Figure 1.

Multifactorial physicochemical requirements for C. burnetii replication. The ability of C. burnetii to replicate with alteration of major physiologically relevant physicochemical variables was tested by incubating C. burnetii in ACCM-2 under indicated conditions over 8 days. (A) Under standard culture conditions at 37°C in an atmosphere of 5% O₂ and 5% CO₂ the pH optimum for replication was between 4.5 and 4.75. Under optimal pH conditions, a combination of reduced O₂ (B) and elevated CO₂ (C) was necessary for replication. (D) Under conditions of optimal pH, O₂, and CO₂, a reduction in culture temperature from 37° to 27°C resulted in an extended lag phase. Data are presented as the mean ± SD (n = 3), asterisk indicates statistical significance (ANOVA, Sidak's post-test, P < 0.05).