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Janović A, Maldener I, Menzel C, Parrett GA, Risser DD. The role of FraI in cell-cell communication and differentiation in the hormogonia-forming cyanobacterium Nostoc punctiforme. mSphere 2024:e0051024. [PMID: 39037261 DOI: 10.1128/msphere.00510-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2024] [Accepted: 06/21/2024] [Indexed: 07/23/2024] Open
Abstract
Multicellular cyanobacteria, like Nostoc punctiforme, rely on septal junctions for cell-cell communication, which is crucial for coordinating various physiological processes including differentiation of N2-fixing heterocysts, spore-like akinetes, and hormogonia-short, motile filaments important for dispersal. In this study, we functionally characterize a protein, encoded by gene Npun_F4142, which in a random mutagenesis approach, initially showed a motility-related function. The reconstructed Npun_F4142 knockout mutant exhibits further distinct phenotypic traits, including altered hormogonia formation with significant reduced motility, inability to differentiate heterocysts and filament fragmentation. For that reason, we named the protein FraI (fragmentation phenotype). The mutant displays severely impaired cell-cell communication, due to almost complete absence of the nanopore array in the septal cell wall, which is an essential part of the septal junctions. Despite lack of communication, hormogonia in the ΔfraI mutant maintain motility and phototactic behavior, even though less pronounced than the wild type (WT). This suggests an alternative mechanism for coordinated movement beyond septal junctions. Our study underscores the significance of FraI in nanopore formation and cell differentiation, and provides additional evidence for the importance of septal junction formation and communication in various differentiation traits of cyanobacteria. The findings contribute to a deeper understanding of the regulatory networks governing multicellular cyanobacterial behavior, with implications for broader insights into microbial multicellularity. IMPORTANCE The filament-forming cyanobacterium Nostoc punctiforme serves as a valuable model for studying cell differentiation, including the formation of nitrogen-fixing heterocysts and hormogonia. Hormogonia filaments play a crucial role in dispersal and plant colonization, providing a nitrogen source through atmospheric nitrogen fixation, thus holding promise for fertilizer-free agriculture. The coordination among the hormogonia cells enabling uniform movement toward the positive signal remains poorly understood. This study investigates the role of septal junction-mediated communication in hormogonia differentiation and motility, by studying a ΔfraI mutant with significantly impaired communication. Surprisingly, impaired communication does not abolish synchronized filament movement, suggesting an alternative coordination mechanism. These findings deepen our understanding of cyanobacterial biology and have broader implications for multicellular behavior in prokaryotes.
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Affiliation(s)
- Ana Janović
- Interfaculty Institute of Microbiology and Infection Medicine Tübingen, Organismic Interactions, University of Tübingen, Tübingen, Germany
| | - Iris Maldener
- Interfaculty Institute of Microbiology and Infection Medicine Tübingen, Organismic Interactions, University of Tübingen, Tübingen, Germany
| | - Claudia Menzel
- Interfaculty Institute of Microbiology and Infection Medicine Tübingen, Organismic Interactions, University of Tübingen, Tübingen, Germany
| | - Gabriel A Parrett
- Department of Biology, University of Colorado, Colorado Springs, Colorado, USA
| | - Douglas D Risser
- Department of Biology, University of Colorado, Colorado Springs, Colorado, USA
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Parrett GA, Brones PD, Jenkins GM, Mounts SM, Nguyen A, Risser DD. Identification of a morphogene required for tapered filament termini in filamentous cyanobacteria. MICROBIOLOGY (READING, ENGLAND) 2023; 169. [PMID: 37971486 DOI: 10.1099/mic.0.001416] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2023]
Abstract
Although the photosynthetic cyanobacteria are monophyletic, they exhibit substantial morphological diversity across species, and even within an individual species due to phenotypic plasticity in response to life cycles and environmental signals. This is particularly prominent among the multicellular filamentous cyanobacteria. One example of this is the appearance of tapering at the filament termini. However, the morphogenes controlling this phenotype and the adaptive function of this morphology are not well defined. Here, using the model filamentous cyanobacterium Nostoc punctiforme ATCC29133 (PCC73102), we identify tftA, a morphogene required for the development of tapered filament termini. The tftA gene is specifically expressed in developing hormogonia, motile trichomes where the tapered filament morphology is observed, and encodes a protein containing putative amidase_3 and glucosaminidase domains, implying a function in peptidoglycan hydrolysis. Deletion of tftA abolished filament tapering inidcating that TftA plays a role in remodelling the cell wall to produce tapered filaments. Genomic conservation of tftA specifically in filamentous cyanobacteria indicates this is likely to be a conserved mechanism among these organisms. Finally, motility assays indicate that filaments with tapered termini migrate more efficiently through dense substratum, providing a plausible biological role for this morphology.
