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Nutrition in prokaryotic cells (Bacteria).pptx
- 2. Essential Nutrients for Microbial Growth microbial cell composition shows that over 95% of cell dry weight is made up of a few major elements: carbon, oxygen, hydrogen, nitrogen, sulfur, phosphorus, potassium, calcium, magnesium, and iron Macro-nutrients Micro-nutrients (trace elements) C, O, H, N, S, and P are components of carbohydrates, lipids, proteins, and nucleic acids The remaining four macroelements exist in the cell as cations and play a variety of roles. For example, potassium (K) is required for activity by a number of enzymes, including some of those involved in protein synthesis. Calcium (Ca2+), among other functions, contributes to the heat resistance of bacterial endospores. Magnesium (Mg2+) serves as a cofactor for many enzymes, complexes with ATP, and stabilizes ribosomes and cell membranes. Iron (Fe2 and Fe3) is a part of cytochromes and a cofactor for enzymes and electron-carrying proteins The micronutrientsmanganese, zinc, cobalt, molybdenum, nickel, and copper are needed by most cells. However, cells require such small amounts that contaminants from water, glassware, and regular media components often are adequate for growth. In nature, micronutrients are ubiquitous and probably do not usually limit growth.
- 3. Growth Factors Growth factors are organic compounds that some microbes cannot synthesize but are necessary for growth. These include: - Amino acids: Needed for protein synthesis. - Purines and pyrimidines: Essential for nucleic acid synthesis (DNA and RNA). - Vitamins: Serve as coenzymes in various enzymatic reactions. For example, vitamin B1 (thiamine) is required in carbohydrate metabolism
- 4. Nutritional types of microorganisms
- 6. Nutrient uptake mechanisms Passive diffusion: Molecules move from an area of high concentration to low concentration without energy input (e.g., gases like O , CO ). Very small molecules such as H2O, O2, and CO2 often move across membranes by passive diffusion. Larger molecules, ions, and polar substances must enter the cell by other mechanisms.
- 7. Nutrient uptake mechanisms Facilitated diffusion: Uses specific transport proteins to move substances down their concentration gradient (e.g., glycerol transport in bacteria). The rate of diffusion across selectively permeable membranes is greatly increased by using carrier proteins, sometimes called permeases, which are embedded in the plasma membrane. Diffusion involving carrier proteins is called facilitated diffusion. The rate of facilitated diffusion increases with the concentration gradient much more rapidly and at lower concentrations of the diffusing molecule than that of passive diffusion
- 8. Nutrient uptake mechanisms Active transport: Requires energy (usually from ATP or proton motive force) to move substances against their concentration gradient. Active transport is the transport of solute molecules to higher concentrations, or against a concentration gradient, with the input of metabolic energy Types include: - Primary active transport: Direct use of ATP (e.g., ABC transporters). - Secondary active transport: Uses energy from ion gradients (symport or antiport systems).
- 9. Environmental Factors Affecting Microbial Nutrition
- 10. Environmental Factors Affecting Microbial Nutrition Microbial growth is influenced not just by the availability of nutrients but also by environmental factors such as: - Temperature: Most microbes grow optimally within a certain temperature range dictated by the ability of proteins within the cell to function.. Psychrophiles are extremophilic organisms that are capable of growth and reproduction in low temperatures, ranging from 20 属C to 20 属C. They are found in places that are permanently cold, such as the polar regions and the deep sea. Mesophile is an organism that grows best in moderate temperature, neither too hot nor too cold, with an optimum growth range from 20 to 45 属C. The optimum growth temperature for these organisms is 37 属C. Thermophile is an organisma type of extremophilethat thrives at relatively high temperatures, between 41 and 122 属C. Many thermophiles are archaea, though some of them are bacteria and fungi. Thermophilic eubacteria are suggested to have been among the earliest bacteria Hyperthermophile is an organism that thrives in extremely hot environmentsfrom 60 属C upwards. An optimal temperature for the existence of hyperthermophiles is often above 80 属C (176 属F).Hyperthermophiles are often within the domain Archaea.
