Hydrogen-Based Activity Enhancement in Sediment Cultures and Intact Sediments

The potential for hydrogen gas to stimulate microbial respiratory activity in sediments was investigated. Cell elutions from Passaic River (NJ), San Diego Bay (CA), and Marine Harbor sediments were amended with hydrogen gas to evaluate its impact on microbial activity measured by intracellular reduction of 5-cyano-2,3-ditolyl tetrazolium chloride (CTC). The transferability of this approach to sediment slurries and static sediment columns was evaluated based on microbial activity enhancement in Marine Harbor sediments. Results indicate that microbial activity can be increased by a factor of 2–3 at a threshold hydrogen concentration range (0.5 to 1.5 μM). Terminal restriction fragment (T-RF) length polymorphism analysis indicated that the community response to hydrogen resulted in the emergence of previously recessive populations. The causal relationship between hydrogen amendment and an increase in CTC-active cells was most likely due to community structure shifts, as evidenced by the emergence of new T-RFs (19% of total) at hydrogen concentrations above 1.5 μM. No RF was dominant within this emergent group, and no chlororespirers were detected within this group, the latter probably due to the lack of enrichment of halogenated compounds. Nevertheless, the transferability of the observed relationship between hydrogen gas amendment and microbial activity to complex sediment samples suggests a promising remedial strategy for in place contaminated estuarine sediments.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/63230/1/ees.2006.0078.pd

Hierarchical cluster analysis of polychlorinated dioxins and furans in Michigan, USA, soils: Evaluation of industrial and background congener profiles

As part of the University of Michigan Dioxin Exposure Study, soil samples were collected from 766 residential properties near the Tittabawassee River between Midland and Saginaw; near the Dow Chemical Facility in Midland; and, for comparison, in the other areas of Midland and Saginaw Counties and in Jackson and Calhoun Counties, all located in the state of Michigan, USA. A total of 2,081 soil samples were analyzed for 17 polychlorinated dibenzo- p -dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). In order to better understand the distribution and sources of the PCDD/F congeners in the study area, hierarchical cluster analysis (HCA) was used to statistically group samples with similar congener patterns. The analysis yielded a total of 13 clusters, including: 3 clusters among the soils impacted by contamination present in the Tittabawassee River sediments, a cluster comprised mainly of samples collected within the depositional area of the Dow incinerator complex, a small cluster of samples with elevated 2,3,7,8-tetrachlorinated dibenzo- p -dioxin (TCDD), and several clusters exhibiting background patterns. The clusters related to the Tittabawassee River floodplain contamination all contained elevated PCDF levels and were differentiated from one another primarily by their relative concentrations of higher-chlorinated PCDDs, a difference likely related to both extent and timing of impacts from Tittabawassee sediments. The background clusters appear to be related to combustion processes and are differentiated, in part, by their relative fractions of TCDD. Thus, HCA was useful for identifying congener profile characteristics in both contaminated and background soil samples. Environ. Toxicol. Chem. 2010;29:64–72. © 2009 SETACPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/64530/1/24_ftp.pd

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