Week 4 of notes for BISC 300
Week 4 of notes for BISC 300 BISC300
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This 3 page Class Notes was uploaded by Jj Lynch on Saturday March 5, 2016. The Class Notes belongs to BISC300 at University of Delaware taught by Carlton Cooper in Summer 2015. Since its upload, it has received 28 views. For similar materials see Microbiology in Biological Sciences at University of Delaware.
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Date Created: 03/05/16
Monday Notes • Harold Aimos à first African American microbiologist o Studied E. coli and phages o Worked in cancer biology o Studied bacterial metabolism • Phage reproduction far more complex than virus o Phage gets through cell was because it attacks bacteria • Virus and phage attaches, injects DNA, synthesis and genomes and protein, does assembly and releases • Virus can get in through membrane fusion (if enveloped) and endocytosis (if enveloped or enveloped) • All viruses have a capsid to hold genome • Virus entry is membrane receptor mediated • Viral proteins go to plasma membrane, attract and bind to formed capsid, virus leaves through protein spot through budding • When viral genetic material enters it is replicated and the genes are expressed • Double stranded DNA follows central dogma (DNAàRNAàProtein) • RNA viruses have to bring in or synthesize the proteins they need for synthesis of genome and proteins • + RNA is mRNA, - RNA is a template • Membrane of the envelope can be from plasma, golgi, ER etc. • Types of infection o Acuteàcell dies when virus is released o Latent à (ie/ herpes) prolonged, genetic material is there but not replicating o Chronic à (ie/ HIV) always replicating slowly o Transformation into malignant cell (carcinogenesis)à oncogenes (cancer causing genes) from virus or host (proto-oncogenes-regulate cell growth/differentiation) (ie/Hep B and C, Epstein-Bar) § Tumor suppressants can also be inactivated to cause cancer • Phages: o Virulentà lyses host, destroys host DNA, replicates its own, synthesizes more phage DNA and proteins, assembles phages, releases enzyme to break cell wall and lyse cell § No budding § LYTIC PHASE o Temperantàphage DNA integrates into host DNA (prophage), when host replicates prophage is replicated too § When host is under stress prophage goes back to phage to prepare to leave (goes to lytic phase) § LYSOGENIC PHASE Wednesday Notes • Mitochondria was aerobic bacteria ingested by a prokaryote o Led to animal cells • Some of these prokaryotes also ingested cyanobacteria (became chloroplasts) o Led to plant cells • The aerobic bacteria and cyanobacteria were eventually unable to live on their own without the prokaryote • Mitochondria and chloroplasts reproduce asexually on their own within the cell • Bacteria reproduce asexually through binary fission o 1) Cell wall, membrane and volume enlarge and DNA starts to replicate o 2) Chromosomes separate and septum starts to grow inward o 3) Septum grows completely through center separating cell into 2 o 4) Daughter cells could separate completely or stay attached in chains or doublets • Bacteria usually have 1 circular chromosome • Has a single origin of replication • Terminus- spot on chromosome where replication stops • Antibiotics may cause side effects if they attack bacterial proteins that are homologues of eukaryotic ones • Bacterial proteins: o FtsZ is involved in initiation of septum formation o MinCDE determines FtsZ and septum location o MreB is involved in cell shape, coordinates cell wall rebuilding • MreB organizes peptidoglycan synthesis during fission, distributes peptidoglycan in cell wall to reform it • MinCDE oscillates back and forth so that FtsZ can only form in the center of the cell o FtsZ can’t form in high MinCDE concentration. The high conc. of it moves back and forth to keep FtsZ away from the cell sides • Vibrio (comma shaped) bacteria has protein crescentin (intermediate filament homolog) that accumulates on curved side of cell • Min system uses ATP to move back and forth (???) • Also bind to parts of the 2 chromosome copies to put them in the correct spot for fission (????) • Bacterial growth curve: o Lag phaseàacclimation of cell in environment, preparing for cell division o Exponential phaseàbinary fission o Stationary phaseàtoo much bacteria in population o Death phaseàpopulation drops because it ran out of resources o Long term stationary phaseàmost resilient bacteria left behind Friday Notes • Bacterial growth curve only relates to closed experimental environment • Bacteria’s plasmid holds its resistance to its own antibiotics • Lag phase shortens when bacteria is brought from nutrient poor to nutrient rich environment o Opposite for rich to poor • Yield cell count and growth rate curves do not look the same o Growth rate plateaus once all proteins are saturated, can’t keep taking in nutrients o Cells continue to divide (yield) but the rate (growth rate) slows down after saturation • Experiments should be done on bacteria during the exponential phase because all bacteria will be uniform. They should not be done in the lag phase because the cells are building up at different rates • Antibiotics aren’t effective in lag phase bacteria o Take antibiotics for entire length of time of growth curve • Some bacteria can preserve and eventually form endospores when faced with starvation