Previous Article | Next Article 
Journal of Bacteriology, October 2000, p. 5787-5792, Vol. 182, No. 20
Departamento de Biología Molecular, Instituto de
Investigaciones Biomédicas,1 and
Departamento de Genética Molecular, Instituto de
Fisiología Celular, UNAM,2 04510 Mexico City,
Mexico
Received 9 June 2000/Accepted 25 July 2000
Gene expression of the flagellar system is tightly controlled by
external stimuli or intracellular signals. A general picture of this
regulation has been obtained from studies of Salmonella enterica serovar Typhimurium. However, these regulatory
mechanisms do not apply to all bacterial groups. In this study, we have
investigated regulation of the flagellar genetic system in
Rhodobacter sphaeroides. Deletion analysis,
site-directed mutagenesis, and 5'-end mapping were conducted in
order to identify the fliO promoter. Our results indicate
that this promoter is recognized by the factor The flagellum is the structure
responsible for the motility of many bacteria. Some of its structural
features include the basal body, the hook, and the helical filament. In
Salmonella enterica serovar Typhimurium, biosynthesis of the
flagellum depends on the expression of more than 40 genes. The products
of these genes are required for several flagellar processes, including assembly, export, and transcriptional control (for recent reviews, see
references 1 and 16).
The expression of these genes follows a hierarchical pattern that is
highly regulated. At the top of the hierarchy is the flhDC
operon, encoding two proteins which form the
heterotetrameric positive transcriptional regulator of the class II
genes. Global regulators, such as the cyclic AMP receptor protein,
DnaA, and the nucleoid-associated protein H-NS, influence the
expression level of this operon and consequently the formation
of flagella (18, 21, 23). The expression of class II genes
is dependent on the RNA polymerase- The flagellar genetic system of Rhodobacter sphaeroides
is poorly understood. Detailed analyses of some structural components of the flagellum have been described, but nothing is known about the
factors that regulate gene expression. Recently, genetic evidence has
suggested the location of functional flagellar promoters in this
organism. Complementation studies have indicated the presence of
promoters at the fliN-fliO intercistronic region
(7), upstream of the flgBCDEF operon (T. Ballado, L. Camarena, B. González-Pedrajo, E. Silva-Herzog, and
G. Dreyfus, unpublished data) and upstream of motA
(6). However, no physical evidence supporting these results
has been reported.
In this work we show evidence that a Bacterial strains and growth conditions.
R.
sphaeroides cells were grown in Sistrom's succinate-basal
salt medium at 30°C (20). Heterotrophic growth conditions
were achieved by growing 10-ml cultures in 250-ml Erlenmeyer flasks with strong shaking (300 rpm) in the dark. Phototrophic conditions were
achieved by growing cultures in completely filled screw-cap tubes under
continuous illumination. Cultures were harvested at an optical density
at 600 nm of 0.5 ± 0.05 (mean ± standard deviation). When
required, spectinomycin (15 µg/ml), kanamycin (25 µg/ml), or
tetracycline (1 µg/ml) was added to the culture medium.
Escherichia coli strains were grown aerobically at 37°C on
Luria-Bertani medium. Antibiotics were added at the following
concentrations: ampicillin, 100 µg/ml; tetracycline, 10 µg/ml; and
kanamycin, 50 µg/ml.
Recombinant DNA techniques.
Routine genetic manipulations
were performed as described elsewhere (2). Restriction
enzymes, alkaline phosphatase, T4 ligase, and T4 polynucleotide kinase
were purchased from GIBCO-BRL. Plasmid DNA was isolated from E. coli using Qiagen columns and procedures. Sequencing was carried
out using a Thermosequenase kit (Amersham) on single-stranded DNA.
Conjugal mating.
Plasmid DNA was mobilized into R. sphaeroides cells by conjugation according to procedures
previously reported (5).
Site-directed mutagenesis.
Site-directed mutagenesis was
performed according to the method of Kunkel (14) with a
uracil-containing single-stranded DNA as the template. The
oligonucleotides used for mutagenesis were
5'-CTGCAACATCCGTGACGCCCGCCCGCG-3',
5'-CTGCAACATCCGTGCTGCCCGCCCGCG-3', 5'-GTCCCCCTCCGCTACAACATCCGTGCCG-3',
and 5'-GTCCCCCTCCGCAACAACATCCGTGCCG-3'.
