BIO 207C 1st Edition Lecture 3Microbial Nutrition and GrowthMicrobial NutritionI. Bacteria require substances from their habitat in order to liveII. Organisms require a source of elements such as carbon, hydrogen, oxygen, phosphorous, as well as othersIII. Essential nutrient-any substance that must be provided to an organismIV. Macronutrientsa. Needed in large amountsb. Play large role in cell structure and metabolismV. Micronutrientsa. Needed in trace elementsb. Play role in enzyme function and maintenanceVI. Inorganic Nutrienta. Not containing hydrogren and carbonVII. Organic nutrient a. Contains hydrogen and carbonComposition of Cell CytoplasmI. Water-70%II. Proteins III. Organic compounds-97% of dry weightIV. Elements CHONPS-96% of dry weightWhat Microbes EatI. Carbon Sourcesa. Heterotrophsb. AutotrophsII. Energy sourcesThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.a. Phototrophsb. ChemotrophsEnergy Sources of Heterotrophs I. Parasitesa. Gets its nutrition from a living hostb. Pathogens-cause damage to hosti. Most pathogens are chemotrophsHow Microbes EatI. Transport of nutrients occurs across the cell membranea. Brought about by movement of atoms and moleculesi. Diffusion1. All molecules are in continuous motion2. Movement increases as temperature increases3. As they move they collide with other particles, making their movements randomThe Movement of Water: OsmosisI. Osmosis is the diffusion of water through a selectively permeable membraneII. Membrane allows water to pass through but blocks other moleculesIII. If the solutions on either side of the membrane have different concentrations, water will diffuse from the side that has more water to the side that has lessIV. Living membranes block the transport of large moleculesV. Cells are surrounded by water so the amount entering of leaving is important to the cellVI. 3 different scenarios can exist:a. Isotonic conditionsi. The solute concentration is the same outside the cell as the insideii. This means that the concentration of water is the same in both placesb. Hypotonic conditionsi. Solute concentration of the external environment is lower than that of the cell’s internal environmentii. This means that there is more water outside the cell than inc. Hypertonic conditionsi. The environment has a higher solute concentration than that of the cellii. This means that there is more water inside the cell than outsideVII. Some substances cannot pass through the membraneVIII. Reason is because they are too large or they are polarIX. They are transported via protein channels in the cell membraneTransportI. Active Transporta. Transports substances against the concentration gradientb. Requires energyc. Uses proteins in the cell membraneEnvironmental Influences on MicrobesI. Environment plays a role on the metabolism and survival of microbesII. Microbes prefer to be in an “optimal” environment, one its best suited forIII. These include:a. Temperaturei. Psychrophiles1. Prefer colder temperatures2. Optimal temperature is below 150C3. Incubate in refrigerated conditions4. Rarely pathogenicii. Mesophiles1. Prefer temperatures between 20-400C2. Includes the human pathogensiii. Thermophiles1. Optimal temperature above 450C2. Found in hot springs, hot tubs, compost pilesb. Gasesi. The gases that influence microbial growth are O2 and CO2ii. O2 has the greatest impact1. Microbes fall into 3 categoriesa. Capnophilesi. Organisms that prefer high CO2 concentrationsii. Neisseriaiii. Brucellaiv. Streptococcus pneumoniaepHI. pH is the acidity or alkalinity of a solutiona. Expressed on a numerical scale from 0-14b. 7 is considered neutralc. Below 7 is acidicd. Above 7 is alkalineII. Acidophilesa. Prefer acidic environmentsb. Can survive very acidic environments such as the stomachIII. Neutrophilesa. Prefer neutral environmentsb. Majority of human pathogensIV. Alkalinophilesa. Prefer alkaline conditionsb. Can make their own environmentOsmotic PressureI. Can survive high osmotic pressuresII. Osmophilesa. High sugar contentIII. Halophilesa. High salt contentRadiationI. Phototrophs use radiation as an energy source (light)II. Many others are harmed by radiationIII. Ultraviolet and ionizing radiation can be used to control microbial growthSymbiosesI. Symbioses describes a situation where 2 organisms live togethera. Mutualismi. Both organisms benefitb. Commensalismi. One benefits, the other is unaffectedc. Parasitismi. One benefits, one is harmedBiofilmsI. Mixed communities of microbesII. Form a multilayer conglomerateIII. Interact with each other through quorum sensingIV. Microbes in biofilms behave differently than those that are nota. Different genes are activatedb. Respond differently to the environmentPopulation GrowthI. Bacteria reproduce by binary fissionII. Generation time refers to time required to complete a life cycleIII. For bacteria this means that the population doubles with each life cycleIV. Can go on indefinitely if environmental conditions are favorableV. Causes a rapid increase in numbersVI. Different microbes have different generation timesGrowth CurveI. There are 4 stages in the growth curvea. Lag phasei. When microbe is introduced into environmentii. Reproduction is not at maximum rateb. Exponential Phasei. Growth increases rapidlyii. Continues as long as environment is favorablec. Stationary Phasei. Division is slowing down, numbers are stableii. Resources are being depletedd. Death Phasei. Cells die at a rapid rateii. Due to no resources and presence of waste productsImportance of Growth CurveI. Has implications for microbial control, food microbiologyII. Microbes in exponential phase are more vulnerable to antimicrobial agents and heatIII. Growing cells are more vulnerable to agents that disrupt metabolism and reproductionIV. The microbes are more likely to be shed by the host in early and middle stagesAnalyzing Population SizeI. Can use several methods to calculate population size of microbesa. Turbidityi. Nutrient solution becomes cloudy as microbes growb. Genetic ProbingUses PCR to quantify bacteria or other