Cellular Energy and Metabolism: Underlying Chemical PrinciplesIntroduction Cells capture and utilize energy through a series of chemical reactions which involve: Rearrangement of electrons within the molecules involved in the reaction. Redistribution of energy that these molecules contain. Some molecules end up with more energy than they began while some end up with less. Metabolism complex network of reactions inside the cell that captures the energy and raw materials of its environment and allows them to be changed into forms that are used to sustain cells.Energy Change in Chemical Reactions All chemical reactions are accompanied by a net energy change, which depends on how much energy is taken in by the chemicals when chemical bonds form and how much energy is released when bonds break. In chemical reactions, there is a balance between energy taken when chemicals break, energy released when chemical bonds form and energy exchanged with surroundings. As a result, there is overall loss of usable energy. Change in Free Energy Change in free energy (G) = change in the usable energy that is available for doing work Positive G: Reaction will not proceed spontaneously. It is work-requiring (endergonic.) Negative G: Reaction will proceed spontaneously. It is work-producing (exergonic.)

ATP and Free Energy Some molecules like ATP (adenosine triphosphate) contain bonds that are called high energy phosphate bonds.

Cells capture energy as chemical energy stored with molecules of ATP. This captured energy is used to drive energy-requiring reactions. ATP is considered the central currency of energy in the cell. Why? Because it is a high energy molecule that is used in many different reactions throughout the cell as the energy source. You can make or use ATP, like making or using Philippine peso in normal currency. Also, some reactions might need more than other reactions, just like how some items cost more than others. But like what was said before, ATP is not only used, it can also be produced by energy-producing processes just like how jobs can produce Philippine peso. Some pathways require inputs of ATP and use the energy of ATP to drive endergonic reactions. Living cells continuously form and consume ATP.Activation Energy Input of energy which all chemical reactions begin with whether they eventually take in or release energy overall. Chemical reactions begin with collision between reactant molecules. Activation energy is required in a collision to initiate a chemical reaction.Enzymes and Activation Energy Enzymes are globular proteins with characteristic 3-dimensional shapes that act as biological catalysts to speed up the rates at which chemical reactions occur by lowering the activation energy. Lock and Key Model Enzyme and substrate are available. Substrate attach to the active site of the enzyme in order to produce an enzyme-substrate complex. Substrate is converted to product. Product is released and enzyme goes back into its original state. Enzymes are not consumed or modified in the overall course of the reactions they catalyze. The active site is the binding site for the enzymes substrate. Enzymes are specific for substrate molecules. These are all shape-driven, so anything that alters the shape of the active site will affect enzymatic activity. Enzymes are efficient, can operate at relatively low temperatures and are subject to various cellular controls. Enzyme exhibit very precise substrate specificity, i.e. each enzyme can bind to and catalyze the reactions of only a very small range of molecules. The specificity of enzymes for a particular substrate depends on the precise structure of each enzymes active site. Fundamental unity at the cellular level exists among all living organisms. The uniqueness of a certain type of cell or organism is not due to uniqueness of substances and enzymes found in it, but rather due to the uniqueness of combinations of substances and enzymes found in them.Factors affecting Enzyme Activity At high temperatures, enzymes undergo denaturation and lose their catalytic properties; at low temperatures, the reaction rate decreases. The rate at which enzymatic reactions process is sensitive to temperature. Above about 40C, most enzymes become structurally altered via denaturation. The pH at which enzymatic activity is maximal is known as the optimum pH. Enzymes are proteins and their molecular structure is affected by pH. Catalysis by enzymes is highly dependent on molecular structure thus enzyme activity is sensitive to pH change. Within limits, enzymatic activity increases as substrate concentration increases. At some high concentration of the substrate, so that all the enzymes active sites are occupied, increasing the substrate concentration will not further increase the rate of the reaction. At this substrate concentration, the maximum rate of enzymatic reaction (Vmax) has been reached. Michaelis-Menten Equation The dependence of the rate of enzymatic reaction (V) on substrate concentration [S] is given by