RNA isolation and Northern blot analysis.
Total RNA was
isolated from heterotrophic cultures as described previously
(24). For Northern blotting, 20 µg of each RNA sample was
separated electrophoretically on agarose-formaldehyde gels and
transferred by capillary action onto nylon membranes with a pore size
of 0.45 µm. Filter hybridizations were performed as described
previously (2). The DNA probe used was a 1.1-kb PstI-BglII fragment from fliC, labeled
with [ Primer extension analysis.
Reactions were performed as
described previously (2). Total RNA (50 µg for
fliO and flgB reactions and 100 µg for
fliK reactions) was annealed with a specific primer at
42°C in the presence of 50% formamide. Oligonucleotides used as
primers for cDNA synthesis were 5' end labeled with T4 polynucleotide
kinase and 20 µCi of [
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
54 Promoters Control Expression of Genes Encoding
the Hook and Basal Body Complex in Rhodobacter
sphaeroides
ABSTRACT
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
54.
Additionally, 5'-end mapping of the flgB and
fliK transcripts suggests that these mRNAs are also
transcribed from 54 promoters. Finally, we showed
evidence that suggests that fliC transcription is not
entirely dependent on the presence of a complete basal body-hook
structure. Our results are discussed in the context of a possible
regulatory hierarchy controlling flagellar gene expression in R. sphaeroides.
INTRODUCTION
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
70 holoenzyme
(E70) and FlhD-FlhC. Proteins involved in the formation
of the hook and the basal body complex (HBB), as well as the regulatory
proteins FlgM and FliA, belong to this class (11). FliA is a
specific sigma factor (28) required for the expression
of class III genes, while FlgM is an anti-sigma factor that inhibits
FliA activity. The release of FliA from the inhibitory action of FlgM
occurs when the HBB structure is completed, allowing FlgM export out of
the cell. FliA is then free to associate with the RNA polymerase core
enzyme in order to transcribe class III genes (10, 15).
54 promoter is
located at the fliN-fliO intercistronic region and is
responsible for the transcription of the fliOPQR flhB
operon. In addition, primer extension experiments revealed
transcription start sites upstream of flgB and
fliK. In these two cases, a sequence similar to that of the
54 promoter was also identified a few base pairs
upstream of the transcription start sites. These results indicate that
E54 is responsible for the expression of genes encoding
structural components of the flagellar export apparatus, the motor, the
hook, and the basal body proteins. We also determined that mutations in
the fliM, fliK, and fliR genes did not
affect the expression of other flagellar genes dependent on
54. In contrast, fliC mRNA was reduced in
fliM or flgE strains. These results allow us to
propose a regulatory hierarchy controlling the expression of the
flagellar genes in R. sphaeroides.
MATERIALS AND METHODS
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
-32P]dCTP by nick translation.
-32P]ATP at 37°C for 30 min.
Unincorporated nucleotides were removed by chromatography. The primer
elongation reactions were carried out with avian myeloblastosis virus
reverse transcriptase (Promega). Unlabeled primers were used to
generate a nucleotide sequence ladder.
-Glucuronidase activity assay. -Glucuronidase assays
employed 4-methylumbelliferyl--D-glucuronide as
a substrate along with sonicated cell extracts as described previously
(12). Samples of 100 µl were taken at three time points
between 10 and 40 min and then mixed with 0.9 ml of stop buffer (0.2 M
Na2CO3). Fluorimetric determinations were made
with a Perkin-Elmer LS-5 apparatus (excitation wavelength, 360 nm;
emission wavelength, 446 nm). The fluorimeter was calibrated using
4-methylumbelliferone standards. Specific enzyme activity in cell
extracts was expressed as micromoles of 4-methylumbelliferone per
minute per milligram of protein. Protein content was determined using
the Bio-Rad protein assay kit, with bovine serum albumin as a standard.
| |
RESULTS |
|---|
|
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
|
|---|
Transcriptional organization of the flagellar cluster fliHIJKLMNOPQR flhB. A large flagellar cluster was previously identified which contained 12 flagellar genes from fliH to fliR and flhB (3, 7). The transcriptional organization of this region was inferred from a complementation study on a strain carrying a polar insertion in the fliM gene (fliM::uidA-aadA). This study indicated the presence of a promoter downstream of fliN (7).
