Factors Influencing the Persistence of Fecal Bacteroidesin Stream Water (original) (raw)
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Applied and Environmental Microbiology, 2010
Given the interest in Bacteroides species as microbial source tracking (MST) markers, and the limited knowledge of the survival of Bacteroides species in the environment, here we examine the survival of Bacteroides fragilis, B. thetaiotaomicron, and environmental species of Bacteroides by use of culture techniques and molecular tools. Two kinds of experiments were performed: (i) on-site experiments, in which bacteria were exposed to changes in the levels of several environmental parameters in a river, and (ii) microcosm assays in the laboratory, with controlled temperatures. On-site experiments showed different survival patterns for the cultivable Bacteroides strains. B. fragilis die-off rate was strongly affected by the combined effect of high temperatures and grazing predators, which were more active under warmer conditions. However, the survival rates of cultivable B. thetaiotaomicron and environmental Bacteroides spp. were more affected by dissolved oxygen (DO) concentration in water. Environmental Bacteroides strains survived longer than either type strain, due to better adaptation to environmental conditions. However, the period of their survival was shorter than that observed for fecal coliforms and enterococci, suggesting Bacteroides species as markers of recent fecal pollution. The total Bacteroides species were detected by molecular techniques throughout the experiment in winter, but they were detected on only two or three days in the summer. This indicates that temperature is the main factor affecting DNA degradation, regardless of species. The use of microcosms in the laboratory also pointed to temperature as the main factor affecting Bacteroides survival, regardless of species. However, the conditions in the laboratory may mask the effects of the environmental factors and their interactions. The observed variability in die-off rate as a function of the species analyzed, the experimental conditions, and the methodology used should be taken into consideration in future persistence studies.
Applied and Environmental Microbiology, 2010
Fecal indicator bacteria (FIB), commonly used to regulate sanitary water quality, cannot discriminate among sources of contamination. The use of alternative quantitative PCR (qPCR) methods for monitoring fecal contamination or microbial source tracking requires an understanding of relationships with cultivated FIB, as contamination ages under various conditions in the environment. In this study, the decay rates of three Bacteroidales 16S rRNA gene markers (AllBac for general contamination and qHF183 and BacHum for human-associated contamination) were compared with the decay rate of cultivated Escherichia coli in river water microcosms spiked with human wastewater. The following five sets of microcosms were monitored over 11 days: control, artificial sunlight, sediment exposure, reduced temperature, and no autochthonous predation. Decay was characterized by estimation of the time needed to produce a 2-log reduction (t 99 ). No treatmentassociated differences in the decay of the 4 targets were evident except with reduced predation, where E. coli, qHF183, and BacHum markers had lower levels of decay by day 3. However, there were substantial targetassociated differences. Decay curves for the AllBac marker indicated a larger persistent population than those of the other targets. Exposure to sunlight, sediment, and reduced predation resulted in more rapid decay of the human-associated markers relative to cultivable E. coli, but there were no differences in t 99 values among the 4 targets under control conditions or at reduced temperatures. Further evaluation of epidemiological relationships will be needed in order to relate the markers directly to health risk. These findings suggest that the tested human-associated markers can complement E. coli as indicators of the human impact on sanitary water quality under the constrained conditions described in this paper.
