Microbial Physiology notes lec9 10-13-10

Microbial Physiology notes lec9 10-13-10 - Microbial physio...

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Microbial physio Bimm130 Lecture 9: October 13, 2010 Cell-cell interactions in Embryogenesis and Bacteria (Myxococcus Xanthus) (continued) Three types of cues: -intracellular -environment these are the 3 cues that determine the mammalian -intercellular program of differentiation The same cues are operative in bacteria: Caulobacter has an intracellular cue for differentiation all signals are intracellular and they aren’t influenced by any external conditions o i.e MCPs, cheW, cheA, TipN, TipF Bacillus(gram+ rod shaped bacteria i.e E.coli) has an environmental cue starvation signal for differentiation extracellular signaling mechanism Myxobactera has an intercellular and extracellular signal for differentiation stimulus which starts from cell-cell surface contact o i.e csg and asg ( intercellular), and starvation(extracellular) -Myxococcus xanthus : there are at least 6 signals: B D A + P E C Genes: bsg dsg asg psg esg csg -upon starvation, the bacterial initiate a process of aggregation, then differentiation occurs once the aggregate is in place and then they go through several stages - in addition to the stages they can only progress from one stage to the next if they have contacts with their neighbors and specific molecules are involved in the signaling between cells -Signals represent cell-cell interaction type signals there are 6 signals that were discovered A B C D E P 1. Mutations in each signal arrests development at a specific stage discontinuity of the program -mutations were identified based on mutant analysis gene mutations were called bsg, dsg, asg, psg, esg, csg all of these mutants have been isolated - The genes code for the signal which is expressed, and then the protein goes to the cell surface or to the medium and gives rise to the phenotype -Figure: gene expression of myxococcus xanthus over a period of 12 hrs that is how long it takes differentiation for sporulation to occur
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-normally in the wild, xanthus forms fruiting bodies before sporulation occurs, and there are a lot of events that occur before the spores are actually formed, but its also possible to elicit sporulation in the absence of fruiting body formation it’s a chemically induced phenomenon, but it’s accompanied correctly by the succession of gene expression events which dictate the fruiting body and sporulation developmental events - in the figure, for the % of gene expression seen there are a bunch of random genes that are important for differentiation, and those genes are now fused to beta- galactosidase, to measure the expression of each of those genes, where each gene fusion with beta-galatosidase is encoded by a separate gene, and each of those fused genes is expressed in a separate strain so we can look at all of these different strains that are identical, except for the presence of the beta-galatosidase fusion mutation then can introduce the 2 mutations: the asg mutant which blocks
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This note was uploaded on 01/09/2011 for the course BIMM 130 taught by Professor Saier during the Fall '10 term at UCSD.

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Microbial Physiology notes lec9 10-13-10 - Microbial physio...

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