REDUCTION BY NEAR‐ULTRAVIOLET (334 nm) LIGHT OF E. COLI CAPACITY FOR PHAGE GROWTH DEPENDS UPON THE rel GENE AND 4‐THIOURIDINE

Abstract

Abstract— Near‐ultraviolet radiation (near UV; 300–380 nm) has long been known to produce a transient reduction of the capacity of bacteria to support phage growth. The present work shows that, at high fluenœs (40–100 kJ/m2), 85% of 334‐nm‐induced reduction of capacity in Escherichia coli B/r requires the rel gene; that is, it results from rel‐gene activity caused by the near‐UV treatment. This rel‐gene activity leads to (1) a bacterial growth delay and concomitantly lowered bacterial metabolism, and (2) a parallel delay in phage development, with a considerable depression of burst size. We propose that the observed effects on phage development are a consequence primarily of the lowered bacterial metabolism, but they may also result partly from a direct inhibition of phage DNA synthesis by the rel gene product, these effects together leading to the observed reduction of capacity in a rel+ strain. The remaining 15% of capacity reduction, observed in a rel strain, has an unknown mechanism, but does appear to involve a delay in phage development. At least 95% of the total capacity reduction observed in the rel+ strain in the range 40–100 kJ/m2 requires the presence of 4‐thiouridine, an unusual base in E. coli transfer RNA, which is presumably both the chromophore and the target for near‐UV‐induced capacity reduction.

Characterization of Pseudomonas aeruginosa Bacteriophage UNL-1, a Bacterial Virus with a Novel UV-A-Inducible DNA Damage Reactivation Phenotype

“…In contrast, the longer-wavelength solar UV radiation bands (UV-A [320 to 400 nm] and UV-B [290 to 320 nm]) do penetrate the stratospheric ozone layer and substantially impact many ecosystems (7,16). Solar UV exposure not only results in viral DNA damage and inactivation but also reduces the capacity of an infected host cell to support bacteriophage replication (16,38).…”