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Semester 2: Microbial Physiology and Metabolism
Physiology of microbial growth Batch continuous - synchronous cultures Growth Curve and measurement method turbidity, biomass, and cell count
Physiology of Microbial Growth
Types of Culture
Synchronous Cultures
Growth Curve
Measurement Methods
Nutrition requirements - Photoautotrophs, Photoorganotrophs, Chemolithotrophs Ammonia, Nitrite, Sulfur, Hydrogen, Iron oxidizing Bacteria, Chemoorganotrophs
Introduction to Nutrition Requirements
Nutritional requirements are essential for the growth and metabolism of microorganisms. Different microorganisms have varying nutritional needs based on their metabolic capabilities.
Photoautotrophs
Photoautotrophs utilize light energy to convert carbon dioxide and water into organic compounds through photosynthesis. They require sunlight, carbon dioxide, and minerals for growth.
Photoorganotrophs
Photoorganotrophs utilize light as an energy source but rely on organic compounds as carbon sources. They can metabolize organic substrate in a manner similar to heterotrophic organisms.
Chemolithotrophs
Chemolithotrophs derive energy from inorganic compounds such as ammonia, nitrite, sulfur, and hydrogen. They play a crucial role in biogeochemical cycles and often use carbon dioxide as a carbon source.
Ammonia and Nitrite Utilization
Certain bacteria can oxidize ammonia to nitrite, a process known as nitrification. This is significant in nitrogen cycling and wastewater treatment.
Sulfur-oxidizing Bacteria
Sulfur-oxidizing bacteria are chemolithotrophs that obtain energy by oxidizing sulfur compounds to sulfate, contributing to the sulfur cycle and influencing environmental sulfur levels.
Hydrogen-oxidizing Bacteria
Hydrogen-oxidizing bacteria utilize hydrogen gas as an energy source, often found in anaerobic environments, contributing to various ecological and industrial processes.
Iron-oxidizing Bacteria
Iron-oxidizing bacteria transform ferrous iron to ferric iron, aiding in iron cycling in the environment. They are important in bioremediation and bioleaching.
Chemoorganotrophs
Chemoorganotrophs obtain energy by oxidizing organic compounds, requiring organic substrates for growth. They are critical in decomposing organic matter and recycling nutrients.
Nutrition transport mechanisms Passive diffusion and Active transport
Nutrition transport mechanisms
Overview of Nutrient Transport
Nutrient transport is essential for microbial physiology and metabolism, involving movement of substances across cell membranes to maintain homeostasis and support growth.
Passive Diffusion
Passive diffusion is a process where molecules move from an area of higher concentration to an area of lower concentration without the need for energy. Small and non-polar molecules, such as oxygen and carbon dioxide, can easily diffuse through the lipid bilayer of cell membranes.
Factors Affecting Passive Diffusion
The rate of passive diffusion is influenced by factors such as concentration gradient, membrane permeability, and temperature. A steeper concentration gradient increases diffusion rate, while membrane fluidity also plays a significant role.
Facilitated Diffusion
Facilitated diffusion involves the use of transport proteins to aid the movement of molecules across the membrane. This method also does not require energy and allows larger or polar molecules, like glucose, to enter the cell.
Active Transport
Active transport requires energy, usually in the form of ATP, to move substances against their concentration gradient. This is crucial for uptake of nutrients, particularly in environments where nutrient concentrations are low.
Types of Active Transport
Two main types of active transport exist: primary active transport, which directly uses ATP to transport molecules, and secondary active transport, which relies on the gradient created by primary transport.
Importance of Transport Mechanisms
Both passive and active transport mechanisms are vital for microbial survival, influencing nutrient uptake, waste removal, and overall cellular function.
Factors affecting microbial growth
Factors affecting microbial growth
Nutritional Factors
Microorganisms require a variety of nutrients to grow, including carbon, nitrogen, sulfur, phosphorus, and trace elements. The availability of these nutrients can significantly affect microbial growth rates. Different microbes have varying nutritional requirements, with some being capable of using alternative nutrient sources.
Physical Factors
Temperature, pH, and osmotic pressure are critical physical factors affecting microbial growth. Each microorganism has a specific range of temperatures and pH levels optimal for growth. Extremes of temperature or pH can lead to cell death or inhibit growth.
Environmental Factors
Oxygen levels influence the growth of microbes. Aerobic organisms require oxygen, while anaerobic organisms grow in its absence. Some microbes are facultative anaerobes and can adapt to both conditions. Other environmental factors include light exposure and moisture levels.
Biotic Interactions
Microbial growth is also influenced by interactions with other organisms. Competition for resources, predation, and symbiotic relationships can impact microbial populations and growth. Pathogenic microbes may also affect their hosts by altering nutrient availability.