Km, the Michaelis constant, is the substrate concentration that results in a reaction rate one-half times the maximum (Vmax). Km is a measure of the affinity of the enzyme for a particular substance. The greater the affinity is, the lower the Km is.Enzyme Regulation Cofactors Many enzymes need a cofactor (inorganic substances such as minerals) to activate them. Without the cofactor, the enzyme cant lock the substrate into its active site, so the reaction cant take place. The cofactor can be a metal ion(e.g. Fe2+) or a complex inorganic molecule known as coenzyme (e.g. NAD+) Allosteric effectors The rate of enzymatic reactions can be altered by molecules that can act as allosteric effectors which are molecules that bind at the enzyme and deform the active site which disables substrate to bind with the enzyme. Competitive inhibitors compete with the normal substrate for the active site of the enzyme. Noncompetitive inhibitors act on other parts of the apoenzyme or on the cofactor and decrease the enzymes ability to combine with the normal substrate. How do enzyme regulation work? A substrate binds with enzyme 1 and produces intermediate A which becomes the substrate that will bind at the active site of enzyme 2. This process will produce intermediate B that will now bind with enzyme 3 to produce the end product which when attaches to enzyme 1 will stop the production of intermediate A and eventually, the whole process.Oxidation-Reduction Reactions Many metabolic reactions, including those involved in energy capture and utilization are reactions that involve electron transfer. Many enzymatic reactions require coenzymes (small non-protein organic substances that bind loosely to specific enzymes and assist in their catalytic function). They can accept a chemical group (or an electron) produced by one enzymatic reaction, hold on to it for a short time and then donate it to the substrate of another reaction. Oxidation of a substrate is often coupled to the simultaneous reduction of a coenzyme.Reduction Potential Molecules vary with regard to how easily they gain or accept electrons. This ability is reflected in the value of their reduction potential, which is a value indicating how readily a substance accepts/donates electrons. The substance with the most positive reduction potential has the greatest potential to accept electron.Electrical Potential The electrical potential (rxn) is related to the free energy (G) by

Where n = number of electrons transferredF = Faradays constant (96,485 Coulombs/mole) The higher the electrical potential of a reduction half-reaction, the greater the tendency for the species to accept an electron.Metabolic Strategies for Generating ATP Via metabolic pathways: Chemical energy or light energy -> energy stored in ATP Cell obtains C for synthesis of new cell materials Synthesis of ATP Through metabolism of inorganic substances Through the conversion of light energy -> chemical energy Utilization of organic substances

Two different mechanisms for generating ATP: Substrate-level phosphorylation ChemiosmosisSubstrate-level phosphorylation Free energy released from exergonic reactions supplies the free energy required to combine inorganic phosphate (Pi) or phosphate from an organic molecule and ADP to form ATP. In a substrate level phosphorylation, ATP is made during the conversion of an organic molecule from one form to another. Energy released during the conversion is partially conserved during the synthesis of the high energy bond of ATP. SLP occurs during fermentations and respiration (the TCA cycle), and even during some lithotrophic transformations of inorganic substrates. Example: Phosphoenolpyruvate -> pyruvate(exergonic) ADP -> ATP(endergoniChemiosmosis ADP -> ATP(endergonic) Movement of electrons down a proton gradient across a membrane (exergonic)Autotrophic Metabolism Self-feeding Uses inorganic CO2 as carbon sourceHeterotrophic Metabolism Requires supply of preformed organic matter for the production of cellular biomass and as a source of chemical energy used to form ATP Involves conversion of the organic substrate molecule to end products via a metabolic pathway that releases sufficient energy for it to be couples to the formation of ATP. Two basic types: Respiration FermentationRespiration Requires an external electron acceptor not derived from the organic substrate. Reduction of final electron acceptor balances the oxidation of initial substrate (electron transport system)Fermentation Metabolism in which energy is derived from the partial oxidation of an organic compound using organic intermediates as electron donors and electron acceptors. No outside electron acceptors are involved; no membrane or electron transport system is required. All ATP is produced by substrate-level phosphorylation.Respiratory Metabolism Aerobic respiration begins with an organic molecule and combines it with oxygen in an oxidation-reduction process that ends with the formation of CO2 and H2O plus a substantial amount of ATP. 3 Phases of Respiratory Metabolism A catabolic pathway during which the organic molecule is broken down into smaller molecules usually with the generation of some ATP and reduced coenzymes. The tricarboxylic acid cycle (TCA), during which the small organic molecules produced in the first phase are oxidized to inorganic carbon dioxide and water, accompanied with more production of more ATP and reduced coenzymes Oxidative phosphorylation, during which The reduced enzymes are reoxidized The electrons they release are transported through a series of membrane-bound carriers to establish a proton gradient across a membrane (electron transport system) A terminal acceptor such as oxygen is reduced and ATP is synthesizedTricarboxylic Acid (TCA) cycle At the end of the TCA cycle, all the carbon has been converted to CO2. TCA plays a central role in the flow of carbon through the cell. It supplies organic precursor molecules to many biosynthetic pathways. Some of the intermediates in the TCA cycle must be resynthesized to maintain TCA cycle.Electron Transport Chain Electrons are brought to the electron transport chain by NADH. The electron transport chain consists of membrane-bound carriers, including flavoproteins, cytochromes and ubiquinones. Electrons from the reduced coenzymes NADH and FADH2 are passed from one carrier with low reduction potential to carriers with higher reduction potential. The energy gained from each electron-transfer step is used to drive proton pumps, or move protons against a concentration gradient, from the matrix to the intermembrane space. The final/terminal electron acceptor is irreversibly reduced; it may be oxygen (aerobic) or another inorganic molecule (anaerobic). ETP requires that electrons removed from substrates be dumped into an electron transport system (ETS) contained within a membrane. The electrons are transferred through the ETS to some final electron acceptor in the membrane (like O2 in aerobic respiration) , while their traverse through the ETS results in the extrusion of protons and the establishment of a proton motive force (pmf) across the membrane. The idea in electron transport phosphorylation is to drive electrons through an ETS in the membrane, establish a pmf, and use the pmf to synthesize ATP.Aerobic Respiration: Overall Process A substrate such as glucose is completely oxidized to CO2 by the combined pathways of glycolysis and the TCA cycle. Electrons removed from the glucose by NAD are fed into the electron transport chain in the membrane. As the electrons traverse the electron transport chain, a proton motive force becomes established across the membrane. The electrons eventually reduce an outside electron acceptor, O2 and reduce it to H2O. The proton motive force on the membrane is used by the ATPase enzyme to synthesize ATP by a process referred to as oxidative phosphorylation.Anaerobic Respiration The final electron acceptors in anaerobic respiration include NO3-, SO42- and CO32-. NO3- is reduced to NO2- SO42- is reduced to H2S. CO32- is reduced to CH4. The total ATP yield is less than in anaerobic respiration because only part of the Krebs cycle operates under anaerobic conditions.Fermentation Fermentation is any process that releases energy from sugars or other organic molecules by oxidation, does not require O2, the Krebs cycle, or an electron transport chain, and uses an organic molecule as the final electron acceptor. Fermentation is metabolism in which energy is derived from the partial oxidation of an organic compound using organic intermediates as electron donors and electron acceptors. No outside electron acceptors are involved; no membrane or electron transport system is required; all ATP is produced by substrate level phosphorylation. Fermentation can sometimes occur in the presence of O2. Fermentation produces 2 ATP molecules by substrate-level phosphorylation. Electrons removed from the substrate reduce NAD+ to NADH. Uses a terminal electron acceptor derived from organic substrate. Both the electron donor and electron acceptor are internal to the organic substrate in a fermentation pathway, i.e. the eventual electron acceptor. Can occur in the absence of air because there is no requirement for O2 or an external electron acceptor to achieve a balance in the oxidation-reduction reaction. Yields less ATP per substrate molecule than respiration (because the organic substrate molecule must serve as both the internal electron donor and internal electron acceptor). ATP generation is only during glycolysis. Not all C and H are oxidized to CO2 and H2O. C and H are rearranged into a form containing less chemical energy than that with which they began.Catabolism of Lipids Lipase hydrolyze lipids into glycerol and fatty acids. Fatty acids and other hydrocarbons are catabolized by beta oxidation. Beta oxidation produces two carbon units that are linked to CoA to make acetyl-CoA. Catabolic products can be further broken down into glycolysis and the Krebs cycle.Transamination of amino acids Before amino acids can be catabolized, they must be converted to various substances that enter the Krebs cycle or glycolysis. Transamination (transfer of NH2), decarboxylation (removal of COOH), and dehydrogenation (H2) reactions convert the amino acids to be catabolized into substances that enter the glycolytic pathway or Krebs cycle.

