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 ••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 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 ––Problem – some molecules in the environment are macromolecules – too large to get through cell wall and membrane! 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••Saprobes ––Most fungi, many bacteria, some protozoa ••Commensals ––Bacteria, protozoa, fungi ••Parasites (pathogens) ––Bacteria, fungi, protozoa, viruses Bacterial Growth ••Microbiologists measure the growth of a population ••Types of Growth: ––Open system ––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 10ºC) ––High temps will eventually degrade proteins ••Membrane fluidity –– temp fluidity ––High temps will melt/disintegrate membraneTemperature 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
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