The Formation of Spore-Like Akinetes: A Survival Strategy of Filamentous Cyanobacteria

Some cyanobacteria of the order Nostocales can form akinetes, spore-like dormant cells resistant to various unfavorable environmental fluctuations. Akinetes are larger than vegetative cells and contain large quantities of reserve products, mainly glycogen and the nitrogen storage polypeptide polymer cyanophycin. Akinetes are enveloped in a thick protective coat containing a multilayered structure and are able to germinate into new vegetative cells under suitable growth conditions. Here, we summarize the significant morphological and physiological changes that occur during akinete differentiation and germination and present our investigation of the physiological function of the storage polymer cyanophycin in these cellular processes. We show that the cyanophycin production is not required for formation and germination of the akinetes in the filamentous cyanobacterium <i>Anabaena variabilis</i> ATCC 29413.

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Intercellular Diffusion of a Fluorescent Sucrose Analog via the Septal Junctions in a Filamentous Cyanobacterium

mBio ◽

10.1128/mbio.02109-14 ◽

2015 ◽

Vol 6 (2) ◽

Cited By ~ 57

Author(s):

Dennis J. Nürnberg ◽

Vicente Mariscal ◽

Jan Bornikoel ◽

Mercedes Nieves-Morión ◽

Norbert Krauß ◽

...

Keyword(s):

Gap Junctions ◽

Cell Types ◽

Cell Junctions ◽

Filamentous Cyanobacterium ◽

Nitrogen Fixing ◽

Filamentous Cyanobacteria ◽

Triple Mutant ◽

Vegetative Cells ◽

Metabolite Exchange ◽

Import System

ABSTRACTMany filamentous cyanobacteria produce specialized nitrogen-fixing cells called heterocysts, which are located at semiregular intervals along the filament with about 10 to 20 photosynthetic vegetative cells in between. Nitrogen fixation in these complex multicellular bacteria depends on metabolite exchange between the two cell types, with the heterocysts supplying combined-nitrogen compounds but dependent on the vegetative cells for photosynthetically produced carbon compounds. Here, we used a fluorescent tracer to probe intercellular metabolite exchange in the filamentous heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120. We show that esculin, a fluorescent sucrose analog, is incorporated by a sucrose import system into the cytoplasm of Anabaena cells. The cytoplasmic esculin is rapidly and reversibly exchanged across vegetative-vegetative and vegetative-heterocyst cell junctions. Our measurements reveal the kinetics of esculin exchange and also show that intercellular metabolic communication is lost in a significant fraction of older heterocysts. SepJ, FraC, and FraD are proteins located at the intercellular septa and are suggested to form structures analogous to gap junctions. We show that a ΔsepJΔfraCΔfraDtriple mutant shows an altered septum structure with thinner septa but a denser peptidoglycan layer. Intercellular diffusion of esculin and fluorescein derivatives is impaired in this mutant, which also shows a greatly reduced frequency of nanopores in the intercellular septal cross walls. These findings suggest that FraC, FraD, and SepJ are important for the formation of junctional structures that constitute the major pathway for feeding heterocysts with sucrose.IMPORTANCEAnabaena and its relatives are filamentous cyanobacteria that exhibit a sophisticated form of prokaryotic multicellularity, with the formation of differentiated cell types, including normal photosynthetic cells and specialized nitrogen-fixing cells called heterocysts. The question of how heterocysts communicate and exchange metabolites with other cells in the filament is key to understanding this form of bacterial multicellularity. Here we provide the first information on the intercellular exchange of a physiologically important molecule, sucrose. We show that a fluorescent sucrose analog can be imported into the Anabaena cytoplasm by a sucrose import system. Once in the cytoplasm, it is rapidly and reversibly exchanged among all of the cells in the filament by diffusion across the septal junctions. Photosynthetically produced sucrose likely follows the same route from cytoplasm to cytoplasm. We identify some of the septal proteins involved in sucrose exchange, and our results indicate that these proteins form structures functionally analogous to metazoan gap junctions.

