Effect of Nutritional State and Other Conditions on Ultraviolet Resistance and Photoreactivation in Yeast

Abstract

Starvation of protozoans increases their sensitivity to ultraviolet radiations and affects the photoreversibility of ultraviolet injury by visible light (Giese and Reed, 1940; Giese et al., 1954; Brandt et al., 1955). The present study on the variation with nutritional state of the sensitivity of yeast to ultraviolet and its photoreversal was initiated with the aim of relating the specific nutrients or enzyme systems involved in the changed ultraviolet sensitivity resulting from starvation. In addition the effects on ultraviolet injury and its photoreversal of some factors which affect the physiological state of the yeast, especially oxygen tension and selective enzyme poisons, were investigated; findings which emerged are presented below.

ULTRAVIOLET EXPOSURE STUDIES ON A GAMMA RADIATION RESISTANT MICROCOCCUS ISOLATED FROM FOODa,b,c,

“…No difference in the rate of kill was observed. Oxygen has been reported to have some influnce on rates of UVL induced mutations in Serratia waarcescens (4) but not on U V L inactivation of yeasts (3). Likewise, irradiation in phosphate buffer containing 100 to 500 p.p.m.…”

Photoreactivation

“…Since, at the dose rate used, at about 4 hr at 37 C indicate that metabolism is least 20 min exposure is required for maximum also involved. per cent PR, the decrease in maximum per cent Giese et al (55) showed that starvation of PR is caused by a limitation in the time during yeast (S. cereviseae) for 6 days causes a drop in which PR can be effected, this time being 20 to photoreactivability to about 10 per cent of nor-30 min. In other words, photoreactivability in mal if carbohydrate is withheld, and to about this system remains constant for a certain time 1 per cent if nitrogen is withheld.…”

“…In E. coli B (148) it is found damage (presumably caused by organic perox-that PR raises the survival level to that of heat ides) than does PR.10 Catalase restoration is restoration (at 44 C), after which both survivals presumed to be linked to the peroxidasic remain parallel. In S. cereviseae (55), heat restorarather than the catalatic activity of catalase tion raises the survival level to that of PR, after (106).…”

Effects of salinity and temperature on inactivation and repair potential of Enterococcus faecalis following medium- and low-pressure ultraviolet irradiation

“…NER has been demonstrated to increase with temperature between 5 and 28°C in yeast (Giese et al . ). Based on the results of Ent.…”

“…CPDs can be removed by nucleotide excision repair (NER), a multistep, multienzyme process (Sinha and H€ ader 2002), which is one of the pathways of dark repair. NER has been demonstrated to increase with temperature between 5 and 28°C in yeast (Giese et al 1957). Based on the results of Ent.…”