Effects of Dairy Manure Management Systems and Wastewater Disinfection Processes on E. coli Phylotype Distribution

Sections of streams located downstream from dairy farms and wastewater treatment plants (WWTPs) in central Texas are listed on the 303 (d) List of Impaired Waters due to bacterial contamination (possibly due to fecal contamination), specifically Escherichia coli (E. coli). E. coli can be subtyped into phylogroups that indicate potential pathogenicity; including A, B1, B2, C, D, E, F, and clades I-V; phylogroups B2 and D are considered potentially pathogenic. E. coli phylotype distributions were studied throughout dairy manure management systems, and before and after disinfection at WWTPs to better understand pathogenicity and reactivation of E. coli in downstream environments. Four dairy farms in the Leon River Watershed of central Texas, each utilizing a different dairy manure management practice, were sampled for E. coli using EPA Method 1603, with a percentage of E. coli isolates phylotyped using the Clermont quadruplex PCR method. E. coli phylotypes showed no seasonal or management practice trend. B1 was the most common phylotype isolated from all dairies and time periods. Effluent from two WWTPs (one utilizing chlorination disinfection, the other Ultra Violet (UV) light) in central Texas were sampled before and after disinfection using EPA Method 1603 for E. coli enumeration, and a portion of isolates were phylotyped using Clermont quadruplex PCR. E. coli from effluent post-disinfection was composed of higher proportions of potentially pathogenic phylotypes. A Quantitative Microbial Risk Assessment (QMRA) revealed swimming downstream from the WWTP employing UV-irradiation may result in a slightly elevated risk of infection due to a higher portion of potentially pathogenic E. coli, compared to the WWTP employing chlorination. Photoreactivation and dark repair of E. coli were studied in effluent from the WWTP employing UV irradiation. E. coli photoreactivation rates were higher than dark repair rates at 12 & 48 hours. Potentially pathogenic phylotypes represented two-thirds of all E. coli detected immediately after UV irradiation. However, treated effluent kept in dark conditions showed a steady decrease in potentially pathogenic phylotypes. Results from this research could help wastewater stewards lower E. coli concentrations and potentially pathogenic phylotype proportions in WWTP effluent

No evidence for allelopathic effects of arbuscular mycorrhizal fungi on the non-host plant Stellaria media

Background and aims: Increasing evidence suggests that several plants, particularly non-mycorrhizal species, are negatively affected by the presence of arbuscular mycorrhizal fungi (AMF). Mechanisms explaining suppressive effects of AMF are, however, still poorly understood. Here we test whether growth suppression of the non-host weed Stellaria media in the presence of AMF can be explained by mycorrhizal alellopathy. Methods: We grew S. media in microcosms where an active AM mycelium was supported by neighboring wheat (Triticum aestivum) plants. To test for allelopathy, we added activated carbon (AC) to the soil substrate. In addition, we performed two complementary experiments where extracts from roots extensively colonized by AMF (AMexudates) were directly applied to S. media seeds and seedlings. Results: Stellaria media plants grown in microcosms with AM mycelium showed an 8-fold biomass reduction compared to microcosms where AMF were absent. The addition of AC, which is thought to reduce allelopathic effects by binding organic compounds, did not greatly mitigate the negative effect of AM mycelium on S. media growth. Moreover, AM exudates did not significantly reduce S. media germination and growth. Conclusions: Results from this study confirm that nonhosts like S. media can be highly suppressed in the presence of AMF. However, we found no evidence that mycorrhizal allelopathy was a major mechanism responsible for growth suppression of S. media in the presence of AMF. Other mechanisms might therefore be more significant in explaining suppressive effects of AMF on non-host plant species

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

No evidence for allelopathic effects of arbuscular mycorrhizal fungi on the non-host plant Stellaria media

Background and aims: Increasing evidence suggests that several plants, particularly non-mycorrhizal species, are negatively affected by the presence of arbuscular mycorrhizal fungi (AMF). Mechanisms explaining suppressive effects of AMF are, however, still poorly understood. Here we test whether growth suppression of the non-host weed Stellaria media in the presence of AMF can be explained by mycorrhizal alellopathy. Methods: We grew S. media in microcosms where an active AM mycelium was supported by neighboring wheat (Triticum aestivum) plants. To test for allelopathy, we added activated carbon (AC) to the soil substrate. In addition, we performed two complementary experiments where extracts from roots extensively colonized by AMF (AMexudates) were directly applied to S. media seeds and seedlings. Results: Stellaria media plants grown in microcosms with AM mycelium showed an 8-fold biomass reduction compared to microcosms where AMF were absent. The addition of AC, which is thought to reduce allelopathic effects by binding organic compounds, did not greatly mitigate the negative effect of AM mycelium on S. media growth. Moreover, AM exudates did not significantly reduce S. media germination and growth. Conclusions: Results from this study confirm that nonhosts like S. media can be highly suppressed in the presence of AMF. However, we found no evidence that mycorrhizal allelopathy was a major mechanism responsible for growth suppression of S. media in the presence of AMF. Other mechanisms might therefore be more significant in explaining suppressive effects of AMF on non-host plant species