Toxic Substances
The presence of toxic substances, such as heavy metals and antibiotics, can inhibit or promote microbial growth. Some microbes have developed resistance mechanisms to survive in the presence of these substances, while others may be sensitive and unable to thrive.
An overview of Metabolism - Embden Meyerhof Pathway, Entner- Doudoroff Pathway, Pentose Phosphate Pathway, Tricarboxylic Acid Cycle
Introduction to Metabolism
Metabolism refers to the set of life-sustaining chemical reactions in organisms. It involves catabolic and anabolic pathways to convert food into energy and to build cellular structures.
Embden-Meyerhof Pathway
The Embden-Meyerhof pathway, also known as glycolysis, is a series of reactions that convert glucose into pyruvate, yielding ATP and NADH. It occurs in the cytoplasm and consists of two phases: the energy investment phase and the energy payoff phase.
Entner-Doudoroff Pathway
The Entner-Doudoroff pathway is an alternative pathway for glucose metabolism found in some bacteria. It converts glucose into 2-keto-3-deoxy-6-phosphogluconate, which is then cleaved into pyruvate and glyceraldehyde-3-phosphate, producing ATP and NADPH.
Pentose Phosphate Pathway
The Pentose Phosphate Pathway, also known as the hexose monophosphate shunt, is a metabolic pathway parallel to glycolysis. It generates NADPH and pentoses (5-carbon sugars) for nucleotide synthesis. It plays a crucial role in cellular metabolism and antioxidant defense.
Tricarboxylic Acid Cycle (TCA)
The Tricarboxylic Acid Cycle, or Krebs cycle, is a central metabolic pathway that completes the oxidation of glucose derivatives. It occurs in the mitochondria and produces ATP, NADH, and FADH2, which are essential for aerobic respiration.
Electron Transport Chain and Oxidative Phosphorylation
Introduction to Electron Transport Chain
The electron transport chain is a series of protein complexes located in the inner mitochondrial membrane of eukaryotes and the plasma membrane of prokaryotes. It plays a critical role in cellular respiration by facilitating the transfer of electrons from electron donors to electron acceptors through redox reactions.
Components of the Electron Transport Chain
The main components involved in the electron transport chain include NADH dehydrogenase, cytochrome b-c1 complex, cytochrome c oxidase, and ATP synthase. Each component has a specific function in transferring electrons and pumping protons.
Role of NADH and FADH2
NADH and FADH2 are key electron carriers generated during glycolysis and the Krebs cycle. They donate electrons to the electron transport chain, initiating the process of oxidative phosphorylation.
Proton Gradient and Chemiosmosis
As electrons pass through the electron transport chain, protons are pumped from the mitochondrial matrix into the intermembrane space, creating a proton gradient. This gradient stores potential energy that is used by ATP synthase to synthesize ATP from ADP and inorganic phosphate.
Oxidative Phosphorylation
Oxidative phosphorylation is the final stage of cellular respiration, where the energy from the electron transport chain is coupled with ATP synthesis. Oxygen acts as the final electron acceptor in the electron transport chain, forming water as a byproduct.
Importance in Microbial Metabolism
In microbes, the electron transport chain can vary, allowing for the utilization of different electron donors and acceptors. Understanding this process is crucial for studying microbial physiology, energy production, and metabolic pathways.
ATP synthesis
ATP synthesis
Overview of ATP
ATP, or adenosine triphosphate, is the primary energy currency of cells. It provides energy for various biochemical processes and is essential for metabolism.
ATP Synthesis Mechanisms
ATP synthesis occurs through three main mechanisms: substrate-level phosphorylation, oxidative phosphorylation, and photophosphorylation.
Substrate-Level Phosphorylation
This process occurs in the cytoplasm during glycolysis and in the mitochondria during the Krebs cycle. It involves the direct transfer of a phosphate group to ADP to form ATP.
Oxidative Phosphorylation
Oxidative phosphorylation occurs in the inner mitochondrial membrane. It involves the electron transport chain and chemiosmosis, where energy from electrons is used to pump protons across the membrane, creating a gradient that drives ATP synthesis through ATP synthase.
Photophosphorylation
Photophosphorylation is the process where light energy is converted into chemical energy, occurring in photosynthetic organisms. It takes place in the thylakoid membranes of chloroplasts.
Role of Enzymes in ATP Synthesis
Various enzymes, such as ATP synthase and dehydrogenases, play vital roles in facilitating reactions involved in ATP production.
Significance of ATP in Microbial Metabolism
ATP is crucial for microbial growth and metabolism. It fuels cellular processes such as nutrient uptake, biosynthesis, and motility.
Regulation of ATP Production
ATP production is regulated by the availability of substrates and the energy needs of the cell, ensuring a balance between supply and demand.