Lithotrophic Metabolism Lithotrophy the use of an inorganic compound as a source of energy Most lithotrophic bacteria are aerobic respirers. Get e- from inorganic compound e- -> electron transport chain to produce ATP Some lithotrophs are facultative litotrophs. Organic or inorganic compound as source of energy Lithoautotrophs A very diverse group of prokaryotes. Able to oxidize an inorganic compound as an energy source.Lithotrophic Metabolism: Hydrogen Oxidation Hydrogen bacteria oxidize hydrogen gas as an energy source. Most are nutritionally-versatile, i.e. use a wide range of carbon and energy sources. Some have NAD-linked hydrogenase that transfers electrons from hydrogen to NAD in a one-step process. NAD then delivers the electrons to the electron transport system. Others have hydrogenase enzymes that pass electrons to different carriers in the bacterial electron transport system.Lithotrophic Metabolism: Autotrophic Methanogenesis Methanogens the most prevalent and diverse group of Archaea and able to oxidize hydrogen as a sole source of energy while transferring the electrons from hydrogen to carbon dioxide in its reduction to methane. Metabolism of the methanogens is absolutely unique. Methanogens use H2 and CO2 to produce cell material and methane. They have unique coenzymes and electron transport processes. Their type of energy generating metabolism is never seen in the Bacteria, and their mechanism of autotrophic CO2 fixation is very rare.Lithotrophic Metabolism: Oxidation of Carbon monoxide Carboxydobacteria able to oxidize CO to CO2 using an enzyme CODH (carbon monoxide dehydrogenase) The enzyme CODH used by the carboxydobacteria to oxidize CO to CO2 is used by methanogens for the reverse reaction the reduction of CO2 to CO during CO2 fixation by the CODH pathway.Lithotrophic Metabolism: Nitrification The nitrifying bacteria are represented by two genera, Nitrosomonas and Nitrobacter. Together these bacteria can accomplish the oxidation of NH3 to NO3, known as the process of nitrification. No single organism can carry out the whole oxidative process. Nitrosomonas oxidizes ammonia to NO2 and Nitrobacter oxidizes NO2 to NO3. Nitrifying bacteria grow in environments rich in ammonia, where extensive protein decomposition is taking place. Nitrification in soil and aquatic habitats is an essential part of the nitrogen cycle.

