title: Impact of pulsed Nd:YAG laser on the marine biofilm-forming bacteria Pseudoalteromonas carrageenovora: significance of physiological status.
abstract: The impact of pulsed Nd:YAG (neodymium-doped yttrium/aluminium garnet) laser irradiation on the marine biofilm-forming bacteria Pseudoalteromonas carrageenovora during two growth stages (log phase and stationary phase) and under two stresses (reduced temperature and nutrient limitation) was investigated. Bacteria were exposed to a laser fluence of 0.1 J x cm(-2) for 5, 10, and 15 min with a peak power of 20 MW x cm(-2), a pulse width of 5 ns, and an average power of 1 W x cm(-2) with a repetition rate of 10 Hz. The mortality of bacteria immediately after the irradiation as well as after a set period of time was determined. Mortality was higher among log-phase bacteria (72%) than bacteria in the stationary phase (51%) and those grown under nutrient limitation (51%). Bacteria grown at reduced temperature had a mortality of 49%. However, the differences in cell density of log-phase, stationary-phase, nutrient-limited, and low-temperature irradiated samples compared with controls after 5 h of incubation were 96, 93, 94, and 86%, respectively. The mortality values suggest that the same laser fluence has different degrees of effectiveness, depending on the physiological state of the bacteria.
authors.affiliation: Marine Eco-materials Research Group, National Institute of Advanced Industrial Science and Technology (AIST), Marine Resources and Environment Research Institute, Kagawa, Japan. n-kanavillil@aist.go.jp
authors.forename: Kanavillil
authors.initials: K
authors.lastname: Nandakumar
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Shinozaki
authors.forename: Hideki
authors.initials: H
authors.lastname: Obika
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Ooie
authors.forename: Akihiro
authors.initials: A
authors.lastname: Utsumi
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Yano
mesh_terms: D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D002455:Cell Division / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D006358:Hot Temperature; D007834:Lasers; D031161:Pseudoalteromonas / Q000502:physiology* / Q000528:radiation effects*; D011829:Radiation Dosage; D015019:Yttrium
chemical_list: D015019:Yttrium