Characterization of molecular mechanisms controlling fabAB transcription in Pseudomonas aeruginosa.
BACKGROUND
The FabAB pathway is one of the unsaturated fatty acid (UFA) synthesis pathways for Pseudomonas aeruginosa. It was previously noted that this operon was upregulated in biofilms and repressed by exogenous UFAs. Deletion of a 30 nt fabA upstream sequence, which is conserved in P. aeruginosa, P. putida, and P. syringae, led to a significant decrease in fabA transcription, suggesting positive regulation by an unknown positive regulatory mechanism.


RESULTS
Here, genetic and biochemical approaches were employed to identify a potential fabAB activator. Deletion of candidate genes such as PA1611 or PA1627 was performed to determine if any of these gene products act as a fabAB activator. However, none of these genes were involved in the regulation of fabAB transcription. Use of mariner-based random mutagenesis to screen for fabA activator(s) showed that several genes encoding unknown functions, rpoN and DesA may be involved in fabA regulation, but probably via indirect mechanisms. Biochemical attempts performed did fail to isolate an activator of fabAB operon.


CONCLUSIONS
The data suggest that fabA expression might not be regulated by protein-binding, but by a distinct mechanism such as a regulatory RNA-based mechanism.
Department of Microbiology, Immunology, and Pathology, IDRC at Foothills Campus, Colorado State University, Fort Collins, Colorado, United States of America.
Herbert P
HP
Schweizer
Kyoung-Hee
KH
Choi
D015099:3-Oxoacyl-(Acyl-Carrier-Protein) Synthase / Q000235:genetics / Q000378:metabolism; D020121:5' Untranslated Regions / Q000235:genetics; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D004251:DNA Transposable Elements / Q000235:genetics; D054889:Fatty Acid Synthase, Type II / Q000235:genetics / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D006836:Hydro-Lyases / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009690:Nucleic Acid Conformation; D009876:Operon; D011401:Promoter Regions, Genetic / Q000235:genetics; D011550:Pseudomonas aeruginosa / Q000235:genetics* / Q000378:metabolism; D016958:Pseudomonas putida / Q000235:genetics / Q000378:metabolism; D044224:Pseudomonas syringae / Q000235:genetics / Q000378:metabolism; D012329:RNA, Bacterial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000235:genetics*
D020121:5' Untranslated Regions; D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D005231:Fatty Acids, Unsaturated; D012329:RNA, Bacterial; D015534:Trans-Activators; D015099:3-Oxoacyl-(Acyl-Carrier-Protein) Synthase; D006836:Hydro-Lyases; D054889:Fatty Acid Synthase, Type II