Determining the mechanistic basis for the antimicrobial activity of citrus EO on the bank of mutants of Saccharomyces cerevisiae Σ1278b

Saccharomyces cerevisiae is one of the well characterised eukaryotic organisms, both physiologically and at the molecular level. Nowadays, a famous laboratory strain is frequently used “Σ1278b” where a systematic deletion collection has been constructed in this strain background. Here, we screened the library of Σ1278b for S. cerevisiae mutants resistant to the citral. Resistant mutants are those that can grow at EO concentrations previously found to inhibit the wild-type parent strain's growth. To better understand mechanism behind this behaviour, mutants were grouped into cellular component, biological process, and molecular function respectively. We chose to focus on resistant mutants, specifically those involved in Reactive Oxygen Species (fRMsr, AFG1, GRE3, TIM18, YNL080C…) as results postulating that citral has an antioxidant role, may have an anti-microbial function by inducing Yap1p and elevating the level of intracellular ROS, or decreasing the pentose phosphate pathway via the reactions of detoxification, or triggering the role of other proteins involved in the membrane-embedded core of the TIM22 complex by stopping apoptosis, or compensating the function of enzymes that detoxify H2O2. After screening the entire bank, sub minimum inhibitory concentration was used for both strains Wild type and DeltaSFL1. In the mutant deltaSFL1, the expression of FLO11 was increased by 21.63 fold when compared with the WT. The relative quantification of the gene expression was analyzed by Livak-Schimttgen method, revealing the citral potential in inhibiting visible growth of the yeasts. Moreover, the quantification was expressed with a higher expression for WT with 0.1% glucose (3.46 fold) followed by WT with 2% glucose (1.61 fold). As a result, in case of WT strain treated with citral, we hypothesized that the component may be acting as a quorum sensing inhibitor since its inhibiting the function of QSM, while in DeltaSFL1 strain it may be acting as a QSM.

Saccharomyces cerevisiae is one of the well characterised eukaryotic organisms, both physiologically and at the molecular level. Nowadays, a famous laboratory strain is frequently used “Σ1278b” where a systematic deletion collection has been constructed in this strain background. Here, we screened the library of Σ1278b for S. cerevisiae mutants resistant to the citral. Resistant mutants are those that can grow at EO concentrations previously found to inhibit the wild-type parent strain's growth. To better understand mechanism behind this behaviour, mutants were grouped into cellular component, biological process, and molecular function respectively. We chose to focus on resistant mutants, specifically those involved in Reactive Oxygen Species (fRMsr, AFG1, GRE3, TIM18, YNL080C…) as results postulating that citral has an antioxidant role, may have an anti-microbial function by inducing Yap1p and elevating the level of intracellular ROS, or decreasing the pentose phosphate pathway via the reactions of detoxification, or triggering the role of other proteins involved in the membrane-embedded core of the TIM22 complex by stopping apoptosis, or compensating the function of enzymes that detoxify H 2 O 2 . After screening the entire bank, sub minimum inhibitory concentration was used for both strains Wild type and DeltaSFL1. In the mutant deltaSFL1, the expression of FLO11 was increased by 21.63 fold when compared with the WT. The relative quantification of the gene expression was analyzed by Livak-Schimttgen method, revealing the citral potential in inhibiting visible growth of the yeasts. Moreover, the quantification was expressed with a higher expression for WT with 0.1% glucose (3.46 fold) followed by WT with 2% glucose (1.61 fold). As a result, in case of WT strain treated with citral, we hypothesized that the component may be acting as a quorum sensing inhibitor since its inhibiting the function of QSM, while in DeltaSFL1 strain it may be acting as a QSM.