John Jagger

NEAR-UV RADIATION EFFECTS ON MICROORGANISMS

This review covers effects in microorganisms produced primarily by near-ultraviolet radiation (near UV), or by radiation referred to as ‘UV-A’ (32HOO nm). Effects occurring only at shorter wavelengths. in the ‘mid UV’ or ‘UV-B’ (29Ck320nm) are often not considered. since the mechanisms of action in the UV-B region are more similar to those produced by far-UV or ‘UV-c‘ radiation (2W290 nm). Yearly Reviews. in June 1976 by Jagger [21]. in December 1977 by Thomas [58] and in a review restricted to physiological effects in June 1979 by Fraikin and Rubin [13]. The present review attempts to cover the literature from January 1978 through June 1981 that is not covered in the Fraikin and Rubin review. For purposes of continuity, of course, sope references will date further back Extensive reviews in Photochemical and Photohiologicul Recirws of lethal and mutagenic effects appeared in Vol. 2 [74]. and of physiological effects will appear in Vol. 7 1233.

PHOTOREACTIVATION OF KILLING IN STREPTOMYCES: ACTION SPECTRA AND KINETIC STUDIES*

Abstract— An action spectrum was obtained for photoreactivation of killing (PR) of Streptomyces griseus conidia. This spectrum shows a major peak around 436 nm, originally observed by A. Kelner, and a secondary peak at 313 nm not previously reported. The rate of PR shows a strong dependence upon temperature and dose rate of the PR light at 436 nm, but this decreases to only a slight dependence upon these parameters at 313 nm. These findings suggested that PR at 436 nm in this organism is of the usual photoenzymatic type, but that PR at 313 nm might be of a different kind.

THYMINE‐DIMER AND ACTION‐SPECTRUM EVIDENCE FOR INDIRECT PHOTOREACTIVATION IN ESCHERICHIA COLI*

Abstract— Cells of Escherichia coli B and B phr‐ were labeled with tritiated thymidine, exposed to inactivating ultraviolet radiation at 254 nm, given photoreactivation (PR) treatment immediately thereafter, and then immediately hydrolyzed and assayed for thymine‐containing dimers. It was found that (1) PR treatment of strain B phr‐ does not split thymine dimers and (2) the amount of splitting of thymine dimers in strain B at 334 nm is only 45 per cent of the amount of splitting observed at 405 nm for the same amount of biological PR. These findings show that all of the PR in E. coli B phr‐, and part of the PR at 334 nm in E. coli B, is indirect (does not use PR enzyme) and is not due to thymine‐dimer splitting.

Physiological Effects of Near-Ultraviolet Radiation on Bacteria

Near-ultraviolet (near-UV) radiation (also called “UV-A”) can be considered to lie in the wavelength range 320–400 nm. The long-wavelength limit represents the beginning of the visible spectrum, while the short-wavelength limit corresponds roughly to the point below which proteins and nucleic acids begin to absorb significantly. Below this region is the “mid-UV” region or UV-B (290–320 nm), where proteins and nucleic acids begin to absorb, and where sunburn and skin cancer are most effectively produced. “Solar-UV radiation” (UV radiation present in sunlight at the surface of the Earth at noon in clear weather) includes both the near-UV and the mid-UV regions.* Because nucleic acid and protein do not absorb significantly in the near-UV region, one can expect a wide variety of other chromophores to become important in this region, producing a wide variety of biological effects. It is also expected that the fluences required to produce these effects will be considerably higher than those required for killing by far-UV radiation (“UV-C”; 190–280 nm), because the target molecules are not as crucial to the cell as nucleic acid.

ACTION OF PHOTOREACTIVATING LIGHT ON PYRIMIDINE HETEROADDUCT IN BACTERIA

Abstract— In stationary‐phase Escherichia coli B/r, photoreactivation (PR) at 313 nm of ultraviolet (u.v.) killing is inefficient compared with PR at 405 nm, and can be explained solely by photoenzymatic reversal of pyrimidine dimers.

