Genome-wide analysis of the RpoN regulon in Geobacter sulfurreducens.
BACKGROUND
The role of the RNA polymerase sigma factor RpoN in regulation of gene expression in Geobacter sulfurreducens was investigated to better understand transcriptional regulatory networks as part of an effort to develop regulatory modules for genome-scale in silico models, which can predict the physiological responses of Geobacter species during groundwater bioremediation or electricity production.


RESULTS
An rpoN deletion mutant could not be obtained under all conditions tested. In order to investigate the regulon of the G. sulfurreducens RpoN, an RpoN over-expression strain was made in which an extra copy of the rpoN gene was under the control of a taclac promoter. Combining both the microarray transcriptome analysis and the computational prediction revealed that the G. sulfurreducens RpoN controls genes involved in a wide range of cellular functions. Most importantly, RpoN controls the expression of the dcuB gene encoding the fumarate/succinate exchanger, which is essential for cell growth with fumarate as the terminal electron acceptor in G. sulfurreducens. RpoN also controls genes, which encode enzymes for both pathways of ammonia assimilation that is predicted to be essential under all growth conditions in G. sulfurreducens. Other genes that were identified as part of the RpoN regulon using either the computational prediction or the microarray transcriptome analysis included genes involved in flagella biosynthesis, pili biosynthesis and genes involved in central metabolism enzymes and cytochromes involved in extracellular electron transfer to Fe(III), which are known to be important for growth in subsurface environment or electricity production in microbial fuel cells. The consensus sequence for the predicted RpoN-regulated promoter elements is TTGGCACGGTTTTTGCT.


CONCLUSIONS
The G. sulfurreducens RpoN is an essential sigma factor and a global regulator involved in a complex transcriptional network controlling a variety of cellular processes.
Leang
Ching
C
Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USA. leang@microbio.umass.edu
Krushkal
Julia
J
Ueki
Toshiyuki
T
Puljic
Marko
M
Sun
Jun
J
Juárez
Katy
K
Núñez
Cinthia
C
Reguera
Gemma
G
DiDonato
Raymond
R
Postier
Bradley
B
Adkins
Ronald M
RM
Lovley
Derek R
DR
D001426:Bacterial Proteins / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D055106:Genome-Wide Association Study; D045302:Geobacter / Q000235:genetics*; D005810:Multigene Family; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic; D051877:RNA Polymerase Sigma 54 / Q000235:genetics*; D018085:Regulon
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D051877:RNA Polymerase Sigma 54