Aquatic Microbial Biochemistry PDF

AQUATIC BIOCHEMICAL PROCESSES Microorganisms such as bacteria, fungi, protozoa, and algae act as Microorganisms living catalysts for a wide range of chemical processes in water and soil. Major chemical reactions in water, especi...

AQUATIC BIOCHEMICAL PROCESSES Microorganisms such as bacteria, fungi, protozoa, and algae act as Microorganisms living catalysts for a wide range of chemical processes in water and soil. Major chemical reactions in water, especially those involving Chemical organic matter and oxidation-reduction processes, occur through bacterial intermediaries. Reactions in Water Algae are the main producers of biological organic matter in water. Microorganisms are responsible for the formation of sediment and mineral deposits, as well as playing a dominant role in secondary Role of waste treatment. Microorganisms They also have a historical association with waterborne diseases, emphasizing the importance of water purification. MICROORGANISMS AT INTERFACES Aquatic Microorganisms Characteristics of Concerns and and Interfaces Bacteria at the Air-Water Implications Interface Aquatic microorganisms tend Bacteria at the air-water Bacteria at the air-water to grow at interfaces. interface have a hydrophobic interface can be incorporated cell character and are different into aerosol water droplets Many such microorganisms from those in the body of and carried by wind when grow on solids that are water. surface bubbles burst. suspended in water or are present in sediments. They are in contact with air, This raises concerns about which is essential for their sewage treatment plants as a Large populations of aquatic metabolic processes, and also possible vector for spreading bacteria typically reside on accumulate food in the form of disease-causing the surface of water at the lipids, polysaccharides, and microorganisms. air-water interface. proteins. Effects of microorganisms on the chemistry of water in nature. ALGAE Characteristics of Algae Classes of Unicellular Nutrient Requirements Algae and Role Algae are generally The four main classes of Algae require carbon, microscopic organisms that unicellular algae are: nitrogen, phosphorus, sulfur, subsist on inorganic nutrients Chrysophyta (yellow-green and trace elements for and produce organic matter or golden-brown color), growth. through photosynthesis. Chlorophyta (green algae), They play a vital role in Pyrrophyta (dinoflagellates), They can grow as single cells, aquatic systems by Euglenophyta. filaments, sheets, and colonies. producing biomass. Each class has unique Some algae, like marine kelps, In the absence of light, characteristics and can be are large multicellular algae can metabolize found in different aquatic organisms. organic matter or utilize environments. stored starches or oils for energy. FUNGI Morphology Fungi are non-photosynthetic, often filamentous organisms with diverse morphology. Aerobic Fungi are aerobic and can thrive in acidic media and high Nature concentrations of heavy metal ions. Environmental Fungi play a crucial role in the environment, especially in the Impact breakdown of cellulose in plant materials. PROTOZOA Classification Protozoa are classified based on morphology, means of locomotion, presence or absence of chloroplasts, presence or absence of shells, ability to form cysts, and ability to form spores. Morphology and Protozoa occur in a wide variety of shapes and exhibit fascinating movement under a microscope. Locomotion They can have flagella, cilia, or pseudopodia for locomotion. Significance in the Protozoa play a role in environmental processes such as disease Environment transmission, the formation of limestone deposits, sewage treatment, and influencing bacterial populations. BACTERIA Bacteria can be shaped as rods (bacillus), spheres (coccus), or spirals Shape and Size (vibrios, spirilla, spirochetes). They range in size from 0.3-50 μm, with most falling in the range of 0.5-3.0 μm. Most bacteria have a semirigid cell wall, are motile with flagella, are Characteristics unicellular (although clusters are common), and multiply by binary fission. They also produce spores. Bacteria have a high surface-to-volume ratio, allowing for rapid chemical Metabolic Activity reactions. They excrete exoenzymes to break down solid food material for digestion. AUTOTROPHIC AND HETEROTROPHIC BACTERIA Heterotrophic Bacteria Autotrophic Bacteria Cyanobacteria Heterotrophic bacteria depend Autotrophic bacteria thrive in an Some bacteria, like on organic compounds for inorganic medium and use cyanobacteria, are capable of energy and carbon to build carbon dioxide or other photosynthesis to supply their their biomass. carbonate species as a carbon energy and carbon. They are primarily responsible source. Cyanobacteria blooms in water for the breakdown of pollutant They obtain energy from reservoirs can cause water organic matter in water and biologically mediated chemical quality problems, especially in organic wastes in biological reactions and are involved in agricultural areas that receive waste treatment processes. many geochemical fertilizer-contaminated runoff. transformations. OXIC AND ANOXIC BACTERIA Oxic Bacteria Oxic bacteria require oxygen as an electron receptor. (Aerobic) Anoxic bacteria function only in the complete absence of molecular Anoxic oxygen. Bacteria They may be quite toxic to molecular oxygen. (Anaerobic) Facultative bacteria utilize free oxygen when available, and use other Facultative substances as electron receptors when molecular oxygen is not Bacteria available. Common substitutes in water are nitrate ion and sulfate ion. KINETICS OF BACTERIAL GROWTH Population The population curve for a bacterial culture Curve shows the population size of bacteria and unicellular algae as a function of time in a growth culture. Phases of The population curve consists of four regions: Bacterial lag phase, log phase, stationary phase, and Growth death phase. The lag phase is the first region characterized Lag Phase by little bacterial reproduction. It occurs because the bacteria must become acclimated to the new medium. BACTERIAL METABOLISM Bacterial Metabolism Divisions of Bacterial Metabolism Bacteria obtain energy and