PHOTOPROTECTION FROM KILLING IN ULTRAVIOLET‐SENSITIVE <i>Escherichia coli</i> K‐12 MUTANTS: INVOLVEMENT OF EXCISION‐RESYNTHESIS REPAIR*

Lakchaura, B. D.

doi:10.1111/j.1751-1097.1972.tb06291.x

Cited by 21 publications

(10 citation statements)

References 10 publications

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“…We find (results not shown) that the hcr-strain does not show photoprotection effects as indicated by its survival curve and the fact that respiration does not resume as early as it does for the her' strain. This finding is difficult to fit in with our proposal that near-UV prevents cessation of respiration by some of the far-UV irradiated hcrcells; however, it is in agreement with the report of Lakchaura (1972) that the uvrA gene is necessary for photoprotection to occur. Also in agreement with Lakchaura is our finding (results not shown) that strain WP2 recA-exhibits a photoprotection effect, although it is not nearly as great as the one reported by him.…”

Section: Discussionsupporting

confidence: 48%

“…Apart from the work of Lakchaura (1972), who used several strains of E . coli K 12, most photoprotection experiments have been done with E. coli strain B.…”

Section: Discussionmentioning

confidence: 99%

“…Also in agreement with Lakchaura is our finding (results not shown) that strain WP2 recA-exhibits a photoprotection effect, although it is not nearly as great as the one reported by him. Lakchaura (1972) suggests that E. coli B/r and K12 do not show photoprotection under certain cultural conditions, has not been able to photoprotect a wildto benefit from the treatment. This idea is supported by the fact that Lakchaura, under his experimental conditions has not been able to photoprotect a wildtype E. coli K12 strain (AB 1157).…”

Section: Discussionmentioning

confidence: 99%

“…In each case a portion of the cells in the irradiated culture appear to have their survival limited by a different step. Growth and division delays, to allow extra time for repair, have been proposed to be the common mechanism for photoprotection in E. coli B (Jagger et a!., 1964) and E. coli K12 r e c A - (Lakchaura, 1972) (cases 1 and 2). In this paper we have presented evidence that growth and division delays may not be playing important roles in preventing death due to causes associated with respiratory failure in cells grown on glycerol (case 3).…”

Section: Discussionmentioning

confidence: 99%

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PHOTOPROTECTION OF E. COLI B/r: RESPIRATION, GROWTH, MACROMOLECULAR SYNTHESIS AND REPAIR OF DNA*

Swenson

Ives

Schenley

1975

Photochem & Photobiology

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Photoprotecting effects of near UV radiations ( 3 W 4 0 0 nm, maximum at 360 nm) against far UV radiations (primarily 254 nm) have been studied in Escherichia coli B/r cells in minimal medium with glycerol as a carbon source. Near UV light (lo5 J.m-2) has a negligible effect on survival, but causes transitory inhibition of respiration, growth, DNA, RNA, and protein syntheses and cell division. Far UV (52 J m-*) reduces survival to about 0.5 per cent; respiration, growth and RNA and protein syntheses proceed for about 60 min, after which they nearly cease for several hours. Near UV given before this fluence of far UV increases survival 10-fold and the above processes resume at times and with kinetics characteristic of those produced by lower fluences of far UV. Single-strand breaks appear in the DNA of both unprotected and photoprotected cells; repair of the breaks is essentially complete in protected but not unprotected cells. The viability kinetics for far-UV-irradiated cells with and without photoprotecting treatment are identical except that the curve for the latter is displaced upward about 1 log; exponential increases (cell division) begin at 120 min in each case. The data suggest that, in B/r cells grown under our particular conditions, namely in minimal medium with glycerol, photoprotection is not the result of growth or division delays, but reflects an increased repair capability due to continued respiration.

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Section: Discussionsupporting

confidence: 48%

“…Apart from the work of Lakchaura (1972), who used several strains of E . coli K 12, most photoprotection experiments have been done with E. coli strain B.…”

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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PHOTOPROTECTION OF E. COLI B/r: RESPIRATION, GROWTH, MACROMOLECULAR SYNTHESIS AND REPAIR OF DNA*

Swenson

Ives

Schenley

1975

Photochem & Photobiology

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show abstract

“…He discussed the process of photoprotection, in which the purely lethal effect of far UV is protected against by a prior near-UV dose. Data taken by Lakchaura (1972), with E. coli repair mutants, showed that the excision system must be present for photoprotection to be observed; the rec system is not involved. He went on to show the similarities between photoprotection and growth delay.…”

Section: Webb Pointed Out That Mutation Induction To T5mentioning

confidence: 99%