Carnitine acts as a compatible solute in Brevibacterium linens

Area of Science:

• Microbiology
• Biochemistry
• Molecular Biology

Background:

• Carnitine, a trimethyl amino acid, is abundant in animal-derived materials.
• Brevibacterium linens ATCC 19391 is a bacterium relevant to food science and biotechnology.
• Osmotic stress significantly impacts microbial growth and metabolism.

Purpose of the Study:

• To investigate the role of L-carnitine as an osmoprotectant for Brevibacterium linens.
• To elucidate the metabolic fate and pathway of carnitine in B. linens under hyperosmotic conditions.
• To compare the effects of L-carnitine and its D-enantiomer on B. linens growth and osmolyte accumulation.

Main Methods:

• Microbial growth assays in media with varying osmotic strengths.
• Spectroscopic analysis (NMR) to identify accumulated compounds.
• Electrophoretic analysis to study protein expression related to osmolyte pathways.

Main Results:

• L-carnitine significantly stimulated B. linens growth under osmotic stress, comparable to glycine betaine.
• B. linens transiently accumulated L-carnitine and converted it into glycine betaine.
• The L-carnitine to glycine betaine conversion pathway is inducible by L-carnitine.
• D-carnitine did not enhance growth but was accumulated, and both isomers repressed ectoine synthesis.

Conclusions:

• L-carnitine serves as an effective osmoprotectant for B. linens, functioning through conversion to glycine betaine.
• The bacterium possesses an inducible metabolic pathway for utilizing exogenous carnitine under osmotic stress.
• Carnitine isomers modulate osmolyte profiles in B. linens, impacting endogenous osmolyte production.