Effects of visible light and UV radiation on photosynthesis in a population of a hot spring cyanobacterium, a Synechococcus sp., subjected to high-temperature stress

Scott R. Miller, Christopher E. Wingard, Richard W. Castenholz

Research output: Contribution to journalArticlepeer-review

48 Scopus citations

Abstract

Assays of photosynthesis were conducted with a biofilm population of a cyanobacterium, a Synechococcus sp., growing at ~70°C in a Yellowstone National Park hot spring to test whether cells growing near the upper temperature limit of photosynthetic life are optimally adapted to their mean environmental temperature. Cell suspensions were assayed at 70, 65, and 55°C while being simultaneously exposed to modified solar environments, including reduction of total irradiance and exclusion of UV radiation. Carbon fixation was greatest at 65°C, while 70 and 55°C were always supraoptimal and suboptimal for photosynthesis, respectively. The degree of temperature stress was dependent upon light intensity, and this light-dependent temperature effect may involve both reduced quantum efficiency at subsaturating irradiances and a lower saturating irradiance at both supraoptimal and suboptimal temperatures. The Synechococcus sp. was also more susceptible to UV inhibition of photosynthesis at nonoptimal temperatures. These results suggest that this population is persisting at a nearly lethal temperature and is consequently subject to greater damage by both visible and UV radiation, but it is speculated that these cells may be avoiding competition with other photoautotrophs under these nonoptimal conditions. In separate experiments monitoring diurnal patterns of photosynthesis, cells exhibited peak productivity during the morning, followed by an afternoon decline. No recovery of photosynthesis was observed during the remaining daytime, and carbon fixation was always IN inhibited under conditions of photosynthetically saturating light.

Original languageEnglish
Pages (from-to)3893-3899
Number of pages7
JournalApplied and Environmental Microbiology
Volume64
Issue number10
DOIs
StatePublished - Oct 1998

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