Microbial Physiology notes lec24 11-22-10

Microbial Physiology notes lec24 11-22-10 - Microbial...

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Microbial Physio Lecture 24: November 22, 2010 Circadian Rhythm in Cyanobacteria (Synechococcus elongatus) (handout) 1. Characteristics of any circadian clock a. Occurs in ~ 24 hr cycle i. needs continuous entrainment in order to keep it on the daily cycle ii. sometimes the cycle is as long as 26 hrs and as short as 22 hr periods 1. mutants have been found isolated which are drastically altered w/ respect to their period length b. continues several cycles w/o entrainment i. w/o entrainment the cycle continues. But slightly out of phase for a number of times, sometimes the cycle can continue for as long as 12 cycles, which means ~12 days ii. e.g w/o external stimulus input (external stimulus input=entrainment) c. Circadian clock is subject to entrainment by light/dark, warm/cold, humidity changes and/or redox cycles i. In both eukaryotes and prokaryotes, the redox cycles can be used for purpose of entrainment ii. This is particularly likely in organisms where the sun gives rise to increase in electron transport, and hence they can use this as a secondary signal to indicate the presence of day versus night d. Temperature compensated i. The clock will run almost the same regardless of temperature, and this is true for warm and cold blooded animals ii. If the animal is warm blooded, then the temperature is constant anyways, so why should they have a circadian rhythm? 1. why is there temperature compensation for the circadian clock in a warm blooded animal? a. Because in the instance that you get a fever and become really hot, or in freezing conditions and you get really cold, in which you body temperature rises above and below body temperature but since there is temperature compensation for the circadian clock, then it will continue on at the same rate e. Multicomponent f. Subject to feedback/forward controls g. Genetically determined under genetic control i. The clock has to consist of proteins that are encoded by genes, hence it should be possible to isolate mutants that are defective for
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the protein components and the entrainment components that make up the circadian rhythm h. Regulated: i. Gene expression ii. Metabolism iii. Behavior i. Advantages: i. Optimizes activities w/ light and temperature 1. i.e night workmen, regardless of your occupation is, regardless of the way you’ve changed your schedule, so that you’re functioning at night rather than in the day, the circadian clock still goes on at the same time and demands the same thing, therefore a person who is staying up at night and sleeping during the day isn’t functioning optimally there performance is far lower than people who are following their circadian clock ii. Utilized for predation iii. Mating 1. testosterone levels are at their highest in the morning this is a secondary cause of the circadian rhythm, and therefore as a tertiary response of the clock would be sexual activity runs according to the clock iv. Differentiation 1. it has to be coordinated, and it makes sense that these steps
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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 lec24 11-22-10 - Microbial...

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