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A study was conducted to compare the decay rates of three Bacteroidales 16S rRNA gene markers (AllBac for general contamination and qHF183 and BacHum for human-associated contamination) with the decay rate of cultivated Escherichia coli in river water microcosms spiked with human wastewater. The findings indicated that the tested human-associated markers could complement E. coli as indicators of the human impact on sanitary water quality under the constrained conditions.

The development, performance and validation of D source tracking (MST) methods are described.

Edaphic and hydrologic influences on floodplain soil nutrient dynamics must be characterized in order to more fully understand ecosystem functions of forested floodplains. The objective of this study was to characterize the impacts of microtopography and depth on soil microbial processes related to nutrient dynamics in a forested floodplain soil. Nutritional and biological parameters were measured seasonally for 2 yr at paired plots representing two microtopographic classes (swales and slopes) and three soil profile locations--surface organic material, root zone (RZ, 0-0.1 m), and sub-root zone (SR, 0.2-0.3 m)--on the Coosawhatchie River floodplain, South Carolina. Litter decomposition dynamics followed trends previously described in the literature: N and P concentrations increased relative to C following litterfall, and the relative increase was greater in swales than on slopes. Mineral soil on the Coosawhatchie floodplain was rich in total P compared with other sites. Soil N pools fluctuated together with C, while P was redistributed by floodwater independently of major C and N pools. As a result, P accumulated more in swale soil. Carbon/ N ratios in RZ soil were seasonally constant, averaging 14 in swales and 19 on slopes. Carbon/total P ratios were more variable, ranging from 77 to 118 in swales and 151 to 246 on slopes. Microtopographic differences ([is less than] 1 m) profoundly influenced nutrient dynamics, particularly P, of surface organic material and soil on this floodplain.

The Deepwater Horizon ( DWH) accident in 2010 created a deepwater plume of small oil droplets from a deepwater well in the Mississippi Canyon lease block 252 (' Macondo oil'). A novel laboratory system was used in the current study to investigate biodegradation of Macondo oil dispersions (10 μm or 30 μm median droplet sizes) at low oil concentrations (2 mg l−1) in coastal Norwegian seawater at a temperature of 4-5°C. Whole metagenome analyses showed that oil biodegradation was associated with the successive increased abundances of Gammaproteobacteria, while Alphaproteobacteria ( P elagibacter) became dominant at the end of the experiment. Colwellia and Oceanospirillales were related to n-alkane biodegradation, while particularly C ycloclasticus and M arinobacter were associated with degradation of aromatic hydrocarbons ( HCs). The larger oil droplet dispersions resulted in delayed sequential changes of Oceanospirillales and C ycloclasticus, related with slower degradation of alkanes and aromatic HCs. The bacterial successions associated with oil biodegradation showed both similarities and differences when compared with the results from DWH field samples and laboratory studies performed with deepwater from the Gulf of Mexico. [ABSTRACT FROM AUTHOR]

Better understanding of Escherichia coli population dynamics and genetic variability in the secondary habitat is essential to improve fecal contamination monitoring and contamination pathway characterization. In this study, water samples were collected monthly over a one-year period at eight locations in the Catoma Creek watershed, a mixed land-use watershed in Central Alabama. E. coli concentrations varied from 17 to 12,650 CFU/100 ml and were well correlated with stream flow rates. Repetitive sequence-based PCR DNA fingerprinting was used to generate 271 unique DNA fingerprint patterns from 502 E. coli isolated from water samples. Cluster analysis showed an overall similarity of 32.8% across all DNA fingerprints. Multivariate analysis of variance (MANOVA) showed that E. coli genotypes had a tendency to cluster according to season and stream flow rather than sampling sites. MANOVA of a subset of data within a given season and flow rate, however, revealed some geographical differentiation between urban and rural sampling sites. The results indicate that genetic diversity of E. coli populations was not only high in the secondary habitat but also varied with season, flow conditions and, to a lesser extent, sampling location. To our knowledge, this is the first report relating E. coli genotype to stream flow. [ABSTRACT FROM AUTHOR]