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Identification of Putative Biosynthetic Gene Clusters for Tolyporphins in Multiple Filamentous Cyanobacteria

Life ◽

10.3390/life11080758 ◽

2021 ◽

Vol 11 (8) ◽

pp. 758

Author(s):

Xiaohe Jin ◽

Yunlong Zhang ◽

Ran Zhang ◽

Kathy-Uyen Nguyen ◽

Jonathan S. Lindsey ◽

...

Keyword(s):

Gene Cluster ◽

Gene Clusters ◽

Biosynthetic Gene Cluster ◽

Filamentous Cyanobacterium ◽

Biosynthetic Gene ◽

Filamentous Cyanobacteria ◽

Biosynthetic Gene Clusters ◽

Common Component ◽

Homology Searching ◽

Similar Gene

Tolyporphins A–R are unusual tetrapyrrole macrocycles produced by the non-axenic filamentous cyanobacterium HT-58-2. A putative biosynthetic gene cluster for biosynthesis of tolyporphins (here termed BGC-1) was previously identified in the genome of HT-58-2. Here, homology searching of BGC-1 in HT-58-2 led to identification of similar BGCs in seven other filamentous cyanobacteria, including strains Nostoc sp. 106C, Nostoc sp. RF31YmG, Nostoc sp. FACHB-892, Brasilonema octagenarum UFV-OR1, Brasilonema octagenarum UFV-E1, Brasilonema sennae CENA114 and Oculatella sp. LEGE 06141, suggesting their potential for tolyporphins production. A similar gene cluster (BGC-2) also was identified unexpectedly in HT-58-2. Tolyporphins BGCs were not identified in unicellular cyanobacteria. Phylogenetic analysis based on 16S rRNA and a common component of the BGCs, TolD, points to a close evolutionary history between each strain and their respective tolyporphins BGC. Though identified with putative tolyporphins BGCs, examination of pigments extracted from three cyanobacteria has not revealed the presence of tolyporphins. Overall, the identification of BGCs and potential producers of tolyporphins presents a collection of candidate cyanobacteria for genetic and biochemical analysis pertaining to these unusual tetrapyrrole macrocycles.

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Inactivation of a Heterocyst-Specific Invertase Indicates a Principal Role of Sucrose Catabolism in Heterocysts of Anabaena sp.

Journal of Bacteriology ◽

10.1128/jb.00776-10 ◽

2010 ◽

Vol 192 (20) ◽

pp. 5526-5533 ◽

Cited By ~ 49

Author(s):

Rocío López-Igual ◽

Enrique Flores ◽

Antonia Herrero

Keyword(s):

Fluorescent Protein ◽

Northern Analysis ◽

Filamentous Cyanobacterium ◽

Nitrogen Deprivation ◽

Vegetative Cells ◽

Anabaena Sp ◽

Green Fluorescent ◽

Pcc 7120 ◽

Diazotrophic Growth

ABSTRACT Anabaena sp. strain PCC 7120 is a filamentous cyanobacterium that carries out N2 fixation in specialized cells called heterocysts, which exchange nutrients and regulators with the filament's vegetative cells that perform the photosynthetic fixation of CO2. The Anabaena genome carries two genes coding for alkaline/neutral invertases, invA and invB. As shown by Northern analysis, both genes were expressed monocistronically and induced under nitrogen deprivation, although induction was stronger for invB than for invA. Whereas expression of an InvA-N-GFP fusion (green fluorescent protein [GFP] fused to the N terminus of the InvA protein [InvA-N]) was homogeneous along the cyanobacterial filament, consistent with the lack of dependence on HetR, expression of an InvB-N-GFP fusion upon combined nitrogen deprivation took place mainly in differentiating and mature heterocysts. In an hetR genetic background, the InvB-N-GFP fusion was strongly expressed all along the filament. An insertional mutant of invA could grow diazotrophically but was impaired in nifHDK induction and exhibited an increased frequency of heterocysts, suggesting a regulatory role of the invertase-mediated carbon flux in vegetative cells. In contrast, an invB mutant was strongly impaired in diazotrophic growth, showing a crucial role of sucrose catabolism mediated by the InvB invertase in the heterocysts.