To analyze this possibility, transcriptional fusions of the fliM and fliR genes to the promoterless 'uidA gene were made. These fusions were used to replace either the fliM+ or the fliR+ genes from the chromosomes of the wild-type WS8 strain and from the PG2 strain, which carries the mutation fliK::TnphoA (8). Correct replacement in each of these four strains was confirmed by Southern blot analysis (data not shown). The expression level of-glucuronidase dependent on
flagellar promoters was determined under heterotrophic
growth conditions. Strains carrying the
fliM::uidA-aadA or the
fliR::uidA-aadA fusion in a wild-type background
showed a high level of activity (Table 1). In contrast, when fusions were placed
in the fliK::TnphoA background, only the strain
carrying the fliR::uidA-aadA allele showed
-glucuronidase activity. This result can be explained in terms of a
polar effect exerted by the TnphoA transposon over genes in the same transcriptional unit. Therefore, fliK,
fliL, and fliM appear to belong to the same
transcriptional unit, whereas fliR belongs to a different
operon.
|
Deletion mapping of a transcriptionally active flagellar region. To identify the promoter controlling transcription of fliR, deletion analysis of a 4.4-kb EcoRI fragment carrying the fliR::uidA-aad allele was performed. This fragment, which incorporates sequences from the middle of fliM to the middle of flhB, was cloned into the pRK415 vector in an orientation opposite to that of the pRK415 promoters.
WS8 cells carrying this plasmid were grown to mid-log phase and the level of-glucuronidase was determined in a cell extract. This
construct produces high levels of -glucuronidase (Fig.
1, construct 1). The 'uidA
gene was cloned into pRK415 in both orientations with respect to the
pRK415 promoters for use as controls (Fig. 1, constructs 6 and 7).
-Glucuronidase activity was detected only when uidA was
transcribed from the known pRK415 promoters.
|
-glucuronidase activity
(Fig. 1, construct 3). Therefore, the sequence from the SstI
site to the SalI site spanning from the middle of
fliN to fliP (1.1 kb) contains a functional promoter.
To further define this promoter region, a 600-bp SacII
fragment, spanning from the 3' end of fliN to the 5' end of
fliO, was cloned upstream of the 'uidA gene (Fig.
1, construct 4). This region was fully functional for promoting
uidA transcription. Further deletion of 180 bp from the
fliN side only modestly affected the transcriptional
capability of this fragment (Fig. 1, construct 5).
In summary, these results localize a functional flagellar
promoter to a 420-bp region (SstI-SacII
fragment) (Fig. 1, construct 5). Previous sequence analysis of this
region did not show a good match with the consensus promoter sequence
for 70; instead, a putative 54
promoter sequence was clearly identified (7).
Site-directed mutagenesis of the 54 consensus
region.
It is known that the most conserved regions of the
promoters recognized by E54 are the dinucleotides
GG and GC located near positions 
24 and 12 upstream from the
transcription start site. Changes in these bases interfere with
the ability of 54 to promote transcription
(4).
54
consensus promoter region present in the
SstI-SacII fragment. The putative nucleotides in
the 25, 24, and 12 positions were replaced by the nucleotide T. After mutagenesis and sequencing, this region was cloned upstream
of the 'uidA gene in pRK415 (Fig.
2).
|
-Glucuronidase activity was determined for each construct using cell
extracts. All mutational changes negatively affected -glucuronidase
activity (Fig. 2). The control contained a mutation at the 18
position, which is irrelevant for promoter recognition (4).
In this case, -glucuronidase activity was very similar to that of
the wild type (Fig. 2). These results provide evidence that promoter
activity detected in this region is dependent on the RNA polymerase
associated with the 54 factor.
It is known that integration host factor protein (IHF) binds to
specific sites placed between the 54 promoters and the
activator binding sites, which are usually located upstream of the
initiation site at approximately 100 to 150 bp. Therefore, it has
been proposed that IHF bends DNA, favoring contact of the activator
with E54 bound at the promoter. The 420-bp region
proposed to carry a flagellar promoter was analyzed using the program
Seqscan at www.bmb.psu.edu/nixon/webtools/molbiol.htm in order to
identify any potential IHF binding site. No matches above the program
threshold were found. However, it is still possible that a low-affinity
binding site with a poor match with the consensus sequence may exist.
