BIOLOGY 207 1st Edition Lecture 7 Outline of Previous Lecture I. DNA ReplicationII. TranscriptionIII. TranslationOutline of Current Lecture I. Basic aspects of microbial growthII. Central metabolism in biosynthesisIII. Evolution and synthetic biologyCurrent LectureMicrobial GrowthI. Basic aspects of microbial growtha. Bacteria have an extremely rapid growth rate given the right circumstances; when in the correct conditions for life, they have exponential growth factorsb. Cell chemistry and nutrition: all cells require certain nutrientsi. Carbon1. Requirement in every cell2. Typically around 50% of the cell’s dry weight comes from carbon3. It is a major element in all macromoleculesa. As a 4 bond atom, it is a central feature that ties things together everywhere in macromolecules4. For autotrophs, carbon comes from CO25. For heterotrophs, carbon comes from organic sourcesii. Nitrogen1. Typically around 13% of a cell’s dry weight2. It is a key element for proteins, nucleic acids, and other compounds3. Some sources include ammonia or nitrate; microbes are good at identifying sources for inorganic nitrogen usageiii. Hydrogen and OxygenThese 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.1. Both key elements for hydration and other key cell functions; cells are in an aqueous environment, meaning that much of these nutrients come from wateriv. Phosphorus1. Key element in nucleic acids and phospholipidsa. Phosphodiester backbonev. Sulfur1. Some amino acids and some vitamins contain sulfurvi. Many other transition metals appear as trace elements involved in cell growth and redox reactions, necessary for enzyme functionc. Bacterial growth by binary fissioni. The first generation cell replicates its genome1. The genome replication can take 40minutesii. Cell physically grows largeriii. Lays down septum and splits in twoiv. The growth of microbes is exponential; µ is the growth constantChromosomeSingle replication forkGeneration time, 1 h; replication time, 40 min.ChromosomeMultiple replication forksGeneration time, 20 min; replication time, 40 min.v. The microbial growth curve begins with a lag period1. Organism must adjust to its environment before it commences division2. Makes proteins necessary for a new cell, including appropriate transporters for the nutrients in the new environment3. Makes ribosomes to maximize rate for growth in new cellvi. The microbe quits after an exponential growth, upon running out of nutrients or accumulation of waste byproductsd. Exponential growth rate used to characterize microbesi. Protein fold and function at certain temperatures, and denature when thetemperature is too hot or coldii. Similar situation for pH measures iii. Standard tools for measuring exponential growth rates under preferred conditions and suchLogarithmicplotArithmeticplote. Response of microbes to O2i. Depending on the type of microbe, the responses and results are vastly different (pinkish area depicts O2 area)1. Aerobic: only grow in areas with oxygen present2. Anaerobic: only grow where oxygen is not present at all3. Faculatative anaerobic: able to grow without oxygen, but utilizes itwhen present4. Microaerophile: prefers low oxygen areasII. Central metabolism in biosynthesisa. Biosynthesis of amino acidsi. Intermediates of glycolysis and the citric acid cycle are used for biosynthesisii. The NADPH provides the reducing power for several different biosyntheticstepsiii. Some of the key features of biosynthesis used in amino acids are shown belowiv. Can be used for catabolic reactions (breaking down) of organic compounds for energy, or anabolic reactions (building up)Oxic zoneAnoxic zoneb. For bacteria and achaea growing on organic compounds with fewer than 6C, glycolysis is reversed to synthesize the glucosei. Eg: acetate has 2C; uses reverse glycolysis to make glucoseii. If the bacteria isn’t given C, it must make itiii. Glucose is needed for many cell functions, including synthesis of ribonucleotides for RNA and DNAc. Synthesis of nucleotides from glucosei. Anabolism required reducing power from NADPHIII. Evolution and synthetic biologya. Richard Lenski began an experiment to track evolution in e. coli cells over the past 25 yearsi. Took one cell sample and inoculated it in glucose and saltsii. Transferred the cells onto 12 plates, then began to transfer the cells onto fresh media every day1. Over the past 25 years, he has gotten over 58,000 generations of e. coli2. He is able to note the differences and ask questions on the evolutions and how different pathways are chosen3. By freezing the previous generations, he is able to go back and compare generations as he pleasesa. Why do certain strains survive longer than others? How do they compare to strains from years ago?4. Evolved generations are seen to become more fit with