, suggesting that jellyfish blooms can induce durable changes in the bacterial community structure in coastal lagoons.