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Affiliation(s)
- Gabriel A Parrett
- Department of Biology, University of Colorado Colorado Springs, Colorado Springs, CO 80918, USA
| | - Peyton D Brones
- Department of Biology, University of Colorado Colorado Springs, Colorado Springs, CO 80918, USA
| | - Garrett M Jenkins
- Department of Biology, University of Colorado Colorado Springs, Colorado Springs, CO 80918, USA
| | - Savanna M Mounts
- Department of Biology, University of Colorado Colorado Springs, Colorado Springs, CO 80918, USA
| | - Alicia Nguyen
- Department of Biology, University of Colorado Colorado Springs, Colorado Springs, CO 80918, USA
| | - Douglas D Risser
- Department of Biology, University of Colorado Colorado Springs, Colorado Springs, CO 80918, USA
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3
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Toida K, Kushida W, Yamamoto H, Yamamoto K, Ishii K, Uesaka K, Kanaly RA, Kutsuna S, Ihara K, Fujita Y, Iwasaki H. The GGDEF protein Dgc2 suppresses both motility and biofilm formation in the filamentous cyanobacterium Leptolyngbya boryana. Microbiol Spectr 2023; 11:e0483722. [PMID: 37655901 PMCID: PMC10581220 DOI: 10.1128/spectrum.04837-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Accepted: 06/30/2023] [Indexed: 09/02/2023] Open
Abstract
Colony pattern formations of bacteria with motility manifest complicated morphological self-organization phenomena. Leptolyngbya boryana is a filamentous cyanobacterium, which has been used as a genetic model organism for studying metabolism including photosynthesis and nitrogen fixation. A widely used type strain [wild type (WT) in this article] of this species has not been reported to show any motile activity. However, we isolated a spontaneous mutant strain that shows active motility (gliding activity) to give rise to complicated colony patterns, including comet-like wandering clusters and disk-like rotating vortices on solid media. Whole-genome resequencing identified multiple mutations in the genome of the mutant strain. We confirmed that inactivation of the candidate gene dgc2 (LBDG_02920) in the WT background was sufficient to give rise to motility and morphologically complex colony patterns. This gene encodes a protein containing the GGDEF motif which is conserved at the catalytic domain of diguanylate cyclase (DGC). Although DGC has been reported to be involved in biofilm formation, the dgc2 mutant significantly facilitated biofilm formation, suggesting a role for the dgc2 gene in suppressing both gliding motility and biofilm formation. Thus, Leptolyngbya is expected to be an excellent genetic model for studying dynamic colony pattern formation and to provide novel insights into the role of DGC family genes in biofilm formation. IMPORTANCE Self-propelled bacteria often exhibit complex collective behaviors, such as formation of dense-moving clusters, which are exemplified by wandering comet-like and rotating disk-like colonies; however, the molecular details of how these structures are formed are scant. We found that a strain of the filamentous cyanobacterium Leptolyngbya deficient in the GGDEF protein gene dgc2 elicits motility and complex and dynamic colony pattern formation, including comet-like and disk-like clusters. Although c-di-GMP has been reported to activate biofilm formation in some bacterial species, disruption of dgc2 unexpectedly enhanced it, suggesting a novel role for this GGDEF protein for inhibiting both colony pattern formation and biofilm formation.
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Affiliation(s)
- Kazuma Toida
- Department of Electrical Engineering and Bioscience, Graduate School of Sciences and Engineering, TWIns, Waseda University, Tokyo, Japan
| | - Wakana Kushida
- Department of Electrical Engineering and Bioscience, Graduate School of Sciences and Engineering, TWIns, Waseda University, Tokyo, Japan
| | - Hiroki Yamamoto
- Department of Electrical Engineering and Bioscience, Graduate School of Sciences and Engineering, TWIns, Waseda University, Tokyo, Japan
| | - Kyoka Yamamoto
- Department of Electrical Engineering and Bioscience, Graduate School of Sciences and Engineering, TWIns, Waseda University, Tokyo, Japan
| | - Kaichi Ishii
- Department of Electrical Engineering and Bioscience, Graduate School of Sciences and Engineering, TWIns, Waseda University, Tokyo, Japan
| | - Kazuma Uesaka
- Center for Gene Research, Nagoya University, Nagoya, Japan
| | - Robert A. Kanaly
- Graduate School of Nanobioscience, Yokohama City University, Yokohama, Japan
| | - Shinsuke Kutsuna
- Graduate School of Nanobioscience, Yokohama City University, Yokohama, Japan
| | - Kunio Ihara
- Center for Gene Research, Nagoya University, Nagoya, Japan
| | - Yuichi Fujita
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | - Hideo Iwasaki
- Department of Electrical Engineering and Bioscience, Graduate School of Sciences and Engineering, TWIns, Waseda University, Tokyo, Japan
- metaPhorest, Bioaesthetics Platform, Waseda University, Tokyo, Japan
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4
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Risser DD. Hormogonium Development and Motility in Filamentous Cyanobacteria. Appl Environ Microbiol 2023; 89:e0039223. [PMID: 37199640 PMCID: PMC10304961 DOI: 10.1128/aem.00392-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/19/2023] Open
Abstract
Filamentous cyanobacteria exhibit some of the greatest developmental complexity observed in the prokaryotic domain. This includes the ability to differentiate nitrogen-fixing cells known as heterocysts, spore-like akinetes, and hormogonia, which are specialized motile filaments capable of gliding on solid surfaces. Hormogonia and motility play critical roles in several aspects of the biology of filamentous cyanobacteria, including dispersal, phototaxis, the formation of supracellular structures, and the establishment of nitrogen-fixing symbioses with plants. While heterocyst development has been investigated extensively at the molecular level, much less is known about akinete or hormogonium development and motility. This is due, in part, to the loss of developmental complexity during prolonged laboratory culture in commonly employed model filamentous cyanobacteria. In this review, recent progress in understanding the molecular level regulation of hormogonium development and motility in filamentous cyanobacteria is discussed, with a focus on experiments performed using the genetically tractable model filamentous cyanobacterium Nostoc punctiforme, which retains the developmental complexity of field isolates.
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Affiliation(s)
- Douglas D. Risser
- Department of Biology, University of Colorado Colorado Springs, Colorado Springs, Colorado, USA
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A DnaK(Hsp70) Chaperone System Connects Type IV Pilus Activity to Polysaccharide Secretion in Cyanobacteria. mBio 2022; 13:e0051422. [PMID: 35420478 PMCID: PMC9239167 DOI: 10.1128/mbio.00514-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Surface motility powered by type IV pili (T4P) is widespread among bacteria, including the photosynthetic cyanobacteria. This form of movement typically requires the deposition of a motility-associated polysaccharide, and several studies indicate that there is complex coregulation of T4P motor activity and polysaccharide production, although a mechanistic understanding of this coregulation is not fully defined. Here, using a combination of genetic, comparative genomic, transcriptomic, protein-protein interaction, and cytological approaches in the model filamentous cyanobacterium N. punctiforme, we provided evidence that a DnaK-type chaperone system coupled the activity of the T4P motors to the production of the motility-associated hormogonium polysaccharide (HPS). The results from these studies indicated that DnaK1 and DnaJ3 along with GrpE comprised a chaperone system that interacted specifically with active T4P motors and was required to produce HPS. Genomic conservation in cyanobacteria and the conservation of the protein-protein interaction network in the model unicellular cyanobacterium Synechocystis sp. strain PCC 6803 imply that this system is conserved among nearly all motile cyanobacteria and provides a mechanism to coordinate polysaccharide secretion and T4P activity in these organisms.
