Special Issue "Cellular and Molecular Strategies in Cyanobacterial Survival"

A special issue of Life (ISSN 2075-1729). This special issue belongs to the section "Microbiology and Engineering".

Deadline for manuscript submissions: 31 July 2020.

Special Issue Editors

Dr. Iris Maldener
E-Mail Website
Guest Editor
Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, 72074 Tübingen, Germany
Interests: microbial cell biology; filamentous cyanobacteria; heterocysts; cell–cell communication; septal junctions; akinetes; stress adaptation; ABC-transporter
Dr. Khaled Selim
E-Mail Website
Co-Guest Editor
Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, 72074 Tübingen, Germany
Interests: cell signaling in cyanobacteria; molecular mechanisms of carbon/nitrogen regulations; cyanobacterial carbon concentrating mechanisms; PII and PII-like signal transduction proteins; developmental and structural biology

Special Issue Information

Dear Colleagues,

All species of cyanobacteria are capable of oxygenic photosynthesis. Despite this common mode of metabolism, they exist in different morphologies as single cells or as multicellular filaments, which may even differentiate specialized cells. Furthermore, cyanobacteria occupy almost all illuminated aquatic and terrestrial habitats, including harsh environments of deserts, oceans, and hypersaline, volcanic, and thermal biospheres. Therefore, they represent one of the quantitatively most abundant organisms on earth and can be dated back in evolution for more then 2.4 billion years. In addition to this biodiversity, many species have developed strategies to adapt to various stress conditions, including nutrient starvation, occurring in their own habitat.

In recent years, our knowledge on cyanobacterial survival strategies has increased tremendously by applying global studies like transcriptomics and proteomics, as well as advanced microscopic technics. Protein structure and function analysis have revealed the great potential of cellular and metabolic adaptation mechanisms of single cells and multicellular filaments towards environmental stress, including cell differentiation, signal transduction, formation of reserve materials, and resuscitation from dormant states, just to name a few examples.

In this Special Issue of Life, we invite researchers from all over the world to share with us the advances in our understanding of ecological, cellular, and molecular mechanisms of cyanobacterial survival. This includes original work and review articles dealing with signaling pathways, strategies of gene and protein regulation, global studies, and new discoveries related to differentiation of spore like akinetes, motile hormogonia, and nitrogen-fixing heterocysts.

Dr. Iris Maldener
Dr. Khaled Selim
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Life is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.


  • akinete
  • carbon concentrating mechanisms
  • cell–cell communication
  • cell differentiation
  • C/N balancing
  • cyanobacterial OMICS
  • heterocyst
  • reserve compounds
  • signal transduction
  • transcription regulation

Published Papers

This special issue is now open for submission, see below for planned papers.

Planned Papers

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.

Title: Inactivation of three RG(S/T)GR pentapeptide-containing negative regulators of HetR results in lethal differentiation of Anabaena PCC 7120

Author: Khudyakov Ivan Yakovlevich

Abstract: HetR protein is called the master regulator of patterned differentiation of heterocysts - terminally differentiated cells specialized for aerobic nitrogen fixation. In Anabaena PCC 7120, two negative regulators of HetR, a short peptide PatS and the protein HetN, both contain an RGSGR pentapeptide essential for their activity and are known to guide heterocyst pattern formation by controlling the binding of HetR to DNA and the protein's turnover. Recently a gene encoding a third small protein, PatX, with a similar RGTGR motif was found in this strain and shown to repress heterocyst differentiation when overexpressed. Its orthologs are present in all HetR-containing filamentous cyanobacteria, and many heterocyst-forming strains encode additional PatS and a few also HetN regulators.
In Anabaena PCC 7120, inactivation of patX does not produce discernible phenotype. However, mutational analysis revealed that PatX has partially overlapping functions with PatS in controlling heterocyst differentiation. Deprivation of all three negative regulators – PatS, PatX and HetN – results in synchronous differentiation of all vegetative cells into heterocysts in combined nitrogen-free medium; in nitrogen-replete medium an extensive fragmentation, cell lysis and aberrant differentiation take place. Thus HetR activity unrestrained by RG(S/T)GR-containing negative regulators is lethal under different growth conditions. Tight control and fine tuning of HetR is needed both for vegetative growth and for complex developmental programs.


