Differentiation and development are largely characteristics of
multicellular organisms. Because most prokaryotes grow as
single cells, few show differentiation. Nonetheless, occasional
examples among single-celled prokaryotes illustrate the basic
principle of differentiation, namely that one cell gives rise to two
genetically identical descendants that perform different roles and
must therefore express different sets of genes. Here we discuss
three well-studied examples: the formation of endospores in the
gram-positive bacterium Bacillus; the formation of two cell types,
motile and stationary, in the gram-negative bacterium Caulobacter;
and the formation of heterocysts in the nitrogen-fixing
cyanobacterium Anabaena.
Although forming just two different cell types may seem superficially
simple, the regulatory systems that control these processes
are highly complex. There are three major phases for the regulation
of differentiation: (1) triggering the response, (2) development
of the differentiated cell, and (3) reciprocal communication
between the two differentiating and undifferentiated cells.
Differentiation and development are largely characteristics ofmulticellular organisms. Because most prokaryotes grow assingle cells, few show differentiation. Nonetheless, occasionalexamples among single-celled prokaryotes illustrate the basicprinciple of differentiation, namely that one cell gives rise to twogenetically identical descendants that perform different roles andmust therefore express different sets of genes. Here we discussthree well-studied examples: the formation of endospores in thegram-positive bacterium Bacillus; the formation of two cell types,motile and stationary, in the gram-negative bacterium Caulobacter;and the formation of heterocysts in the nitrogen-fixingcyanobacterium Anabaena.Although forming just two different cell types may seem superficiallysimple, the regulatory systems that control these processesare highly complex. There are three major phases for the regulationof differentiation: (1) triggering the response, (2) developmentof the differentiated cell, and (3) reciprocal communicationbetween the two differentiating and undifferentiated cells.
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