The strains employed in this study included methicillin-susceptible strain SH1000 [63 (link)] and a TTO-selected SCV, SH1000-TTORS-1 [30 (link)]. Mueller Hinton broth (MHB), Luria broth (LB), and bacteriological-grade agar were purchased from Becton Dickinson and Company (Franklin Lakes, NJ). All chemicals were purchased from Sigma Aldrich Co. (St. Louis, MO), unless otherwise noted. TTO utilized for this study was purchased from Aura Cacia (Urbana IA, Melaleuca alternifolia product code A191139) and contained 44.1% terpinen-4-ol and 3.9% α-terpineol (v/v) which complies with the TTO International Standard (ISO 4730).
Gradient plate analysis was performed with MHB overnight cultures and Mueller Hinton agar (MHA) as previously described [64 (link)], and confluent growth along the gradient was measured in mm ± standard deviation (n = 3). Colony size determination was carried out as previously described [29 (link)] by diluting overnight MHB cultures and plating on MHA and MHA containing 0.1% (v/v) Tween 80. Random colonies were then measured for each strain grown on both media using a caliper in mm ± standard deviation (n = 10).
Gradient plate analysis was performed with MHB overnight cultures and Mueller Hinton agar (MHA) as previously described [64 (link)], and confluent growth along the gradient was measured in mm ± standard deviation (n = 3). Colony size determination was carried out as previously described [29 (link)] by diluting overnight MHB cultures and plating on MHA and MHA containing 0.1% (v/v) Tween 80. Random colonies were then measured for each strain grown on both media using a caliper in mm ± standard deviation (n = 10).
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