PI-142 (JTK):

Incorporation of exogenous fatty acids by Pseudomonas nitroreducens TX1 grown solely on Tween emulsifiers

Tween emulsifiers were generally regarded as safe and are commonly used in food additives. Also, Tween 80 is implicated in the inhibition of biofilm formation by Pseudomonas aeruginosa colonizing medical implants. However, recent literatures related to effect of Tween on gut and medically relevant strains were scarce. The Gram-negative Gammaproteobacteria Pseudomonas nitroreducens strain TX1 is placed in the P. aeruginosa group. TX1 uses Tween 60, Tween 80, as well as the fatty acid oleate as sole carbon source in minimal mineral agar medium to grow. Tween 60 and Tween 80 are PEG-ylated sorbitan esterified with the fatty acids stearate and oleate, respectively. Opaque halos beneath agar surface were found on media supplemented with 0.5% Tween 60 and Tween 80, suggesting lipolytic activity. Subsequent total fatty acid analysis showed that 24% stearic acid and 33% of oleic acid were found in TX1 grown on Tween 60 and Tween 80 media, respectively. Less than 2% of the above two fatty acids were found in LB, nutrient agar, and succinate supplemented media. Also, TX1 has 25% oleate in its fatty acid composition while grown solely on oleate as carbon source. This suggest the bacteria take up fatty acids from the environments, and may thereby have its membrane properties, such as permeability, rigidity, etc., changed in regard to which fatty acids were taken up. The change in membrane properties could in turn impact gut microbiota when Tween emulsifiers are consumed, or it could contribute to the biofilm inhibition capability of Tween. This study shows strain TX1, a close relative of the medically-important P. aeruginosa, takes up exogenous fatty acids, which can be used as a model system to study impact of fatty acid-bearing emulsifier on Gram-negative bacteria. Whether the fatty acids are stored intracellularly or incorporated to membranes, as well as cell envelope properties will be studied to evaluate effects of exogenous fatty acids on cells.

keywords:*Pseudomonas nitroreducens*,fatty acids,Tween,emulsifiers