Lithotrophic Metabolism: Sulfur Oxidation Lithotrophic sulfur oxidizers include both Bacteria (e.g. Thiobacillus) and Archaea (e.g. Sulfolobus). Sulfur oxidizers oxidize H2S (sulfide) or S (elemental sulfur) as a source of energy. The purple and green sulfur bacteria oxidize H2S or S as an electron donor for photosynthesis, and use the electrons for CO2 fixation (the dark reaction of photosynthesis). Lithoautotrophic sulfur oxidizers are found in environments rich in H2S, such as volcanic hot springs and fumaroles, and deep-sea thermal vents. Some are found as symbionts and endosymbionts of higher organisms. Since they can generate energy from an inorganic compound and fix CO2 as autotrophs, they may play a fundamental role in primary production in environments that lack sunlight. As a result of their lithotrophic oxidations, these organisms produce sulfuric acid (SO4), and therefore tend to acidify their own environments. Some of the sulfur oxidizers are acidophiles that will grow at a pH of 1 or less. Some are hyperthermophiles that grow at temperatures of 115 degrees C.Lithotrophic Metabolism: Iron Oxidation Iron bacteria oxidize Fe++ (ferrous iron) to Fe+++ (ferric iron). At least two bacteria probably oxidize Fe++ as a source of energy and/or electrons and are capable of lithoautotrophic growth the stalked bacterium Gallionella, which forms flocculant rust-colored colonies attached to objects in nature Thiobacillus ferrooxidans, which is also a sulfur-oxidizing lithotroph.Phototrophic Metabolism Phototrophy is the use of light as a source of energy for growth, more specifically the conversion of light energy into chemical energy in the form of ATP. Procaryotes that can convert light energy into chemical energy include The cyanobacteria conduct plant photosynthesis, called oxygenic photosynthesis; the purple and green bacteria conduct bacterial photosynthesis or anoxygenic photosynthesis; the extreme halophilic archaea use a type of nonphotosynthetic photophosphorylation mediated by bacteriorhodopsin to transform light energy into ATP. Photosynthesis is a type of metabolism separable into a catabolic and anabolic component. The catabolic component of photosynthesis is the light reaction, wherein light energy is transformed into electrical energy, then chemical energy. The Light Reactions depend upon the presence of chlorophyll, the primary light-harvesting pigment in the membrane of photosynthetic organisms. Absorption of a quantum of light by a chlorophyll molecule causes the displacement of an electron at the reaction center. The displaced electron is an energy source that is moved through a membrane photosynthetic electron transport system, being successively passed from an iron-sulfur protein (X ) to a quinone to a cytochrome and back to chlorophyll. As the electron is transported, a proton motive force is established on the membrane, and ATP is synthesized by an ATPase enzyme. This manner of converting light energy into chemical energy is called cyclic photophosphorylation. In a noncyclic photophosphorylation, the electrons are used to reduce NADP+, and the electrons are returned to chlorophyll from H2O or H2S. The anabolic component involves the fixation of CO2 and its use as a carbon source for growth, usually called the dark reaction. In photosynthetic procaryotes there are two types of photosynthesis and two types of CO2 fixation. The functional components of the photochemical system are light harvesting pigments, a membrane electron transport system, and an ATPase enzyme. The photosynthetic electron transport system of is fundamentally similar to a respiratory ETS, except that there is a low redox electron acceptor (e.g. ferredoxin) at the top (low redox end) of the electron transport chain, that is first reduced by the electron displaced from chlorophyll. There are several types of pigments distributed among various phototrophic organisms. Chlorophyll is the primary light-harvesting pigment in all photosynthetic organisms. The chlorophylls are partially responsible for light harvesting at the photochemical reaction center. Carotenoids are always associated with the photosynthetic apparatus. They function as secondary light-harvesting pigments. Carotenoids transfer energy to chlorophyll, at near 100 percent efficiency, from wave lengths of light that are missed by chlorophyll. In addition, carotenoids have an indispensable function to protect the photosynthetic apparatus from photooxidative damage. Phycobiliproteins are the major light harvesting pigments of the cyanobacteria. They also occur in some groups of algae. Being closely linked to chlorophyll they can efficiently transfer light energy to chlorophyll at the reaction center. The normally cyclical flow of electrons during bacterial photosynthesis must be opened up in order to obtain electrons for CO2 fixation. In the case of the purple sulfur bacteria, they use H2S as a source of electrons. The oxidation of H2S is coupled to PSI. Light energy boosts an electron, derived from H2S, to the level of ferredoxin, which reduces NADP to provide electrons for autotrophic CO2 fixation.Light-Dependent Reaction: Calvin-Benson Cycle CO2 is used to synthesize sugars in the Calvin-Benson cycle CO2 is ligated to ribulose diphosphate (5-carbon molecule) to produce glucose Three CO2 molecules and three RuDP molecules yield six glyceraldehydes-3-phosphate molecules. Five glyceraldehydes molecules are converted to three RuDP molecules and one glyceraldehydes 3-phosphate is ligated to another to form glucose.Additional Notes: What are metabolism, catabolism and anabolism?Metabolism is the general term for all chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments.Metabolism can be divided into two general types of reactions. Catabolism is all of the chemical