Figure 3: PAO1 HCN emission during growth.

(a) Optical density (OD₆₀₀) growth curve for PAO1 in LB medium at 37 °C. The lag phase takes about 2 hours, followed by the log phase until about 4–6 hours’ growth after which the stationary state occurs. Final OD absorbance is about 1.7 at 600 nm. (b) Intensity of cumulated cyanide peaks from PAO1 during growth. The cumulated Raman intensity is the (2135 + 2189) cm⁻¹ SERS intensity on the PAO1 exposed substrate minus the background signal of the substrate exposed to LB emissions. It is seen that PAO1 starts producing HCN after 4 hours’ growth, which is at the end of its exponential/beginning of stationary growth phase. After 20 hours HCN is still detectable, although not as intense as after 4 hours. The shape of the CN curve resembles previous studies on P. aeruginosa HCN emission during growth^8,28.