Enhancing low pH tolerance of Candida glabrata Δmed15B by overexpressing genes elo1 and ole1

[Objective] To investigate the effect of mediator subunit Med15B mediated fatty acid metabolism on Candida glabrata low pH tolerance. [Methods] Overexpression of genes elo1 and ole1, encoding fatty acid elongase and Δ9 desaturase, in strain Δmed15B we obtained an overexpressed strain Δmed15B/elo1-ole1. The expression level of genes elo1 and ole1, the membrane fatty acid composition, the membrane integrity and stress tolerance of parent strain ATCC55, strain Δmed15B and overexpression strain Δmed15B/elo1-ole1 were determined and compared at pH 2.0 and pH 6.0. [Results] At pH 2.0, the expression level of genes elo1 and ole1 in overexpression strain Δmed15B/elo1-ole1 was increased by 4.1-fold and 3.3-fold compared to those of strain Δmed15B, and increased by 2.5-fold and 2.2-fold compared to those of parent strain ATCC55, respectively. The average acyl-chain length of overexpression strain Δmed15B/elo1-ole1 reached 17.4 longer than that of the deletion strain (16.8) and parent strain (17.1), and the ratio of unsaturated fatty acid to saturated fatty acid (UFA/SFA ratio) increased by 53.1% and 41.5%, respectively. Furthermore, the percentage of propidium iodide (PI)-stained cell in overexpression strain Δmed15B/elo1-ole1 was decreased by 60.8% and 37.7%, respectively, compared to that of strain Δmed15B and parent strain ATCC55. Similarly, overexpression strain Δmed15B/elo1-ole1 exhibited more tolerance to low pH and the half-maximal inhibition (IC50) values for pH stress was reached pH 2.3, which was pH 3.7 of strain Δmed15B and pH 3.1 of parent strain ATCC55. [Conclusion] These results indicated that overexpression genes elo1 and ole1 in strain Δmed15B can enhance cell tolerance to low pH by increasing the content of long chain and unsaturated fatty acids.

Duke Scholars

Author Pei Zhou Biochemistry