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Heat shock factor is required for growth at normal temperatures in the fission yeast Schizosaccharomyces pombe

Molecular and Cellular Biology ◽

10.1128/mcb.13.2.749-761.1993 ◽

1993 ◽

Vol 13 (2) ◽

pp. 749-761

Author(s):

G J Gallo ◽

H Prentice ◽

R E Kingston

Keyword(s):

Heat Shock ◽

Schizosaccharomyces Pombe ◽

Normal Growth ◽

Growth Conditions ◽

Heat Shock Factor ◽

Binding Ability ◽

Lower Growth ◽

General Role ◽

Functional Conservation ◽

Cellular Processes

Schizosaccharomyces pombe is becoming an increasingly useful organism for the study of cellular processes, since in certain respects, such as the cell cycle and splicing, it is similar to metazoans. Previous biochemical studies have shown that the DNA binding ability of S. pombe heat shock factor (HSF) is fully induced only under stressed conditions, in a manner similar to that of Drosophila melanogaster and humans but differing from the constitutive binding by HSF in the budding yeasts. We report the isolation of the cDNA and gene for the HSF from S. pombe. S. pombe HSF has a domain structure that is more closely related to the structure of human and D. melanogaster HSFs than to the structure of the budding yeast HSFs, further arguing that regulation of HSF in S. pombe is likely to reflect regulation in metazoans. Surprisingly, the S. pombe HSF gene is required for growth at normal temperatures. We show that the S. pombe HSF gene can be replaced by the D. melanogaster HSF gene and that strains containing either of these genes behave similarly to transiently heat-shocked strains with respect to viability and the level of heat-induced transcripts from heat shock promoters. Strains containing the D. melanogaster HSF gene, however, have lower growth rates and show altered morphology at normal growth temperatures. These data demonstrate the functional conservation of domains of HSF that are required for response to heat shock. They further suggest a general role for HSF in growth of eukaryotic cells under normal (nonstressed) growth conditions.

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A Tripartite, Hierarchical Sigma Factor Cascade Promotes Hormogonium Development in the Filamentous Cyanobacterium Nostoc punctiforme

mSphere ◽

10.1128/msphere.00231-19 ◽

2019 ◽

Vol 4 (3) ◽

Cited By ~ 8

Author(s):

Alfonso Gonzalez ◽

Kelsey W. Riley ◽

Thomas V. Harwood ◽

Esthefani G. Zuniga ◽

Douglas D. Risser

Keyword(s):

Sigma Factor ◽

Dominant Role ◽

Sigma Factors ◽

Oxygenic Photosynthesis ◽

Model Organisms ◽

Filamentous Cyanobacterium ◽

Nostoc Punctiforme ◽

Filamentous Cyanobacteria ◽

Content Type ◽

Nitrogen Cycles

ABSTRACT Cyanobacteria are prokaryotes capable of oxygenic photosynthesis, and frequently, nitrogen fixation as well. As a result, they contribute substantially to global primary production and nitrogen cycles. Furthermore, the multicellular filamentous cyanobacteria in taxonomic subsections IV and V are developmentally complex, exhibiting an array of differentiated cell types and filaments, including motile hormogonia, making them valuable model organisms for studying development. To investigate the role of sigma factors in the gene regulatory network (GRN) controlling hormogonium development, a combination of genetic, immunological, and time-resolved transcriptomic analyses were conducted in the model filamentous cyanobacterium Nostoc punctiforme, which, unlike other common model cyanobacteria, retains the developmental complexity of field isolates. The results support a model where the hormogonium GRN is driven by a hierarchal sigma factor cascade, with sigJ activating the expression of both sigC and sigF, as well as a substantial portion of additional hormogonium-specific genes, including those driving changes to cellular architecture. In turn, sigC regulates smaller subsets of genes for several processes, plays a dominant role in promoting reductive cell division, and may also both positively and negatively regulate sigJ to reinforce the developmental program and coordinate the timing of gene expression, respectively. In contrast, the sigF regulon is extremely limited. Among genes with characterized roles in hormogonium development, only pilA shows stringent sigF dependence. For sigJ-dependent genes, a putative consensus promoter was also identified, consisting primarily of a highly conserved extended −10 region, here designated a J-Box, which is widely distributed among diverse members of the cyanobacterial lineage. IMPORTANCE Cyanobacteria are integral to global carbon and nitrogen cycles, and their metabolic capacity coupled with their ease of genetic manipulation make them attractive platforms for applications such as biomaterial and biofertilizer production. Achieving these goals will likely require a detailed understanding and precise rewiring of these organisms’ GRNs. The complex phenotypic plasticity of filamentous cyanobacteria has also made them valuable models of prokaryotic development. However, current research has been limited by focusing primarily on a handful of model strains which fail to reflect the phenotypes of field counterparts, potentially limiting biotechnological advances and a more comprehensive understanding of developmental complexity. Here, using Nostoc punctiforme, a model filamentous cyanobacterium that retains the developmental range of wild isolates, we define previously unknown definitive roles for a trio of sigma factors during hormogonium development. These findings substantially advance our understanding of cyanobacterial development and gene regulation and could be leveraged for future applications.

