Lecture 15-1 Microbial Ecology

Transcription

1 Microbial Habitats, nutrient cycles, and interactions with Plants and Animals Lecture 15-1 Microbial Ecology Chapter 19 in BROCK BIOLOGY OF MICROORGANISMS School of Life Science and Biotechnology

2 I. MICROBIAL ECOSYSTEMS 15.1 Populations, Guilds, and Communities p.614

3 Components of Microbial Ecosystem Populations Individual cells grow to form populations 群体由单个细胞共同组成 Guilds 种群 Metabolically related populations constitute groupings called guilds 代谢相关的一群同种生物构成种群 Communities 群落 Sets of guilds conducting complementary physiological processes interact to form microbial communities 一系列种群相互作用及生理互补构成群落

4 Guilds and communities 种群与群落 Various microbial community structure in a lake ecosystem. 湖泊生态系统中的群落组成 For the sediment community, major guilds are indicated. 层积层群落中的主要种群

5 Microbial ecology 微生物生态学 Microbial ecologists primarily focus on two areas of study: Biodiversity: biodiversity of microorganisms in nature and how different guilds interact in microbial communities 微生物的多样性 Activities: activities of microorganisms in nature and monitor their effects on ecosystems 微生物的活性

6 15.2 Environments and Microenvironments 环境与微环境 Growth of microorganisms in nature Resources (nutrients available) Proper Conditions Temperature ph Water availability Light Oxygen Slow growth in nature than in pure culture E. coli doubling time: 12 hour in intestine, 20 min in culture

7 Microenvironment 微环境 Niche for microorganism 微生物的小生境 ( 生态位 ) Prime niche: a habitat defined by the type and quantity of different resources and the physicochemical conditions in which a microorganism is most successful 原始小生境 : 自然界中微生物最适宜的小环境 Think small-microenvironment (p.635) 3 mm to E. coli just as the same of 2 km to a man

8 15.3 Microbial Growth on Surfaces and Biofilms 表面生长与生物膜 p.617 Surfaces are important microbial habitats because 固体表面是重要的微生物生活环境 : Nutrients can adsorb to them; 营养可吸附于表面 ; In the microenvironment of a surface, nutrient level may be much higher than they are in the bulk solution. 微环境的固体表面有更高的营养物水平 ( 与水环境相比 ) A surface may itself also be a nutrient, such as a particle of organic matter. 固体表面可能本身就是营养 Microscope slides can be used as experimental surfaces to which organisms can attach and grow. 显微用玻片可作为微生物附着和生长的表面

9 Fig Bacterial microcolonies developing on a microscope slide immersed in a small river. The bright particles are mineral matter. 小河中玻片长出的微菌落, 亮颗粒是矿物颗粒.

10 (b) Fluorescence photomicrograph of a natural microbial community colonizing plant roots in soil. Note microcolony development. 荧光照片 : 土壤根际的自然微生物群落, 注意其中的微菌落. (stained with acridine orange) 丫啶橙染色

11 Biofilms 生物膜 Biofilms are encased microcolonies of bacterial cells attached to a surface by way of adhesive polysaccharides excreted by the cells. 生物膜 : 通过细胞分泌的粘性多糖, 附着在物体表面的被包裹的细菌微型菌落 Biofilms typically contain many layers. 生物膜通常由许多层次组成 Function: trap nutrients and prevent detachment of cells on surfaces when presenting in flowing systems. 作用 : 便于捕获营养及防止细胞的分散

12 Fig Microbial biofilms. A biofilm of iron-oxidizing prokaryotes on the surface of iron-rich rocks. 富铁岩石表面由铁氧化菌形成的生物膜

13 Sequence of biofilm formation 生物膜形成过程

14 Fig.19.5 Formation of a bacterial biofilm

15 Elasticity of Biofilm 生物膜的弹性

16 Fig A DAPI-stained biofilm that developed on a stainless steel pipe. 不锈钢管中的生物膜

17 Significance of biofilms In medicine Biofilms formed on human tissue surface or on medical implants can lead to serious problems 生物膜可有人体组织或医学植入物表面形成, 带来问题 Cells inside the biofilm are not reached by immune system and highly resistant to antibiotics 生物膜对免疫系统及抗生素有抗性 Dental plague-a typical biofilm of acid producing bacteria to cause cavities 牙斑是一种产酸菌的典型生物膜

18 Significance of biofilms In industry Blockage of pipelines Corrosions of pipes or submerged objects

19 Biofilm control 生物膜的控制 p.619 Interference with cell-cell communication in clinical medicine: discoveries of new antibiotics that can penetrate biofilms and drugs that prevent biofilm formation by interfering with intercellular communication. E.g. Furanone produced by red alga Delisea pulchra can bind to AHL receptor to prevent binding of AHL, disable communication and switch off surface colonization.furanone 可结合于 AHL 受体, 使之不能与 AHL 结合, 从而扰乱细菌间信息传递和生物膜形成

20 II. SOIL AND FRESHWATER MICROBIAL HABITATS 土壤与淡水微生物生境

21 15.4 Terrestrial Environments Soil formation: a result of combined physical, chemical, and biological processes. 1. Algae, lichens or mosses-phototrophic, produce organic matter, which supports the growth of chemoorganotrophic bacteria and fungi. 藻类 地衣 苔藓产生有机物, 支持了化能有机营养细菌和真菌生长 2. Chemoorganotrophic bacteria and fungi-produce carbonic and organic acids, which promote the dissolution of rock into smaller particles 3. Pioneering higher plants: promote the development of a rhizosphere microflora( 根际微生物区系 )

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23 Figure 19-6 Lower than at A horizon

24 Microenvironments in soil particles 土壤颗粒微环境 Very few microorganisms are found free in the soil solution; most of them occur as microcolonies attached to the soil particles. 土壤颗粒上的微菌落

25 (c) Fungal hyphae Fig 19.8 Microorganisms on the surface of soil particles (a) short, rod-shaped bacteria (b) Actinomycete spores

26 15.5 Freshwater habitats 淡水生境 Primary producers 初级生产者 Algae Phytoplankton 浮游生物 Benthic algae 深水藻类 Phototrophic bacteria Oxygenic phototrophic Cyanobacteria Anoxygenic phototrophic bacteria

27 Oxygen availability is a key factor in aquatic environments 氧气是关键因素 lake during the summer in temperate climates is a Stratified water body 温带的夏季湖泊是一种分层的水体 Warmer, less dense surface layer-epilimnion 变温层 Layer that temperature change quickly-thermocline 温跃层 Colder, denser bottom layer-hypolimnion 均温层

28 Macroprofiles of O 2, H 2 S and Tm Oxic-anoxic-oxic: summer-winter-summer 变温层 温跃层 均温层 Figure: 19-09

29 Figure: 19-10a Biochemical oxygen demand (BOD) River: Response of O 2 level and bacterial numbers to a spike of organic matter

30 A eutrophic lake: algae, cyanobacteria, and macrophytes develop in response to pollution by inorganic nutrients. Degradation of Dead plant and algal material results in largescale O 2 depletion, then sulfate-reducing bacteria, and many other anaerobes will develop. 富营养化湖 : 因无机营养物 ( 污染 ) 的加入, 藻类 兰细菌 大型植物大量生长, 而死亡植物及藻类的腐化导致氧气耗尽

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