reactions that break down molecules, either to extract energy or to produce simple molecules for constructing others. Anabolism refers to all of the metabolic reactions that build or assemble more complex molecules from simpler ones. Catabolism and anabolism are intimately connected, and one really cannot occur without the other. Catabolism is also known as a "downhill" process during which energy is released, while anabolism requires the input of energy, and is therefore an energetically "uphill" process. At certain points in the anabolic pathway, the cell must put more energy into a reaction than is released during catabolism. Such anabolic steps require a different series of reaction than are used at this point during catabolism. What are metabolic pathways?The chemical reactions of metabolism do not happen randomly. They are organized into metabolic pathways, in which one molecule is converted through a series of steps into another molecule. For example, the metabolic pathway called glycolysis converts glucose into pyruvate, producing ATP. Glycolysis is a catabolic pathway, and all life depends on it. It is the central metabolic pathway. Metabolic pathways are interconnected. Cells use molecules produced in one pathway to make others. How are metabolic pathways controlled?Each step in a metabolic pathway will be catalyzed by an enzyme. These enzymes are crucial to metabolism for several reasons. They help all metabolic reactions occur faster and more efficiently. Without a catalyst, some of the metabolic reactions require conditions that are more extreme than what we see in cells (higher temperatures, extremes of pH, etc.) Metabolic enzymes lower the activation energy of reactions so they can occur in more moderate conditions. Some of the steps in metabolic pathways require energy, and do not happen spontaneously. Enzymes can couple these reactions to ATP cleavage, which releases the energy needed to drive the reaction.Enzymes also let cells regulate metabolic pathways in response to changes in the environment or signals from other cells. Every metabolic pathway will have at least one rate-limiting enzyme. If that enzyme is missing, the entire pathway stops. Cells can control the activity of the entire pathway by: Increasing or decreasing the amount of that one enzyme. Adding or removing molecules that inhibit that enzyme. Separating the enzyme and substrates in the pathway. Separating enzymes that normally are together in a group. Very often, enzymes in a metabolic pathway are located next to each other, either in an organelle or in the membrane of an organelle, or held together by another protein. Removing one of the enzymes from the group slows down the reaction process. Adding or removing a phosphate, which changes the enzyme's activity.

MICROBIOLOGY OF WASTE WATER TREATMENTIntroduction Microorganisms play a major role in organic matter, N and P removal in wastewater treatment systems. Conversions in wastewater treatment are linked to the growth of the microorganisms. Microorganisms derive energy from substances present in wastewater. Growth of microorganisms is dependent on some factors such as growth requirements and environmental factors.The Cell The cell is a complex chemical system that can be distinguished from non-living entities. Cells are capable of growth and reproduction. They can self-produce another entity essentially identical to themselves. Cells are highly organized and selectively restrict what crosses their boundaries. Cells are at low entropy compared to their environment. Cells are composed of major elements (C,N,O,S..) that are chemically reduced. Cells take up necessary elements, electrons, and energy from their external environment to create and maintain themselves as reproducing, organized and reduced entities.Essential Components of Cells Cell membrane a barrier between the cell and its environment Cell wall a structural member that confers rigidity to the cell and protects the membrane. Cytoplasm comprises most of the inside of the cell water and substances (including macromolecules) that cell needs in order to function Chromosome contains the genetic code for the cells heredity and biochemical function Ribosome converts the genetic code into working catalysts for the cells reaction Enzymes proteins that acts as catalysts for the cells reactionsAnatomical Features of Bacterial Cell Capsule, slime layer protection Cell wall provides structural strength and protection against mechanical and osmotic injury Cytoplasmic membrane - regulates transport in and out of the cell and site of many enzymes Flagella convert chemical energy into kinetic energy for locomotion Nuclear zone carries and transfers genetic information Ribosomes sites of protein synthesis Chromatophores convert radiant energy into chemical energy Endospores preservation under adverse conditionsProkaryotic vs Eukaryotic Cell Eukaryotic cells contain membrane-bound organelles, such as the nucleus, while prokaryotic cells do not. Differences in cellular structure of prokaryotes and eukaryotes include the presence of mitochondria and chloroplasts, the cell wall, and the structure of chromosomal DNA. Prokaryotes are usually much smaller than eukaryotic cells. Prokaryotes also differ from eukaryotes in that they contain only a single loop of stable chromosomal DNA stored in an area named the nucleoid, while eukaryote DNA is found on tightly bound and organised chromosomes. Although some eukaryotes have satellite DNA structures called plasmids, these are generally regarded as a prokaryote feature and many important genes in prokaryotes are stored on plasmids. Prokaryotes have a larger surface area to volume ratio giving them a higher metabolic rate, a higher growth rate and consequently a shorter generation time compared to Eukaryotes.