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Principles of RNA and nucleotide discrimination by the RNA processing enzyme RppH

Nucleic Acids Research ◽

10.1093/nar/gkaa024 ◽

2020 ◽

Vol 48 (7) ◽

pp. 3776-3788 ◽

Cited By ~ 3

Author(s):

Ang Gao ◽

Nikita Vasilyev ◽

Abhishek Kaushik ◽

Wenqian Duan ◽

Alexander Serganov

Keyword(s):

Rna Processing ◽

Reaction Rates ◽

Growth Conditions ◽

Rna Degradation ◽

Nudix Hydrolase ◽

X Ray ◽

E Coli ◽

Cellular Processes ◽

Protein Factor ◽

Hydrolysis Of

Abstract All enzymes face a challenge of discriminating cognate substrates from similar cellular compounds. Finding a correct substrate is especially difficult for the Escherichia coli Nudix hydrolase RppH, which triggers 5′-end-dependent RNA degradation by removing orthophosphate from the 5′-diphosphorylated transcripts. Here we show that RppH binds and slowly hydrolyzes NTPs, NDPs and (p)ppGpp, which each resemble the 5′-end of RNA. A series of X-ray crystal structures of RppH-nucleotide complexes, trapped in conformations either compatible or incompatible with hydrolysis, explain the low reaction rates of mononucleotides and suggest two distinct mechanisms for their hydrolysis. While RppH adopts the same catalytic arrangement with 5′-diphosphorylated nucleotides as with RNA, the enzyme hydrolyzes 5′-triphosphorylated nucleotides by extending the active site with an additional Mg2+ cation, which coordinates another reactive nucleophile. Although the average intracellular pH minimizes the hydrolysis of nucleotides by slowing their reaction with RppH, they nevertheless compete with RNA for binding and differentially inhibit the reactivity of RppH with triphosphorylated and diphosphorylated RNAs. Thus, E. coli RppH integrates various signals, such as competing non-cognate substrates and a stimulatory protein factor DapF, to achieve the differential degradation of transcripts involved in cellular processes important for the adaptation of bacteria to different growth conditions.

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A Putative O-Linked β-N-Acetylglucosamine Transferase Is Essential for Hormogonium Development and Motility in the Filamentous Cyanobacterium Nostoc punctiforme

Journal of Bacteriology ◽

10.1128/jb.00075-17 ◽

2017 ◽

Vol 199 (9) ◽

Cited By ~ 7

Author(s):

Behzad Khayatan ◽

Divleen K. Bains ◽

Monica H. Cheng ◽

Ye Won Cho ◽

Jessica Huynh ◽

...

Keyword(s):

