Richard hypothesis 

d/w = resource separation ratio.

d/w < 1, species cannot coexist;

1 < d/w < 3, there will be some competition between species

d/w > 3, species coexist harmoniously

TLS Online TPP Program

#Id: 6393

#Unit 2. Cellular Organization

The E. coli trp operon contains the 5 genes Trp-EDCBA for the anabolic enzymes to make the tryptophan.

TLS Online TPP Program

#Id: 6394

#Unit 2. Cellular Organization

Major enzyme is Tryptophan Synthase

TLS Online TPP Program

#Id: 6395

#Unit 2. Cellular Organization

Major enzyme is Tryptophan Synthase whose activity is reduced when trp concentration is high

TLS Online TPP Program

#Id: 6396

#Unit 2. Cellular Organization

Trp operon is negatively regulated by two ways

 Repression

Attenuation

TLS Online TPP Program

#Id: 6397

#Unit 2. Cellular Organization

Why is this extra control of two layers on trp operon needed?  The answer probably lies in the fact that repression of the trp operon is weak—much weaker.

TLS Online TPP Program

#Id: 6398

#Unit 2. Cellular Organization

Repression-Trp aporepressor dimer binds high tryptophan, changes conformation with high affinity for trp operator

Tryptophan is a corepressor