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Enzymes in the Environment: Activity, Ecology and Applications - Chapter 14

Bởi vì hầu hết các vi khuẩn trong đất không thể phát triển trên phương tiện truyền thông tiêu chuẩn phòng thí nghiệm, một sự khác biệt của một số đơn đặt hàng của độ lớn giữa kết quả trực tiếp bằng kính hiển vi và tính khả thi-tế bào (1). Lý do cho sự khác biệt này là một trong những câu hỏi quan trọng nhất trong hệ sinh thái vi sinh vật (2). Sự khác biệt này có thể phản ánh sự không hoàn hảo của kỹ thuật nuôi của chúng tôi, mặc dù nỗ lực để cải. | 14 Molecular Methods for Assessing and Manipulating the Diversity of Microbial Populations and Processes Soren J. Sorensen Anne Kirstine Muller Lars H. Hansen and Lasse Dam Rasmussen University of Copenhagen Copenhagen Denmark Julia R. de Lipthay Geological Survey of Denmark and Greenland Copenhagen Denmark Tamar Barkay Cook College Rutgers University New Brunswick New Jersey I. INTRODUCTION Because most soil bacteria cannot grow on standard laboratory media a discrepancy of several orders of magnitude between direct microscopic- and viable-cell counts results 1 . The reason for this discrepancy is one of the most important questions in microbial ecology 2 . This difference most likely reflects the imperfections of our culturing techniques although attempts to improve these techniques produce only a minimal quantitative change 3 . In addition some bacteria while remaining viable may lose the ability to grow on media on which they are routinely cultured in response to certain environmental stresses. This suggests that stress may induce a viable but nonculturable VBNC physiological state 4 . This inability to culture most bacteria present in natural soils has until recently impaired studies of the relationships between the structure and function of soil microbial communities. One such relationship is flat between soil enzyme activities and the microbial populations that express the genes encoding for these enzymes. This shortcoming may now be remedied by the application of a rapidly growing number of molecular-based techniques that allow detection enumeration and characterization of microbial populations in natural environments but that do not depend on cultivation. This evolution has been facilitated by the studies of Carl Woese and coworkers who introduced the concept of 16S ribosomal deoxyribonucleic acid- rDNA -based molecular phylogeny 5 and its application to the analysis of microbial communities in their natural habitats 6 . The introduction of specific .