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Han Y, Jakob A, Engel S, Wilde A, Nils S. PATAN-domain regulators interact with the Type IV pilus motor to control phototactic orientation in the cyanobacterium Synechocystis. Mol Microbiol 2021; 117:790-801. [PMID: 34936151 DOI: 10.1111/mmi.14872] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Revised: 12/19/2021] [Accepted: 12/20/2021] [Indexed: 11/28/2022]
Abstract
Many prokaryotes show complex behaviors that require the intricate spatial and temporal organization of cellular protein machineries, leading to asymmetrical protein distribution and cell polarity. One such behavior is cyanobacterial phototaxis which relies on the dynamic localization of the Type IV pilus motor proteins in response to light. In the cyanobacterium Synechocystis, various signaling systems encompassing chemotaxis-related CheY- and PatA-like response regulators are critical players in switching between positive and negative phototaxis depending on the light intensity and wavelength. In this study, we show that PatA-type regulators evolved from chemosensory systems. Using fluorescence microscopy and yeast-two-hybrid analysis, we demonstrate that they localize to the inner membrane, where they interact with the N-terminal cytoplasmic domain of PilC and the pilus assembly ATPase PilB1. By separately expressing the subdomains of the response regulator PixE, we confirm that only the N-terminal PATAN domain interacts with PilB1, localizes to the membrane, and is sufficient to reverse phototactic orientation. These experiments established that the PATAN domain is the principal output domain of PatA-type regulators which we presume to modulate pilus extension by binding to the pilus motor components.
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Affiliation(s)
- Yu Han
- Molecular Genetics, Institute of Biology III, University of Freiburg, 79104, Freiburg, Germany
| | - Annik Jakob
- Molecular Genetics, Institute of Biology III, University of Freiburg, 79104, Freiburg, Germany
| | - Sophia Engel
- Molecular Genetics, Institute of Biology III, University of Freiburg, 79104, Freiburg, Germany
| | - Annegret Wilde
- Molecular Genetics, Institute of Biology III, University of Freiburg, 79104, Freiburg, Germany
| | - Schuergers Nils
- Molecular Genetics, Institute of Biology III, University of Freiburg, 79104, Freiburg, Germany
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7
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Yamamoto H, Fukasawa Y, Shoji Y, Hisamoto S, Kikuchi T, Takamatsu A, Iwasaki H. Scattered migrating colony formation in the filamentous cyanobacterium, Pseudanabaena sp. NIES-4403. BMC Microbiol 2021; 21:227. [PMID: 34399691 PMCID: PMC8365994 DOI: 10.1186/s12866-021-02183-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Accepted: 04/08/2021] [Indexed: 12/12/2022] Open
Abstract
Background Bacteria have been reported to exhibit complicated morphological colony patterns on solid media, depending on intracellular, and extracellular factors such as motility, cell propagation, and cell-cell interaction. We isolated the filamentous cyanobacterium, Pseudanabaena sp. NIES-4403 (Pseudanabaena, hereafter), that forms scattered (discrete) migrating colonies on solid media. While the scattered colony pattern has been observed in some bacterial species, the mechanism underlying such a pattern still remains obscure. Results We studied the morphology of Pseudanabaena migrating collectively and found that this species forms randomly scattered clusters varying in size and further consists of a mixture of comet-like wandering clusters and disk-like rotating clusters. Quantitative analysis of the formation of these wandering and rotating clusters showed that bacterial filaments tend to follow trajectories of previously migrating filaments at velocities that are dependent on filament length. Collisions between filaments occurred without crossing paths, which enhanced their nematic alignments, giving rise to bundle-like colonies. As cells increased and bundles aggregated, comet-like wandering clusters developed. The direction and velocity of the movement of cells in comet-like wandering clusters were highly coordinated. When the wandering clusters entered into a circular orbit, they turned into rotating clusters, maintaining a more stable location. Disk-like rotating clusters may rotate for days, and the speed of cells within a rotating cluster increases from the center to the outmost part of the cluster. Using a mathematical modeling with simplified assumption we reproduced some features of the scattered pattern including migrating clusters. Conclusion Based on these observations, we propose that Pseudanabaena forms scattered migrating colonies that undergo a series of transitions involving several morphological patterns. A simplified model is able to reproduce some features of the observed migrating clusters. Supplementary Information The online version contains supplementary material available at 10.1186/s12866-021-02183-5.
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Affiliation(s)
- Hiroki Yamamoto
- Department of Electrical Engineering and Bioscience, Waseda University, Shinjuku, Tokyo, 162-8480, Japan
| | - Yuki Fukasawa
- Department of Electrical Engineering and Bioscience, Waseda University, Shinjuku, Tokyo, 162-8480, Japan
| | - Yu Shoji
- Department of Electrical Engineering and Bioscience, Waseda University, Shinjuku, Tokyo, 162-8480, Japan
| | - Shumpei Hisamoto
- Department of Electrical Engineering and Bioscience, Waseda University, Shinjuku, Tokyo, 162-8480, Japan
| | - Tomohiro Kikuchi
- Department of Electrical Engineering and Bioscience, Waseda University, Shinjuku, Tokyo, 162-8480, Japan
| | - Atsuko Takamatsu
- Department of Electrical Engineering and Bioscience, Waseda University, Shinjuku, Tokyo, 162-8480, Japan
| | - Hideo Iwasaki
- Department of Electrical Engineering and Bioscience, Waseda University, Shinjuku, Tokyo, 162-8480, Japan.
