Effect of solar radiation and the subsequent dark periods on two newly isolated and characterized Antarctic marine bacteria

HERNÁNDEZ, E.. G.A. FERREYRA, W.P. MAC CORMACK

Polar Research

Año: 2004 vol. 23 p. 67 - 77

'lwo strainso fpsychrotoleranAt ntarcticm arineb acteriaw erci solatedand characlerizcuds ingb iochemicaal ndm oleculartc chniquesS. equencinogt 163 rRNA gene showed that UVvi strafu belongs to Ihe genrs Arthrobacter whereas UVps strain is relatedtothe Flexibacter q)bPhag.! Bactercides (FCB)g roup.R esponseofthest rainst o solarr adiationw ass tudiedd uring the summcr of 1999 in Potter Cove, near Jubany station (South Shetland Island,A ntarctica).T he effect of photosyntheticallayv ailabler adiation (PAR,400 - 700 nn). ultraviolelA (UV-A, 320 400 nm) and ultravioletB radiation (UV-8, 280-320 nm) on ccll viability was studied using mixed culluresinq uartzb ottlesc overcdw ilh interferentiafli ltersa ndexposedto solarr adiation.I n all experimentsf,o ur treatmentsw ereu sed:d ark (with light screenedo ut),P AR (with UV tadiations creenedo ut),P AR+UV-A (UV B screenedo ut) and PAR+UV A+UV-B. Undert he assayedc ordirions. PAR+UV-A and PAR+UV-A+UV-B radiation showed similar negative effects on the viabilily of the studied strains. However at the end ofthe exposureti me, mortality valuesi n PAR+UV-A+UV-B trea! ments were higher than those observed under PAR+UV-A lrcatments. ln both PAR+UV-A and PAR+UV-A+UV-B treatmentsw c observed high levels of hydrogcn peroxide compared with the da* control. The A hrcbacter UVvr sl|rain showed significant recovery in dark condilions after exposureto the PAR+ UV-A but not after the PAR+UV A +UV B treatmentT. his straiflo rovedt o be more resistant o UV radiationt han the FCB group-rclatcdU Vps strain.T he resultss howedt hal UV radiation has a deleteriouse ffecto n theseA ntarcticm arineb acteriaa nd also revealcdt hat the analysedc omponentos f the Antarcticb acterioplankton may havcd ifferentr esponsews hent hey are erposedt o the samei rradiance conditions.