Fermentation-Homolactic Fermentation, Heterolactic Fermentation, Mixed Acid Fermentation, Butanediol Fermentation
Fermentation
Homolactic Fermentation
Homolactic fermentation is a type of fermentation in which glucose is converted primarily into lactic acid. The process is facilitated by lactic acid bacteria such as Lactobacillus. This reaction occurs without the production of gas and is important in the production of yogurt and certain cheeses.
Heterolactic Fermentation
Heterolactic fermentation involves the conversion of glucose into multiple products, including lactic acid, ethanol, and carbon dioxide. This process is also mediated by lactic acid bacteria but produces a mixture of end products. It is commonly found in the fermentation of sourdough and in certain pickled vegetables.
Mixed Acid Fermentation
Mixed acid fermentation is characterized by the production of a variety of organic acids, including acetic acid, lactic acid, and others. This type of fermentation is performed by several genera of bacteria, including Escherichia and Enterobacter. It is significant in the anaerobic breakdown of carbohydrates and contributes to the flavor of fermented foods.
Butanediol Fermentation
Butanediol fermentation is a specific pathway within mixed acid fermentation where glucose is converted into butanediol, ethanol, and carbon dioxide. Organisms such as Enterobacter aerogenes participate in this process. It is important in the production of certain alcoholic beverages and contributes to the flavor profiles in some fermented products.
Photosynthesis - An Overview of chloroplast structure
Photosynthesis - An Overview of Chloroplast Structure
Introduction to Photosynthesis
Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy into chemical energy stored in glucose. It primarily occurs in chloroplasts located in plant cells.
Chloroplast Structure
Chloroplasts are organelles with a double membrane, consisting of an outer membrane and an inner membrane. Inside, they contain thylakoids, which are membrane-bound structures that contain chlorophyll.
Thylakoids and Chlorophyll
Thylakoids are stacked in structures called grana, resembling coins. Chlorophyll, the green pigment, is embedded in the thylakoid membranes and is crucial for light absorption.
Stroma
Stroma is the fluid-filled space surrounding the thylakoids within the chloroplast. It contains enzymes, DNA, and ribosomes necessary for the synthesis of glucose during the Calvin cycle.
Light-dependent Reactions
These reactions occur in the thylakoid membranes and convert solar energy into chemical energy in the form of ATP and NADPH. Water is split, releasing oxygen as a byproduct.
Calvin Cycle
The Calvin cycle occurs in the stroma, utilizing ATP and NADPH produced in the light-dependent reactions to convert carbon dioxide into glucose.
Photosynthetic Pigments, Light Reaction-Cyclic and non-cyclic Photophosphorylation
Photosynthetic Pigments, Light Reaction-Cyclic and Non-Cyclic Photophosphorylation
Photosynthetic Pigments
Photosynthetic pigments are molecules that absorb light energy for photosynthesis, mainly chlorophylls and carotenoids. Chlorophyll a and b are the primary pigments found in plants, capturing light energy primarily in the blue-violet and red wavelengths. Carotenoids assist in light capture by absorbing light in other wavelengths and also provide photoprotection by dissipating excess light energy.
Light Reactions Overview
Light reactions, also known as photophosphorylation, occur in the thylakoid membranes of chloroplasts. They convert light energy into chemical energy in the form of ATP and NADPH. This process involves the absorption of sunlight, splitting of water molecules, and the generation of oxygen as a by-product.
Non-Cyclic Photophosphorylation
Non-cyclic photophosphorylation involves two photosystems (PSI and PSII) and produces ATP, NADPH, and oxygen. Electrons are excited by light energy, travel through an electron transport chain, and are replaced by electrons from water molecules. The processes generate an electrochemical gradient that helps in ATP synthesis via ATP synthase.
Cyclic Photophosphorylation
Cyclic photophosphorylation occurs when excited electrons from PSI return back to the same photosystem instead of moving to NADP+. This process generates ATP but not NADPH, allowing the cell to balance the ATP/NADPH ratio during photosynthesis when there is an excess of NADPH.
Dark Reaction - Calvin Cycle
Dark Reaction - Calvin Cycle
Introduction to Calvin Cycle
The Calvin Cycle, also known as the dark reactions, is a series of biochemical processes that take place in the stroma of chloroplasts during photosynthesis. It does not require light directly and converts carbon dioxide and other compounds into glucose.
Stages of the Calvin Cycle
The Calvin Cycle consists of three main stages: Carbon Fixation, Reduction Phase, and Regeneration of RuBP. Carbon dioxide is fixed into an organic molecule, then reduced using ATP and NADPH to produce G3P, and finally, RuBP is regenerated to continue the cycle.
