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A gene coding for a putative sigma 54 activator is developmentally regulated in Caulobacter crescentus
M V Marques1, S L Gomes, J W Gober
1Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, Brazil. mvmarque@usp.br
Journal of Bacteriology
|September 1, 1997
Summary
Researchers identified TacA, a novel sigma54 activator in Caulobacter crescentus, which does not affect flagellar motility but influences cell division and phage interactions, suggesting a new role for sigma54 in cell differentiation.
Area of Science:
- Microbiology
- Molecular Biology
- Bacterial Genetics
Background:
- The alternative sigma factor sigma54 regulates late flagellar gene expression in Caulobacter crescentus, with temporal and spatial control.
- FlbD is the sole known sigma54 activator, mediating flagellar gene expression and fliF promoter repression.
Purpose of the Study:
- To explore novel roles of sigma54 in Caulobacter crescentus metabolism and differentiation.
- To clone and characterize a potential new sigma54 activator, named tacA.
Main Methods:
- Cloning and characterization of the tacA gene.
- Sequence analysis of TacA, revealing similarity to NtrC family activators.
- Construction and analysis of a tacA insertional mutant (strain SP2016).
Main Results:
- TacA is not essential for flagellar biogenesis or motility, as the mutant retains polar structures and motility.
- The tacA mutant exhibits a high percentage of filamentous cells and a clear-plaque phenotype with phage phiCb5.
- TacA shares promoter sequence elements with class II flagellar genes and exhibits similar temporal expression patterns.
Conclusions:
- TacA represents a novel sigma54 activator in Caulobacter crescentus.
- TacA's function appears independent of flagellar biogenesis, suggesting a role in other cellular pathways.
- The findings indicate TacA may mediate sigma54 effects on pathways distinct from flagellar assembly, potentially impacting cell division and phage susceptibility.