Impact of Pulsed Nd:YAG Laser Irradiation on the Growth and Mortality of the Biofilm Forming Marine Bacterium Pseudoalteromonas carrageenovora

Nandakumar, Kutty Selva; Obika, Hideki; Shinozaki, Tatsuya; Ooie, Toshihiko; Utsumi, Akihiro; Yano, Tetsuo

doi:10.1080/08927010290032377

Cited by 20 publications

(33 citation statements)

References 14 publications

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“…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).…”

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“…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.…”

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In Vitro Laser Ablation of Natural Marine Biofilms

Nandakumar

Obika

Utsumi

et al. 2004

Appl Environ Microbiol

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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...

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In Vitro Laser Ablation of Natural Marine Biofilms

Nandakumar

Obika

Utsumi

et al. 2004

Appl Environ Microbiol

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“…All the mechanisms, which lead to death in bacteria due to treatment using visible laser light, are not clearly understood (Ward et al, 2000). 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).…”

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

Nandakumar

Keeler

Schraft

et al. 2006

Biotech & Bioengineering

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The role of stationary phase sigma factor gene (rpoS) in the stress response of Moraxella strain when exposed to radiation was determined by comparing the stress responses of the wild-type (WT) and its rpoS knockout (KO) mutant. The rpoS was turned on by starving the WT cultures for 24 h in minimal salt medium. Under non-starved condition, both WT and KO planktonic Moraxella cells showed an increase in mortality with the increase in duration of irradiation. In the planktonic non-starved Moraxella, for the power intensity tested, UV radiation caused a substantially higher mortality rate than did by the visible laser light (the mortality rate observed for 15-min laser radiation was 53.4 +/- 10.5 and 48.7 +/- 8.9 for WT and KO, respectively, and 97.6 +/- 0 and 98.5 +/- 0 for 25 s of UV irradiation in WT and KO, respectively). However, the mortality rate decreased significantly in the starved WT when exposed to these two radiations. In comparison, rpoS protected the WT against the visible laser light more effectively than it did for the UV radiation. The WT and KO strains of Moraxella formed distinctly different types of biofilms on stainless steel coupons. The KO strain formed a denser biofilm than did the WT. Visible laser light removed biofilms from the surfaces more effectively than did the UV. This was true when comparing the mortality of bacteria in the biofilms as well. The inability of UV radiation to penetrate biofilms due to greater rates of surface absorption is considered to be the major reason for the weaker removal of biofilms in comparison to that of the visible laser light. This result suggests that high power visible laser light might be an effective tool for the removal of biofilms.

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“…The pulsed laser irradiations are harmful to various spectrums of bacteria (Nandakumar et al, 2002a;Okamoto et al, 1992;Ward et al, 2000;Yeo et al, 1998). These irradiations have therefore been used to sterilize surgical instruments (Powell and Whisenant, 1991).…”

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Laser impact assessment in a biofilm‐forming bacterium Pseudoalteromonas carrageenovora using a flow cytometric system

Nandakumar¹,

Obika²,

Shinozaki³

et al. 2003

Biotech & Bioengineering

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Impact by pulsed laser irradiations from an Nd:YAG laser on the marine biofilm-forming bacterium Pseudoalteromonas carrageenovora has been studied using a flow cytometric system. The biofilm-forming bacteria in the planktonic state have been irradiated while flowing, and the mortality and bacterial attachment have been determined by exposing TiN coupons in the system. Coupons suspended in the non-irradiated bacterial flow were treated as the control. The fluence used in the study was 0.1 J/cm(2). Three flow rates (14, 28, and 42 cm/min) and two exposure durations (15 and 30 min) were tested. The results showed the increase in bacterial mortality with the decrease in flow rate. The maximum mortality of 27.5% was observed when the flow rate was 14 cm/min. The bacterial attachment increased with the increase in flow rate and exposure duration. The area of bacterial attachment on the experimental coupons exposed to the irradiated sample was significantly lesser than that for the nonirradiated sample. The results thus show in a flowing system, low power pulsed laser irradiations could reduce the bacterial attachment even though it did not cause significant mortality.

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Impact of Pulsed Nd:YAG Laser Irradiation on the Growth and Mortality of the Biofilm Forming Marine Bacterium Pseudoalteromonas carrageenovora

Cited by 20 publications

References 14 publications

In Vitro Laser Ablation of Natural Marine Biofilms

In Vitro Laser Ablation of Natural Marine Biofilms

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

Laser impact assessment in a biofilm‐forming bacterium Pseudoalteromonas carrageenovora using a flow cytometric system

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