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8
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Chen Z, Shang JL, Hou S, Li T, Li Q, Yang YW, Hess WR, Qiu BS. Genomic and transcriptomic insights into the habitat adaptation of the diazotrophic paddy-field cyanobacterium Nostoc sphaeroides. Environ Microbiol 2021; 23:5802-5822. [PMID: 33848055 DOI: 10.1111/1462-2920.15521] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2020] [Revised: 03/25/2021] [Accepted: 04/08/2021] [Indexed: 12/13/2022]
Abstract
Nitrogen-fixing cyanobacteria are common in paddy fields, one of the most productive wetland ecosystems. Here, we present the complete genome of Nostoc sphaeroides, a paddy-field diazotroph used for food and medicine for more than 1700 years and deciphered the transcriptional regulation during the developmental transition from hormogonia to vegetative filaments with heterocysts. The genome of N. sphaeroides consists of one circular chromosome (6.48 Mb), one of the largest ever reported megaplasmids (2.34 Mb), and seven plasmids. Multiple gene families involved in the adaption to high solar radiation and water fluctuation conditions were found expanded, while genes involved in anoxic adaptation and phosphonate utilization are located on the megaplasmid, suggesting its indispensable role in environmental adaptation. Distinct gene expression patterns were observed during the light-intensity-regulated transition from hormogonia to vegetative filaments, specifically, genes encoding proteins involved in photosynthetic light reaction, carbon fixation, nitrogen metabolism and heterocyst differentiation were significantly upregulated, whereas genes related to cell motility were down-regulated. Our results provide genomic and transcriptomic insights into the adaptation of a filamentous nitrogen-fixing cyanobacterium to the highly dynamic paddy-field habitat, suggesting N. sphaeroides as an excellent system to understand the transition from aquatic to terrestrial habitats and to support sustainable rice production.
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Affiliation(s)
- Zhen Chen
- School of Life Sciences, Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan, Hubei, 430079, China.,Hubei Key Laboratory of Edible Wild Plants Conservation and Utilization, Hubei Normal University, Huangshi, Hubei, 435002, China
| | - Jin-Long Shang
- School of Life Sciences, Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan, Hubei, 430079, China
| | - Shengwei Hou
- Department of Biological Sciences, University of Southern California, CA, Los Angeles, 90089, USA
| | - Tao Li
- Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Science, Wuhan, Hubei, 430072, China
| | - Qi Li
- Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Science, Wuhan, Hubei, 430072, China
| | - Yi-Wen Yang
- School of Life Sciences, Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan, Hubei, 430079, China
| | - Wolfgang R Hess
- Genetics and Experimental Bioinformatics, Institute of Biology III, Faculty of Biology, University of Freiburg, Freiburg, 79104, Germany
| | - Bao-Sheng Qiu
- School of Life Sciences, Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan, Hubei, 430079, China
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9
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The cyanobacterial taxis protein HmpF regulates type IV pilus activity in response to light. Proc Natl Acad Sci U S A 2021; 118:2023988118. [PMID: 33723073 DOI: 10.1073/pnas.2023988118] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Motility is ubiquitous in prokaryotic organisms including the photosynthetic cyanobacteria where surface motility powered by type 4 pili (T4P) is common and facilitates phototaxis to seek out favorable light environments. In cyanobacteria, chemotaxis-like systems are known to regulate motility and phototaxis. The characterized phototaxis systems rely on methyl-accepting chemotaxis proteins containing bilin-binding GAF domains capable of directly sensing light, and the mechanism by which they regulate the T4P is largely undefined. In this study we demonstrate that cyanobacteria possess a second, GAF-independent, means of sensing light to regulate motility and provide insight into how a chemotaxis-like system regulates the T4P motors. A combination of genetic, cytological, and protein-protein interaction analyses, along with experiments using the proton ionophore carbonyl cyanide m-chlorophenyl hydrazine, indicate that the Hmp chemotaxis-like system of the model filamentous cyanobacterium Nostoc punctiforme is capable of sensing light indirectly, possibly via alterations in proton motive force, and modulates direct interaction between the cyanobacterial taxis protein HmpF, and Hfq, PilT1, and PilT2 to regulate the T4P motors. Given that the Hmp system is widely conserved in cyanobacteria, and the finding from this study that orthologs of HmpF and T4P proteins from the distantly related model unicellular cyanobacterium Synechocystis sp. strain PCC6803 interact in a similar manner to their N. punctiforme counterparts, it is likely that this represents a ubiquitous means of regulating motility in response to light in cyanobacteria.
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10
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Springstein BL, Nürnberg DJ, Weiss GL, Pilhofer M, Stucken K. Structural Determinants and Their Role in Cyanobacterial Morphogenesis. Life (Basel) 2020; 10:E355. [PMID: 33348886 PMCID: PMC7766704 DOI: 10.3390/life10120355] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Revised: 12/04/2020] [Accepted: 12/09/2020] [Indexed: 12/16/2022] Open
Abstract
Cells have to erect and sustain an organized and dynamically adaptable structure for an efficient mode of operation that allows drastic morphological changes during cell growth and cell division. These manifold tasks are complied by the so-called cytoskeleton and its associated proteins. In bacteria, FtsZ and MreB, the bacterial homologs to tubulin and actin, respectively, as well as coiled-coil-rich proteins of intermediate filament (IF)-like function to fulfil these tasks. Despite generally being characterized as Gram-negative, cyanobacteria have a remarkably thick peptidoglycan layer and possess Gram-positive-specific cell division proteins such as SepF and DivIVA-like proteins, besides Gram-negative and cyanobacterial-specific cell division proteins like MinE, SepI, ZipN (Ftn2) and ZipS (Ftn6). The diversity of cellular morphologies and cell growth strategies in cyanobacteria could therefore be the result of additional unidentified structural determinants such as cytoskeletal proteins. In this article, we review the current advances in the understanding of the cyanobacterial cell shape, cell division and cell growth.
