Reactive oxygen species generated by infrared laser light in optical tweezers inhibits the germination of bacterial spores

Abstract

Bacterial spores are highly resistant to heat, radiation and various disinfection chemicals. The impact of these on the biophysical and physicochemical properties of spores can be studied on the single‐cell level using optical tweezers. However, the effect of the trapping laser on spores' germination rate is not fully understood. In this work, we assess the impact of 1064 nm laser light on the germination of Bacillus thuringiensis spores. The results show that the germination rate of spores after laser exposure follows a sigmoid dose‐response relationship, with only 15% of spores germinating after 20 J of laser light. Under anaerobic growth conditions, the percentage of germinating spores at 20 J increased to 65%. The results thereby indicate that molecular oxygen is a major contributor to the germination‐inhibiting effect observed. Thus, our study highlights the risk for optical trapping of spores and ways to mitigate it.

Hypervirulent R20291 Clostridioides difficile spores show disinfection resilience to sodium hypochlorite despite structural changes

“…In general, we operated the laser at a fixed output power of 100 mW corresponding to a power of about 60 mW in the sample (total energy of 1.2 J when exposed for 20 seconds). This power chosen was well below those previously recorded to damage spores [ 61 , 62 ].…”

Monitoring bacterial spore metabolic activity using heavy water-induced Raman peak evolution

“…Thus, we acquire data from 30 spores for each experiment and the results of this study are based on 30 technical replicates and 3 biological replicates. The laser power and accumulation times result in a total applied energy of ∼6 J on the spores, well below the 20 J shown to cause spore damage [26], with previous studies suggesting extensive laser light exposure may inhibit spore germination and growth via generation of reactive oxygen species [27]. We keep the spores trapped at a consistent height of 100 µm above the glass surface to maintain a consistent baseline for the spectra with minimal influence from the coverslip.…”

A Lab-on-A-Chip Utilizing Microwaves for Bacterial Spore Disruption and Detection

“…When measuring Raman spectra, we used ~60 mW laser power (in the sample) and performed 2 accumulations of 10 s each. This dose of 785 nm light is significantly lower than what is harmful to spores and does not disrupt the spore bodies (Malyshev et al, 2022d(Malyshev et al, , 2022b. We measured at least 100 individual spores for each experimental set.…”