- 11. Environmental Factors Affecting Microbial Nutrition -pH: Most bacteria prefer neutral pH (6.5-7.5), though acidophiles and alkaliphiles can thrive in extreme pH environments. Moderate changes in pH modify the ionization of amino-acid functional groups and disrupt hydrogen bonding, which, in turn, promotes changes in the folding of the molecule, promoting denaturation and destroying activity Alkaliphiles are microbes that thrive in alkaline (pH 9-11) environments. Acidophiles organisms are those that thrive under highly acidic conditions (usually at pH 2.0 or below) -Oxygen: Based on oxygen requirements, microorganisms are classified into aerobes, anaerobes, facultative anaerobes, microaerophiles, and aerotolerant anaerobes. Obligate anaerobes cannot grow in the presence of oxygen. They depend on fermentation and anaerobic respiration using a final electron acceptor other than oxygen. Facultative anaerobes show better growth in the presence of oxygen but will also grow without it. Aerotolerant anaerobes do not perform aerobic respiration, they can grow in the presence of oxygen. Microaerophiles need oxygen to grow, albeit at a lower concentration than 21% oxygen in air
- 12. Environmental Factors Affecting Microbial Nutrition -Osmotic Pressure: Microorganisms are surrounded by a selectively- permeable, plasma membrane that helps sense environmental cues. The plasma membrane's function can be affected by osmotic pressure. This pressure is a result of different solute concentrations separated on opposing sides of the membrane. Halophiles, for example, are adapted to high salt concentrations
- 13. Types of culture media
- 14. Defined (Synthetic) Media Defined media are composed of precise amounts of pure chemicals. Every component and its concentration are known, making this media type ideal for studying the specific nutrient requirements of a microorganism. Defined media are often used to culture photolithotrophic autotrophs such as cyanobacteria and photosynthetic protists. They can be grown on relatively simple media containing CO2 as a carbon source (often added as sodium carbonate or bicarbonate), nitrate or ammonia as a nitrogen source, sulfate, phosphate, and a variety of minerals. Defined (Synthetic) Media for E. coli
- 15. Complex (General) Media Complex media contain ingredients that are not chemically defined. These media often include extracts or digests of plant or animal products, such as: - Peptones: Partially digested proteins. - Yeast extract: Provides a rich supply of B vitamins, amino acids, and other growth factors. -Beef extract: Contains peptides, amino acids, and water-soluble vitamins. Such media are very useful, as a single complex medium may be sufficiently rich to completely meet the nutritional requirements of many different microorganisms. In addition, complex media often are needed because the nutritional requirements of a particular microorganism are unknown, and thus a defined medium cannot be constructed. Some common complex Media
- 16. Selective Media Selective media are designed to suppress the growth of some microorganisms while encouraging the growth of others. They contain selective agents, such as: - Antibiotics: Used to select for antibiotic-resistant bacteria. - Salts or dyes: Can inhibit the growth of specific microbes (e.g., crystal violet in MacConkey agar suppresses Gram-positive bacteria). Selective media are essential in clinical and environmental microbiology for isolating specific groups of organisms from mixed populations. For example: - MacConkey agar: Selects for Gram-negative bacteria by using bile salts and crystal violet to inhibit Gram-positive bacteria. - Mannitol salt agar (MSA): Selects for Staphylococcus species, as it contains high concentrations of sodium chloride that inhibit other bacteria.
- 17. Differential Media Differential media are used to distinguish between different microbial species based on their biological characteristics. These media contain indicators (such as pH indicators or dyes) that change color in response to microbial metabolism. The key purpose is to visually differentiate between species or groups based on specific metabolic properties. Examples of differential media: - Blood agar: Used to differentiate bacterial species based on their hemolytic activity. Hemolysis patterns include: - Beta-hemolysis: Complete lysis of red blood cells, producing a clear zone around colonies. - Alpha-hemolysis: Partial lysis, resulting in a greenish discoloration. - Gamma-hemolysis: No hemolysis. - MacConkey agar: Differentiates between lactose-fermenting (pink colonies) and non-lactose fermenting (colorless colonies) Gram-negative bacteria. The pH indicator neutral red turns pink when lactose is fermented, indicating acid production.
- 18. Mechanism of action of some selective and differential media
- 19. Enriched Media Enriched media contain additional nutrients to support the growth of fastidious microorganisms, which require specific nutritional supplements to grow. These microbes may have complex or unique nutritional requirements that standard media cannot meet. Examples of enriched media: - Chocolate agar: A variant of blood agar where the red blood cells have been lysed by gentle heating, releasing growth factors like NAD (nicotinamide adenine dinucleotide) and hemin. This medium is used to grow organisms like Neisseria and Haemophilus species, which require these factors Classification of Bacterial Culture Media
- 20. Isolation of pure cultures The Spread Plate The Streak Plate The Pour Plate In natural habitats microorganisms usually grow in complex, mixed populations with many species. This presents a problem for microbiologists because a single type of microorganism cannot be studied adequately in a mixed culture. One needs a pure culture, a population of cells arising from a single cell, to characterize an individual species. If a mixture of cells is spread out on an agar surface at a relatively low density, every cell grows into a completely separate colony, a macroscopically visible growth or cluster of microorganisms on a solid medium. Because each colony arises from a single cell, each colony represents a pure culture
- 21. The Spread Plate Technique
- 22. The Streak Plate Technique
- 23. The Pour Plate Technique
- 24. Bacterial colony morphology on agar plate