raw materials Catabolism: Energy-yielding degradative for metabolic processes and reproduction metabolism that breaks down through chemical reactions. macromolecules into small monomeric constituents. Bacterial species have evolved to utilize a large number of chemical reactions. Anabolism: Synthetic metabolism that assembles small molecules into large ones. Bacteria play a crucial role in biogeochemical processes in water and soil. They are involved in elemental cycles of nitrogen, carbon, sulfur, and contribute to the formation of mineral deposits. FACTORS AFFECTING BACTERIAL METABOLISM Substrate Enzyme activity increases in a linear fashion up to a saturation Concentration value of the enzyme activity beyond which it levels off. Enzyme activity increases with temperature up to a maximum growth rate at an optimum temperature. Temperature Above this temperature, an abrupt drop-off occurs due to enzyme denaturation. Enzymes typically have a pH optimum around neutrality, but pH become denatured at pH extremes. MICROBIAL OXIDATION AND REDUCTION Definition Microbial oxidation and reduction are metabolic processes in which bacteria obtain energy through oxidation–reduction reactions. Oxidation During oxidation, bacteria transfer electrons from a donor molecule to an acceptor molecule, releasing energy in the process. Reduction In reduction, bacteria gain electrons from an electron donor molecule, which is then used in various metabolic processes. MICROBIAL TRANSFORMATIONS OF CARBON Carbon Composition Carbon is an essential element in microorganisms and makes up a in Microorganisms significant portion of their dry mass. Oxidation State of Most energy-yielding or energy-consuming metabolic processes in Carbon microorganisms involve changes in the oxidation state of carbon. Microbial transformations of carbon have important environmental Environmental implications, such as the release of energy and consumption of Implications oxygen during bacterial decomposition. BIODEGRADATION OF ORGANIC MATTER The biodegradation Effects of Organic Pollutants Biodegradation Process The biodegradation of organic Some organic pollutants, such The biodegradation of organic matter in the aquatic and as fungicides, can be biocidal matter by microorganisms terrestrial environments is a and harm beneficial saprophytic occurs through stepwise, crucial environmental process. fungi and bacteria. microbially catalyzed reactions. MICROBIAL TRANSFORMATIONS OF NITROGEN The Nitrogen Cycle The nitrogen cycle describes the dynamic processes through which nitrogen is interchanged among the atmosphere, organic matter, and inorganic compounds. It is one of nature’s most vital dynamic processes. The cycle includes important biochemical transformations such as nitrogen fixation, nitrification, nitrate reduction, and denitrification. Microbes play a crucial role in each step of the nitrogen cycle, facilitating the conversion of nitrogen from one form to another. NITROGEN FIXATION Microbial Process of Aquatic Microorganisms Rhizobium and Symbiotic Nitrogen Fixation and Nitrogen Fixation Relationship Nitrogen fixation is a complex Certain aquatic Rhizobium bacteria, found in biochemical process that microorganisms, including root nodules of leguminous involves the binding of photosynthetic bacteria and plants, form a symbiotic atmospheric nitrogen in a cyanobacteria, can fix relationship with these plants. chemically combined form. atmospheric nitrogen. They convert atmospheric It is essential for plant However, most fixed nitrogen to a form that can be growth in the absence of nitrogen in water bodies absorbed by the plant. synthetic fertilizers. comes from external sources, such as fertilizer runoff. NITRIFICATION Nitrification is a crucial process in nature because nitrogen, an essential Importance of nutrient for plants, is absorbed in the form of nitrate (NO3-). Nitrification Nitrate is the preferred nitrogen source for most plants, and it plays a vital role in their growth and development. In the aquatic environment, nitrogen exists as nitrate (NO3-) in Nitrogen thermodynamic equilibrium with air. Oxidation States However, in most biological compounds, nitrogen is present in other forms, such as amino acids where it is found in -NH2 groups. Nitrification is carried out by two groups of bacteria: Nitrosomonas and Nitrobacter. Nitrification Process Nitrosomonas bacteria convert ammonium nitrogen to nitrite, while Nitrobacter bacteria convert nitrite to nitrate. Both of these bacteria are obligate aerobes, requiring molecular oxygen for their metabolic processes. NITRATE REDUCTION Nitrate Reduction by Microbes Nitrate reduction refers to microbial processes by which nitrogen in chemical compounds is reduced to lower oxidation states. In the absence of free oxygen, some bacteria can use nitrate as an alternate electron receptor. Sodium nitrate has been used as an emergency source of oxygen in oxygen-deficient sewage lagoons. Nitrate functioning as an electron receptor may produce nitrite , which can build up to toxic levels and inhibit further microbial growth.  DENITRIFICATION Denitrification: Nitrogen Gas Energy Yield and Electron Importance of Production Consumption Denitrification Denitrification is a nitrate The energy yield per mole of Denitrification allows fixed reduction process that nitrate reduced to N2 is lower nitrogen to return to the results in nitrogen gas (N2). than that for the reduction of atmosphere. It involves the conversion of nitrate to nitrite (NO2-). It's used in water treatment nitrate (NO3-) to N2. However, it consumes five for nutrient nitrogen removal. electrons. MICROBIAL TRANSFORMATIONS OF PHOSPHORUS AND SULFUR Phosphorus Compounds Sulfur Compounds Microbial Transformations Microbial action on phosphorus Sulfur compounds are found in Bacteria can oxidize sulfide to compounds provides a source water. sulfate or reduce sulfate to of algal nutrient sulfide. orthophosphate from the Their degradation can hydrolysis of polyphosphates. sometimes cause water quality They can also degrade organic issues, such as the production sulfur compounds, producing It also deactivates toxic of hydrogen sulfide (H2S). volatile compounds and organophosphates. hydrogen sulfide H2S.