Photophysiological and Photosynthetic Complex Changes during Iron Starvation in Synechocystis sp. PCC 6803 and Synechococcus elongatus PCC 7942

Abstract

Iron is an essential component in many protein complexes involved in photosynthesis, but environmental iron availability is often low as oxidized forms of iron are insoluble in water. To adjust to low environmental iron levels, cyanobacteria undergo numerous changes to balance their iron budget and mitigate the physiological effects of iron depletion. We investigated changes in key protein abundances and photophysiological parameters in the model cyanobacteria Synechococcus PCC 7942 and Synechocystis PCC 6803 over a 120 hour time course of iron deprivation. The iron stress induced protein (IsiA) accumulated to high levels within 48 h of the onset of iron deprivation, reaching a molar ratio of ∼42 IsiA : Photosystem I in Synechococcus PCC 7942 and ∼12 IsiA : Photosystem I in Synechocystis PCC 6803. Concomitantly the iron-rich complexes Cytochrome b6f and Photosystem I declined in abundance, leading to a decrease in the Photosystem I : Photosystem II ratio. Chlorophyll fluorescence analyses showed a drop in electron transport per Photosystem II in Synechococcus, but not in Synechocystis after iron depletion. We found no evidence that the accumulated IsiA contributes to light capture by Photosystem II complexes.

Acclimation to environmentally relevantMn concentrations rescues a cyanobacterium from the detrimental effects of iron limitation

“…Furthermore, the presence of isiA did not increase the resistance to externally applied hydrogen peroxide treatment (Shcolnick et al ., ). Under Fe− conditions, isiA is one of the fastest and strongest responding transcripts to Fe−, and its function is considered a major factor in the iron limitation response (Ryan‐Keogh et al ., ; Fraser et al ., ).…”

“…In aquatic environments, iron is a significant limiting factor (Morel and Price, 2003;Morel, 2008), with concentrations of bioavailable Fe in the sub-nanomolar (von der Heyden et al, 2012). The effects of Fe limitation on the growth and physiology of eukaryotic and prokaryotic phytoplankton, as well as the consequences for global primary productivity, have been the subject of numerous studies (Martin et al, 1990;Katoh et al, 2000;Duhring et al, 2006;Ivanov et al, 2006;Fraser et al, 2013).…”

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

“…Photosynthesisirradiance can be quantified using a variety of techniques, including measuring the oxygen production rate, 42,43 measuring the inorganic carbon consumption rate, tracking radioactively labelled carbon 27 or measuring the photosynthetic electron transport using fluorimetry. 47 Figure 3d shows photosynthesis-irradiance measured over one and two days of growth, as quantified through the relative fluorescence increase of each microreactor. In accordance with common practices, 43,48 our data is fitted to the exponential function:…”

Samples of cyanobacterium Calothrix sp. ISC 65 collected from oil polluted regions respond to combined effects of salinity, extremely low-carbon dioxide concentration and irradiance

“…Ростовые характеристики культур, состав пигментов и состояние фикобилисом определяли с помощью микроскопов спектроскопически после 24, 48, 72 и 96 ч воздействия NaCl (культуральная среда без дополнительного внесения соли, содержащая около 17, 160 мM и изредка 80 мM) по методике Fraser et al (2013). Соотношение фотосистем и их характеристики определяли спектрофлуориметром (Inoue-Kashino et al, 2005;Zorz et al, 2015).…”