The below list represents only planned manuscripts. Some of these
manuscripts have not been received by the Editorial Office yet. Papers
submitted to MDPI journals are subject to peer-review.
Type of Paper: Article
Title: The Interplay between Iron Bioavailability and Transport Strategies in Aquatic Cyanobacteria
Authors: Hagar Lis 2,3, Chana Kranzler 1,2, Yeala Shaked 2,3 and Nir Keren 1
1 Department of Plant and Environmental Sciences, The Alexander Silberman Institute of Life Sciences, Edmond J. Safra Campus, Givat Ram, Hebrew University of Jerusalem, Jerusalem, Israel
2 Interuniversity Institute for Marine Sciences in Eilat, POB 469, Eilat 88103, Israel
3 The Freddy and Nadine Herrmann Institute of Earth Sciences, Edmond J. Safra Campus, Givat Ram, Hebrew University of Jerusalem, Jerusalem, Israel
Abstract: Cyanobacteria are a diverse and highly successful group of organisms, prevalent throughout aquatic ecosystems. Due to their taxonomic affiliation, these photosynthetic prokaryotes are often associated with the siderophore mediated iron uptake strategy employed by heterotrophic bacteria. However, siderophore production is not well suited to dilute heterogeneous ocean environments in which diffusive losses pose significant challenges to this strategy. Moreover, genetic studies show that open ocean cyanobacteria possess neither siderophore biosynthesis nor siderophore transporter genes—capabilities which seem to be limited to freshwater, brackish and coastal environments. Recent studies uncovered an alternative high affinity iron uptake pathway functioning in Fe-limited model cyanobacteria—reduction of Fe(III) species prior to transport though the plasma membrane. In this contribution, we examine the prevalence of this mechanism amongst genetically and ecologically diverse cyanobacterial strains and across several Fe-substrates. Interestingly, we found that siderophore producers are able to acquire iron via the reductive pathway, although implementation of this strategy seems to depend on the chemical nature of the Fe-substrate. Results of short term iron uptake assays also confirm the presence of the reductive strategy in a number of marine species. Thus, reductive iron uptake appears to be a prevalent strategy amongst both fresh water and marine cyanobacteria in the uptake of various Fe-substrates. These findings lend insight into the relationship between environmental pressures and the evolution of cyanobacterial iron uptake strategies.
Type of Paper: Article
Title: Novel DNA Taxonomy Approaches in Cyanobacteria
Author: Ester Eckert, Diego Fontaneto, Manuela Coci, Gianluca Corno and Cristiana Callieri
Affiliation: CNR – Institute of Ecosystem Study, Verbania, Italy
Abstract: Taxonomy in Cyanobacteria is mostly based on 16S sequences, as for all prokaryotes. Nevertheless, the most common approach in DNA taxonomy for cyanobacteria is still based on genetic distances, without incorporating any of the theoretical advances in DNA taxonomy that have been recently developed for eukaryotes. Several methods based on maximum likelihood and Bayesian statistical approaches, also including coalescent theory, have been developed for DNA taxonomy in eukaryotes, but are not yet applied in prokaryotes. Here we demonstrate their reliable and useful application in the case of Cyanobacteria. We test the output of different methods in DNA taxonomy (e.g., ABGD, GMYC, PTP) on 16S sequences of Cyanobacteria cladesand investigate the ecological and physiological independence of the taxonomic units.
Title: Advances in understanding carboxysome assembly in Prochlorococcus and Synechococcus.
Authors: Fei Cai 1,2, Sabine Heinhorst 3, Gordon C. Cannon 3 and Cheryl A. Kerfeld1,2,4,*
Affiliations:1 Department of Plant and Microbial Biology, University of California, Berkeley, California 94720, USA
2 Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
3 Department of Chemistry and Biochemistry, The University of Southern Mississippi, Hattiesburg, Mississippi 39406-5043, USA
4 MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
Abstract: The Marine Synechococcus and Prochlorococcus are numerically dominant cyanobacteria in the open ocean. They have evolved a CO2-concentrating-mechanism (CCM) to improve photosynthetic performance, and therefore play an important role in global carbon fixation. Carboxysomes, the central component of the CCM, are self-assembling proteinaceous organelles. Two types of carboxysome, α and β, encapsulating the form IA and form IB D-ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) respectively, differ in gene organization and associated proteins. Relative to the β-carboxysome, the assembly process of the α-carboxysome is enigmatic. A large (>760 amino acids) protein, CsoS2, has no counterpart in the β-carboxysomes and appears to play an essential role in the formation and function of α-carboxysomes. Biochemical, genetic, and structural studies revealed that it is vital for α-carboxysome biogenesis. The primary structure of CsoS2 is distinctive and appears to be composed of three domains: N-terminal, Middle (M)-, and C-terminal domains. Repetitive motifs can be identified in N- and M-domain, respectively. This protein has proven recalcitrant to crystallization and multiple lines of evidence suggested CsoS2 is highly flexible. In this study, we took bioinformatic, biophysical, genetic, biochemical approaches, including peptide array scanning for protein-protein interaction discovery, to understand the role of CsoS2 in the structure, function and assembly of the α-carboxysome.
