Types proteins carbohydrates lipids nucleic acids Many are macromolecules Synthesized from smaller inorganic or small organic molecules Growth factors Organic molecules that cannot be synthesized and must be taken into the cell from the environment Problem some molecules in the environment are macromolecules too large to get through cell wall and membrane Microbial Nutrition and Growth Microbial Nutrition Elements Major Bioelements bulk elements C H N O P S Minor Bioelements Ca Na K Cl Fe Micronutrients trace minerals Mn Zn Cu others Microbial Nutrition Molecules Organic Biomolecules Microbial Nutrition How do microbes acquire nutrients Transport across cell membrane Small inorganic and organic molecules Salts ions simple sugars amino acids Carbon dioxide Most bacteria and fungi many protozoa Acquiring nutrients from large molecules How do microbes acquire nutrients cont Phagocytosis and Ingestion Some protozoa Metabolic Categories Nutritional types Based on how microorganisms obtain Carbon Energy Metabolic Categories Types of Chemoheterotrophs Predators Some protozoa few bacteria and fungi Microbiologists measure the growth of a population Types of Growth Open system Most fungi many bacteria some protozoa Saprobes Commensals Bacteria protozoa fungi Parasites pathogens Bacteria fungi protozoa viruses Bacterial Growth Closed system Method of reproduction Binary fission Growth in open system Doubling or exponential growth Doubling Time Generation Time time required for the population to double in size Growth in closed system Standard Normal growth curve Methods of Enumeration Standard viable Plate Count Turbidity Spectrophotometric Direct Count total cell count Microscopy Flow cytometry Standard Plate Count Direct Count Microscopy Factors Influencing Growth Nutrient limitation waste accumulation physical space Other physical and chemical forces Temperature Oxygen levels Hydrogen ions pH Osmotic forces salt concentration Growth Response Temperature Effects on Growth Enzymes Effects rate of catalysis temp rate 2x per 10 C High temps will eventually degrade proteins Membrane fluidity temp fluidity High temps will melt disintegrate membrane Temperature Isolating Thermophiles Oxygen Effect on Growth Oxygen needed for energy metabolism cellular respiration by some microbes Must be able to deal with toxic O2 derivatives Super oxides peroxides others Have enzymes to remove toxic derivatives Superoxide dismutase Catalase and peroxidase Oxygen Effect on Growth Other microbes use alternate energy pathways that do no require oxygen fermentation and anaerobic respiration Oxygen not required or may even be toxic to microbe lack of dismutase and catalase enzymes Oxygen Other Environmental Factors Influencing Growth Hydrogen ion concentration pH Alkaphiles Acidophiles Salts halophiles Pressure barophiles Radiation radiophiles Growth in Aquatic Environments Planktonic free floating Biofilms A microbial community of cells and extracellular matrix attached to a surface Implies close associations and interactions among microbes in the biofilm Biofilms cont Medical implications Dental disease Bacterial endocarditis Osteomyelitis Medical implants and indwelling devices End Go to Physical and Chemical Control of Microorganisms
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