RESUMO
The uncontrolled release of the industrial solvent methylene chloride, also known as dichloromethane (DCM), has resulted in widespread groundwater contamination in the United States. Here we investigate the role of groundwater bacterial communities in the natural attenuation of DCM at an undisclosed manufacturing site in New Jersey. This study investigates the bacterial community structure of groundwater samples differentially contaminated with DCM to better understand the biodegradation potential of these autochthonous bacterial communities. Bacterial community analysis was completed using high-throughput sequencing of the 16S rRNA gene of groundwater samples (n = 26) with DCM contamination ranging from 0.89 to 9,800,000 µg/L. Significant DCM concentration-driven shifts in overall bacterial community structure were identified between samples, including an increase in the abundance of Firmicutes within the most contaminated samples. Across all samples, a total of 6,134 unique operational taxonomic units (OTUs) were identified, with 16 taxa having strong correlations with increased DCM concentration. Putative DCM degraders such as Pseudomonas, Dehalobacterium and Desulfovibrio were present within groundwater across all levels of DCM contamination. Interestingly, each of these taxa dominated specific DCM contamination ranges respectively. Potential DCM degrading lineages yet to be cited specifically as a DCM degrading organisms, such as the Desulfosporosinus, thrived within the most heavily contaminated groundwater samples. Co-occurrence network analysis revealed aerobic and anaerobic bacterial taxa with DCM-degrading potential were present at the study site. Our 16S rRNA gene survey serves as the first in situ bacterial community assessment of contaminated groundwater harboring DCM concentrations ranging over seven orders of magnitude. Diversity analyses revealed known as well as potentially novel DCM degrading taxa within defined DCM concentration ranges, indicating niche-specific responses of these autochthonous populations. Altogether, our findings suggest that monitored natural attenuation is an appropriate remediation strategy for DCM contamination, and that high-throughput sequencing technologies are a robust method for assessing the potential role of biodegrading bacterial assemblages in the apparent reduction of DCM concentrations in environmental scenarios.
RESUMO
The demographic transition of the 1930s-1960s dramatically improved life expectancy in some developing countries. Cohorts born during this time are increasingly characterized by their survivorship of poor early-life conditions, such as poor nutrition and infectious diseases. As a result, they are potentially more susceptible to the effects of these conditions at older ages. This study examines this conjecture by comparing obesity, diabetes, and hypertension in older adults born in the beginning portion of the 1930s-1960s across different mortality regimes using a subset of harmonized cross-national data from seven low- and middle-income countries (RELATE, n = 16,836). Using birthplace and height as indicators of early-life conditions, the results show (1) higher prevalence of obesity and diabetes and higher likelihood of obesity, diabetes, and hypertension in middle-income countries, but (2) no convincing evidence to indicate stronger effects of early-life conditions on health in these countries. However, shorter adults living in urban areas were more likely to be obese, indicating the overall importance of early-life conditions and the potential negative impact of urban exposures during adulthood. Obesity results may foreshadow the health of future cohorts born in the later portion of the 1930s-1960s as they reach older ages (60+).