Finally, two different palindromic sequences which may represent the
activator binding site were located at 145 and 127 bp upstream of
the 54 promoter (data not shown).
5' end mapping of the flagellar mRNA dependent on
54 promoters.
Putative 54 promoter
sequences have been identified upstream of the flagellar genes
flgB, fliK, and motA (GenBank
accession number U86454) (6; Ballado et al., unpublished). The
nucleotide sequence of each of these regions was aligned with the
sequence of the functional 54 promoter in the
fliN-fliO intercistronic region. The nucleotide residues
GGCA and TTGC are present in all sequences (data not shown). In order
to obtain evidence that these sequences correspond to functional
flagellar promoters, we examined if specific mRNA transcripts were
produced from these putative promoters.
|
54. Transcription of flgB and
fliK started 35 and 17 nt upstream of the ATG start
codon, respectively (data not shown). In all cases, the distance
between the 54 promoter sequence and the transcription
start site is consistent with the distance reported for functional
54 promoters (4).
The 5' end of the mRNA located upstream of fliO,
together with other evidence presented here, indicates that the
expression of the fliO operon depends on
E54. Moreover, a stable 5'-end mRNA was detected
upstream of other regions thought to carry a
54-dependent promoter. Therefore, these sequences
may represent the functional promoters of the
flgBCDEF and the fliKLMN operons in R. sphaeroides. Nevertheless, to obtain additional
evidence supporting the above conclusions it would be necessary to
determine the expression level of these promoters in an
rpoN background (lacking the rpoN1 and
rpoN2 genes).
Expression of the flagellar fliO promoter is not
dependent on growth conditions.
It has been shown for several
bacterial groups that flagellar synthesis is affected by environmental
conditions (9, 13). In the case of R. sphaeroides, flagellar control signals might be related to the
cell cycle and possibly independent of environmental conditions. To determine if growth conditions affect the
expression of fliOp, WS8 cells carrying the fusion
fliOp-'uidA in pRK415 were grown heterotrophically or
photoheterotrophically. No significant difference in the level of
-glucuronidase activity was observed, suggesting that the expression
of some of the components involved in flagellar synthesis is not
significantly affected by these growth conditions (Fig. 1). Since our
results are focused on only two extreme conditions, i.e., light and
oxygen, it remains to be investigated if other environmental conditions
modify the expression level of the flagellar promoters.
Is flagellar gene expression in R. sphaeroides hierarchical? In enteric bacteria, the best-characterized checkpoint in flagellar assembly is controlled by the protein FlgM (10, 15). To test if this checkpoint exists in R. sphaeroides, we investigated whether a functional HBB structure was necessary for flagellin gene expression.
Expression of fliC was evaluated by Northern blot analysis using total RNA from wild-type WS8 cells and from cells carrying a mutation in either the fliM or flgE gene. Transcripts of fliC were clearly detected in RNA preparations from wild-type and mutant strains (Fig. 4). However, the mutant strains showed a decrease in the quantity of fliC mRNA produced compared to that of WS8 cells. This result may be due to either a reduction in the amount of mRNA synthesized or a reduction in its stability. Despite this, fliC expression does not appear to be absolutely dependent on the presence of a functional HBB structure.
|
54 consensus promoter. However, in
agreement with a previous report, a sequence similar to that of the
28 consensus promoter (GenBank accession number
Y14687) is located approximately 51 bp upstream of the putative
ATG start codon (Fig. 4).
| |
DISCUSSION |
|---|
|
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
|
|---|
Structural components of the flagellum of R. sphaeroides have been recently characterized (3, 6, 7, 8, 19; Ballado et al., unpublished). However, still nothing is known about the factors that regulate the expression of the genes involved in motility. In this work, we identified several promoters responsible for the transcription of the flagellar genes involved in the formation of the basal body, the switch, and the hook.
This work showed that fliOp is a functional
54 promoter. Our results support the idea that this
promoter is responsible for the expression of fliO,
fliP, fliQ, fliR, and probably
flhB. Additional studies are in progress to define whether
this operon includes flhB and beyond.
