Abstract
The 6.10-Mb genome sequence of the aerobic chitin-digesting gliding bacterium
Flavobacterium johnsoniae
(phylum
Bacteroidetes
) is presented.
F. johnsoniae
is a model organism for studies of bacteroidete gliding motility, gene regulation, and biochemistry. The mechanism of
F. johnsoniae
gliding is novel, and genome analysis confirms that it does not involve well-studied motility organelles, such as flagella or type IV pili. The motility machinery is composed of Gld proteins in the cell envelope that are thought to comprise the “motor” and SprB, which is thought to function as a cell surface adhesin that is propelled by the motor. Analysis of the genome identified genes related to
sprB
that may encode alternative adhesins used for movement over different surfaces. Comparative genome analysis revealed that some of the
gld
and
spr
genes are found in nongliding bacteroidetes and may encode components of a novel protein secretion system.
F. johnsoniae
digests proteins, and 125 predicted peptidases were identified.
F. johnsoniae
also digests numerous polysaccharides, and 138 glycoside hydrolases, 9 polysaccharide lyases, and 17 carbohydrate esterases were predicted. The unexpected ability of
F. johnsoniae
to digest hemicelluloses, such as xylans, mannans, and xyloglucans, was predicted based on the genome analysis and confirmed experimentally. Numerous predicted cell surface proteins related to
Bacteroides thetaiotaomicron
SusC and SusD, which are likely involved in binding of oligosaccharides and transport across the outer membrane, were also identified. Genes required for synthesis of the novel outer membrane flexirubin pigments were identified by a combination of genome analysis and genetic experiments. Genes predicted to encode components of a multienzyme nonribosomal peptide synthetase were identified, as were novel aspects of gene regulation. The availability of techniques for genetic manipulation allows rapid exploration of the features identified for the polysaccharide-digesting gliding bacteroidete
F. johnsoniae
.