Biology Reference
In-Depth Information
581221, 581781, 582766, and 583769. One gene, VIMSS583068, encodes a putative
2,079 amino acid fi lamentous haemagglutinin, as well as a hasA-like domain, making
it a candidate for hasA-like function (hasA is a hemophore that captures heme for iron
acquisition [46]).
Type II Secretion
Besides the constitutive Sec and Tat pathways,
D. aromatica
has several candi-
dates for dedicated export secretons of unknown function, with 3-4 putative or-
thologs of PulDEFG interspersed with a lytic transglycosylase and a hemolysin
(VIMSS582071-582085). The region from VIMSS581889 to VIMSS581897 includes
pulDEFG type subunits and an exeA ATPase like protein. It is bracketed by signaling
components comprised of a histidine kinase, adenylate cyclase, and a protein bearing
similarity to the nitrogen response regulator glnG (VIMSS581898), which has been
shown to be involved in NH
3
assimilation in other species [47].
In addition, there is a nine-gene cluster that encodes several proteins related to
toluene resistance (VIMSS581899-581906).
A pilus-like gene cluster (which can also be classifi ed as type IV secretion) occurs
in VIMSS580547-580553, encoding a putative lytic transglycosylase, ABC permease,
cation transporter, pilin peptidase, pilin ATPase, and PulF-type protein. This assembly
resembles other pilin assemblies associated with attachment to a substrate, such as the
pilus structure responsible for chitin/host colonization in
Vibrio cholerae
[48].
Another large pilus-like cluster (VIMSS584160-584173) occurs in close proxim-
ity to the
mhp
CEFDBAR oxygenase genes (see e.g., VIMSS584157,
mhp
R).
Type III Secretion
Dechloromonas aromatica
has been shown to be chemotactic under various circum-
stances. The flagellar proteins (FliAEFGHIJKLMNOPQR, FlaABCDEFGHIJK)
are followed by an additional cluster of 15 chemotaxis/signal transduction genes
(VIMSS580462-580476), and homologs of FlhC and D regulatory elements required
for the expression of flagellar proteins (VIMSS582640 and 582641) [49], identified by
phylogenetic clustering, are also present. Since
D. aromatica
has a flagellum and dis-
plays chemotactic behavior, it is likely that the flagellar gene cluster is solely related
to locomotion, though type III secretion systems can also encode dedicated protein
translocation machineries that deliver bacterial pathogenicity proteins directly to the
cytosol of eukaryotic host cells [50].
Type IV Secretion
There are two copies of a 21 gene cluster that includes 10 putative conjugal transfer
(Tra) sex-pilus type genes in the
D. aromatica
genome (VIMSS582582-582601 and
VIMSS582864-582884), indicating a type IV secretion structure that is related to non-
pathogenic cell-cell interactions [51].
Type VI Secretion
A large cluster of transport proteins that is related to the virulence associated genetic
locus HIS-1 of
Pseudomonas aeruginosa
and the VAS genes of
V. cholerae
[52, 53]