A sequence similar to that of the 54 consensus promoter
was identified upstream of the fliK gene. The functionality
of this promoter sequence was supported by the identification of
the fliK 5'-end mRNA, the start site of which is within
the expected range for a functional 54 promoter (Fig.
3). On the other hand, the polar effect exerted by the mutation
fliK::TnphoA over fliM expression
suggests that fliK and fliM belong to the same
operon (Table 1). Together, these results support the idea that
the 54 promoter located upstream of fliK is
responsible for transcribing the fliK,
fliL, fliM, and fliN genes as a single
transcriptional unit. The inclusion of the fliN gene in this
operon was previously proposed from a complementation study of
a strain carrying the fliM::uidA-aadA mutation
(7).
A third transcriptional start site defined in this work was
located upstream of flgB. A sequence similar to that
of the 54 consensus promoter is at a proper
distance from the flgB mRNA initiation site.
Consequently, we suggest that this sequence is the functional
54 promoter responsible for the expression of the
flgB, flgC, flgD, flgE, and
flgF genes. The internal organization of this region has
been recently elucidated, and genetic evidence supports the idea that
these genes form an operon (Ballado et al., unpublished).
The data presented here allow us to propose that in
R. sphaeroides the expression of the flagellar
genes, whose products are involved in the assembly of the basal body,
the switch, and the hook structures, is dependent on
E54. This is in contrast with the situation found in
both S. enterica serovar Typhimurium and E. coli,
where the flagellar genes involved in the synthesis of these structures
are dependent on E70 and the FlhD-FlhC activator
complex. At a glance, R. sphaeroides flagellar gene
expression would appear to be similar to that observed in
Caulobacter crescentus, where the genes involved in the
formation of the rod and the hook are dependent on E54
(22). However, several of the genes reported here as
being dependent on 54 are dependent on
E73 in C. crescentus. Moreover, two flagellin
genes of C. crescentus are dependent on E54
(22), whereas the regulatory region of fliC of
R. sphaeroides shows a sequence resembling that of a
28 promoter, as occurs in enteric bacteria (E. coli and Salmonella). Therefore, the flagellar genetic
system of R. sphaeroides seems to combine features from
these two systems.
As mentioned before, in S. enterica serovar Typhimurium the
flagellar genes follow a hierarchical order of expression; therefore, the transcription of the genes placed at a low level of the hierarchy is dependent on the expression of the genes at a higher level. In this
regard, in R. sphaeroides the activity of
fliOp and the expression of the fliM gene, both
of which were tested as the activity of the 'uidA reporter
gene, have been shown to be insensitive to the presence of other
mutations in flagellar genes, such as fliR, fliM,
and flgE (this work and data not shown). Therefore, we
suggest that all these genes belong to the same transcriptional class
and may be assigned to class II. Interestingly, genetic evidence has
suggested that the motA gene may be dependent on E54 (6). Therefore, motA could be
expressed simultaneously with the genes encoding the structural
components of the basal body and the hook. Additional studies are
required to define whether the mot genes, together with the
fli and the flg genes, can be grouped within the
same transcriptional class.
According to current knowledge of the 54 factor
(17), the existence of an activator protein must be
considered. This protein may represent the flagellar class I
in R. sphaeroides. Although its identity remains
to be elucidated, it could be suggested that this protein would
belong to the family of 54-dependent activator proteins.
Finally, the class III genes could be transcribed by
E28, as seems to be the case for the fliC
gene (Fig. 4). The reduction in the amount of the fliC
mRNA observed in the flgE and fliM strains may represent the control that class II genes exert over the expression of 28-dependent genes. This negative control does not
seem to be absolute and allows a certain level of fliC
expression even in the absence of a functional HBB structure.
Supporting the idea that class III genes are expressed from
E28 promoters, we have found that fliD, which
is expected to belong to this class, also shows a 28
consensus promoter a few base pairs upstream of the putative initiation
codon (data not shown).
