Analysis of the fnrL gene and its function in Rhodobacter capsulatus

Area of Science:

• Bacterial Physiology
• Gene Regulation
• Microbial Metabolism

Background:

• The fnr gene encodes a regulatory protein essential for bacterial oxygen response.
• In Rhodobacter sphaeroides, the fnrL gene is vital for anaerobic photosynthetic growth and anaerobic respiration with alternative electron acceptors.
• FnrL is not essential for aerobic growth in R. sphaeroides.

Purpose of the Study:

• To clone and sequence the fnrL locus from Rhodobacter capsulatus.
• To investigate the role of the fnrL gene in R. capsulatus anaerobic growth and respiration.
• To compare the function of FnrL in R. capsulatus and R. sphaeroides.

Main Methods:

• Gene cloning and sequencing of the fnrL locus in R. capsulatus.
• Construction and phenotypic analysis of an R. capsulatus fnrL deletion mutant.
• Assessment of anaerobic growth with alternative electron acceptors (DMSO, trimethylamine oxide).
• Analysis of c-type cytochrome and reductase synthesis under anaerobic conditions.

Main Results:

• R. capsulatus strains with a deleted fnrL gene exhibit wild-type growth under photosynthetic or aerobic conditions.
• The R. capsulatus fnrL mutant fails to grow anaerobically with alternative electron acceptors like DMSO.
• Anaerobic DMSO-induced c-type cytochrome and reductase synthesis is abolished in R. capsulatus fnrL mutants.
• Similar to R. capsulatus, R. sphaeroides fnrL mutants also fail to synthesize the anaerobically, DMSO-induced reductase.

Conclusions:

• FnrL plays a critical role in anaerobic respiration with alternative electron acceptors in Rhodobacter species.
• FnrL regulates the synthesis of specific enzymes, such as DMSO-induced reductases, required for anaerobic growth.
• The findings highlight conserved and potentially divergent mechanisms of FnrL function across different Rhodobacter species.