Project description:In this study, we characterized the homeostasis of the marine cyanobacteria Synechococcus sp. PCC7002 (BMB04) growing in chemically characterized synthetic seawater with three different levels of iron limitation representative of the modern ocean. Using transcriptomic approach, we identified the sequence of physiological responses to increasing Fe limitation. Our results showed an increase in the number of dysregulated genes and in the complexity of the response to increasing Fe limitation. Genes involved in photosynthesis were strongly down-regulated under MiFeL, while membrane transporters were up-regulated. Genes involved in regulation of energy metabolism responded under strong Fe limitation, while fine metabolic regulation of co-factors expression and activation of specific cellular mechanisms to minimize oxidative stress were only observed under severe Fe limitation. Additionally, our results demonstrate the limitations in the construct of the bioreporter BMB04 that hamper its application in areas of the ocean strongly Fe limited.
Project description:Cyanobium sp. NIES-981 is a marine cyanobacterium isolated from tidal flat sands in Okinawa, Japan. Here, we report the complete 3.0-Mbp genome sequence of NIES-981, which is composed of a single chromosome, and its annotation. This sequence information may provide a basis for developing an ecotoxicological bioassay using this strain.
Project description:In the absence of an exogenous ligand, the hemoglobins from the cyanobacteria Synechocystis sp. PCC 6803 and Synechococcus sp. PCC 7002 coordinate the heme group with two axial histidines (His46 and His70). These globins also form a covalent linkage between the heme 2-vinyl substituent and His117. The in vitro mechanism of heme attachment to His117 was examined with a combination of site-directed mutagenesis, NMR spectroscopy, and optical spectroscopy. The results supported an electrophilic addition with vinyl protonation being the rate-determining step. Replacement of His117 with a cysteine demonstrated that the reaction could occur with an alternative nucleophile. His46 (distal histidine) was implicated in the specificity of the reaction for the 2-vinyl group as well as protection of the protein from oxidative damage caused by exposure to exogenous H(2)O(2).
Project description:Total RNA was extracted from Anabaena 7120, hetZ mutant and hetP mutant at 24 h after nitrogen stepdown with two independent biological replicates. To maintain the integrity of coding RNAs, total RNA were sequenced without ribosomal RNA elimination. Strand-specific RNA-Seq libraries were prepared and sequenced using the Illumina HiSeq 2500 sequencing instrument to generate paired-end reads with length of 125 bp.
Project description:Many heme proteins undergo covalent attachment of the heme group to a protein side chain. Such posttranslational modifications alter the thermodynamic and chemical properties of the holoprotein. Their importance in biological processes makes them attractive targets for mechanistic studies. We have proposed a reductively driven mechanism for the covalent heme attachment in the monomeric hemoglobins produced by the cyanobacteria Synechococcus sp. PCC 7002 and Synechocystis sp. PCC 6803 (GlbN) (Nothnagel et al. in J Biol Inorg Chem 16:539-552, 2011). These GlbNs coordinate the heme iron with two axial histidines, a feature that distinguishes them from most hemoglobins and conditions their redox properties. Here, we uncovered evidence for an electron exchange chain reaction leading to complete heme modification upon substoichiometric reduction of GlbN prepared in the ferric state. The GlbN electron self-exchange rate constants measured by NMR spectroscopy were on the order of 10(2)-10(3) M(-1) s(-1) and were consistent with the proposed autocatalytic process. NMR data on ferrous and ferric Synechococcus GlbN in solution indicated little dependence of the structure on the redox state of the iron or cross-link status of the heme group. This allowed the determination of lower bounds to the cross-exchange rate constants according to Marcus theory. The observations illustrate the ability of bishistidine hemoglobins to undergo facile interprotein electron transfer and the chemical relevance of such transfer for covalent heme attachment.
