Fig. 6

Growth curves and specific growth rates of mutants at 40 °C with the concentration of tetracycline at 0 or 0.2 µg/mL. The tetracycline concentration in the culture medium of figures a, c, e and g was 0 µg/mL, while the tetracycline concentration in the culture medium of figures b, d, f and h was 0.2 µg/mL. The media in figures a–d and the left of the red dashed line in figure g and h were RM, while the media in figures e, f and the right of the red dashed line in figure g and h were RM supplemented with 50 µg/mL spectinomycin. ZM4 was wild-type strain used as the control for mutants with the native promoter replaced by an inducible promoter P_tet. ZM4 (pEZ_Ep) was ZM4 strain containing a shuttle vector pEZ15Asp as the control for recombinant strains over-expressing candidate genes. ZM4_XXX referred to mutants with native promoters replaced by an inducible promoter P_tet (for example, ZM4_005 and ZM4_1465 referred to gene pZYM36_005 and ZMO1465 with their native promoters replaced by the inducible promoter P_tet, respectively.). ZM4 (pEZ_XXX) referred to recombinant strains over-expressing candidate genes. For example, ZM4 (pEZ_clpB) referred to ZM4 with an extra copy of clpB driving by P_tet on the shuttle vector pEZ15Asp except that groESL in ZM4 (pEZ_groESL) was driven by its native promoter. One-way ANOVA of specific growth rate of mutants at 40 °C were conducted with ZM4 or ZM4 (pEZ_Ep) as the control, * represents a significant difference (0.01 < P-value < 0.05), ** represents a very significant difference (P-value < 0.01), *** represents P-value < 0.001, **** represents P-value < 0.0001