MICRB 106 1st Edition Exam 2 Study Guide Chapter 6 Cultivating Microorganism Know the nutritional requirements for microorganisms Understand the factors that affect microbial growth Know the processes of growing microorganisms in a lab measuring microbial population growth and how to eliminate microbes and prevent their growth What Microorganisms Need to Grow All microorganisms need plentiful amounts of carbon nitrogen phosphorus sulfur and oxygen in order to grow new macromolecules Other smaller nutrients needed for growth are potassium sodium magnesium calcium and iron These micronutrients are often used in protein structures and activity Microorganisms assimilate important nutrients such as carbon in two different ways depending on whether or not they are a heterotroph or autotroph Heterotrophs assimilate carbon molecules from an already formed organic substance Autotrophs assimilate carbon from inorganic sources Assimilation is defined as cells taking in a molecule and incorporating it into their cellular components Another important nutrient would be nitrogen Nitrogen is extremely important in the production of large amounts of macromolecules specifically important for protein production A common form of nitrogen would be Ammonia Microorganisms also need energy Further Chemotrophs acquire energy from chemicals while phototophs get their energy from light Chemotrophs oxidize organic and inorganic compounds taken from the environment An example would be how glycolysis breaks down glucose to provide synthesis of macromolecules and provide the power to produce ATP Phototrophs capture energy from the light photons and produces chemical energy through photosynthesis in order to fix carbon These do not need any organic materials just light from the sun Electron sources include organotrophs and lithotrophs Organotrophs get electrons from organic molecules Lithotrophs acquire electrons from inorganic reduced molecules Factors Affecting Microorganisms Effects of Nutritional Factors on Microbial Growth When nutrient molecules enter a cell s cytoplasm it will either help with growth or production of ATP Growth rate is best described as the cell s ability to get ahold of these nutrients process and assemble them into macromolecules to form structures If a cell cannot duplicate its genome double its mass containing nucleic acids proteins and lipids then it will not attain all of the genetic information necessary to be sustainable Therefore there are two types of nutrients that are readily accessible to microbes They are prototrophs and auxotrophs Prototrophs can use organic carbon sources and inorganic precursors to synthesize the cellular constituents it needs This process does not generate as much ATP as an auxotroph because it has to use more energy to make its own organic materials from scratch Auxotrophs need to be in the right area where all of its required organic molecules are available Auxotrophs can produce new proteins faster than phototrophs because it takes less energy to import materials from the environment and link them together Nutrient concentration affects growth rate of microbes When there is an increase in nutrients available the growth rate of microbes also increases Effects of Oxygen on Microbial Growth Aerobes grow in areas with oxygen available Obligate aerobes are completely dependent on the presence of oxygen Anaerobic growth occurs without the presence of oxygen Aerotolerant anaerobes can grow in the presence of oxygen but do not use it to grow Obligate anaerobes cannot grow in the presence of oxygen Facultative anaerobes Ex E coli can use oxygen to grow but do not need to use it in order to grow Effects of oxygen on a cell can be determined by the defenses available to the cell Effects of pH on Microbial Growth pH affects structures of macromolecules by changing the protein functions present and also the transmembrane electrochemical gradients Each microbe has a certain range of pH that they can grow best in Neutrophiles grow best in pH values between 5 5 to 8 5 Acidophiles grow best in pH values less than 5 5 Alkalophiles grow best in pH values greater than 8 5 Effects of Osmotic Pressure and Water Availability on Microbial Growth Environments with different concentrations of solute cause water to move in or out of a cell due to its semi permeable membrane This can cause influx of water into the cell or efflux of water out of the cell These types of stress on the cell could result in it shrinking or swelling Water must be accessible for microorganisms to grow Water activity is the measurement of water availability in an environment The water activity can be decreased by interactions with solutes Effects of Temperature on Microbial Growth Microbes grow in environments with all kinds of temperatures from mesophiles psychrophiles to thermophiles and hyperthermophiles Temperature affects the rate of chemical reactions Increases in temperature raise the thermal energy in a microbe which causes them to react more Decreasing temperatures decrease energy available to microbes for reactions NEED MORE INFO Chapter 7 Know the role of DNA Understand DNA replication transcription and translation Know the effects of mutations DNA is the hereditary molecule Griffith Experiment one of the first experiments to determine that DNA was the hereditary molecule using smooth and rough molecules strains of S pnueumoniae His experiment showed that a nonpathogenic R strain could be turned into a pathogenic S strain when mixed together Avery Macleod and McCarty experiment tried to figure out if DNA RNA or protein was responsible for the transformation of the R strain into the S strain in Griffith s experiment Used mixtures from S strain and digested away RNA DNA and protein one at a time DNA was found to be the only one that could mix R cells into S cells when it the only component left in the mix This showed that DNA was responsible for the transformation Hershey Chase experiment used radioactive labeling of proteins or DNA in bacteriophages to determine which one was responsible for the transformation in Griffith s experiment The labeled phage that got further in the cell was DNA determining that DNA could infect the cell and protein could not Therefore they also found that DNA was responsible for transforming the R strain into the S strain DNA Structure Rosalind Franklin James Watson and Francis Crick discovered that DNA has a double stranded helix structure Each nucleotide