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UID:DSC-16835
DTSTART;TZID=Europe/Berlin:20200203T140000
SEQUENCE:1580771186
TRANSP:OPAQUE
DTEND;TZID=Europe/Berlin:20200203T150000
URL:https://www.dresden-science-calendar.de/calendar/en/detail/16835
LOCATION:MPI-CBG\, Pfotenhauerstraße 10801307 Dresden
SUMMARY:Vucelja: Adaptation of bacteria with CRISPR and adaptation on a rug
 ged fitness landscape
CLASS:PUBLIC
DESCRIPTION:Speaker: Marija Vucelja\nInstitute of Speaker: University of Vi
 rginia\, USA\nTopics:\n\n Location:\n  Name: MPI-CBG (MPI-CBG Galleria)\n 
  Street: Pfotenhauerstraße 108\n  City: 01307 Dresden\n  Phone: +49 351 2
 10-0\n  Fax: +49 351 210-2000\nDescription: I will tell you two stories of
  adaptation of populations aided and enriched by statistical physics appro
 aches.    The first story is about the adaptation of bacteria with CRISPR.
  CRISPR-Cas is a famous biology buzz word\, due to its applications to gen
 e editing. However\, CRISPR-Cas is also a prokaryote immune system. It wor
 ks as a “library” of previous infections. This library contains snippe
 ts of exogenous genetic material. With a new infection\, the library is co
 nsulted\, and if a match is found\, the attempt will be made to neutralize
  the intruding genome. Bacteria use CRISPR-Cas as an immune system against
  phages and plasmids. Such immunity is hereditary and dynamic — it can b
 e gained and lost during the lifetime of the single bacteria. Also\, the p
 rocess of acquiring snippets when exposed to the same phage is stochastic\
 , and the same strain bacteria in a population contain different CRISPR lo
 ci content and thus variable immunity to the phage. We use dynamical syste
 ms approaches to predict the shape of this diverse distribution of CRISPR 
 loci content within a bacterial population as a function of two crucial pa
 rameters — the rate of acquisition and the immunity to the phage.  The s
 econd story is about adaptation on a rugged fitness landscape. A crude mea
 sure of adaption to a new environment called fitness. Often one defines fi
 tness as the expected growth rate. The higher the fitness\, the more thriv
 ing is a population. What happens over long times for a population with a 
 finite genome — when all beneficial\, fitness mutations\, are exhausted?
  Contrary to expectations\, the experiments show that fitness does not rea
 ch a plateau. Here we introduce a spin-glass microscopic model\, where a g
 enome can be represented as a spin configuration\, and individual spins ar
 e genes. The fitness plays the role of minus the Hamiltonian of the system
 . We use numerical approaches and estimates to study hopping between metas
 table states on a rugged fitness landscape. We show that with gene interac
 tions (interacting spins)\, double beneficial mutations (flipping of pairs
  of spins) can lead to a slow\, logarithmic increase of fitness in a wide 
 class of cases.
DTSTAMP:20260425T153319Z
CREATED:20191211T230725Z
LAST-MODIFIED:20200203T230626Z
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