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Affiliation(s)
- Benjamin L. Springstein
- Department of Microbiology, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Dennis J. Nürnberg
- Department of Physics, Biophysics and Biochemistry of Photosynthetic Organisms, Freie Universität Berlin, 14195 Berlin, Germany;
| | - Gregor L. Weiss
- Department of Biology, Institute of Molecular Biology & Biophysics, ETH Zürich, 8092 Zürich, Switzerland; (G.L.W.); (M.P.)
| | - Martin Pilhofer
- Department of Biology, Institute of Molecular Biology & Biophysics, ETH Zürich, 8092 Zürich, Switzerland; (G.L.W.); (M.P.)
| | - Karina Stucken
- Department of Food Engineering, Universidad de La Serena, La Serena 1720010, Chile;
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11
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Springstein BL, Nürnberg DJ, Woehle C, Weissenbach J, Theune ML, Helbig AO, Maldener I, Dagan T, Stucken K. Two novel heteropolymer-forming proteins maintain the multicellular shape of the cyanobacterium Anabaena sp. PCC 7120. FEBS J 2020; 288:3197-3216. [PMID: 33205554 DOI: 10.1111/febs.15630] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 10/29/2020] [Accepted: 11/13/2020] [Indexed: 12/14/2022]
Abstract
Polymerizing and filament-forming proteins are instrumental for numerous cellular processes such as cell division and growth. Their function in stabilization and localization of protein complexes and replicons is achieved by a filamentous structure. Known filamentous proteins assemble into homopolymers consisting of single subunits - for example, MreB and FtsZ in bacteria - or heteropolymers that are composed of two subunits, for example, keratin and α/β tubulin in eukaryotes. Here, we describe two novel coiled-coil-rich proteins (CCRPs) in the filament-forming cyanobacterium Anabaena sp. PCC 7120 (hereafter Anabaena) that assemble into a heteropolymer and function in the maintenance of the Anabaena multicellular shape (termed trichome). The two CCRPs - Alr4504 and Alr4505 (named ZicK and ZacK) - are strictly interdependent for the assembly of protein filaments in vivo and polymerize nucleotide independently in vitro, similar to known intermediate filament (IF) proteins. A ΔzicKΔzacK double mutant is characterized by a zigzagged cell arrangement and hence a loss of the typical linear Anabaena trichome shape. ZicK and ZacK interact with themselves, with each other, with the elongasome protein MreB, the septal junction protein SepJ and the divisome associate septal protein SepI. Our results suggest that ZicK and ZacK function in cooperation with SepJ and MreB to stabilize the Anabaena trichome and are likely essential for the manifestation of the multicellular shape in Anabaena. Our study reveals the presence of filament-forming IF-like proteins whose function is achieved through the formation of heteropolymers in cyanobacteria.
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Affiliation(s)
| | | | | | | | - Marius L Theune
- Institute of General Microbiology, University of Kiel, Germany
| | - Andreas O Helbig
- AG Proteomics & Bioanalytics, Institute for Experimental Medicine, Christian-Albrechts-Universität zu Kiel, Germany
| | - Iris Maldener
- Interfaculty Institute of Microbiology and Infection Medicine Tübingen/Organismic Interactions, University of Tübingen, Germany
| | - Tal Dagan
- Institute of General Microbiology, University of Kiel, Germany
| | - Karina Stucken
- Department of Food Engineering, University of La Serena, Chile
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12
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Inactivation of Three RG(S/T)GR Pentapeptide-Containing Negative Regulators of HetR Results in Lethal Differentiation of Anabaena PCC 7120. Life (Basel) 2020; 10:life10120326. [PMID: 33291589 PMCID: PMC7761841 DOI: 10.3390/life10120326] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2020] [Revised: 11/27/2020] [Accepted: 12/01/2020] [Indexed: 12/19/2022] Open
Abstract
The filamentous cyanobacterium Anabaena sp. PCC 7120 produces, during the differentiation of heterocysts, a short peptide PatS and a protein HetN, both containing an RGSGR pentapeptide essential for activity. Both act on the master regulator HetR to guide heterocyst pattern formation by controlling the binding of HetR to DNA and its turnover. A third small protein, PatX, with an RG(S/T)GR motif is present in all HetR-containing cyanobacteria. In a nitrogen-depleted medium, inactivation of patX does not produce a discernible change in phenotype, but its overexpression blocks heterocyst formation. Mutational analysis revealed that PatX is not required for normal intercellular signaling, but it nonetheless is required when PatS is absent to prevent rapid ectopic differentiation. Deprivation of all three negative regulators—PatS, PatX, and HetN—resulted in synchronous differentiation. However, in a nitrogen-containing medium, such deprivation leads to extensive fragmentation, cell lysis, and aberrant differentiation, while either PatX or PatS as the sole HetR regulator can establish and maintain a semiregular heterocyst pattern. These results suggest that tight control over HetR by PatS and PatX is needed to sustain vegetative growth and regulated development. The mutational analysis has been interpreted in light of the opposing roles of negative regulators of HetR and the positive regulator HetL.
