Nandakumar Kanavillil, Shinozaki Tatsuya, Obika Hideki, Ooie Toshihiko, Utsumi Akihiro, Yano Tetsuo
Marine Eco-materials Research Group, National Institute of Advanced Industrial Science and Technology (AIST), Marine Resources and Environment Research Institute, Kagawa, Japan.
Can J Microbiol. 2002 Apr;48(4):326-32. doi: 10.1139/w02-028.
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.
