Previous Article |
Table of Contents
| Next Article 
BIOLOGICAL SCIENCES / EVOLUTION
Stepwise formation of the bacterial flagellar system
,
Departments of *Biochemistry and Molecular Biophysics and Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721
Edited by Francisco J. Ayala, University of California, Irvine, CA, and approved March 8, 2007 (received for review January 11, 2007)
Elucidating the origins of complex biological structures has been one of the major challenges of evolutionary studies. The bacterial flagellum is a primary example of a complex apparatus whose origins and evolutionary history have proven difficult to reconstruct. The gene clusters encoding the components of the flagellum can include >50 genes, but these clusters vary greatly in their numbers and contents among bacterial phyla. To investigate how this diversity arose, we identified all homologs of all flagellar proteins encoded in the complete genome sequences of 41 flagellated species from 11 bacterial phyla. Based on the phylogenetic occurrence and histories of each of these proteins, we could distinguish an ancient core set of 24 structural genes that were present in the common ancestor to all Bacteria. Within a genome, many of these core genes show sequence similarity only to other flagellar core genes, indicating that they were derived from one another, and the relationships among these genes suggest the probable order in which the structural components of the bacterial flagellum arose. These results show that core components of the bacterial flagellum originated through the successive duplication and modification of a few, or perhaps even a single, precursor gene.
bacterial evolution | biological complexity | gene duplication
Author contributions: R.L. and H.O. designed research; R.L. performed research; R.L. and H.O. analyzed data; and R.L. and H.O. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS direct submission.
This article contains supporting information online at www.pnas.org/cgi/content/full/0700266104/DC1.
To whom correspondence should be addressed. E-mail: hochman{at}email.arizona.edu
© 2007 by The National Academy of Sciences of the USA
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg What's this?
This article has been cited by other articles in HighWire Press-hosted journals:
|
|
 |
|
  R. Liu and H. Ochman Origins of Flagellar Gene Operons and Secondary Flagellar Systems J. Bacteriol., October 1, 2007; 189(19): 7098 - 7104. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. Huitema and P. H. Viollier Break on through to the other side: outer membrane penetration of the nascent flagellum by a stop-polymerization mechanism Genes & Dev., September 15, 2007; 21(18): 2253 - 2257. [Full Text] [PDF]
|
|