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Conradi FD, Mullineaux CW, Wilde A. The Role of the Cyanobacterial Type IV Pilus Machinery in Finding and Maintaining a Favourable Environment. Life (Basel) 2020; 10:life10110252. [PMID: 33114175 PMCID: PMC7690835 DOI: 10.3390/life10110252] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Revised: 10/18/2020] [Accepted: 10/21/2020] [Indexed: 12/11/2022] Open
Abstract
Type IV pili (T4P) are proteinaceous filaments found on the cell surface of many prokaryotic organisms and convey twitching motility through their extension/retraction cycles, moving cells across surfaces. In cyanobacteria, twitching motility is the sole mode of motility properly characterised to date and is the means by which cells perform phototaxis, the movement towards and away from directional light sources. The wavelength and intensity of the light source determine the direction of movement and, sometimes in concert with nutrient conditions, act as signals for some cyanobacteria to form mucoid multicellular assemblages. Formation of such aggregates or flocs represents an acclimation strategy to unfavourable environmental conditions and stresses, such as harmful light conditions or predation. T4P are also involved in natural transformation by exogenous DNA, secretion processes, and in cellular adaptation and survival strategies, further cementing the role of cell surface appendages. In this way, cyanobacteria are finely tuned by external stimuli to either escape unfavourable environmental conditions via phototaxis, exchange genetic material, and to modify their surroundings to fit their needs by forming multicellular assemblies.
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Affiliation(s)
- Fabian D. Conradi
- School of Biological and Chemical Sciences, Queen Mary University of London, London E1 4NS, UK; (F.D.C.); (C.W.M.)
| | - Conrad W. Mullineaux
- School of Biological and Chemical Sciences, Queen Mary University of London, London E1 4NS, UK; (F.D.C.); (C.W.M.)
| | - Annegret Wilde
- Institute of Biology III, University of Freiburg, Schänzlestr. 1, 79104 Freiburg; Germany
- Correspondence:
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14
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Zuniga EG, Boateng KKA, Bui NU, Kurnfuli S, Muthana SM, Risser DD. Identification of a hormogonium polysaccharide-specific gene set conserved in filamentous cyanobacteria. Mol Microbiol 2020; 114:597-608. [PMID: 32614458 DOI: 10.1111/mmi.14566] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Revised: 06/23/2020] [Indexed: 01/09/2023]
Abstract
Cyanobacteria comprise a phylum defined by the capacity for oxygenic photosynthesis. Members of this phylum are frequently motile as well. Strains that display gliding or twitching motility across semisolid surfaces are powered by a conserved type IV pilus system (T4P). Among the filamentous, heterocyst-forming cyanobacteria, motility is usually confined to specialized filaments known as hormogonia, and requires the deposition of an associated hormogonium polysaccharide (HPS). The genes involved in assembly and export of HPS are largely undefined, and it has been hypothesized that HPS exits the outer membrane via an atypical T4P-driven mechanism. Here, several novel hps loci, primarily encoding glycosyl transferases, are identified. Mutational analysis demonstrates that the majority of these genes are essential for both motility and production of HPS. Notably, most mutant strains accumulate wild-type cellular levels of the major pilin PilA, but not extracellular PilA, indicating dysregulation of the T4P motors, and, therefore, a regulatory interaction between HPS assembly and T4P activity. A co-occurrence analysis of Hps orthologs among cyanobacteria identified an extended set of putative Hps proteins comprising most components of a Wzx/Wzy-type polysaccharide synthesis and export system. This implies that HPS may be secreted through a more canonical pathway, rather than a T4P-mediated mechanism.
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Affiliation(s)
| | | | - Nhi U Bui
- Department of Biology, University of the Pacific, Stockton, CA, USA
| | - Shadi Kurnfuli
- Department of Biology, University of the Pacific, Stockton, CA, USA
| | - Sawsan M Muthana
- Department of Biology, University of the Pacific, Stockton, CA, USA
| | - Douglas D Risser
- Department of Biology, University of the Pacific, Stockton, CA, USA
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15
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The Hybrid Histidine Kinase HrmK Is an Early-Acting Factor in the Hormogonium Gene Regulatory Network. J Bacteriol 2020; 202:JB.00675-19. [PMID: 31792014 DOI: 10.1128/jb.00675-19] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Accepted: 11/27/2019] [Indexed: 01/15/2023] Open
Abstract
Filamentous, heterocyst-forming cyanobacteria belonging to taxonomic subsections IV and V are developmentally complex multicellular organisms capable of differentiating an array of cell and filament types, including motile hormogonia. Hormogonia exhibit gliding motility that facilitates dispersal, phototaxis, and the establishment of nitrogen-fixing symbioses. The gene regulatory network (GRN) governing hormogonium development involves a hierarchical sigma factor cascade, but the factors governing the activation of this cascade are currently undefined. Here, using a forward genetic approach, we identified hrmK, a gene encoding a putative hybrid histidine kinase that functions upstream of the sigma factor cascade. The deletion of hrmK produced nonmotile filaments that failed to display hormogonium morphology or accumulate hormogonium-specific proteins or polysaccharide. Targeted transcriptional analyses using reverse transcription-quantitative PCR (RT-qPCR) demonstrated that hormogonium-specific genes both within and outside the sigma factor cascade are drastically downregulated in the absence of hrmK and that hrmK may be subject to indirect, positive autoregulation via sigJ and sigC Orthologs of HrmK are ubiquitous among, and exclusive to, heterocyst-forming cyanobacteria. Collectively, these results indicate that hrmK functions upstream of the sigma factor cascade to initiate hormogonium development, likely by modulating the phosphorylation state of an unknown protein that may serve as the master regulator of hormogonium development in heterocyst-forming cyanobacteria.IMPORTANCE Filamentous cyanobacteria are morphologically complex, with several representative species amenable to routine genetic manipulation, making them excellent model organisms for the study of development. Furthermore, two of the developmental alternatives, nitrogen-fixing heterocysts and motile hormogonia, are essential to establish nitrogen-fixing symbioses with plant partners. These symbioses are integral to global nitrogen cycles and could be artificially recreated with crop plants to serve as biofertilizers, but to achieve this goal, detailed understanding and manipulation of the hormogonium and heterocyst gene regulatory networks may be necessary. Here, using the model organism Nostoc punctiforme, we identify a previously uncharacterized hybrid histidine kinase that is confined to heterocyst-forming cyanobacteria as the earliest known participant in hormogonium development.
