Lethal Effects of Natural Solar Ultraviolet Radiation in Repair Proficient and Repair Deficient Strains of Escherichia Coli: Actions and Interactions

Inactivation of Pseudomonas aeruginosa by Direct Sunlight

“…The time around solar noon that we found was needed to reduce the bacterial load of P. aeruginosa by 4 Log 10 was 39 min (9.7 min per Log 10 ) on June 29 near Hamburg, Germany (53°0′N latitude). This inactivation rate obtained a few days after the summer solstice was compared with previous experiments exposing a repair‐proficient control strain (K12 AB 1157) of E. coli in Rio de Janeiro (22°54′S latitude) during December 21, 1978 which is the summer solstice in the Southern hemisphere . The patterns of solar inactivation kinetics of P. aeruginosa presented here and of E. coli AB 1157 previously reported were similar with both inactivation curves showing a shoulder region followed by a relatively rapid linear decay (comparing data in Fig.…”

“…of the present manuscript and in Ref. ). From the linear portion of the inactivation curves, it can be calculated that it took 24 min of noon sunlight in Rio de Janeiro at the summer solstice to inactivate one Log 10 of (strain AB1157) E. coli (obtained from Ref.…”

“…From the linear portion of the inactivation curves, it can be calculated that it took 24 min of noon sunlight in Rio de Janeiro at the summer solstice to inactivate one Log 10 of (strain AB1157) E. coli (obtained from Ref. ) as 156–84 = 72 min divided by the corresponding 3 Log 10 = 24 min to inactivate 1 Log 10 of E. coli ). This is more than twice the time that took to inactivate a similar one Log 10 of P. aeruginosa near Hamburg at a date close to the summer solstice in the Northern hemisphere.…”

“…Sunlight radiation is the main environmental germicide, but few studies have investigated the effect of solar ultraviolet (UV) radiation on bacteria that can persist in varied environments and cause human disease. Experimental data on the inactivation of Bacillus spores , of repair‐deficient and ‐proficient mutant strains of Escherichia coli , and of Burkholderia pseudomallei by sunlight has been reported previously. The objective of this study was to determine the inactivation rate of P. aeruginosa exposed to sunlight, to gain an insight about the ability of this organism to survive in the environment from where it can disperse and cause disease to humans.…”