In summary, our results support the idea that in R. sphaeroides the expression of the flagellar genes is
controlled according to a hierarchical pattern. Class II genes are
dependent on E54, whereas class III genes seem to be
dependent on E28. The control that class II genes
exert over the expression of class III genes does not seem to be tight,
and the molecular bases underlying this weak regulation are under
investigation in our laboratory.
| |
ACKNOWLEDGMENTS |
|---|
We are indebted to Laura Velázquez for her comments and critical review of the manuscript. We thank T. Ballado for technical assistance. We also thank Luis Servín-González and E. Silva-Herzog for helpful discussions.
This work was supported in part by DGAPA grant IN221598 to G.D. and L.C.
| |
FOOTNOTES |
|---|
* Corresponding author. Mailing address: Departamento de Biología Molecular, Instituto de Investigaciones Biomédicas, UNAM, Ap. Postal 70-228, 04510 Mexico City, Mexico. Phone: (525) 622 38 24. Fax: (525) 622 38 91. E-mail: rosal{at}servidor.unam.mx.
| |
REFERENCES |
|---|
|
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
|
|---|
| 1. | Aizawa, S.-I. 1996. Flagellar assembly in Salmonella typhimurium. Mol. Microbiol. 19:1-5[CrossRef][Medline]. |
| 2. | Ausubel, F. M., R. E. Kingston, D. D. Moore, J. G. Seidman, J. A. Smith, and K. Struhl (ed.). 1987. Current protocols in molecular biology. John Wiley and Sons, New York, N.Y. |
| 3. | Ballado, T., A. Campos, L. Camarena, and G. Dreyfus. 1996. Flagellar genes from Rhodobacter sphaeroides are homologous to genes of the fliF operon of Salmonella typhimurium and to the type-III secretion system. Gene 170:69-72[CrossRef][Medline]. |
| 4. |
Barrios, H.,
B. Valderrama, and E. Morett.
1999.
Compilation and analysis of 54-dependent promoter sequences.
Nucleic Acids Res.
27:4305-4313 |
| 5. |
Davis, J.,
T. J. Donohue, and S. Kaplan.
1988.
Construction, characterization, and complementation of a Puf mutant of Rhodobacter sphaeroides.
J. Bacteriol.
170:320-329 |
| 6. | Deepan, S. H., and R. E. Sockett. 1995. Analysis of the motA flagellar motor gene from Rhodobacter sphaeroides, a bacterium with a unidirectional, stop-start flagellum. Mol. Microbiol. 17:961-969[CrossRef][Medline]. |
| 7. |
García, N.,
A. Campos,
A. Osorio,
S. Poggio,
B. González-Pedrajo,
L. Camarena, and G. Dreyfus.
1998.
The flagellar switch genes fliM and fliN of Rhodobacter sphaeroides are contained in a large flagellar gene cluster.
J. Bacteriol.
180:3978-3982 |
| 8. |
González-Pedrajo, B.,
T. Ballado,
A. Campos,
R. E. Sockett,
L. Camarena, and G. Dreyfus.
1997.
Structural and genetic analysis of a mutant of Rhodobacter sphaeroides WS8 deficient in hook length control.
J. Bacteriol.
179:6581-6588 |
| 9. | Heuner, K., B. Brand, and J. Hacker. 1999. The expression of the flagellum of Legionella pneumophila is modulated by different environmental factors. FEMS Microbiol. Lett. 175:69-77[CrossRef][Medline]. |
| 10. |
Hughes, K. T.,
K. L. Gillen,
M. J. Semon, and J. E. Karlinsey.
1993.
Sensing structural intermediates in bacterial flagellar assembly by export of a negative regulator.
Science
262:1277-1280 |
| 11. | Ikebe, T., S. Iyoda, and K. Kutsukake. 1999. Promoter analysis of the class 2 flagellar operons of Salmonella. Genes Genet. Syst. 74:179-183[CrossRef][Medline]. |
| 12. |
Jefferson, R. A.,
S. M. Burgess, and D. Hirsh.
1986.
-Glucuronidase from Escherichia coli as a fusion marker.
Proc. Natl. Acad. Sci. USA
83:8447-8451 |
| 13. | Kapatral, V., J. W. Olson, J. C. Pepe, and S. A. Minnich. 1996. Temperature-dependent regulation of Yersinia enterocolitica class III flagellar genes. Mol. Microbiol. 19:1061-1071[CrossRef][Medline]. |
| 14. |
Kunkel, T. A.
