POSTERS - BLAST X - University of Utah

BLAST X Thurs. Morning Session
RHODOBACTER SPHAEROIDES, A BACTERIUM WITH TWO FLAGELLAR SYSTEMS AND
MULTIPLE CHEMOTAXIS GENE HOMOLOGS
Ana Martínez del Campo 1 , Sebastian Poggio 2 , Teresa Ballado 1 , Aurora Osorio 2 , Javier de la
Mora 1 , Laura Camarena 2 and Georges Dreyfus 1
Instituto de Fisiología Celular 1 , Instituto de Investigaciones Biomédicas 2 , Universidad Nacional
Autónoma de México, 04510 México DF, México.
Rhodobacter sphaeroides has two flagellar systems (fla1 and fla2). One of these
systems has been shown to be functional and is required for the synthesis of the wellcharacterized
single subpolar flagellum (fla1), while the other was found only after the genome
sequence of this bacterium was completed (fla2). In this work we found that the second flagellar
system of R. sphaeroides can be expressed and encodes a functional flagellum. This second
flagellar system produces polar flagella that are required for swimming. Phylogenic analysis
suggests that the flagellar system that was initially characterized, was in fact, acquired by
horizontal transfer from a γ-proteobacterium, while the second flagellar system contains the
native genes.
In addition to having two flagellar systems, this photosynthetic bacterium posses several
reiterated chemotactic genes (2 cheB, 3 cheR, 4 cheA and cheW and 6 cheY), which are
encoded in three operons (cheOp1, cheOp2 and cheOp3). In spite of this, only some of the
gene copies are required when the cell is swimming with the fla1 flagellum. The presence of a
second functional flagellum (fla2) suggests that some of these genes could be involved in its
tactic control. To test this hypothesis we proceeded to individually mutate each cheY gene. We
show evidence that CheY1, CheY2 and CheY5 control de chemotactic behavior mediated by
fla2 flagella. Additionally, we identified that open reading frame RSP6099 encodes the fla2 FliM
protein. Furthermore CheY1, CheY2 and CheY5 are located within cheOp1, which is not
essential for chemotaxis mediated by the fla1 system. This raises the question: What is the role
of cheOp1?
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