PHOTOREACTIVATION OF KILLING IN STREPTOMYCES-III. ACTION SPECTRA FOR PHOTOLYSIS OF PYRIMIDINE DIMERS AND ADDUCTS IN S. GRISEUS AND S. GRISEUS PHR-l*

Abstract— Photolysis of tritium‐labelled thymine‐derived photoproducts by 254‐nm ultraviolet radiation (u.v.) in conidia of Streptomyces griseus was measured by chromatography of cell hydrolysates. The relative photolysis cross‐sections of uracilthymine dimer (UT○) at various wavelengths are the same as those of thymine‐thymine dimer (TT○), and their ratios at 313, 365, 405 and 436 nm are 2:1:2:3. Except at 436 nm, these relative values agree very well with cross‐sections previously reported for photoreactivation of u.v. killing in this organism, leading to the conclusion that photoreactivation in the wild type is due to repair of cyclobutane‐type pyrimidine dimers. In a mutant showing restricted photoreactivation (S. griseus PHR‐1), post‐u.v. treatments at the above wavelengths did not affect UT○ and TT○ in the conidia, supporting the earlier suggestion that this organism does not contain active PR enzyme. Another u.v. photoproduct, the precursor of a pyrimidine adduct (PO‐T) that appears in cell hydrolysates, was removed from both wild‐type and mutant cells very efficiently at 313 nm. This is presumably a direct photochemical reaction. In addition, in wild‐type cells, the precursor of PO‐T appeared to be inefficiently removed photoenzymatically at all wavelengths. Removal of the precursor of PO‐T appears to be biologically significant, however, only in the mutant.

In vivo induction of 4-thiouridine-cytidine adducts in tRNA of E. coli B/r by near-ultraviolet radiation.

Abstract— Near‐ultraviolet (near‐UV; 320–405 nm) irradiation of Escherichia coli B/r induces the formation in vivo of 4Srd‐Cyd adducts in transfer RNA, as evidenced by (1) fluorescence spectrum changes of tRNA extracted from irradiated cells and reduced with NaBH4, (2) thin‐layer chromatography on cellulose of hydrolysates of trichloroacetic acid‐precipitable extracts of irradiated cells, and (3) comparison of these findings with adduct formation induced by near‐UV irradiation of purified mixed tRNA from E. coli.

PHOTOREACTIVATION OF KILLING IN STREPTOMYCES‐II. KINETICS OF FORMATION AND PHOTOLYSIS OF PYRIMIDINE DIMERS AND ADDUCTS IN S. COELICOLOR AND S. GRISEUS PHR‐1*

Abstract— A pyrimidine adduct, 6‐4‘‐[pyrimidine‐2’‐one] thymine (PO‐T)‡, observed in DNA hydrolysates of 254‐nm ultraviolet (u.v.) irradiated conidia of Streptomyces coelicolor, increases linearly with u.v. dose up to 2 × 105 ergs/mm2. Yields of thymine dimer (T○) and uracil‐thymine dimer (U○) level off at much lower doses. Initial relative rates of formation of these u.v. photoproducts are: 1:1.3:4.8 for PO‐T, T○ and U○, respectively. Similar results were obtained with a Streptomyces griseus mutant, PHR‐1.

INHIBITION BY SUNLIGHT OF THE GROWTH OF ESCHERICHIA COLI B/r*

A wide variety of biological systems are adversely affected by near-ultraviolet (near-UV ; 300-380 nm) radiation. One of the most sensitive indicators of such effects is cell growth, which is strongly inhibited in many systems at fluences that are not lethal for most of the population. This inhibition of growth in bacteria shows a rather narrow action spectrum, peaking at 340nm; a similar spectral region also inhibits growth of plant and animal cells (see Jagger, 1972, for review). Since near-UV radiation represents about 4% of solar radiation at the surface of the Earth at noon in middle latitudes (see Cadle and Allen, 1970), one suspects that normal solar fluences may have important deleterious biological effects. Lethal effects have already been demonstrated (Harm, 1969; Billen and Fletcher, 1974). The present report provides an estimate of the ability of solar radiation to inhibit growth of Escherichia coli B/r. A window-glass filter was used in these experiments to minimize complications introduced by lethal effects and their concurrent photoreactivation (see Harm, 1969). Such a filter cuts off the shortest 10-20nm of solar radiation on a bright summer day but may mimic rather well the near-UV solar spectrum on an average day.

Ultraviolet action spectrum (238-405 nm) for inhibition of glycine uptake in E. coli.

Abstract— Initial rate of uptake of 3H‐glycine by Escherichia coli B/r was measured immediately after irradiation with monochromatic light. Uptake was proportional to time for at least 2 min in both control and irradiated samples. Inhibition of uptake is an exponential function of fluence to about 20% remaining activity, beyond which it is much more resistant to irradiation, suggesting two different uptake systems. The principal (sensitive) system shows an F37 of 2.2 kJ/m2 at 280 nm and 110 kJ/m2 at 334 nm. The response is independent of cell killing and of presence of the rel gene. The chromophore remains unidentified, although an action spectrum suggests a protein chromophore in the far‐UV (below 300 nm) region and a menaquinone chromophore in the near‐ultraviolet (above 300 nm).