Effect of mono- and dichromatic light quality on growth rates and photosynthetic performance of Synechococcus sp. PCC 7002

Abstract

Synechococcus sp. PCC 7002 was grown to steady state in optically thin turbidostat cultures under conditions for which light quantity and quality was systematically varied by modulating the output of narrow-band LEDs. Cells were provided photons absorbed primarily by chlorophyll (680 nm) or phycocyanin (630 nm) as the organism was subjected to four distinct mono- and dichromatic regimes. During cultivation with dichromatic light, growth rates were generally proportional to the total incident irradiance at values <275 μmol photons m−2 · s−1 and were not affected by the ratio of 630:680 nm wavelengths. Notably, under monochromatic light conditions, cultures exhibited similar growth rates only when they were irradiated with 630 nm light; cultures irradiated with only 680 nm light grew at rates that were 60–70% of those under other light quality regimes at equivalent irradiances. The functionality of photosystem II and associated processes such as maximum rate of photosynthetic electron transport, rate of cyclic electron flow, and rate of dark respiration generally increased as a function of growth rate. Nonetheless, some of the photophysiological parameters measured here displayed distinct patterns with respect to growth rate of cultures adapted to a single wavelength including phycobiliprotein content, which increased under severely light-limited growth conditions. Additionally, the ratio of photosystem II to photosystem I increased ~40% over the range of growth rates, although cells grown with 680 nm light only had the highest ratios. These results suggest the presence of effective mechanisms which allow acclimation of Synechococcus sp. PCC 7002 acclimation to different irradiance conditions.

Microalgae on display: a microfluidic pixel-based irradiance assay for photosynthetic growth

“…Figure 5a shows that cell growth is increased with both higher irradiance intensity and higher red hue. This general trend is consistent with results from other studies, 22,56 and can be attributed to the absorption of red light by photosynthetic antennae complexes, known as phycobilisomes. The phycobilisomes capture and distribute light energy to photosynthetic reaction centers.…”

The molecular dimension of microbial species: 2. Synechococcus strains representative of putative ecotypes inhabiting different depths in the Mushroom Spring microbial mat exhibit different adaptive and acclimative responses to light

“…The reduction in PBP contents when cells were grown at high irradiance were of similar magnitude, but the levels were slightly lower for the strains representative of PEs A4 and A14 than for the PE A1 strain. These results indicate that all three strains regulate their pigment content as a function of irradiance in a manner similar to other cyanobacteria ( Bernstein et al, 2014 ), but that the PE A4 and A14 strains differ in their specific responses from that of the PE A1 strain.…”

Identification and Regulation of Genes for Cobalamin Transport in the Cyanobacterium Synechococcus sp. Strain PCC 7002

“…strain PCC 7002 is a euryhaline, unicellular cyanobacterium that tolerates high light intensities and a wide range of NaCl concentrations (1,2). This organism has one of the highest growth rates among cyanobacteria (1,3) and is naturally transformable (4). Furthermore, the genome of Synechococcus sp.…”