Organization and Function of Chlorophyll in Membranes of Cyanobacteria during Iron Starvation

Abstract

Cells of Anacystis nidulans strain R2 and of Synechococcus cedrorum were grown in an iron-deficient medium. Iron starvation induced several pronounced effects without influencing the viability of these cells. The phycocyanin and chlorophyll contents of these cells were depressed, and the absorption maxima of membrane-bound chlorophyll was blue-shifted by 5 nanometers. Cells showed a dramatic increase in original and in maximal chlorophyll fluorescence when monitored at room temperature. Low temperature chlorophyll fluorescence revealed a loss in fluorescence at 696 and 716 nanometers; much of the remaining fluorescence emission was at 686 nanometers. These chanes sugest an alteration of membrane composition and structure. This was documented by an electrophoretic analysis of iron-deficient membranes.%The prominent findings were: (a) large chlorophyll-protein complexes were not observed in iron-deficient membranes, although the chlorophyll-binding proteins were present; (b) the staining of acrylamide gels with 3,3',5,5'-tetramethylbenzidine plus peroxide indicated that iron deficiency led to a decrease in the quantity of cytochromes. These results support a stral model of the relation between fluorescence and chlorophyll organization in Anacystis. In addition, they suggest a method for studying cytochrome and chlorophyll protein assembly in these membranes. thesis of nuclear and chloroplastic gene products, and the subsequent assembly of these products into functional membranes (1 1). MATERIALS AND METHODSCells of Synechococcus cedrorum UTEX 1191 were obtained from the Indiana University culture collection, whereasAnacystis nidulans R2 was kindly provided by G. A. van Arkel, University of Utrecht, The Netherlands. These strains differed notably in such characteristics as cold sensitivity and efficiency of genetic transformation (23). However, no major differences were observed in the photosynthetic parameters described here or in the cellular responses to iron deficiency. Cells were routinely monitored for bacterial contamination by microscopic observation and by plating on nutrient agar.Cells were grown in shaking culture (120 rpm) in a manner described previously (7). Illumination was provided by banks of cool-white fluorescent lights at an intensity of approximately 0.4 mw/cm2 (YSI Radiometer). Optimal growth was obtained using Allen's BG-l 1 growth medium (1). Iron-deficient media was prepared by replacing the ferric ammonium citrate stock solution with equal molar amounts of ammonium citrate. Glassware Cells in buffer A were incubated with 10 mM EDTA and lysozyme (10 mg/ml; Sigma) for 2 to 3 h at 37°C. A membrane fraction was obtained by centrifugation after the osmotic rupture of these spheroplasts (8). The Chl-protein organization and the heme-dependent peroxidase profile of membranes were determined using LiDS-PAGE in a manner previously described (8). Polyacrylamide gradient gels were cast and were loaded with samples (80 ,g protein/well) which had been solubilized for 10 min with 1% LiDS (...

Phytoplankton community response to Fe and temperature gradients in the NE (SERIES) and NW (SEEDS) subarctic Pacific Ocean

“…However, Chl-a to C (biomass) ratio may change with time during the incubation because Chl-a quota is affected by Fe nutrition. Chl-a quota is lower under Fe-limited than that under Fe-replete conditions (Guikema and Sherman, 1983,Greene et al, 1992, Kudo et al, 2000, McKay et al, 1997, van Leeuwe and Stefels, 1998.…”

Influence of Iron Deprivation on the Membrane Composition of Anacystis nidulans

“…Cells of A. nidulans R2 were obtained and grown in shaking culture as previously described (8). Optimal growth was obtained using BG-I I growth medium.…”

“…The thylakoid membranes of cyanobacteria show changes in response to iron deprivation (8,(17)(18)(19) 686 nm. These changes in the biophysical parameters spurred an examination of the Chi-protein arrangement of iron-deficient thylakoids.…”

“…When iron was restored to a deficient culture, a metabolic sequence was initiated within the first 12 h after the addition of iron which led to phenotypically normal cells. Pulse labeling with I35Sjsulfate during this period demonstrated that iron addition initiates a coordinated pattern of synthesis that leads to the assembly of normal membranes.The thylakoid membranes of cyanobacteria show changes in response to iron deprivation (8,(17)(18)(19) 686 nm. These changes in the biophysical parameters spurred an examination of the Chi-protein arrangement of iron-deficient thylakoids.…”

Cross‐species Transcriptional Network Analysis Reveals Conservation and Variation in Response to Metal Stress in Cyanobacteria

“…At the same time, the up-regulation of "homologous recombination" might result in an increase of DNA mismatch repair and recombination [39]. Detailed analysis of genes with the same change trends (up-or downregulated) in both PMM and PMT under iron depletion condition suggested the mechanism that cyanobacteria employ to iron deficiency could be: firstly transporters were activated to obtain more iron from the environment [25], and photosynthesis and chlorophyll metabolism was inhibited due to the limited supply of iron [40][41][42], and then oxidative stress was enhanced and may cause RNA degradation, protein translation inhibition and other cellular metabolic changes. All these further resulted in inhibition of DNA replication and cell cycle block, and eventually growth cease.…”