拉萨河流域亏组山植物物种丰富度和群落特征研究

为研究草地植物群落、物种丰富度及其分布格局与影响因子之间的关系,该文以拉萨河流域林周县卡孜乡亏组山为研究地点,对山体垂直样带(3900～5100 m)植物群落特征、植物物种丰富度与各影响因子之间的关系进行了研究.研究区域共设置了13个样带(每隔100 m设一个样带),每样带设置0.5 m×0.5 m的5个样方进行植被调...     

Multidrug-resistant Opportunistic and Pathogenic Bacteria Contaminate Algerian Banknotes Currency

Currency is one of the most exchanged items in human communities as it is used daily in exchange for goods and services. It is handled by persons with different hygiene standards and can transit in different environments. Hence, money can constitute a reservoir for different types of human pathogens. This study aimed to evaluate the potential of Algerian banknotes to shelter opportunistic pathogenic and multiresistant bacteria. To that end, 200 circulating notes of four different denominations were collected from various places and analyzed for their bacterial loads and contents. Besides, predominant strains were identified and characterized by biochemical and molecular methods, and their resistance profiles against 34 antibiotics were determined. Our results indicated that 100% of the studied banknotes were contaminated with bacteria. The total bacterial concentrations were relatively high, and different bacterial groups were grown, showing important diversity. In total, 48 predominant strains were identified as belonging to 17 genera. Staphylococcus and Micrococcus were the most prevalent genera, followed by Bacillus, Pseudomonas, and Acinetobacter. Antibiotic susceptibility testing showed that all the isolates harbored resistance to at least two molecules, and worrying resistance levels were observed. These findings prove that Algerian currency harbors opportunistic multiresistant bacteria and could potentially act as a vehicle for the spread of bacterial diseases and as a reservoir for antibiotic resistance genes among the community. Therefore, no cash payment systems should be developed and generalized to minimize cash handling and subsequent potential health risks.Key words: currency, Algeria, opportunistic bacteria, antibiotic resistance, circulating resistance genes     

COMPARATIVE ANALYSIS OF METHODS FOR THE PURIFICATION OF DNA FROM LOW-BIOMASS SAMPLES BASED ON TOTAL YIELD AND CONSERVED MICROBIAL DIVERSITY

Despite advances in the specificity and sensitivity of molecular biological technologies, the efficient recovery of DNA from low-biomass samples remains extremely challenging. Optimal methods to purify biomolecules from such environments should (1) achieve the greatest total yield and (2) reflect the true microbial diversity of the sample. These attributes were assessed from five DNA purification regimes: a standard-manual procedure, MoBio Ultraclean and Promega Wizard kits, and an automated Axcyte AutoLyser method with and without bead-beating agitation. A homogenous mixture of known concentrations of nine distinct bacterial lineages isolated from low-biomass environments was prepared and suitable aliquots of subsamples were processed in parallel. DNA products from each of these methods were then subjected to polymerase chain reaction (PCR), quantitative PCR and 16S rRNA clone-library analysis. The Axcyte AutoLyser outperformed all other purification regimes examined. This automated method consistently both yielded the highest concentration of PCR-amplifiable DNA, and reported species composition most consistent with the starting solution.

PRACTICAL APPLICATIONS

This communication carefully examines the effectiveness of common DNA purification regimes as well as an automated method. Comparative analyses convincingly demonstrate that the different methods not only result in different recovery of genomic DNA, but more importantly, different estimations of microbial diversity in the sample. This report will hopefully inspire investigators from various industries (pharmaceutical, ecological, medical, semiconductor, etc.) who find themselves in the initial phases of large-scale studies to devote a significant effort into optimizing sample extraction protocols to achieve the most accurate information.