Water Research, 2015
Host-associated Bacteroidales Quantitative PCR Persistence and survival Decay kinetics a b s t r a c t It is difficult to compare decay kinetics for genetic markers in an environmental context when they have been determined at different ambient temperatures. Therefore, we investigated the persistence of the host-associated genetic markers BacHum, BacCow and BacCan as well as the general Bacteroidales marker BacUni in both intact Bacteroidales cells and as total intracellular and extracellular marker DNA in controlled batch experiments at two temperatures using PMA-qPCR. Fecal Bacteroidales cells and DNA persisted longer at the lower temperature. Using the modified Arrhenius function to calculate decay constants for the same temperature, we then compared the decay of host-associated Bacteroidales cells and their DNA at 14 C in field-based flow-through microcosms containing human, cow, and dog feces suspended in freshwater or seawater and previously operated with an identical experimental design. The time for a 2-log reduction (T 99 ) was used to characterize host-associated Bacteroidales decay. Host-associated genetic markers as determined by qPCR had similar T 99 values in freshwater and seawater at 14 C when compared under both sunlight and dark conditions. In contrast, intact Bacteroidales cells measured by PMA-qPCR had shorter T 99 values in seawater than in freshwater. The decay constants of Bacteroidales cells were a function of physical (temperature) and chemical (salinity) parameters, suggesting that environmental parameters are key input variables for Bacteroidales survival in a predictive water quality model. Molecular markers targeting total Bacteroidales DNA were less susceptible to the variance of temperature, salinity and sunlight, implying that measurement of markers in both intact cells and DNA could enhance the predictive ScienceDirect j ou rnal h ome pag e: www.elsevier.com/loca te/watres w a t e r r e s e a r c h 7 0 ( 2 0 1 5 ) 2 0 5 e2 1 3 http://dx.
Applied and Environmental Microbiology, 2008
The bacterial community composition in small streams and a river in central Germany was examined by temperature gradient gel electrophoresis (TGGE) with PCR products of 16S rRNA gene fragments and sequence analysis. Complex TGGE band patterns suggested high levels of diversity of bacterial species in all habitats of these environments. Cluster analyses demonstrated distinct differences among the communities in stream and spring water, sandy sediments, biofilms on stones, degrading leaves, and soil. The differences between stream water and sediment were more significant than those between sites within the same habitat along the stretch from the stream source to the mouth. TGGE data from an entire stream course suggest that, in the upper reach of the stream, a special suspended bacterial community is already established and changes only slightly downstream. The bacterial communities in water and sediment in an acidic headwater with a pH below 5 were highly similar to each other but deviated distinctly from the communities at the other sites. As ascertained by nucleotide sequence analysis, stream water communities were dominated by Betaproteobacteria (one-third of the total bacteria), whereas sediment communities were composed mainly of Betaproteobacteria and members of the Fibrobacteres/Acidobacteria group (each accounting for about 25% of bacteria). Sequences obtained from bacteria from water samples indicated the presence of typical cosmopolitan freshwater organisms. TGGE bands shared between stream and soil samples, as well as sequences found in bacteria from stream samples that were related to those of soil bacteria, demonstrated the occurrence of some species in both stream and soil habitats. Changes in bacterial community composition were correlated with geographic distance along a stream, but in comparisons of different streams and rivers, community composition was correlated only with environmental conditions.
Identification of bacterial populations in drinking water using 16S rRNA-based sequence analyses
Water Research, 2010
Intracellular RNA is rapidly degraded in stressed cells and is more unstable outside of the cell than DNA. As a result, RNA-based methods have been suggested to study the active microbial fraction in environmental matrices. The aim of this study was to identify bacterial populations in drinking water by analyzing 16S rRNA-based clone libraries. Hollow-fiber ultrafiltration was used to concentrate bacterial communities from 40 l of tap water collected at 12 different times during three different summer months from a single point-of-use. Total RNA was extracted from the microbial concentrates and used to develop 16S rRNA-based clone libraries. Phylogenetic analyses of 1231 partial 16S rRNA gene sequences showed that difficult-to-classify bacterial sequences were the most predominant clones, representing 57.6% of the sequences analyzed. Within these unclassified clades, most sequences were closely related to sequences retrieved from previous DNA-and RNA-based drinking water studies. Other bacterial groups represented in this study included Proteobacteria, cyanobacteria, Actinobacteria, Bacteroidetes, and Planctomycetes. Overall, the results suggest that these bacterial groups are amongst potentially active bacteria in drinking water. Diversity analyses of clones generated show that while overall diversity is similar amongst the different months, membership changes with respect to time. The results from this study further improve our understanding of the molecular diversity and bacterial population dynamics of drinking water microbial communities. Moreover, these results provide the sequence foundation for the development of molecular assays that target active drinking water bacteria.