Differentiation and Evolution Some cells may undergo change in form through the process of differentiation. Cells within the body act differently depending upon whether they form part of an eye, a muscle or strand of hair. As part of differentiation, cells can interact with one another through various chemical signals. They can evolve into organisms that are markedly different from the parent. -> slow process Important to the formation of new organisms or to the development of new capabilities that may aid in the survival of the organism.Essential Substances in the Cell and the Process of Growth Chemical analysis of cell-material indicates What elements are required to synthesize the cell What compounds have to be synthesized Essential components of living material: In large amounts: C, H, O, N, P, S In smaller amounts: K, Mg, Mn, Ca, Fe In trace amounts: Co, Cu, Zn, Mo, etc. Variation in composition of living material is due to Hereditary properties of species (what compounds the cell can synthesize) Variation in composition of growth medium and conditions (e.g. T, pH, light, etc.)Process of Growth The integration of dissimilation and assimilation leads to the process of growth. General equation for growth of chemotrophs: Nutrients cell material + waste product Split this reaction into two parts: DissimilationPart of nutrients + ADP + PO43- ATP + waste products AssimilationRest of nutrients + ATP cell material + ADP + PO43- + waste of productsCellular Metabolism Microorganisms derive energy from their substrate. Substrate cell functioning and maintenance + new cells (biomass) + waste (by-products) + heatCell Yield Efficiency of microbial growth (yield of cell material per mole of substrate consumed) Related to the amount of ATP produced per mole of substrate Depends on: Its thermodynamic properties Type of ATP generating pathwayBiological Growth Cellular metabolism involves a series of reduction-oxidation reactions. The available electron donor and electron acceptor determine what microorganisms will grow and the products of degradation.Bacteria classified according to type of electron donor Heterotrophic: organic material as electron donor and source of carbon for cell synthesis Chemoautotrophic (autotrophs): inorganic material as electron donor and CO2 as carbon source. Heterotrophs predominate in wastewater containing mainly organic matter.Microorganisms classified according to type of electron acceptor Obligately aerobic: oxygen as terminal electron acceptor Obligately anaerobic: functions only in the absence of molecular oxygen Facultatively anaerobic: use O2 as electron acceptor when present in sufficient quantity, but can shift to alternative acceptor when O2 is absentEcosystems and factors affecting the growth of microorganisms in different biological treatment processesMicroorganisms in Wastewater Treatment Systems Bacteria: primary and secondary degraders of organic substances, N and P removal, S cycle Archaeabacteria: can grow in extreme environment Algae photosynthetic production of oxygen, symbiotic relation with bacteria Protozoa prey on bacteria, fungi and algae Fungi degradation of organic matter for some industrial wastewaterPhotosynthetic Algae Photosynthetic, produces O2, some motile by means of flagella Bacteria (cyanobacteria) Photosynthetic, produces O2, some motile by means of gliding movement on solid surfaces, many can fix N2, some can use H2S as e- donorProtozoa Non-photosynthetic, motile, eukaryotic microbes, animal-like characteristics Dissimilation: heterotrophic; either osmotrophic (absorbing dissolved nutrients) or phagatrophic (ingestion) Grazing on bacteria, algae and fungi in wastewater treatment systems Serve as food to fishAerobic Wastewater Treatment Systems Aerobic water treatment is a method of treating sewage and wastewater by adding oxygen to the waste. This process encourages naturally occurring bacteria to break down the waste and produce a higher quality effluent that may then be treated with