Title: Chlorophyll biosynthesis of cyanobacteria under low oxygen environments and evolutionary implications
Authors: Rina Aoki, Ryoma Tsujimoto and Yuichi Fujita
Affiliations: Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan
Abstract: Chlorophyll a (Chl), the tetrapyrrole pigment essential for photosynthesis, is produced from glutamate via a complex biosynthetic pathway consisting of at least 15 enzymatic steps. Former half is shared with heme biosynthesis and latter half is specific to Chl a so-called Mg-branch. In addition, bilin pigments such as phycocyanobilin are produced from heme. Some steps in the biosynthetic pathways of Chl and bilins require molecular oxygen (O2) for catalysis such as oxygen-dependent coproporphyrinogen III oxidase. Cyanobacteria thrive in diverse environments in terms of oxygen levels. To cope with Chl deficiency caused by low oxygen conditions, cyanobacteria develop elaborate mechanisms to maintain Chl production even under micro-oxic environments. Use of enzymes specialized for low oxygen conditions such as oxygen-independent coproporphyrinogen III oxidase constitutes a part of the mechanisms. Another layer of the mechanisms is mediated by a transcriptional regulator called ChlR that senses low oxygen to activate the transcription of genes encoding low-oxygen type enzymes. In diazotrophic cyanobacteria this multilayered regulation also contributes in Chl biosynthesis to support energy production for nitrogen fixation that requires low oxygen conditions. Low-oxygen type enzymes appear to be evolutionary older than oxygen-dependent enzymes. We will also discuss evolutionary implications of cyanobacterial Chl biosynthesis and regulation.
Article type: Review
Title: Sucrose in Cyanobacteria: From a Salt-Response Molecule to a Key role in Nitrogen-Fixation
Authors: Graciela L. Salerno *, María A. Kolman, Macarena Perez-Cenci, Carolina Nishi
Affiliation: Instiuto de Investigaciones en Biodiversidad y Biotecnología (INBIOTEC-CONICET) and Fundación para Investigaciones Biológicas Aplicadas (FIBA), Mar del Plata, Argentina
Abstract: In the biosphere, sucrose is synthesized mainly in oxygenic photosynthetic organisms as part of the carbon dioxide assimilation pathway. Its central role in the functional biology of vascular plants is well documented. However, much less is known about the function of sucrose in cyanobacteria, prokaryotes that perform photosynthesis as plants do. Traditionally, sucrose accumulation has been associated with salinity, and, consequently, the disaccharide has been considered as a compatible solute in numerous strains. Also, sucrose has been proposed as the carbon transport molecule in the diazotrophic filaments of heterocyst-forming cyanobacteria. However this has not yet been fully demonstrated. In the last years, functional characterizations of sucrose metabolizing enzymes, metabolic control analysis, cellular localization of encoding gene expression, and reverse genetic experiments, revealed that sucrose metabolism is coordinated with glycogen synthesis and it is crucial in diazotrophic growth. The analysis of more than 20 fully sequenced genomes gave us new insights about the origin of sucrose metabolism and further evolution in the cyanobacterial lineage.
Article type: Review
Title: Cyanobacteria as Chassis for Industrial Biotechnology: Progress and Prospects
Authors: Lamya Al-Haj 1, Yuen Tin Lui 2 and Saul Purton 2,*
Affiliations:1 Sultan Qaboos University, Muscat, Sultanate of Oman
2 Institute of Structural & Molecular Biology, University College London, London WC1E 6BT, UK
Abstract: Cyanobacteriahold significant potential as industrial biotechnology (IB) platforms for the production of a wide variety of bio-products ranging from biofuel molecules such as hydrogen, alcohols and isoprenoids, to high-value bioactives and recombinant proteins. Underpinning this are recent advances in cyanobacterial omics research, the development of improved genetic engineering tools for key species, and the emerging field of cyanobacterial synthetic biology. Such technologies are now making possible elaborate metabolic engineering programs aimed at creating designer strains tailored for different IB applications. In this review, we provide an overview of the current status of the field with specific focus on the molecular tools and technologies, and we consider future commercial applications.