MCB 314 Microorganisms in Natural Ecosystems PDF

E B G IE Z...

E B G IE Z O A L O 1 4 U K 3 B CB U L M O. R D Microorganis ms in Natural Ecosystems  NATURAL ECOSYSTEM  Natural ecosystem is an ecosystem found in nature where organisms freely interact with other components of that environment. It operate under natural conditions without any major interference by man. Types of Natural Ecosystem  Terrestrial:  Forest, grassland, desert, etc.  Aquatic:  freshwater and marine  DOMAINS OF NATURAL ENVIRONMENT Lithospher e Hydrosphe re Atmospher e Biosphere  COMPONENTS OF ECOSYSTEM Abiotic component: The non-living physiochemical factors of the environment.. It includes inorganic substances, organic compounds and climate factors. Biotic component: The living organisms present in an ecosystem. (i) Autotrophic component (ii) Heterotrophic component (a) Macroconsumers: herbivores, carnivores, omnivores (b) Microconsumers: bacteria, actinomycetes and fungi  TERRESTRIAL ECOSYSTEMS These are the richest and the most complex ecosystems which vary from rain forest to desert, with rich diversity of microorganisms in the soil.  The density and composition of microbial species of the soil is affected by environmental conditions.  Surface soils are occupied by indigenous populations of archaea, bacteria, fungi, algae, and protozoa.  The microbial communities within the subsurface are lower in number and less diverse than in surface soils.  nutrients are much more limited in the subsurface, a greater proportion of the population may be in a nonculturable state.  The soil ecosystems contribute to the major biogeochemical cycles, including the water cycle, and the major element (C, N, P,  and others) cycles.  MICROORGANISMS IN TERRESTRIAL ECOSYSTEM Prokaryotes are the most numerous soil inhabitants. Gram-positive (G+) bacteria are more abundant in soils than Gram-negative (G-) bacteria. Among the most common are G (+) spore-forming, rod-shaped bacteria (Bacillus and Clostridium). Filamentous G (+) bacteria of the genus Streptomyces produce well- developed vegetative hyphae. Some G (-) chemoheterotrophic bacteria adapted to live in terrestrial ecosystem are species of Azotobacter, Agrobacterium, Rhizobium and Pseudomonas, and among chemoautotrophs nitrifying bacteria such as species of Nitrosomonas (transform ammonium to nitrite) and Nitrobacter (oxidize nitrite to nitrate). Most fungi are aerobes and they are usually found in the top 10 cm of soil. The soil fungi are crucial in decomposing plant matter, degrading and using complex macromolecules such as lignin and cellulose. Many soil bacteria and fungi are important in nutrient cycling and removal of organic contaminants by the processes of biodegradation and bioremediation. Various protists are also found in most soils. Algae generally depend on sunlight for energy and most protozoans require O2 so they are found near the soil surface.  AQUATIC ECOSYSTEM Aquatic ecosystem occupy more than 70 % of the Earth’s surface and main types are: fresh waters (springs, streams, rivers and lakes), marine environments (seas, oceans) and ground waters. There are many types of springs (cold, thermal, hot and specialized – iron, sulphur, radioactive). Cold springs are habitat for bacteria and algae, Thermal or hot springs for many different species of archaea and thermophilic bacteria, iron springs for bacterial species Gallionella and Sphaerotilus sulphur springs for photosynthetic and nonphotosynthetic sulphur bacteria. Water from a source like a spring, rain or snow melt begins to flow down, and small streams are formed. These streams may slowly join together to form a larger stream or river. Streams and rivers accumulate organic matter and heterotrophic population from surrounding terrestrial environment thus a profile of microorganisms in streams and rivers resembles terrestrial. The types and relative numbers of microorganisms inhabiting lakes and marine environments depend on concentration of dissolved O2 and nutrients, temperature and sunlight. The upper layer is oxygen-rich due to the activities of many photosynthetic  ATMOSPHERE Various layers in the atmosphere can be recognized up to the height of about 1000 km. Although air content and atmospheric pressure vary at different layers, Air suitable for the survival of terrestrial plants and terrestrial animals is currently only known to be found in the Earth’s troposphere. This layer is the nearest to the Earth. Air also contains microorganisms, water droplets, dust particles and other matter. Atmosphere is not a hospitable environment for microorganisms due to temperature variations low amount of organic matter scarcity of available water  BIOAEROSOLS Airborne biological particles are called bioaerosols. They are generated as polydispersed droplets or particles of different sizes (0.5 to 30 µm). Pathway of bioaerosols is as follows: launching into the air from soil or water surfaces, subsequent transport via dispersion in air and deposition on surface. The transport and settling of bioaerosols are affected by their physical properties and environmental factors. The size density shape of the droplets or particles (most important physical characteristics) magnitude of air currents temperature relative humidity (environmental factors)  BIOAEROSOLS AND MICROORGANISMS Note:  Temperature and relative humidity contribute to the influx of airborne microorganisms.  Increased concentrations of some fungal spores (e.g., Cladosporium sp. and Nigrospora) in outdoor air. numbers of bacteria released from plant surfaces is associated with high temperatures and low relative humidity. In wet weather the rain washes the microorganisms from the air. In order to survive in the air, it is important that these microorganisms adapt to environmental stresses (desiccation, humidity and radiation). harsh environmental conditions tend to decrease the number of viable airborne microorganisms,  variability in survival between groups of microorganisms and within genera.  fungal spores and enteric viruses are resistant to environmental stress during transport through air.  Bacteria and algae are more susceptible while bacterial endospores (e.g. Bacillus sp.) are quite resistant. FUNCTIONAL ASPECTS OF AN ECOSYSTEM The rate of biological energy flow, i.e., the production and respiration rates of the community The rate of materials or nutrient cycles Biological or ecological regulation including both regulation of organisms by environment and regulation of environment by the organism. ROLES OF MICROORGANISMS IN ECOSYSTEM Generate Oxygen in the Atmosphere Almost all of the production of oxygen by bacteria on Earth occurs in the oceans by the cyanobacteria or "blue- green algae. Recycle nutrients stored in organic matter to an inorganic form Decomposition releases the mineral nutrients (e.g., N, P, K) bound up in dead organic matter in an inorganic form that is available for primary producers to use. Give Plant Roots Access to Nutrients in the Soil E.g Mycorrhiza ASSIGNMENT Write short note on the following in relation to the ecosystem; Lithosphere Hydrosphere Atmosphere Biosphere Primary Producers Secondary Producers Consumer