Escherichia coli survival in waters: Temperature dependence
Water Research, 2013
Knowing the survival rates of water-borne Escherichia coli is important in evaluating microbial contamination and making appropriate management decisions. E. coli survival rates are dependent on temperature, a dependency that is routinely expressed using an analogue of the Q 10 model. This suggestion was made 34 years ago based on 20 survival curves taken from published literature, but has not been revisited since then. The objective of this study was to re-evaluate the accuracy of the Q 10 equation, utilizing data accumulated since 1978. We assembled a database of 450 E. coli survival datasets from 70 peerreviewed papers. We then focused on the 170 curves taken from experiments that were performed in the laboratory under dark conditions to exclude the effects of sunlight and other field factors that could cause additional variability in results. All datasets were tabulated dependencies "log concentration vs. time." There were three major patterns of inactivation: about half of the datasets had a section of fast log-linear inactivation followed by a section of slow log-linear inactivation; about a quarter of the datasets had a lag period followed by log-linear inactivation; and the remaining quarter were approximately linear throughout. First-order inactivation rate constants were calculated from the linear sections of all survival curves and the data grouped by water sources, including waters of agricultural origin, pristine water sources, groundwater and wells, lakes and reservoirs, rivers and streams, estuaries and seawater, and wastewater. Dependency of E. coli inactivation rates on temperature varied among the water sources. There was a significant difference in inactivation rate values at the reference temperature between rivers and agricultural waters, wastewaters and agricultural waters, rivers and lakes, and wastewater and lakes. At specific sites, the Q 10 equation was more accurate in rivers and coastal waters than in lakes making the value of the Q 10 coefficient appear to be site-specific. Results of this work indicate possible sources of uncertainty to be accounted for in watershed-scale microbial water quality modeling.
The Science of the total environment, 2015
Diverse land use activities can elevate risk of microbiological contamination entering stream headwaters. Spatially distributed water quality monitoring carried out across a 17km(2) agricultural catchment aimed to characterize microbiological contamination reaching surface water and investigate whether winter agricultural land use restrictions proved effective in addressing water quality degradation. Combined flow and concentration data revealed no significant difference in fecal indicator organism (FIO) fluxes in base flow samples collected during the open and prohibited periods for spreading organic fertilizer, while relative concentrations of Escherichia coli, fecal streptococci and sulfite reducing bacteria indicated consistently fresh fecal pollution reached aquatic receptors during both periods. Microbial source tracking, employing Bacteroides 16S rRNA gene markers, demonstrated a dominance of bovine fecal waste in river water samples upstream of a wastewater treatment plant d...
Journal of Water and Health, 2007
Bacteria present in water samples taken on a weekly basis, from June 2004 through June 2005, from three streams, were cultured on Coliscan w Easygel w agar plates. Colonies representative of a variety of colors and morphologies were subjected to amplification and sequencing of a 1000-1100 nt portion of the 16S rRNA gene. A total of 528 colonies were sequenced; these categorized into 26 genera and 78 species. Of 175 dark blue/purple colonies presumed to be E. coli, sequence analysis indicated that 45 (25%) were actually other genera. For the urban stream Gwynns Falls Gwynns Run, E. coli was the most common genus/species encountered, followed by Klebsiella and Aeromonas. For Pond Branch, a stream located in a forested watershed, it was Serratia, followed by Yersinia and Aeromonas. For McDonogh (MCDN), a stream associated with Zea mays (corn) row crop agriculture, E. coli was the most frequently isolated genus/species, followed by Aeromonas and Enterobacter. ERIC-PCR genotyping of isolates from the most prevalent genera/species, indicated a high degree of diversity within-stream for E. coli and K. pneumoniae. Conversely, genotyping of Y. enterocolitica isolates indicated that some were shared between different streams.