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The four different σ 54 factors of Rhodobacter sphaeroides are not functionally interchangeable
Author(s) -
Poggio Sebastian,
Osorio Aurora,
Dreyfus Georges,
Camarena Laura
Publication year - 2002
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2002.03158.x
Subject(s) - rhodobacter sphaeroides , biology , rhodobacter , computational biology , genetics , bacteria , gene , mutant
Summary The σ 54 factor is highly conserved in a large number of bacterial species. From the complete genome sequence of Rhodobacter sphaeroides , it was possible to identify four different sequences encoding potentially functional σ 54 factors. In this work, we provide evidence that one of these copies ( rpoN 2) is specifically required to express the flagellar genes in this bacterium. A mutant strain carrying a lesion in the rpoN2 gene was unable to swim even though the RpoN1 and RpoN3 proteins were present in the cytoplasm. The possibility that the different copies of the σ 54 factor might be specific for the transcription of a particular subset of σ 54 promoters was reinforced by the fact that a mutant strain carrying a lesion in rpoN1 showed a severe growth defect in nitrogen‐free culture medium, even though the rpoN2 and rpoN4 genes were actively transcribed from a plasmid or from the chromosome. Different mech‐anisms that might be responsible for this specificity are discussed.