《环境工程微生物学》课程扩展资料（scientist microbiology from Harvard）Stochasticity in the Bacterial World

Stochasticity and Cell FateRichard LosickHarvard University

Stochasticity and Cell Fate Richard Losick Harvard University

“l, at any rate, am convinced that He does notplay dice."AlbertEinstein

“I, at any rate, am convinced that He does not play dice.” Albert Einstein

Consider life at the micron scale, the world inhabited by bacteriaBacteria must cope with an environment that undergoes changesin temperature, pH, availability of nutrients, and so forth.One way bacteria cope with change is by sensing andresponding to cues from the environment.In sensing systems, all cells in the population respond toenvironmentalchangeinamore-or-lessuniformmannerSometimes, however, the optimal strategy is to entry aspecialized state prior to changed circumstances. That is, inanticipation of change.But bacteria cannot tell the future. Instead, they hedge their betsbystochasticswitching

Consider life at the micron scale, the world inhabited by bacteria. Bacteria must cope with an environment that undergoes changes in temperature, pH, availability of nutrients, and so forth. One way bacteria cope with change is by sensing and responding to cues from the environment. In sensing systems, all cells in the population respond to environmental change in a more-or-less uniform manner. Sometimes, however, the optimal strategy is to entry a specialized state prior to changed circumstances. That is, in anticipation of change. But bacteria cannot tell the future. Instead, they hedge their bets by stochastic switching

Consider the“"persister" state. It has long been knownthat when challenged with ampicillin, certain cells in apopulation of bacteria mysteriously survive theantibiotic treatment without becoming resistant to it bymutation.How is this possible? The answer is that a smallnumber of cells spontaneously and temporarily enter astate in which they stop growing and thereby avoidbeing killed by ampicillin.In other words, certain bacteria are bistable: theystochasticallyswitchbetweenagrowingstateandanon-growing state

Consider the “persister” state. It has long been known that when challenged with ampicillin, certain cells in a population of bacteria mysteriously survive the antibiotic treatment without becoming resistant to it by mutation. How is this possible? The answer is that a small number of cells spontaneously and temporarily enter a state in which they stop growing and thereby avoid being killed by ampicillin. In other words, certain bacteria are bistable: they stochastically switch between a growing state and a non-growing state

C0=00Gro

DE0=000=59145ninGrowthmedium(GM1)

ED0=000=5911456:50miGrowthmedium(Gmi1)AmpiciinA

EODGH0=000=591:456:507:388139GrowthmediumGt1)AmpiciinA)Growthmedium(GM2)

EODGH0=000=591:456:507:388139GrowthmediumGt1)AmpiciinA)Growthmedium(GM2)

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