Title: Diurnal regulation of the in vivo organisation and CO2-fixing activity of carboxysomes in cyanobacteria

Author: Yaqi Sun, Lu-Ning Liu *

Abstract: Diurnal regulation of photosynthesis plays a pivotal role in maintaining carbon fixation. The central carbon-fixation machinery in all cyanobacteria is a proteinaceous organelle, termed the carboxysome. In the diurnal light/dark cycles, carboxysome genes possess cyclic transcriptional regulation. How carboxysome organisation and function are modulated in the day/night transitions remains exclusive. Here, we utilize live-cell confocal microscopy imaging and enzymatic assays to explore the physiological regulation of carboxysomes in response to cyclic light conditions. We observed the changes in the localisation patterns of carboxysomes between diurnal light and dark conditions. Additionally, genetic deletion of the gene encoding the circadian clock protein, KaiA, has an effect on the biogenesis of carboxysomes. We revealed that without KaiA the number of carboxysomes per cell increased whereas the abundance of Rubisco encapsulated within each carboxysome declined, resulting in the reduced carbon fixation during diurnal irradiance cycles. These findings provide new insight into the physiological tuning of carbon fixation of cyanobacterial cells during the diurnal light/dark cycles that are prevalent in the natural habitat of cyanobacteria.

Title: Distinctive features of PipX, a unique signaling protein of cyanobacteria

Author: Asunción Contreras

Abstract: PipX, a protein identified by its ability to bind to cyanobacterial nitrogen regulators PII and NtcA, provides a mechanistic link between signaling the nitrogen/carbon and energy status by the widely distributed protein PII and the control of gene expression by NtcA, a global transcriptional regulator involved in nitrogen assimilation in cyanobacteria. PipX uses the same surface, which involve the KOW or tudor-like domain (TLD), to bind to 2-OG-free PII or, alternatively, to 2-OG-bound NtcA to increase its transcriptional activity. PII-PipX complexes interact with PlmA, a yet poorly characterized transcriptional regulator also restricted to cyanobacteria, presumably to decrease transcriptional activity. In most cyanobacteria, pipX appears to be co-expressed with another gene (pipY), encoding a universally conserved pyridoxal-phosphate binding protein (PLPBP) involved in vitamin B6 and amino acid homeostasis and whose loss-of-function mutations cause B6-dependent epilepsy in humans. Genetic analyses based on transcriptomic and antibiotic-susceptibility comparisons are consistent with functional connections between PipX and PipY, further supported by in silico analysis. PII and PipX display distinct localization patterns during diurnal cycles, co-localizing into the same foci at the periphery and poles of the cells during the dark periods, a circadian independent process requiring a low ATP/ADP ratio. Genetic analyses in S. elongatus emphasize the importance of PII to counteract deleterious PipX activity under different environmental conditions, a phenomenon suggesting the presence of additional and probably essential PipX targets in cyanobacteria. In this overview we propose that the study of the protein-protein interaction and synteny networks involving the unique cyanobacterial protein PipX should speed functional genomics and contribute to understand the peculiarities and idiosyncrasy of signaling pathways in oxygenic photosynthetic organisms, as well as provide insights into new regulatory features and mechanisms that may be widespread.

Title: FUR (ferric uptake regulation) proteins: at the cross-road of metal-responsive regulation and the control of redox homeostasis in cyanobacteria
Authors: María Fillat
Affiliation: Department of Biochemistry and Molecular and Cellular Biology, University of Zaragoza, Zaragoza 50009, Spain
Abstract: Cyanobacterial metabolism is often constrained by metal requirements and the generation of reactive oxygen species (ROS) caused by accumulation of electrons in the photosynthetic electron transport chain. FUR proteins are a paradigm for the coordinated control of metal homeostasis and the response to peroxide in prokaryotes. This review summarizes the major features of FUR paralogs in cyanobacteria, evidencing their dual role as metal regulators and sensors of intracellular redox status. Most studies have been performed in Anabaena sp. PCC7120, where the FUR family consists of the Fur (FurA), Zur (FurB) and PerR (FurC) paralogs. FurA and FurB are redox proteins that, besides their role as metal-dependent transcriptional regulators, can bind heme, a marker of oxidative stress, modulating its affinity for DNA. Moreover, these paralogs integrate the response to metal availability with the redox status through thiol-mediated redox modulation. Overexpression of FurA in Anabaena attenuates intracellular ROS accumulation, while the enhanced expression of FurB increases the tolerance of the cyanobacteria to ROS. Furthermore, FurB itself is able to protect DNA in vitro against oxidative damage or the action of DNaseI. Both, the FurA and the FurB regulons, in addition to major genes involved in iron and zinc homeostasis, include an important set of genes crucial for detoxification of ROS. Consistently with its role as a PerR protein, FurC controls the main genes involved in the response to peroxide, but also several components of the phycobilisome and the thylakoids, among others and responds to peroxide by metal-catalyzed oxidation.

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