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J. Bacteriol., Aug 1997, 4802-4810, Vol 179, No. 15
C Jacob, F Nouzieres, S Duret, JM Bove and J Renaudin
The helical mollicute Spiroplasma citri, when growing on low-agar medium,
forms fuzzy colonies with occasional surrounding satellite colonies due to
the ability of the spiroplasmal cells to move through the agar matrix. In
liquid medium, these helical organisms flex, twist, and rotate rapidly. By
using Tn4001 insertion mutagenesis, a motility mutant was isolated on the
basis of its nondiffuse, sharp-edged colonies. Dark-field microscopy
observations revealed that the organism flexed at a low frequency and had
lost the ability to rotate about the helix axis. In this mutant, the
transposon was shown to be inserted into an open reading frame encoding a
putative polypeptide of 409 amino acids for which no significant homology
with known proteins was found. The corresponding gene, named scm1, was
recovered from the wild-type strain and introduced into the motility mutant
by using the S. citri oriC plasmid pBOT1 as the vector. The appearance of
fuzzy colonies and the observation that spiroplasma cells displayed
rotatory and flexional movements showed the motile phenotype to be restored
in the spiroplasmal transformants. The functional complementation of the
motility mutant proves the scm1 gene product to be involved in the motility
mechanism of S. citri.
Copyright © 1997, American Society for Microbiology
Isolation, characterization, and complementation of a motility mutant of Spiroplasma citri
Laboratoire de Biologie Cellulaire et Moleculaire, Institut National de la Recherche Agronomique and Universite Victor Segalen Bordeaux 2, Villenave d'Ornon, France.
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