Microbial Physiology notes lec11 10-18-10

The eukaryotic cells is 1000xs bigger than the

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The eukaryotic cells is 1000x’s bigger than the prokaryotic cell so in the eukaryotic cell can actually measure the [ ] gradient from its tip to its toe there is enough space in between that it allows them to tell the difference in the [ ] of an attractant over the length of their body b. Myxobacteria feed in packs and move slowly a. Since myxobacteria are always in contact with each other, they can use cell surface signals rather than small diffusible molecules the use of cell surface macromolecules as attractants helps to keep them together (coordinated activity). This is advantageous because they feed in “wolf packs” as “micropredators”
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b. The myxobacteria a single cell doesn’t produce enough proteases and carbohydrases and lipases to digest the whole bacteria individually, they have to work in a pack c. Just as in an embryo all of the cells are together in a ball, and therefore are in contact, and therefore its reasonable that cell surface proteins and glycoproteins mediate the differentiation process d. The bacterium is 1000x’s smaller than a eukaryotic cell its small cell size doesn’t allow for orientation in response to a freely diffusible spatial gradient therefore they use memory and temporal gradients as do all tactile bacteria i. E.coli has memory ii. Short term memory in a bacterium is determined by the same factors and conditions that allow humans to have short term memory can remember stuff anywhere from 1-10 mins depending on how good the short term memory is iii. E.coli has 1-10 mins of short term memory 1. E.coli can remember the [ ] in one point in time and compare it to another [ ] in another point in time, and it can remember this for up to 10 mins this is the outer limit 2. whenever you have memory of this nature, you have to have 2 separate processes a. chemotaxis in E. coli: i. Activation: 1. Phosphorylation of chemotaxis proteins i.e che A autophosphorylating itself and then passing the phosphate to cheY which then goes to the basal region where the flagellar switch is and induces the flagella to change rotation/direction of movement 2. which is the stimulus has to occur very rapidly ii. Adaptation process: Methylation process iii. The crucial thing for these 2 time constants: activation and adaptation are different: 1. in the 1 st case in E.coli, the stimulus has to be sensed in a matter of milliseconds 2. in the case of adaptation, it can occur over a period of 1-10 mins 3. As long as the activation and adaptation is displaced, that is when you can have short term memory
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4. as soon as the bacterium has adapted fully, the bacterium has forgotten what the [ ] was initially Note: In animals, short range, spatially restricted cellular interactions are mediated by cell surface proteins which directs differentiation (i.e mesodermal induction in vertebrate embryos; antigen presentation in antibody producing cells, etc) In this respect, regulation resembles that in the myxobacteria
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