Mutant Strain ◽

Genetic Screen ◽

Molecular Regulation ◽

Filamentous Cyanobacterium ◽

Wild Type ◽

Nostoc Punctiforme ◽

Filamentous Cyanobacteria ◽

Content Type ◽

In The Wild ◽

Acetylglucosamine Transferase

ABSTRACT Most species of filamentous cyanobacteria are capable of gliding motility, likely via a conserved type IV pilus-like system that may also secrete a motility-associated polysaccharide. In a subset of these organisms, motility is achieved only after the transient differentiation of hormogonia, which are specialized filaments that enter a nongrowth state dedicated to motility. Despite the fundamental importance of hormogonia to the life cycles of many filamentous cyanobacteria, the molecular regulation of hormogonium development is largely undefined. To systematically identify genes essential for hormogonium development and motility in the model heterocyst-forming filamentous cyanobacterium Nostoc punctiforme, a forward genetic screen was employed. The first gene identified using this screen, designated ogtA, encodes a putative O-linked β-N-acetylglucosamine transferase (OGT). The deletion of ogtA abolished motility, while ectopic expression of ogtA induced hormogonium development even under hormogonium-repressing conditions. Transcription of ogtA is rapidly upregulated (1 h) following hormogonium induction, and an OgtA-GFPuv fusion protein localized to the cytoplasm. In developing hormogonia, accumulation of PilA but not HmpD is dependent on ogtA. Reverse transcription-quantitative PCR (RT-qPCR) analysis indicated equivalent levels of pilA transcript in the wild-type and ΔogtA mutant strains, while a reporter construct consisting of the intergenic region in the 5′ direction of pilA fused to gfp produced lower levels of fluorescence in the ΔogtA mutant strain than in the wild type. The production of hormogonium polysaccharide in the ΔogtA mutant strain is reduced compared to that in the wild type but comparable to that in a pilA deletion strain. Collectively, these results imply that O-GlcNAc protein modification regulates the accumulation of PilA via a posttranscriptional mechanism in developing hormogonia. IMPORTANCE Filamentous cyanobacteria are among the most developmentally complex prokaryotes. Species such as Nostoc punctiforme develop an array of cell types, including nitrogen-fixing heterocysts, spore-like akinetes, and motile hormogonia, that function in dispersal as well as the establishment of nitrogen-fixing symbioses with plants and fungi. These symbioses are major contributors to global nitrogen fixation. Despite the fundamental importance of hormogonia to the life cycle of filamentous cyanobacteria and the establishment of symbioses, the molecular regulation of hormogonium development is largely undefined. We employed a genetic screen to identify genes essential for hormogonium development and motility in Nostoc punctiforme. The first gene identified using this screen encodes a eukaryotic-like O-linked β-N-acetylglucosamine transferase that is required for accumulation of PilA in hormogonia.

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Viruses Infecting a Freshwater Filamentous Cyanobacterium (Nostocsp.) Encode a Functional CRISPR Array and a Proteobacterial DNA Polymerase B

mBio ◽

10.1128/mbio.00667-16 ◽

2016 ◽

Vol 7 (3) ◽

Cited By ~ 26

Author(s):

Caroline Chénard ◽

Jennifer F. Wirth ◽

Curtis A. Suttle

Keyword(s):

Dna Polymerase ◽

Evolutionary History ◽

Genomic Analysis ◽

Open Reading Frames ◽

Filamentous Cyanobacterium ◽

Filamentous Cyanobacteria ◽

Evolutionary Trajectory ◽

Crispr Array ◽

History Of ◽

Pcc 7120

ABSTRACT Here we present the first genomic characterization of viruses infectingNostoc, a genus of ecologically important cyanobacteria that are widespread in freshwater. Cyanophages A-1 and N-1 were isolated in the 1970s and infectNostocsp. strain PCC 7210 but remained genomically uncharacterized. Their 68,304- and 64,960-bp genomes are strikingly different from those of other sequenced cyanophages. Many putative genes that code for proteins with known functions are similar to those found in filamentous cyanobacteria, showing a long evolutionary history in their host. Cyanophage N-1 encodes a CRISPR array that is transcribed during infection and is similar to the DR5 family of CRISPRs commonly found in cyanobacteria. The presence of a host-related CRISPR array in a cyanophage suggests that the phage can transfer the CRISPR among related cyanobacteria and thereby provide resistance to infection with competing phages. Both viruses also encode a distinct DNA polymerase B that is closely related to those found in plasmids ofCyanothecesp. strain PCC 7424,Nostocsp. strain PCC 7120, andAnabaena variabilisATCC 29413. These polymerases form a distinct evolutionary group that is more closely related to DNA polymerases of proteobacteria than to those of other viruses. This suggests that the polymerase was acquired from a proteobacterium by an ancestral virus and transferred to the cyanobacterial plasmid. Many other open reading frames are similar to a prophage-like element in the genome ofNostocsp. strain PCC 7524. TheNostoccyanophages reveal a history of gene transfers between filamentous cyanobacteria and their viruses that have helped to forge the evolutionary trajectory of this previously unrecognized group of phages.IMPORTANCEFilamentous cyanobacteria belonging to the genusNostocare widespread and ecologically important in freshwater, yet little is known about the genomic content of their viruses. Here we report the first genomic analysis of cyanophages infecting filamentous freshwater cyanobacteria, revealing that their gene content is unlike that of other cyanophages. In addition to sharing many gene homologues with freshwater cyanobacteria, cyanophage N-1 encodes a CRISPR array and expresses it upon infection. Also, both viruses contain a DNA polymerase B-encoding gene with high similarity to genes found in proteobacterial plasmids of filamentous cyanobacteria. The observation that phages can acquire CRISPRs from their hosts suggests that phages can also move them among hosts, thereby conferring resistance to competing phages. The presence in these cyanophages of CRISPR and DNA polymerase B sequences, as well as a suite of other host-related genes, illustrates the long and complex evolutionary history of these viruses and their hosts.

