Microbial Nutrition and GrowthMicrobial NutritionElements- Major Bioelements (bulk elements) ~98% C,H,N,O,P,S- Minor BioelementsCa, Na, K, Cl, Fe- Micronutrients (trace elements)Mn, Zn, Cu, others (metals)Microbial NutritionMoleculesOrganic Biomolecules- Four Types: proteins, carbohydrates, lipids, nucleic acids- Many are macromolecules- Synthesized from smaller inorganic or small organic molecules- Growth factors “vitamins”- Organic molecules that cannot be synthesized and must be taken into the cell from the environment, not all have growth factorsMicrobial NutritionHow do microbes acquire nutrients?• Transport across cell membrane- Small inorganic and organic molecules: salts (ions), simple sugars, amino acids, carbon dioxide, oxygen, water- 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• Microbes secrete digestive enzymes out of the cell ex. bacteria, fungi, protozoa, How do microbes acquire nutrients? (cont.) • Phagocytosis and Ingestion- Some protozoaMetabolic Categories (Nutritional types)Based on how microorganisms obtain:• Carbon (important molecule)• EnergyMetabolic Categories *Picture* - Autotrophs (carbon comes from inorganic molecule - CO2)- Photoautotroph ex. plants, algea- Photosynthetic bacteria ex. cianobacteria (most common in freshwatera)- Chemoautotroph ex. inorganic compounds- Heterotrophs (carbon comes from organic compounds)- Chemoheterotrophs- PhotoheterotrophsTypes of Chemoheterotrophs• Predators (feeds on live organisms)- Some protozoa, few bacteria and fungi • Saprobes/Saprophylic “Decomposers” (living off of dead/decaying material)- Most fungi, many bacteria, some protozoa• Commensals (microbes that live on/in another organism, feeds off organic materials)- Bacteria, protozoa, fungi• Parasites “Pathogens” (causes damage to host organism)- Bacteria, fungi, protozoa, virusesBacterial Growth• Microbiologists measure the growth of a population • Types of Growth:- Open System (ideal conditions and system for growth and reproduction; unlimited nutrients and physical space, NO build up of wastes)- Closed System (limited nutrients and physical space, build up of toxic waste products)• Method of reproduction- Binary fission (original cell divides into two new cells)• Growth in Open System “Doubling/Exponential Growth”• Doubling Time “Generation Time”: time required for the population to double in size - E. coli and most bacteria are rapid reproducers - ...tuberculosis bacteria is one of few that takes a long time to reproduce• Growth in Closed System “Standard/Normal growth curve”- Latent Phase- Exponential Growth Phase: most common- Secondary Phase- Death Phase: more cells dying than being producedMethods of Enumeration “Counting”• Standard “Viable” Plate Count (traditional) - uses petrie plate to grow bacteria, count colonies• Turbidity “Cloudiness”: more bacteria = high turbidity - Spectrophotometer• Direct Count: counts total number of cells- Microscopy- Flow Cytometry: mechanical way to count cells in a sampleStandard Plate Count *Picture*Direct Count Microscopy *Picture*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 *Picture*Temperature Effects on Growth• Enzymes- Effects rate of catalysis increasing temperature, increases rate (2x per 10ºC)- High temperatures will eventually degrade proteins (stop working)• Membrane fluidity- Decreasing temperature, decreases fluidity- High temperatures will melt/disintegrate membraneTemperature *Picture*- Psychorophiles: “cold-loving”~0C- Mesophiles: “middle-loving” found on the human body, ex. pathogens ~37C- Thermophiles: “heat-loving” ~65-70C- Hyperthermophiles ~95-100CIsolating Thermophiles *Picture*Oxygen Effect on Growth• Oxygen needed for energy metabolism (cellular respiration) by some microbes- Must be able to deal with toxic O2 derivatives ex super oxides, peroxides, others - Have enzymes to remove toxic derivatives- Superoxide dismutase- Catalase and peroxidaseOxygen 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 SOD and catalase enzymesOxygen *Picture*- Obligate Aerobe - microbes require most oxygen. only grows at top- SOD and catalase- Facultative Anaerobe - microbes can grow with less oxygen- SOD and catalase- Aerotolerant Anaerobe - microbes can grow with less oxygen- SOD, lacks catalase- Strict Anaerobe - grows at bottom- lacks SOD and catalase - Atmospheric Levels: higher level- Anaerobe “grows at lower levels”Other Environmental Factors Influencing Growth• Hydrogen ion concentration (pH)Alkaphiles - best growth at HIGH pHsAcidophiles - best growth in acidic conditions, LOW pHs• Salts - best growth around 15%halophiles• Pressurebarophiles “HIGH pressure loving”• Radiation - damages nucleic acids of cells, ex ultraviolet lights, radioactive minerals/rocks radiophileGrowth in Aquatic Environments• Planktonic “free floating”• Biofilms “attaches to surface” - microbial community of cells and extracellular matrix attached to a surface - Implies close associations and interactions among microbes in the biofilmBiofilms • Medical implications- Dental disease ex. gum disease- Bacterial endocarditis - inner lining and valves of heart- Osteomyelitis - bone infection- Medical implants and indwelling devices - ex. hip and knee replacement surgeryEndGo to: Physical and Chemical Control of