Effects of UV radiation on DNA photodamage and production in bacterioplankton in the coastal Caribbean Sea

Abstract

ABSTRACT. This study focuses on the effects of ultraviolet radiation (UVR) on bacterioplankton. The effect of different parts of the sunlight spectrum on the leucine and thymidine incorporation and on the induction of DNA damage in natural bacterial populations in the coastal Caribbean Sea off Curaqao were investigated. DNA photodamage in microorganisms and biodosimeters was quantified by the number of cyclobutane dimers (thymine dimers). Increasing DNA damage during the day was found when incubated in full surface solar radiation. When UVBR was excluded no DNA damage was observed, indicating that thymine dimers were only formed by UVB radiation. The amount of thymine dimers in the > 0 . 8 pm fraction was only one-third of the amount of induced thymine dimers in the <0.8 pm fraction, suggesting that phytoplankton is less sensitive to UV-induced DNA damage than bacterioplankton. Protein and DNA synthesis was inhibited to about 30% of the dark control during the day when exposed to surface solar radiation. In both protein and DNA synthesis a trend was found, with the highest inhibition under full solar radiation, lower inhibition when UVBR was shielded off and the lowest inhibition when UVAR (<375 nm) was also shielded off. The intracellular carbohydrate content of the phytoplankton incubated under full solar radiation was not significantly higher than the dark incubation, while the contents after incubation without UVBR were significantly lngher. The carbohydrate content in the samples incubated without UVBR and UVAR (<375 nm) was a little higher than with only UVBR shielded off. In summary, the results show that in the coastal Caribbean Sea UVBR is responsible for DNA damage in bacterio-and phytoplankton, while protein and DNA synthesis in bacterioplankton was inhibited by UVBR. UVAR and PAR and carbohydrate synthesis in phytoplankton by both UVBR and UVAR.

Diurnal variations in depth profiles of UV-induced DNA damage and inhibition of bacterioplankton production in tropical coastal waters

“…The formation of photoproducts disturbs the error-free DNA replication and RNA transcription in cells, which is one of the most important consequences of DNA damage (Karentz et al 1994). As shown previously, DNA damage (by CPDs) is only caused by UVBR (Buma et al 1997, Visser et al 1999. However, inhibition of leucine and thymidine incorporation is also caused by UVAR and PAR (Herndl et al 1993, Aas et al 1996, Visser et al 1999).…”

“…Pyrimidine (6-4) pyrimidone and cyclobutane pyrimidine dimers are the most important photoproducts formed (Karentz et al 1994). The formation of CPDs by UVR in bacterioplankton was shown by Jeffrey et al (1996a,b), Lyons et al (1998) and Visser et al (1999), in the marine diatom Cyclotella sp. by Buma et al (1997) and in phagotrophic protists by Somaruga & Buma (2000).…”

The interaction of phytoplankton and bacteria in a high mountain lake: Importance of the spectral composition of solar radiation

“…Thus, it is known that DNA damage can be repaired by photolyase enzymes (photorepair mechanisms) that are activated at high wavelengths of UVA radiation (370 to 400 nm) and low wavelengths of PAR (400 to 450 nm) and that reverse the dimerizing effects of UVB (Kim and Sancar 1993). These mechanisms would be relevant in our experimental conditions because bacterioplankton had been naturally exposed to full solar radiation for about 5 h immediately prior to the incubations, so that it is highly probable that bacterial DNA was already partially damaged (Visser et al 1999). Hence, we interpreted the significant increase of bacterial […”

“…8). The lack of coupling observed with traditional dark incubations for BP in our study resulted from either an underestimation of actual bacterial production in midsummer or its overestimation in the late open-water period (Visser et al 1999). Thus, our experimental approach could be of value to establish the role of the spectral composition of solar radiation in coupling the algae-bacteria relationship, particularly in shallow and clear-water ecosystems.…”

Spatial and temporal dynamics of virioplankton in a high mountain tropical reservoir, El Neusa (Cundinamarca, Colombia)

“…and cellular components (membrane system, organelles, nucleic acids, etc.) of potential hosts, as well as transformations inflicted on the organic substances that serve as substrates for some of these microorganisms (Visser et al, 1999;Fernández-Zenoff et al, 2006;Ruiz-González et al, 2013). Certain studies suggest that the degree of infectivity and phage production tends to decrease with the increasing of exposure time and the received amount of UV-B radiation (Jeffrey et al, 1996;Noble & Fuhrman, 1997;Weinbauer et al, 1997;Wilhelm et al, 1998Wilhelm et al, , 2003Cheng et al, 2007).…”