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UMass Amherst MICROBIO 310 - History and Characteristics of Microbes

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MICROBIO 310 1st Edition Lecture 2Outline of Last Lecture I. MRSAII. Griffith’s Transformation ExperimentIII. 1.1 Science of MicrobiologyOutline of Current Lecture I. 1.2 Microbial CellsII. 1.3 Microorganisms and Their EnvironmentsIII. 1.4 Evolution and the Extent of Microbial LifeCurrent Lecture1.2 Microbial Cells• The Cell base unit of life– Cytoplasmic (cell) membrane• Barrier that separates the inside of the cell from the outside environment – Cell wall• Present in most microbes, confers structural strength- 90% of bacteria can be characterized by how they build their cell wall• Characteristics of Living Systems– Metabolism: chemical transformation of nutrients– Reproduction: generation of two cells from one– Differentiation: synthesis of new substances or structures that modify the cell (only in some microbes)– Communication: generation of, and response to, chemical signals (only in some microbes)These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.o Quorum sensing– Movement: via self-propulsion, many forms in microbes– Evolution: genetic changes in cells that are transferred to offspring- Properties of all cells:- Compartmentalization- Metabolism- Growth - Evolution- Properties of some cells:- Motility- Differentiation (i.e. forming spores)- Communication (Quorum sensing)• Cells as Catalysts and as Coding Devices 1. Cells carry out chemical reactions • Enzymes: protein catalysts of the cell that accelerate chemical reactions 2. Cells store and process information that is eventually passed on to offspring during reproduction through DNA and evolution • Transcription: DNA produces RNA • Translation: RNA makes proteins1.3 Microorganisms and Their Environments• Microorganisms exist in nature in populations of interacting assemblages called microbial communities • The environment in which a microbial population lives is its habitat• Ecosystem refers to all living organisms plus physical and chemical constituents of theirenvironment• Microbial ecology is the study of microbes in their natural environment • Diversity and abundances of microbes are controlled by resources (nutrients) and environmental conditions (i.e., temp, pH, O2)• The activities of microbial communities can affect the chemical and physical properties of their habitats• Microbes also interact with their physical and chemical environment– Ecosystems are greatly influenced/controlled by microbial activities– Microorganisms change the chemical and physical properties of their habitats through their activities• For example, removal of nutrients from the environment and the excretion of waste products1.4 Evolution and the Extent of Microbial Life• The First Cells– First self-replicating entities may not have beencells (catalytic RNAs)– Last universal common ancestor (LUCA): common ancestral cell from which all cells descended• Life on Earth 4.6 billion years old– First cells appeared between 3.8 and 3.9 billion years ago– The atmosphere was anoxic (=no oxygen) until ~2 billion years ago– Anaerobic until evolution of oxygen-producing phototrophs– Life was exclusively microbial until ~1 billion years ago• The Extent of Microbial Life– Microbes found in almost every environment imaginableo Some can live in very harsh environmentso Bacteria can live off of the oil in your skin– Global estimate of 5 x 10^30 cellso Most microbial cells are found in oceanic and terrestrial subsurfaces– Microbial biomass is significant and cells are key reservoirs of essential nutrients (e.g., C, P,


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