PubMed · 13127537
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K MAIGATTER. 1953. [Preventive measures].. https://pubmed.ncbi.nlm.nih.gov/13127537/
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UNLABELLED: Genomic analysis of mycobacteria has become increasingly crucial for understanding drug-resistance mechanisms, molecular epidemiology, and pathogenesis. However, efficient extraction of high-molecular-weight genomic DNA from these organisms remains challenging because of their thick mycolic acid-rich cell walls. In this study, we report the chloroform-bead method, a universal DNA extraction protocol that combines chemical and mechanical disruptions to overcome these challenges. Multi-laboratory evaluation (16 sites) demonstrated the chloroform-bead method's superiority over conventional methods for Mycobacterium tuberculosis (DNA yield: 17.9 vs 1.9 µg, purity A260/A230: 1.86 vs 1.22, both P < 0.001). Single-facility assessment extended these findings to >32 nontuberculous mycobacterial species (n = 1,058), showing performance comparable to M. tuberculosis (n = 1,000), with both achieving median yields of 22.2 µg DNA and consistent quality metrics. The chloroform-bead method significantly reduced the processing time from 2 to 3 days to 2 h while ensuring complete sample sterilization, eliminating the need for species-specific optimization. This streamlined and universally applicable protocol represents a practical advancement in mycobacterial DNA extraction methodology, ideal for high-throughput genomic studies and routine clinical diagnostics. IMPORTANCE: Mycobacterial genomics is crucial for understanding pathogenesis and drug resistance; however, DNA extraction remains a significant challenge because of its unique cell wall. Traditional methods rely on enzymatic treatments, resulting in complex and time-consuming protocols with variable results. The chloroform-bead method introduces a paradigm shift by chemically and mechanically disrupting the mycolic acid layer and eliminating the need for enzymatic treatment. This standardized approach ensures consistent, high-quality DNA extraction across diverse mycobacterial species, thereby enhancing research capabilities and clinical applications.
The application of FTIR spectroscopy to concentrated solutions of tetrolic acid shows, for the first time, a direct relationship between molecular self association in solution and H-bonded motifs in the subsequently crystallised solid phases.
Field-scale dissolution of a multicomponent DNAPL (dense nonaqueous-phase liquid) source intentionally emplaced below the water table is evaluated in a well-characterized natural aquifer setting. The block-shaped source contained 23 kg of a trichloromethane, trichloroethene, and perchloroethene mixture homogeneously distributed at 5% saturation of pore space. Dissolution was monitored for 3 yr via down-gradient samplers (1-m fence) and occasional intra-source sampling. Although intra-source equilibrium dissolution was shown and endorsed by supporting modeling and literature lab data, less than equilibrium concentrations were predominantly monitored in the 1-m fence. This was ascribed to significant by-passing of the source by groundwater flow due to its low permeability relative to the aquifer and associated dilution of concentrations emitted from the source. Heterogeneous source dissolution occurred despite the relative homogeneity of the source and aquifer and was ascribed to dissolution fingering, which has not been previously field-demonstrated. Bulk bypass of groundwater flow around the source zone caused slow dissolution rates, with 77% of the source remaining after 3 yr and a projected longevity of approximately 25 yr. Observed dissolution fingering would have significantly increased longevity as it increasingly caused intra-source bypass of remaining DNAPL. Our dissolution interpretations were endorsed by additional data collected after 6 yr during source remediation via permanganate oxidation.