Nutrition And Bacterial Metabolism PDF

Chapter III. NUTRITION AND BACTERIAL METABOLISM 2nd-year Natural Sciences Natural Sciences Department Dr. Fatima-Zohra Kenza LABBANI [email protected] PART 1. BACTERIAL NUTRITION...

Chapter III. NUTRITION AND BACTERIAL METABOLISM 2nd-year Natural Sciences Natural Sciences Department Dr. Fatima-Zohra Kenza LABBANI [email protected] PART 1. BACTERIAL NUTRITION I. NUTRITIONAL REQUIREMENTS 1) Definition of Nutrients NUTRITIONAL REQUIRMENTS Definition of Nutrients Nutrients are essential chemical substances required by bacteria for energy production, metabolic processes, growth, and reproduction. NUTRITIONAL REQUIRMENTS Definition of Nutrients These substances are essential for cellular processes and must fulfil the following roles: ✓ Act as constituents of cellular materials. ✓ Support the activity of enzymes and transport systems. ✓ Provide the necessary components for the production of biologically utilisable energy. NUTRITIONAL REQUIRMENTS Chemical Composition of a Bacterial Cell The cellular content of a typical bacterial cell can be divided into two main components: 1) Water: constitutes approximately 80–90% of the cell's total weight. 2) Dry Matter: represents about 10% of the cell's weight, and it is composed of: ✓ Proteins: 52% ✓ Polysaccharides: 17% ✓ Lipids: 9% ✓ RNA: 16% ✓ DNA: 3% 2) Types of Nutrients Types of Nutrients Nutrients can be classified into several categories based on their function and the role they play in bacterial life processes: a) Macronutrients b) Micronutrients c) Growth Factors Types of Nutrients a) Macronutrients: These are nutrients required in large quantities by bacteria and are essential for their growth and metabolism. They include Carbon (C), Nitrogen (N), Oxygen (O), Hydrogen (H), phosphorus (P), and Sulfur (S). Types of Nutrients: Macronutrients 1- Carbon (C) The most abundant constituent element in bacteria (50% of dry cell weight); Essential for the synthesis of cellular materials (Carbohydrates, lipids, proteins and nucleic acids); It serves as a major energy source for bacterial growth and metabolism Types of Nutrients: Macronutrients 1- Carbon (C) Bacteria obtain carbon from various sources depending on their metabolic capabilities: ✓ Autotrophs: use inorganic carbon sources, such as carbon dioxide (CO2) as their primary carbon source through processes like photosynthesis or chemosynthesis. ✓ Heterotrophs: can only utilize carbon from organic sources, such as sugars and alcohols, amino acids, and fatty acids. They are widely distributed and most abundant in nature. Types of Nutrients: Macronutrients 2- Nitrogen (N) Nitrogen makes up 14% of dry cell weight; It is essential for the synthesis of amino acids (building blocks of proteins), nucleotides (for DNA and RNA), and other nitrogen-containing compounds Found in the inorganic forms (Ammonium, Nitrate) and organic forms (amino acids, peptides) Nitrogen-fixing bacteria use nitrogen gas (N2), obtained from the atmosphere Types of Nutrients: Macronutrients 3- Phosphorus (P) Phosphorus is a key component of nucleic acids (DNA and RNA), ATP (the energy currency of cells), and phospholipids in cell membranes. Bacteria typically absorb phosphorus as phosphate ions (PO43-) from their surroundings. Types of Nutrients: Macronutrients 4- Sulfur (S) Sulfur is necessary for synthesising certain amino acids (e.g., cysteine and methionine), vitamins (e.g., biotin and thiamine), and growth factors (e.g. Coenzyme A). Bacteria can utilise sulfur in the inorganic form of sulfate (SO42-) or organic sulfur compounds (e.g., amino acids, vitamins). Types of Nutrients: Macronutrients 5- Oxygen (O) and Hydrogen (H) Oxygen is required for aerobic respiration in many bacteria, serving as the final electron acceptor in the electron transport chain. However, some bacteria are anaerobic and do not require oxygen for growth Hydrogen is involved in maintaining cellular pH balance and is a component of water and organic molecules Types of Nutrients b) Micronutrients: These are required in smaller amounts but are