chlorine to remove the remaining bacteria. Organic matter + O2 CO2, H2O, biomass (cell materials)N, P, S compounds NO3-, PO43-, SO42- Systems in which aerobic degradation of organic matter occurs: Activated sludge process Activated sludge is a complex ecosystem composed mainly of bacteria and protozoa 95% of the BOD is reduced during this stage There should be a good balance between different species for An efficient removal of pollutant (organic matter) A good settleability of flocs in the final clarifier Low level of suspended solids in the effluent Waste stabilization ponds Trickling filtersFactors Affecting Growth of Aerobic Microorganism Substrate (dissolved oxygen, organic matter) Concentration Loading: 0.2-0.5 g BOD/g MLSS/ d Temperature Mesophilic: 35-40C Thermophilic: 45-50CAnaerobic Treatment Systems Anaerobic treatment is a process in which microorganisms convert organic matter into biogas in the absence of oxygen. Anaerobic treatment is an energy-efficient process that is typically utilized to treat high-strength industrial wastewaters that are warm and contain high concentrations of biodegradable organic matter (measured as BOD, COD, and/or TSS). An anaerobic system can be used for pretreatment prior to discharging to a municipal wastewater treatment plant or before polishing in an aerobic process. Anaerobic processes use substantially less energy, require less chemicals, and incur lower sludge handling costs compared to aerobic treatment options. In addition, the biogas produced in the anaerobic process is a source of renewable energy that can be used to displace fossil fuels such as oil or natural gas, or to generate electricity. Substrate concentration determines the species composition in a wastewater treatment system.Factors Affecting Anaerobic Digestion As in aerobic bacteria, the growth of anaerobic microorganisms depend on several factors: Substrate (organic matter) concentration Substrate competition Temperature pH Fermentative (acidogens): from about 4 to neutral Methanogens: optimum around neutral 6.5-7.5, inhibited at very low pH nutrients inhibitory compounds O2 NH3, H2S Aromatic compounds: can be degraded at anaerobic conditions but inhibitory at high levelsWastewater Treatment PondsWaste Stabilization Ponds Waste or Wastewater Stabilization Ponds (WSPs) are large, man-made water bodies in which blackwater, greywater or faecal sludge are treated by natural occurring processes and the influence of solar light, wind, microorganisms and algae. The ponds can be used individually, or linked in a series for improved treatment. There are three types of ponds, (1) anaerobic, (2) facultative and (3) aerobic (maturation), each with different treatment and design characteristics. WSPs are low-cost for O&M and BOD and pathogen-removal is high. However, large surface areas and expert design are required. The effluent still contains nutrients (e.g. N and P) and is therefore appropriate for the reuse in agriculture, but not for direct recharge in surface waters.Nitrification Nitrification is an aerobic process in which bacteria oxidize reduced forms of nitrogen. Nitrifiers: autotrophic bacteria, aerobicFactors affecting nitrification Substrate concentration (depends on ammonium N and O2 level according to Monod kinetics) Temperature (optimum 28-32C) pH: 7.5-8.6 inhibitory substances (HNO2, NH3) 3-5 mg O2/mg NH4+-N DO should be > 1mg/L

Denitrification Denitrification is an anaerobic process by which oxidized forms of nitrogen are reduced to gaseous forms, which can then escape into the atmosphere. The necessary conditions for the denitrification process to develop in an activated sludge process can be summarised as: Presence of a facultative bacterial mass, capable of using oxygen and nitrate or nitrite Presence of nitrate and absence of dissolved oxygen in the mixed liquor (i.e. an anoxic environment) Suitable environmental conditions for bacterial growth Presence of an electron donor (nitrate reductor): i.e. organic material