1985.
Rapid and efficient site-specific mutagenesis without phenotypic selection.
Proc. Natl. Acad. Sci. USA
82:488-492 |
| 15. | Kutsukake, K. 1994. Excretion of the anti-sigma factor through a flagellar substructure couples flagellar gene expression with flagellar assembly in Salmonella typhimurium. Mol. Gen. Genet. 243:605-612[Medline]. |
| 16. | Macnab, R. M. 1996. Flagella and motility, p. 123-145. In F. C. Neidhardt, R. Curtiss III, J. L Ingraham, E. C. C. Lin, K. B. Low, B. Magasanik, W. S. Reznikoff, M. Riley, M. Schaechter, and H. E. Umbarger (ed.), Escherichia coli and Salmonella: cellular and molecular biology, 2nd ed. American Society for Microbiology, Washington, D.C. |
| 17. |
Merrick, M. J.
1993.
In a class of its own the RNA polymerase sigma factor 54 (N).
Mol. Microbiol.
10:903-909[Medline].
|
| 18. | Mizushima, T., R. Koyanagi, T. Katayama, T. Miki, and K. Sekimizu. 1997. Decrease in expression of the master operon of flagellin synthesis in a dnaA46 mutant of Escherichia coli. Biol. Pharm. Bull. 20:327-331[Medline]. |
| 19. |
Shah, D. S. H.,
J. P. Armitage, and R. E. Sockett.
1995.
Rhodobacter sphaeroides WS8 expresses a polypeptide that is similar to MotB of Escherichia coli.
J. Bacteriol.
177:2929-2932 |
| 20. |
Sistrom, W. R.
1962.
The kinetics of the synthesis of photopigments in Rhodopseudomonas sphaeroides.
J. Gen. Microbiol.
28:607-616 |
| 21. |
Soutourina, O.,
A. Kolb,
E. Krin,
C. Laurent-Winter,
S. Rimsky,
A. Danchin, and P. Bertin.
1999.
Multiple control of flagellum biosynthesis in Escherichia coli: role of H-NS protein and the cyclic AMP-catabolite activator protein complex in transcription of the flhDC master operon.
J. Bacteriol.
181:7500-7508 |
| 22. | Wu, J., and A. Newton. 1997. Regulation of the Caulobacter flagellar gene hierarchy; not just for motility. Mol. Microbiol. 24:239. |
| 23. | Yanagihara, S., S. Iyoda, K. Ohnishi, T. Iino, and K. Kutsukake. 1999. Structure and transcriptional control of the flagellar master operon of Salmonella typhimurium. Genes Genet. Syst. 74:105-111[CrossRef][Medline]. |
| 24. |
Zhu, Y. S., and S. Kaplan.
1985.
Effects of light, oxygen, and substrates on steady-state levels of mRNA coding for ribulose-l,5'-bisphosphate carboxylase and light-harvesting and reaction center polypeptides in Rhodopseudomonas sphaeroides.
J. Bacteriol.
162:925-932 |
Journal of Bacteriology, October 2000, p. 5787-5792, Vol. 182, No. 20
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
This article has been cited by other articles:
-
Pena-Sanchez, J., Poggio, S., Flores-Perez, U., Osorio, A., Domenzain, C., Dreyfus, G., Camarena, L.
(2009). Identification of the binding site of the {sigma}54 hetero-oligomeric FleQ/FleT activator in the flagellar promoters of Rhodobacter sphaeroides. Microbiology
155: 1669-1679
[Abstract] [Full Text] -
Poggio, S., Osorio, A., Dreyfus, G., Camarena, L.
(2006). Transcriptional Specificity of RpoN1 and RpoN2 Involves Differential Recognition of the Promoter Sequences and Specific Interaction with the Cognate Activator Proteins. J. Biol. Chem.
281: 27205-27215
[Abstract] [Full Text] -
Ballado, T., Camarena, L., González-Pedrajo, B., Silva-Herzog, E., Dreyfus, G.
(2001). The Hook Gene (flgE) Is Expressed from the flgBCDEF Operon in Rhodobacter sphaeroides: Study of an flgE Mutant. J. Bacteriol.
183: 1680-1687
[Abstract] [Full Text]
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»