critical for bacterial growth. They include trace elements such as Calcium (Ca2+), Magnesium (Mg2+), Potassium (K), Iron (Fe), Magnesium (Mg), Calcium (Ca), and Zinc (Zn). Types of Nutrients: Macronutrients 1- Calcium (Ca2+) Calcium ions play an important role in cell wall stability cofactor for certain enzymes, such as proteases implicated in gene expression, chemotaxis, sporulation and biofilm formation. Types of Nutrients: Macronutrients 2- Magnesium (Mg2+) It is essential for stabilising nucleic acids, ribosomes and membranes A cofactor for many enzymes, including ATPases, and DNA replication (required for the activity of DNA polymerases and other enzymes involved in DNA replication.). A fundamental component of bacterial chlorophyll pigments. 3- Potassium (K) It acts as a cofactor for many enzymes pH regulation (contributes to maintaining intracellular pH) Types of Nutrients: Macronutrients 4- Iron (Fe) It is a crucial cofactor for many enzymes. It participates in fundamental metabolic pathways including electron transport, DNA synthesis, and cellular respiration. 5- Zinc (Zn) Zinc plays a vital role as a cofactor for numerous enzymes, such as those essential for DNA replication (DNA polymerase), and protein synthesis (essential for the function of ribosomal enzymes). Types of Nutrients: Macronutrients 6- Manganese (Mn) Manganese is a cofactor for several enzymes, including those involved in oxidative stress defence. It is also essential for the production of certain amino acids and carbohydrates. Types of Nutrients: Macronutrients 7- Other micronutrients There are a few other trace elements known to be essential for the physiology of most bacteria, including: Molybdenum (Mo): a key component of molybdoenzymes (cofactor of a series of oxidoreductases), which are involved in nitrogen fixation (used in enzymes like nitrate reductase in certain bacteria) and the reduction of nitrate to nitrite. Copper (Cu): it plays a role in respiration, iron acquisition, and defence against oxidative stress. Types of Nutrients: Macronutrients Cobalt (Co): required by some bacteria for the biosynthesis of vitamin B12 (cobalamin). Selenium (Se): which primarily functions as a component of selenoproteins (modified amino acids) that catalyse redox reactions (oxidoreductase enzymes). It also functions as an antioxidant protecting bacterial cells against oxidative stress. Types of Nutrients: Macronutrients Roles of Micronutrients in Bacterial Cells The various micronutrients are integral to bacterial survival and function in several ways: Enzyme Activation and Function: Many enzymes in bacteria require micronutrients as cofactors for catalysis. Without these metals or vitamins, bacteria would not be able to perform critical biochemical reactions. Electron Transfer and Respiration: Micronutrients like iron, copper, and manganese are essential components of electron transport chains and other redox reactions that generate ATP, the energy currency of the cell. Types of Nutrients: Macronutrients DNA and RNA Synthesis: Several micronutrients, including magnesium, and zinc, (and vitamin B), are essential for the synthesis and repair of nucleic acids, ensuring bacterial growth and division. Metabolism and Energy Production: trace metals like magnesium and manganese, (also Vitamins B) play a key role in bacterial metabolism, including the production of ATP. Oxidative Stress Protection: Certain micronutrients like manganese, selenium, and zinc help bacteria combat oxidative stress by supporting the activity of antioxidant enzymes like superoxide dismutase. Types of Nutrients c) Growth Factors: Organic compounds essential for growth; Elements that certain bacteria are unable to synthesize from the nutrients available in the environment Needed in small quantities in the medium; Growth factors can be grouped into vitamins, amino acids, proteins, and nucleic acid-like compounds (purines & pyrimidines bases) The bacteria is termed « Fastidious bacteria » Some bacteria may require just one or two of these compounds, while others need a broader