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16
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Springstein BL, Woehle C, Weissenbach J, Helbig AO, Dagan T, Stucken K. Identification and characterization of novel filament-forming proteins in cyanobacteria. Sci Rep 2020; 10:1894. [PMID: 32024928 PMCID: PMC7002697 DOI: 10.1038/s41598-020-58726-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Accepted: 01/17/2020] [Indexed: 11/09/2022] Open
Abstract
Filament-forming proteins in bacteria function in stabilization and localization of proteinaceous complexes and replicons; hence they are instrumental for myriad cellular processes such as cell division and growth. Here we present two novel filament-forming proteins in cyanobacteria. Surveying cyanobacterial genomes for coiled-coil-rich proteins (CCRPs) that are predicted as putative filament-forming proteins, we observed a higher proportion of CCRPs in filamentous cyanobacteria in comparison to unicellular cyanobacteria. Using our predictions, we identified nine protein families with putative intermediate filament (IF) properties. Polymerization assays revealed four proteins that formed polymers in vitro and three proteins that formed polymers in vivo. Fm7001 from Fischerella muscicola PCC 7414 polymerized in vitro and formed filaments in vivo in several organisms. Additionally, we identified a tetratricopeptide repeat protein - All4981 - in Anabaena sp. PCC 7120 that polymerized into filaments in vitro and in vivo. All4981 interacts with known cytoskeletal proteins and is indispensable for Anabaena viability. Although it did not form filaments in vitro, Syc2039 from Synechococcus elongatus PCC 7942 assembled into filaments in vivo and a Δsyc2039 mutant was characterized by an impaired cytokinesis. Our results expand the repertoire of known prokaryotic filament-forming CCRPs and demonstrate that cyanobacterial CCRPs are involved in cell morphology, motility, cytokinesis and colony integrity.
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Affiliation(s)
- Benjamin L Springstein
- Institute of General Microbiology, Christian-Albrechts-Universität zu Kiel, Kiel, Germany.
- Department of Microbiology, Blavatnick Institute, Harvard Medical School, Boston, MA, USA.
| | - Christian Woehle
- Institute of General Microbiology, Christian-Albrechts-Universität zu Kiel, Kiel, Germany
- Max Planck Institute for Plant Breeding Research, Max Planck-Genome-centre Cologne, Cologne, Germany
| | - Julia Weissenbach
- Institute of General Microbiology, Christian-Albrechts-Universität zu Kiel, Kiel, Germany
- Faculty of Biology, Technion-Israel Institute of Technology, Haifa, Israel
| | - Andreas O Helbig
- Institute for Experimental Medicine, Christian-Albrechts-Universität zu Kiel, Kiel, Germany
| | - Tal Dagan
- Institute of General Microbiology, Christian-Albrechts-Universität zu Kiel, Kiel, Germany
| | - Karina Stucken
- Department of Food Engineering, Universidad de La Serena, La Serena, Chile.
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17
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Jakob A, Nakamura H, Kobayashi A, Sugimoto Y, Wilde A, Masuda S. The (PATAN)-CheY-Like Response Regulator PixE Interacts with the Motor ATPase PilB1 to Control Negative Phototaxis in the Cyanobacterium Synechocystis sp. PCC 6803. PLANT & CELL PHYSIOLOGY 2020; 61:296-307. [PMID: 31621869 DOI: 10.1093/pcp/pcz194] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Accepted: 10/09/2019] [Indexed: 05/22/2023]
Abstract
The cyanobacterium Synechocystis sp. PCC 6803 can move directionally on a moist surface toward or away from a light source to reach optimal light conditions for its photosynthetic lifestyle. This behavior, called phototaxis, is mediated by type IV pili (T4P), which can pull a single cell into a certain direction. Several photoreceptors and their downstream signal transduction elements are involved in the control of phototaxis. However, the critical steps of local pilus assembly in positive and negative phototaxis remain elusive. One of the photoreceptors controlling negative phototaxis in Synechocystis is the blue-light sensor PixD. PixD forms a complex with the CheY-like response regulator PixE that dissociates upon illumination with blue light. In this study, we investigate the phototactic behavior of pixE deletion and overexpression mutants in response to unidirectional red light with or without additional blue-light irradiation. Furthermore, we show that PixD and PixE partly localize in spots close to the cytoplasmic membrane. Interaction studies of PixE with the motor ATPase PilB1, demonstrated by in vivo colocalization, yeast two-hybrid and coimmunoprecipitation analysis, suggest that the PixD-PixE signal transduction system targets the T4P directly, thereby controlling blue-light-dependent negative phototaxis. An intriguing feature of PixE is its distinctive structure with a PATAN (PatA N-terminus) domain. This domain is found in several other regulators, which are known to control directional phototaxis. As our PilB1 coimmunoprecipitation analysis revealed an enrichment of PATAN domain response regulators in the eluate, we suggest that multiple environmental signals can be integrated via these regulators to control pilus function.
