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Enzymes in the Environment: Activity, Ecology and Applications - Chapter 2

Trong thập kỷ qua, một số lượng ngày càng tăng của các nghiên cứu sinh thái được coi là sự phức tạp của các hệ sinh thái nước ngọt. Một trong những kết quả của những nghiên cứu này đã được quan tâm đẩy mạnh vai trò của vi sinh vật dị dưỡng (đặc biệt là vi khuẩn) trong các hoạt động môi trường thủy sản và các quy trình mà theo đó chất hữu cơ có sẵn cho họ (1-4). Những vi sinh vật dị dưỡng này là mức độ dinh dưỡng quan trọng mà tại đó sự chuyển. | 2 Ecology of Microbial Enzymes in Lake ECosystems Ryszard Jan Chrost and Waldemar Siuda University of Warsaw Warsaw Poland I. INTRODUCTION During the past decade an increasing number of ecological studies have considered the complexity of freshwater ecosystems. One major outcome of these studies has been an accelerated interest in the role of heterotrophic microorganisms particularly bacteria in the functioning of aquatic environments and the processes by which organic matter is made available to them 1-4 . These heterotrophic microorganisms are the key trophic level at which the metabolism of the whole ecosystem is affected i.e. organic matter decomposition nutrient cycling and structure of aquatic food webs. The demonstration of the importance of heterotrophic bacteria as a particulate carbon source for higher trophic levels and a major respiratory sink has created a renewed interest in the production and utilization of organic substrates by these microorganisms. Most organic compounds produced in natural waters have a polymeric structure 5 6 and they are too large to be readily assimilated. The transport of organic molecules across microbial cell membranes is an active process mediated by specific enzymes called permeases. Only the low-molecular-weight organic molecules monomers or oligomers can therefore be taken up 7 . In order to be available for microbial metabolism polymeric compounds must be transformed into smaller molecules through enzymatic depolymerization. Besides the physicochemical conditions of aquatic environments the composition and availability of organic matter are the major factors that influence the development and activity of heterotrophic bacteria 8 9 . The heterotrophic bacteria are the only biological populations capable of significantly altering both dissolved DOM and particulate POM organic matter. Microbial enzymes associated with these processes are the principal catalysts for a large number of biochemical transformations of organic .