array depending on their metabolic capabilities. Types of Nutrients c) Growth Factors: Examples of Vitamins: Vitamin B complex, including B1 (Thiamine), B2 (Riboflavin), B3 (Niacin), B5 (Pantothenic Acid), B6 (Pyridoxine), B9 (Folic acid), B12 (Cobalamin), and Vitamin K (Phylloquinone). Examples of amino acids: Arginine, tryptophan, cycteine, leucine, isoleucine, valine II. ENERGY REQUIREMENTS ENERGY REQUIREMENTS Types of energy sources for bacteria Based on their source of energy bacteria can be classified as: a) Phototrophic bacteria b) Chemotrophic bacteria ENERGY REQUIREMENTS a) Phototrophic bacteria Some bacteria, known as Phototrophs, use light as an energy source Process: Through photosynthesis, They convert light energy into chemical energy, which they store as organic compounds. They have photosynthetic pigments, such as bacteriochlorophylls, carotenoids, and phycobiliproteins, that capture light energy. ENERGY REQUIREMENTS a) Phototrophic bacteria Different types of phototrophic bacteria, such as Cyanobacteria Green Sulfur Bacteria Purple Sulfur Bacteria ENERGY REQUIREMENTS b) Chemotrophic bacteria Chemotrophs use chemical compounds (organic or inorganic chemicals) as energy sources. They can be classified into two categories based on the types of chemicals they use to produce energy: ✓ Chemoorganotrophs: They obtain their energy from organic compounds (such as sugars, amino acids, and fatty acids). Example: E. coli uses glucose to produce energy through aerobic or anaerobic respiration. ENERGY REQUIREMENTS b) Chemotrophic bacteria ✓ Lithotrophs (Chemolithotrophs): they obtain their energy from inorganic compounds (e.g., hydrogen gas, sulfur, or iron). Example: Sulfur bacteria (e.g., Thiobacillus) use hydrogen sulfide (H2S) as an electron donor to produce energy. III. NUTRITIONAL TYPES NUTRITIONAL TYPES Based on their nutrition types, bacteria can be classified into four groups: a) Photoautotrophs b) Photoheterotrophs c) Chemoautotrophs d) Chemoheterotrophs NUTRITIONAL TYPES a) Photoautotrophs They are referred to as photosynthetic bacteria They use inorganic carbon (CO2) as their main source of carbon; convert CO2 into organic materials using sunlight as an energy source (Photosynthesis). e.g., Cyanobacteria, Green Sulfur Bacteria, Purple Sulfur Bacteria NUTRITIONAL TYPES b) Photoheterotrophs Photoheterotrophs are bacteria that utilize light as a source of energy but use organic substances as a carbon source. Thus, they are photosynthetic bacteria because they utilize the energy of sunlight to generate ATP. Therefore, they are photoheterotrophic and do not depend on carbon dioxide as their sole source of carbon. The best-known photoheterotrophic bacteria are purple non-sulfur bacteria NUTRITIONAL TYPES c) Chemoautotrophs They oxidize inorganic compounds, such as hydrogen sulfide (H2S), sulfur, ammonia (NH3), nitrites (NO2-), hydrogen gas (H2), or iron (Fe2+) to obtain energy (in the absence of light); They use CO2 as their main carbon source. The energy produced is used to fix CO2, and the organic compounds derived from this are the main source of carbon for the cells. NUTRITIONAL TYPES c) Chemoautotrophs Nitrosomonas (Nitrifying bacteria): oxidizes NH3 to NO2-, and Nitrobacter (Nitrifying bacteria): oxidizes NO2- to NO3- Thiobacillus (Sulfur-oxidizing bacteria): oxidize sulfur compounds like sulfide H₂S, thiosulfate, or elemental sulfur to sulfate Acidithiobacillus ferrooxidans (Iron-oxidizing bacteria): obtains energy by oxidizing ferrous iron (Fe²⁺) to ferric iron (Fe³⁺) and sulfur compounds. NUTRITIONAL TYPES d) Chemoheterotrophs They obtain their energy by oxidizing organic compounds, such as carbohydrates, lipids, and amino acids. These organic substrates constitute their primary source of carbon, Most bacteria are Chemoheterotrophs There are 3 main categories: Saprobic bacteria, Parasitic bacteria, Symbiotic bacteria Chemoheterotrophic examples include Cellulomonas, Azotobacter, Bacillus, and Escherichia coli.  THE END Dr. Fatima-Zohra Kenza LABBANI [email protected] Natural Sciences Department