Genetic analysis of acyl-CoA carboxylases involved in lipid accumulation in Rhodococcus jostii RHA1

Area of Science:

• Biochemistry and Molecular Biology
• Microbial Physiology
• Genomics and Bioinformatics

Background:

• Actinomycetes utilize biotin-dependent acyl-CoA carboxylases (ACCs) with varied structures and substrate specificities.
• Rhodococcus jostii RHA1 possesses numerous putative ACC domains and subunits, suggesting complex metabolic roles.

Purpose of the Study:

• To investigate the roles of specific ACC subunits, RO01202 and RO04222, in Rhodococcus jostii RHA1.
• To determine the essentiality of these ACCs for growth and their contribution to lipid biosynthesis under varying conditions.

Main Methods:

• Bioinformatic analysis of the Rhodococcus jostii RHA1 genome to identify putative ACC domains and subunits.
• Construction and analysis of mutant strains for genes encoding RO01202 and RO04222.
• Assessment of growth rates in rich and minimal media with varying nitrogen concentrations.
• Quantification of triacylglycerol and mycolic acid accumulation in wild-type and mutant strains.

Main Results:

• Neither RO01202 nor RO04222 is essential for R. jostii growth in standard rich or high-nitrogen minimal media, indicating overlapping functions.
• A mutant lacking RO04222 showed reduced accumulation of triacylglycerols and mycolic acids, highlighting its role in lipid biosynthesis.
• RO01202 was found to be essential for growth exclusively in minimal media with low nitrogen concentrations.

Conclusions:

• RO04222 is a multidomain ACC contributing significantly to lipogenesis and lipid accumulation in R. jostii RHA1.
• RO01202 represents a novel essential component for R. jostii growth under specific nutrient-limiting conditions (low nitrogen).
• This study underscores the functional plasticity and condition-dependent essentiality of ACCs within actinobacteria.