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Allelopathic effect of Ulva intestinalis L. on the Baltic filamentous cyanobacterium Nostoc sp.

Annales Universitatis Paedagogicae Cracoviensis Studia Naturae ◽

10.24917/25438832.3.6 ◽

2018 ◽

Author(s):

Gracjana Budzałek ◽

Sylwia Śliwińska-Wilczewska ◽

Adam Latała

Keyword(s):

Control Treatment ◽

Natural Phenomenon ◽

Allelopathic Effect ◽

Filamentous Cyanobacterium ◽

Filamentous Cyanobacteria ◽

The Baltic Sea ◽

Initial Amount ◽

Ulva Intestinalis ◽

The Baltic ◽

First Time

Allelopathy is a prevalent natural phenomenon in aquatic ecosystem. We reported the effects of the green macroalga Ulva intestinalis L. collected from estuaries of the Baltic Sea (Poland) on the growth and chlorophyll fluorescence of common filamentous cyanobacterium Nostoc sp. It was found that the addition of 50 µL mL–1 extracts obtained from U. intestinalis inhibited growth of cyanobacterium and after one week of exposition the reduction was 35% of initial amount of Nostoc sp. In addition, we demonstrated that on the seventh day of the exposition, the values of Fv/Fm of target cyanobacterium after addition of 100 µL mL–1 extracts obtained from U. intestinalis was reduced to 49%, compared to control treatment. These results showed for the first time the allelopathic activity of U. intestinalis on Baltic filamentous cyanobacteria Nostoc sp.

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Cyanobacterial Transposons Tn5469 and Tn5541 Represent a Novel Noncomposite Transposon Family

Journal of Bacteriology ◽

10.1128/jb.180.22.6059-6063.1998 ◽

1998 ◽

Vol 180 (22) ◽

pp. 6059-6063 ◽

Cited By ~ 5

Author(s):

Michael R. Schaefer ◽

Katherine Kahn

Keyword(s):

Sequence Analysis ◽

Dna Hybridization ◽

Unknown Function ◽

Hybridization Analysis ◽

Filamentous Cyanobacterium ◽

Filamentous Cyanobacteria ◽

Fremyella Diplosiphon ◽

Distinguishing Features

ABSTRACT A noncomposite transposon, designated Tn5541, was isolated from strain Fd33 of the filamentous cyanobacteriumFremyella diplosiphon UTEX 481. Sequence analysis showed that Tn5541 is structurally and genetically very similar to Tn5469, which is also endogenous to F. diplosiphon. Both Tn5469 and Tn5541encode homologous forms of an unusual composite transposase and a protein of unknown function. DNA hybridization analysis showed that like Tn5469, Tn5541 was not widely distributed among cyanobacterial genera. A similar analysis showed that Tn5469 and Tn5541 were equally limited to and present as multiple genomic copies in three of six distinct strains comprising the Tolypothrix 1 cluster of heterocyst-forming filamentous cyanobacteria. These and other distinguishing features suggest that Tn5469 and Tn5541 represent a novel noncomposite transposon family.

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