Translation activity under ultraviolet radiation and temperature stress inthe cyanobacterium Nostoc sp.

Stress proteins are known to be expressed as a response to a number of exte rnal factors including ultraviolet radiation (UVR). In the present work, th e translation activity under elevated temperature and UVR stress has been s tudied in a Nostoc species isolated from an Andean lake (Cuzco, Peru). The viability of the cells is not equally affected by the two stresses; while 8 4% of the cells survive exposure to 42 degrees C, the viability after a UVR dose of 50 kJ m(-2) is 40%. Induction of the heat response prior to UV irr adiation does not improve cell survival of Nostoc cells subjected to UVR. A group of nine heat-shock proteins (hsps) is induced by the temperature shi ft from 18 to 50 degrees C (hsp 90, hsp 75, hsp 69, hsp 67, hsp 45, hsp 22, hsp 20, hsp 18 and hsp 16). In contrast to heat stress which enhances prot ein synthesis, UVR seriously impairs translation activity in Nostoc sp. A 1 8 kDa protein is induced by UV-B. (C) 1998 Elsevier Science S.A. All rights reserved.