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Affiliation(s)
- Annik Jakob
- Faculty of Biology, Institute of Biology III, University of Freiburg, 79104 Freiburg, Germany
- Spemann Graduate School of Biology and Medicine (SGBM), University of Freiburg, 79104 Freiburg, Germany
| | - Hiroshi Nakamura
- Graduate School of Bioscience & Biotechnology, Tokyo Institute of Technology, Yokohama, 226-8501 Japan
| | - Atsuko Kobayashi
- Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, 152-8551 Japan
| | - Yuki Sugimoto
- Graduate School of Bioscience & Biotechnology, Tokyo Institute of Technology, Yokohama, 226-8501 Japan
| | - Annegret Wilde
- Faculty of Biology, Institute of Biology III, University of Freiburg, 79104 Freiburg, Germany
- BIOSS Centre of Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany
| | - Shinji Masuda
- Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, 152-8551 Japan
- Center for Biological Resources & Informatics, Tokyo Institute of Technology, Yokohama, 226-8501 Japan
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18
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Gonzalez A, Riley KW, Harwood TV, Zuniga EG, Risser DD. A Tripartite, Hierarchical Sigma Factor Cascade Promotes Hormogonium Development in the Filamentous Cyanobacterium Nostoc punctiforme. mSphere 2019; 4:e00231-19. [PMID: 31043519 PMCID: PMC6495340 DOI: 10.1128/msphere.00231-19] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Accepted: 04/12/2019] [Indexed: 11/24/2022] Open
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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Affiliation(s)
- Alfonso Gonzalez
- Department of Biology, University of the Pacific, Stockton, California, USA
| | - Kelsey W Riley
- Department of Biology, University of the Pacific, Stockton, California, USA
| | - Thomas V Harwood
- Department of Biology, University of the Pacific, Stockton, California, USA
| | - Esthefani G Zuniga
- Department of Biology, University of the Pacific, Stockton, California, USA
| | - Douglas D Risser
- Department of Biology, University of the Pacific, Stockton, California, USA
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19
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Abstract
ABSTRACT
Members of the phylum
Bacteroidetes
have many unique features, including gliding motility and the type IX protein secretion system (T9SS).
Bacteroidetes
gliding and T9SSs are common in, but apparently confined to, this phylum. Most, but not all, members of the phylum secrete proteins using the T9SS, and most also exhibit gliding motility. T9SSs secrete cell surface components of the gliding motility machinery and also secrete many extracellular or cell surface enzymes, adhesins, and virulence factors. The components of the T9SS are novel and are unrelated to those of other bacterial secretion systems. Proteins secreted by the T9SS rely on the Sec system to cross the cytoplasmic membrane, and they use the T9SS for delivery across the outer membrane. Secreted proteins typically have conserved C-terminal domains that target them to the T9SS. Some of the T9SS components were initially identified as proteins required for gliding motility. Gliding does not involve flagella or pili and instead relies on the rapid movement of motility adhesins, such as SprB, along the cell surface by the gliding motor. Contact of the adhesins with the substratum provides the traction that results in cell movement. SprB and other motility adhesins are delivered to the cell surface by the T9SS. Gliding and the T9SS appear to be intertwined, and components of the T9SS that span the cytoplasmic membrane may energize both gliding and protein secretion. The functions of the individual proteins in each process are the subject of ongoing investigations.
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Riley KW, Gonzalez A, Risser DD. A partner-switching regulatory system controls hormogonium development in the filamentous cyanobacterium Nostoc punctiforme. Mol Microbiol 2018; 109:555-569. [PMID: 29995991 DOI: 10.1111/mmi.14061] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/27/2018] [Indexed: 11/29/2022]
Abstract
Filamentous cyanobacteria exhibit developmental complexity, including the transient differentiation of motile hormogonia in many species. Using a forward genetic approach, a trio of genes unique to filamentous cyanobacteria encoding a putative Rsb-like partner-switching regulatory system (PSRS) was implicated in regulating hormogonium development in the model filamentous cyanobacterium Nostoc punctiforme. Analysis of in-frame deletion strains indicated that HmpU (putative serine phosphatase) and HmpV (STAS domain) enhance, while HmpW (putative serine kinase) represses motility and persistence of the hormogonium state. Protein-protein interaction studies demonstrated specificity between HmpW and HmpV. Epistasis analysis between hmpW and hmpV was consistent with HmpV acting as the downstream effector of the system, rather than regulation of a sigma factor by HmpW. Deletion of hmpU or hmpV reduced accumulation of extracellular PilA and hormogonium polysaccharide (HPS), and expression of type IV pilus- and HPS-specific genes was reduced in the ΔhmpV strain. Expression of the Hmp PSRS is induced in hormogonia, and the cytoplasmic localization of HmpV-GFPuv implies that its downstream target is probably cytoplasmic as well. Collectively, these results support a model where HmpU and HmpW antagonistically regulate the phosphorylation state of HmpV, and subsequently, unphosphorylated HmpV positively regulates an undefined downstream target to affect hormogonium-specific gene expression.
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Affiliation(s)
- Kelsey W Riley
- Department of Biology, University of the Pacific, Stockton, CA, 95211, USA
| | - Alfonso Gonzalez
- Department of Biology, University of the Pacific, Stockton, CA, 95211, USA
| | - Douglas D Risser
- Department of Biology, University of the Pacific, Stockton, CA, 95211, USA
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21
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Wilde A, Mullineaux CW. Light-controlled motility in prokaryotes and the problem of directional light perception. FEMS Microbiol Rev 2017; 41:900-922. [PMID: 29077840 PMCID: PMC5812497 DOI: 10.1093/femsre/fux045] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Accepted: 09/12/2017] [Indexed: 12/02/2022] Open
Abstract
The natural light environment is important to many prokaryotes. Most obviously, phototrophic prokaryotes need to acclimate their photosynthetic apparatus to the prevailing light conditions, and such acclimation is frequently complemented by motility to enable cells to relocate in search of more favorable illumination conditions. Non-phototrophic prokaryotes may also seek to avoid light at damaging intensities and wavelengths, and many prokaryotes with diverse lifestyles could potentially exploit light signals as a rich source of information about their surroundings and a cue for acclimation and behavior. Here we discuss our current understanding of the ways in which bacteria can perceive the intensity, wavelength and direction of illumination, and the signal transduction networks that link light perception to the control of motile behavior. We discuss the problems of light perception at the prokaryotic scale, and the challenge of directional light perception in small bacterial cells. We explain the peculiarities and the common features of light-controlled motility systems in prokaryotes as diverse as cyanobacteria, purple photosynthetic bacteria, chemoheterotrophic bacteria and haloarchaea.
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Affiliation(s)
- Annegret Wilde
- Institute of Biology III, University of Freiburg, 79104 Freiburg, Germany
- BIOSS Centre of Biological Signalling Studies, University of Freiburg, 79106 Freiburg, Germany
| | - Conrad W. Mullineaux
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
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