Role of Enzymes
Key enzymes in the Calvin Cycle include ribulose bisphosphate carboxylase/oxygenase (RuBisCO), which catalyzes the first step of carbon fixation, and phosphoribulokinase, which helps regenerate RuBP.
Energy Requirements
The Calvin Cycle uses energy stored in ATP and reducing power from NADPH, both generated from the light-dependent reactions of photosynthesis. Each turn of the cycle requires three ATP and two NADPH.
Importance of the Calvin Cycle
The Calvin Cycle is essential for converting atmospheric CO2 into organic compounds, serving as the foundation of the food web. It impacts various biological and ecological processes including energy flow and matter cycling.
Regulation of the Cycle
The Calvin Cycle is regulated by factors such as light intensity, temperature, and the concentration of CO2. Changes in these factors can influence the rate of photosynthesis and the efficiency of the cycle.
Bacterial reproduction - Binary fission, Budding, Reproduction through conidia, cyst formation, endospore formation
Bacterial reproduction
Binary fission
Binary fission is the most common method of bacterial reproduction. In this a single bacterial cell divides into two identical daughter cells. The process involves DNA replication, cell elongation, and then the formation of a septum that divides the cell into two.
Budding
Budding is a method of asexual reproduction found in some bacteria. In this process, a new organism develops from an outgrowth or bud on the parent organism. The bud develops into a mature cell, which then separates from the parent.
Reproduction through conidia
Conidia are asexual spores produced by some bacteria and fungi. They allow for reproduction without the need for sexual reproduction. Conidia can disperse in the environment and germinate to form new bacterial colonies when conditions are favorable.
Cyst formation
Cyst formation is a survival strategy employed by some bacteria, allowing them to withstand harsh environmental conditions. Bacteria can form a protective shell or cyst around themselves, allowing them to remain dormant until favorable conditions return.
Endospore formation
Endospore formation is a form of reproduction used by some bacteria, particularly in adverse environmental conditions. Endospores are highly resistant structures that protect the bacterial DNA and essential proteins, allowing the bacteria to survive extreme temperatures, desiccation, and radiation. When conditions improve, endospores can germinate back into active bacterial cells.
Fungi asexual and sexual reproduction, Microalgae reproduction
Fungi Asexual and Sexual Reproduction and Microalgae Reproduction
Fungal Asexual Reproduction
Fungi primarily reproduce asexually through processes such as budding, fragmentation, and spore formation. This allows them to quickly colonize environments. Conidia are a common form of asexual spores. They can be produced in large numbers and dispersed by wind or water.
Fungal Sexual Reproduction
Sexual reproduction in fungi occurs through the combination of genetic material from two compatible mating types. This process often involves the formation of specialized sexual structures, such as zygosporangia or ascospores, leading to genetic diversity, essential for adaptation.
Microalgae Asexual Reproduction
Microalgae primarily reproduce asexually through binary fission, where a single cell divides into two identical daughter cells. This process allows rapid population growth under favorable conditions. Some microalgae can also reproduce by fragmentation.
Microalgae Sexual Reproduction
Sexual reproduction in microalgae is less common but occurs in some species. It involves the fusion of gametes, leading to the formation of zygotes. This process enhances genetic variation, which is vital for survival in changing environments.
Asexual and sexual reproduction of protozoa
Asexual and Sexual Reproduction of Protozoa
Introduction to Protozoa
Protozoa are single-celled eukaryotic organisms found in various environments. They display a wide range of morphologies and behaviors, and are important in ecosystems as both predators and prey.
Asexual Reproduction in Protozoa
Asexual reproduction is the primary mode of reproduction in many protozoa. Common methods include binary fission, budding, and schizogony. In binary fission, the organism divides into two equal parts. Budding involves the formation of a new organism from a bud on the parent. Schizogony is a form of multiple fission where the nucleus divides multiple times before the cell divides.
Sexual Reproduction in Protozoa
Sexual reproduction in protozoa is less common but occurs in various forms, such as conjugation, gametogenesis, and syngamy. Conjugation involves the temporary fusion of two protozoan cells, allowing for the exchange of genetic material. Gametogenesis produces specialized reproductive cells called gametes, which can fuse during syngamy to form a zygote.
Factors Influencing Reproductive Strategies
The choice between sexual and asexual reproduction in protozoa can depend on environmental factors such as population density, availability of resources, and stress conditions. In stable environments, asexual reproduction is advantageous for rapid population growth, while sexual reproduction provides genetic diversity that can enhance survival in changing conditions.
Conclusion
Understanding the reproductive strategies of protozoa is essential for comprehending their role in ecosystems and their responses to environmental changes. Both asexual and sexual reproduction contribute to the survival and adaptation of protozoan populations.
