FIG 7 .

Effects of temperature on the expression of the reb operon and R-body formation in free-living A. caulinodans cells. (A) β-Galactosidase activities of reb-lacZ and reb-lacZ ΔpraR strains. Bacterial cells were grown in the defined medium at the indicated temperatures to an OD₆₀₀ of approximately 1.0, and β-galactosidase activities were measured. Data are presented as means ± standard deviations from three replicate cultures. Statistical analysis was carried out for the reb-lacZ ΔpraR strain. Different letters indicate significant differences (P < 0.05, Tukey-Kramer). (B) Quantitative RT-PCR analysis of the reb operon in the WT and ΔpraR, ΔrebR, and ΔpraR ΔrebR mutant strains grown at 26 and 38°C. Data are expressed relative to those from the WT strain grown at 26°C and are presented as means ± standard deviations from three replicate cultures. Statistical analyses were carried out for each strain, respectively. Asterisks indicate significant difference (**, P < 0.01, Student’s t test). (C) TEM observations of free-living WT and ΔpraR strains. Bacterial cells were collected from the same cultures that were used for the quantitative RT-PCR analyses described in panel B. Arrowheads indicate R bodies.