In Vitro Laser Ablation of Natural Marine Biofilms

Abstract

We studied the efficiency of pulsed low-power laser irradiation of 532 nm from an Nd:YAG (neodymiumdoped yttrium-aluminum-garnet) laser to remove marine biofilm developed on titanium and glass coupons. Natural biofilms with thicknesses of 79.4 ؎ 27.8 m (titanium) and 107.4 ؎ 28.5 m (glass) were completely disrupted by 30 s of laser irradiation (fluence, 0.1 J/cm 2 ). Laser irradiation significantly reduced the number of diatoms and bacteria in the biofilm (paired t test; P < 0.05). The removal was better on titanium than on glass coupons.The growth of biofilms on industrially important structures is harmful. Methods commonly employed to prevent its formation include chemical treatment of the water column by biocides or coating the surfaces with antifouling paints. As these methods invariably lead to pollution, environmentally friendly methods are desirable. Electromagnetic radiations such as UV and laser are known to cause bacterial mortality (1,6,7,16). However, the utility of laser irradiation in abating bacterial attachment and removing biofilm has rarely been studied (10,11). Earlier studies showed a considerable reduction in the viable count of the bacterium Pseudoalteromonas carrageenovora at laser fluence of 0.1 J/cm 2 for short duration (10 min). The laser-irradiated bacterial biofilms took considerable time to reach the preirradiated level (15). These observations led us to study the impacts of laser irradiation on natural biofilms developed on experimental coupons exposed to seawater. In this article, we summarize the impacts with emphasis on the bacterial and diatom components of the natural biofilms.Experimental coupons. Borosilicate laboratory glass slides and titanium (Japanese Industrial Standard grade 1) sheets were cut into sections 2 by 1 by 0.1 cm and used as experimental coupons. These materials were selected because (i) they were nontoxic, inert, and resistant to corrosion and (ii) to compare laser impacts on biofilms developed on metallic and nonmetallic hydrophilic surfaces. For example, some part of the irradiation passes through glass, while it gets absorbed and/or reflected from titanium. The temperature rise in the medium and on the coupon surface during irradiation was determined by using a temperature probe (Custom thermometer CT-2310). The titanium coupons were used in the asreceived condition.Laser. The laser used (GCR-170; Spectra-Physics) for this study was an Nd:YAG (neodymium-doped yttrium-aluminumgarnet) laser in the 2nd harmonic mode, delivering green light at 532 nm. The pulse width and repetition rate of this laser were 5 ns and 10 Hz, respectively. The peak power was 20 MW cm Ϫ2 , and the fluence (intensity of laser irradiation expressed as joules per square centimeter) per pulse tested was 0.1 J cm Ϫ2 (kept the same as in our previous studies) (10)(11)(12)14). Laser irradiation in the green light area was used because its attenuation rate in the water column is low.Natural biofilm. In May 2003, 20 coupons each of titanium and glass were fixed onto an assembly and suspende...

Visible laser and UV‐A radiation impact on a PNP degrading Moraxella strain and its rpoS mutant

“…In any case, the laser radiation in the visible area was found to be a promising tool for the removal of biofilms from the surfaces and might be useful in many industrial uses such as dental application or the treatment of ballast water tanks, for example. This observation agrees with earlier studies (Nandakumar et al, 2004a). To conclude, in suspended culture of Moraxella strain UV radiation resulted in a higher killing rate than by the visible laser light.…”

“…Ever since the invention of the laser (Maiman, 1960), its ability to kill bacteria has been explored and practiced (Wilson, 1993;Deckelbaum, 1994). Recently, the ability of visible laser radiation (532 nm) to remove marine and single species biofilms formed on the experimental surfaces has been studied (Nandakumar et al, 2004a). Additionally, reports are also available on the possibility of using visible laser light as an antifouling tool, that is, to kill the larvae of biofouling organisms (Nandakumar et al, 2003b).…”

“…In recent studies, Nandakumar et al (2002;2003a,b) have shown that laser light in the green portion of the visible light region resulted in a significant mortality in a marine bacterium Pseudoalteromonas carrageenovora, marine diatoms Skeletonema costatum and Chaetoceros gracilis, and in the larvae of the fouling barnacle Balanus amphitrite. Additionally, laser light in the green light area has been shown to dislodge marine biofilms from coupon surfaces (Nandakumar et al, 2004a).…”

Isolation and characterization of Pseudoalteromonas ruthenica (SBT033), an EPS-producing biofilm bacterium from the seawater intake point of a tropical power station

“…(Nichols et al 2004;Park et al 2005;Evans et al 2007;Nam et al 2007). Such studies have focused on the isolation of Pseudoalteromonas from diverse habitats, its biopolymer (including EPS) production and biofilm formation (Nichols et al 2004;Nandakumar et al 2004). Recently, Nichols et al (2004) isolated bacteria belonging to the Pseudoalteromonas from Antarctic waters and studied EPS production in batch cultures.…”

Molecular level damages of low power pulsed laser radiation in a marine bacterium Pseudoalteromonas carrageenovora

“…Some of these types of irradiations are used in the treatment of diseases and sterilization of surgical tools (Deckelbaum 1994). On the other hand, recent studies have shown that laser irradiation can be used as a tool to remove biofilms formed on solid surfaces (Nandakumar et al. 2002b, 2004a,b).…”