tailieunhanh - Enzymes in the Environment: Activity, Ecology and Applications - Chapter 3

Vai trò sinh hóa chung của các enzym ngoại bào trong biển tương tự như trong các môi trường dưới nước khác. Tuy nhiên, để hiểu được ý nghĩa sinh thái của các enzym trong biển cụ thể các yếu tố môi trường biển phải được xem xét, ví dụ như, a) nước biển là một phương tiện rất loãng xen kẽ với các điểm nóng về nồng độ chất hữu cơ, tổng hợp và phân hủy (1). b) như là một kết quả của điều kiện thủy văn, các đại dương được đặc trưng bởi zonations riêng biệt ngang. | 3 Ecological Significance of Bacterial Enzymes in the Marine Environment Hans-Georg Hoppe Institute of Marine Science Kiel Germany Carol Arnosti University of North Carolina Chapel Hill North Carolina Gerhard F. Herndl Netherlands Institute of Sea Research NIOZ Den Burg The Netherlands I. INTRODUCTION The general biochemical role of extracellular enzymes in the sea is similar to that in other aquatic environments. However in order to understand the ecological significance of enzymes in the sea specific marine environmental factors have to be considered . a seawater is a highly diluted medium interspersed with hot spots of organic matter concentration aggregation and decomposition 1 . b as a result of hydrographic conditions the oceans are characterized by distinct horizontal and vertical zonations. The deep sea in particular with its enormous volume depends entirely on substrate supply from sinking material produced in the surface layer 2 . c in the sea low-molecular-weight organic matter that persists as dissolved organic carbon DOC is less bioreactive and more strongly diagenetically altered than the bulk of high-molecular-weight matter 3 4 . d the deep seabed receives very little of the total surface-derived primary productivity and much of this organic matter is strongly altered. Finally at chemical and hydrographic discontinuities in the sea . fronts boundary layers and oxygen nutrient and salinity gradients drastic changes occur in microbial species diversity and enzymatic properties. Organic material prone to bacterial degradation on nongeological time scales is actively involved in biogeochemical cycles. Such material originates from phytoplankton primary production and from sloppy feeding of zooplankton as well as from the excretions of all kinds of organisms. Currently the spectrum of extracellular enzymes investigated in the sea is relatively limited comprising principally hydrolytic enzymes such as proteases glucosidases chitinase lipase and .