Global changes in gene expression in Sinorhizobium meliloti 1021 under microoxic and symbiotic conditions.
Sinorhizobium meliloti is an alpha-proteobacterium that alternates between a free-living phase in bulk soil or in the rhizosphere of plants and a symbiotic phase within the host plant cells, where the bacteria ultimately differentiate into nitrogen-fixing organelle-like cells, called bacteroids. As a step toward understanding the physiology of S. meliloti in its free-living and symbiotic forms and the transition between the two, gene expression profiles were determined under two sets of biological conditions: growth under oxic versus microoxic conditions, and in free-living versus symbiotic state. Data acquisition was based on both macro- and microarrays. Transcriptome profiles highlighted a profound modification of gene expression during bacteroid differentiation, with 16% of genes being altered. The data are consistent with an overall slow down of bacteroid metabolism during adaptation to symbiotic life and acquisition of nitrogen fixation capability. A large number of genes of unknown function, including potential regulators, that may play a role in symbiosis were identified. Transcriptome profiling in response to oxygen limitation indicated that up to 5% of the genes were oxygen regulated. However, the microoxic and bacteroid transcriptomes only partially overlap, implying that oxygen contributes to a limited extent to the control of symbiotic gene expression.
Becker
Anke
A
Institut für Genomforschung, Centrum für Biotechnologie, Universität Bielefeld, Postfach 100131, D-33501 Bielefeld, Germany. Anke.Becker@Genetik.Uni-Bielefeld.DE
Bergès
Hélène
H
Krol
Elizaveta
E
Bruand
Claude
C
Rüberg
Silvia
S
Capela
Delphine
D
Lauber
Emmanuelle
E
Meilhoc
Eliane
E
Ampe
Frédéric
F
de Bruijn
Frans J
FJ
Fourment
Joëlle
J
Francez-Charlot
Anne
A
Kahn
Daniel
D
Küster
Helge
H
Liebe
Carine
C
Pühler
Alfred
A
Weidner
Stefan
S
Batut
Jacques
J
D000220:Adaptation, Biological / Q000235:genetics / Q000502:physiology; D020869:Gene Expression Profiling / Q000379:methods; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D009586:Nitrogen Fixation / Q000235:genetics / Q000502:physiology; D010100:Oxygen / Q000494:pharmacology*; D010802:Phylogeny; D040081:Protein Array Analysis / Q000379:methods; D020543:Proteome / Q000235:genetics / Q000378:metabolism; D016962:Sinorhizobium meliloti / Q000235:genetics* / Q000378:metabolism; D013559:Symbiosis / Q000187:drug effects / Q000235:genetics* / Q000502:physiology; D014158:Transcription, Genetic / Q000235:genetics
D020543:Proteome; D010100:Oxygen