Response of two antarctic marine bacterial strains to solar radiation

MAC CORMACK W; HERNÁNDEZ E; VÁZQUEZ S; FERREYRA G

Cancun, Mexico

Simposio; International Symposium on Microbial Ecology, ISME-10; 2004

&amp;amp;amp;lt;!-- /* Font Definitions */ @font-face {font-family:"Cambria Math"; panose-1:2 4 5 3 5 4 6 3 2 4; mso-font-charset:0; mso-generic-font-family:roman; mso-font-pitch:variable; mso-font-signature:-1610611985 1107304683 0 0 159 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-unhide:no; mso-style-qformat:yes; mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; mso-bidi-font-size:10.0pt; font-family:"Times New Roman","serif"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:EN-GB;} .MsoChpDefault {mso-style-type:export-only; mso-default-props:yes; font-size:10.0pt; mso-ansi-font-size:10.0pt; mso-bidi-font-size:10.0pt;} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --&amp;amp;amp;gt; Antarctic ozone depletion causes an increase of the UV-B radiation (280-320 nm). As this increase affect the activity of aquatic microorganisms, the aim of this research was to study the effects of environmental UV-B and UV-A (320-400 nm) on two Antarctic marine bacterial strains (Cithophaga-Flavobacterium-Bacteroides group-related UVps and Arthrobacter-UVvi). Studies were carried out under different irradiance conditions on Potter Cove (South Shetland Islands, Antarctica). In land experiments, quartz bottles containing mixed bacterial cultures were exposed to solar radiation. Four treatments were performed using interferential filters: Dark, PAR (400-700 nm), PAR+UV-A and PAR+UV-A+UV-B. Similar cultures (with and without interferential filter) were submerged in the water column at 0, 1 and 3 m. For both strains, land experiments showed a significant mortality (p<0.05) under treatments PAR+UV-A and PAR+UV-A+UV-B and a significant logistic regression (p<0.05) was obtained between mortality and UV-B dose (UVvi R2: 0.8477, UVps R2: 0.8811). UVps was more sensitive to UVB radiation, showing a LD50 of 1.2 kJ m-2 whereas UVvi showed a LD50 of 2.7 kJ m-2. Differences were not appreciated at UV-B dose higher than 5 kJ m-2. Water column experiments showed that deleterious effect of solar radiation was significant at 1 m but no at 3 m deep. When filters were present, UV-A+UV-B-dependent mortality was higher than those produced by the UV-A. Results suggested that activity of Antarctic marine bacteria could be mainly controlled by the harmful effects of solar UV radiation exposure. This negative effect was significant in the first meter of the water column.