Inhibition ofEscherichia colirespiratory enzymes by short visible femtosecond laser irradiation

Abstract

Abstract:Visible femtosecond laser is shown to be capable of selectively inactivating a wide spectrum of microorganisms in a wavelength and pulse width dependent manner.However, the mechanism of how visible femtosecond laser affects the viability of different microorganisms is still elusive. In this report, the cellular surface properties, membrane integrity and metabolic rate of Escherichia coli (E.coli) irradiated by a visible femtosecond laser (λ=415nm, pulse width=100fs) with different exposure time were investigated. Our results showed that femtosecond laser treatment for 60 minutes (min) led to cytoplasmic leakage, protein aggregation and alternation of the physical properties of E. coli cell membrane. In comparison, a 10 min exposure of bacteriatofemtosecond laser irradiation induced an immediate reduction of 75% of the glucose-dependent respiratory rate, while the cytoplasmic leakage was not detected.Results from enzymatic assays showed that oxidases and dehydrogenases involving in E.coli respiratory chain exhibited divergent susceptibility after laser irradiation. This early commencement of respiratory inhibition after a short irradiation is presumed to play a dominant effect on the early stage of bacteria inactivation.

Transient photothermal inactivation of Escherichia coli stained with visible dyes by using a nanosecond pulsed laser

“…In this study, we demonstrated the efficient inactivation of E. coli stained with safranin or rhodamine B dyes by using a low-power and easily available nanosecond visible pulse laser and obtained 3-log inactivation of E. coli in a short period of treatment time, on the order of 10 min, with a relatively low irradiation dose on the order of 50 kJ/cm 2 . The treatment time and dose magnitude was much faster and much lower, respectively, than those obtained with a fs laser 31,32 . We used a staining treatment for the inactivation of E. coli because, as shown in Fig.…”

“…This method seems to offer minimal concern of adverse effects to the human body 31 . However, fs laser inactivation methods have the following disadvantages: (1) a fs laser system is very expensive and cannot be easily obtained by everybody, (2) the inactivation efficiency is low thus it requires a long treatment time of more than 1 h 26 – 28 for inactivation, and (3) it requires an extremely high peak power of the fs pulse on the order of 100 MW/cm 2 for the inactivation of micrometer-sized bacteria 32 . These features impede the scalability and practical implementation of this photonic inactivation process.…”

Selective Photonic Disinfection of Cell Culture Using a Visible Ultrashort Pulsed Laser

“…The porphyrin molecules produced reactive oxygen species (ROS) upon the 405nm irradiation which damaged nucleic acids of the bacterium, causing the inactivation of MRSA. Lu et al[27] observed that E-coli bacteria could be efficiently inactivated by the USP laser irradiation at a wavelength of 425 nm. They suggested that the density-dependent protein aggregation induced by the visible USP laser irradiation inactivated the E-coli bacteria.…”

Mechanism of transient photothermal inactivation of bacteria using a wavelength-tunable nanosecond pulsed laser

“…This method seems to result in minimal adverse effects on the human body 38 . However, fs laser inactivation methods have the following disadvantages: (i) fs laser systems are very expensive and are not readily available, (ii) the inactivation efficiency is low; thus, it requires a long treatment time of more than 1 h 34 – 36 for inactivation, and (iii) it requires an extremely high peak power of the fs pulse for the inactivation of micrometre-sized bacteria 39 . These features impede the scalability and practical implementation of this photonic inactivation process.…”