33 results found
Viola S, Roseby W, Santabarabara S, et al., 2022, Impact of energy limitations on function and resilience in long-wavelength Photosystem II
<jats:title>Abstract</jats:title><jats:p>Photosystem II (PSII) uses the energy from red light (~680 nm) to split water and reduce quinone, an energy-demanding process based on chlorophyll a (Chl-a) photochemistry. Two kinds of cyanobacterial PSII can use Chl-d and Chl-f to perform the same reactions using lower energy, far-red light (~720 nm). PSII from <jats:italic>Acaryochloris marina</jats:italic> has Chl-d replacing all but one of its 35 Chl-a, while PSII from <jats:italic>Chrooccidiopsis thermalis</jats:italic>, a facultative far-red species, has just 4 Chl-f and 1 Chl-d replacing 5 of the 35 Chl-a. From bioenergetic considerations, the long-wavelength forms of PSII were predicted to lose photochemical efficiency and/or resilience to harmful light-induced charge recombination. Here, we compare enzyme turnover efficiency, forward electron transfer, back-reactions and photodamage in Chl-f-PSII, Chl-d-PSII and Chl-a-PSII. We show: i) all types of PSII have comparably efficient enzyme turnover; ii) the modified energy gaps on the acceptor side of Chl-d-PSII favor recombination by P<jats:sup>+</jats:sup>Phe<jats:sup>-</jats:sup> repopulation and lead to increased singlet oxygen production and sensitivity to high light damage compared to Chl-a-PSII and Chl-f-PSII; ii) the acceptor side energy gaps in Chl-f-PSII are tuned to avoid harmful back reactions, favoring resilience to light damage over light usage efficiency. The results are explained by the differences in the redox tuning of the electron transfer cofactors Phe and Q<jats:sub>A</jats:sub> and in the number and layout of the chlorophylls that share the excitation energy with the primary electron donor. PSII has adapted to low energy in two ways, each appropriate for its specific environment but with different functional penalties.</jats:p><jats:sec><jats:title>Significance statement</jats:title><jats:p>P
Antonaru LA, Cardona T, Larkum AWD, et al., 2022, Global distribution of a chlorophyll f cyanobacterial marker (vol 14, pg 2275, 2020), ISME JOURNAL, ISSN: 1751-7362
MacGregor-Chatwin C, Nurnberg DJ, Jackson PJ, et al., 2022, Changes in supramolecular organization of cyanobacterial thylakoid membrane complexes in response to far-red light photoacclimation, SCIENCE ADVANCES, Vol: 8, ISSN: 2375-2548
Kanevche K, Burr D, Elsaesser A, et al., 2021, Infrared nanoscopy and tomography of intracellular structures, COMMUNICATIONS BIOLOGY, Vol: 4
Chernev P, Fischer S, Hoffmann J, et al., 2021, Light-driven formation of manganese oxide by today's photosystem II supports evolutionarily ancient manganese-oxidizing photosynthesis (vol 11, 6110, 2020), NATURE COMMUNICATIONS, Vol: 12, ISSN: 2041-1723
Springstein BL, Nurnberg DJ, Woehle C, et al., 2020, Two novel heteropolymer-forming proteins maintain the multicellular shape of the cyanobacterium Anabaena sp. PCC 7120, FEBS JOURNAL, Vol: 288, Pages: 3197-3216, ISSN: 1742-464X
Springstein BL, Nuernberg DJ, Weiss GL, et al., 2020, Structural Determinants and Their Role in Cyanobacterial Morphogenesis, LIFE-BASEL, Vol: 10
Chernev P, Fischer S, Hoffmann J, et al., 2020, Light-driven formation of manganese oxide by today's photosystem II supports evolutionarily ancient manganese-oxidizing photosynthesis, NATURE COMMUNICATIONS, Vol: 11, ISSN: 2041-1723
Judd M, Morton J, Nurnberg D, et al., 2020, The primary donor of far-red photosystem II: Chl(D1) or P-D2?, BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS, Vol: 1861, ISSN: 0005-2728
Laura A A, Cardona Londono T, Larkum AWD, et al., 2020, Global distribution of a chlorophyll f cyanobacterial marker, The ISME Journal: multidisciplinary journal of microbial ecology, Vol: 14, Pages: 2275-2287, ISSN: 1751-7362
Some cyanobacteria use light outside the visible spectrum for oxygenic photosynthesis. The far-red light (FRL) region is made accessible through a complex acclimation process that involves the formation of new phycobilisomes and photosystems containing chlorophyll f. Diverse cyanobacteria ranging from unicellular to branched-filamentous forms show this response. These organisms have been isolated from shaded environments such as microbial mats, soil, rock, and stromatolites. However, the full spread of chlorophyll f-containing species in nature is still unknown. Currently, discovering new chlorophyll f cyanobacteria involves lengthy incubation times under selective far-red light. We have used a marker gene to detect chlorophyll f organisms in environmental samples and metagenomic data. This marker, apcE2, encodes a phycobilisome linker associated with FRL-photosynthesis. By focusing on a far-red motif within the sequence, degenerate PCR and BLAST searches can effectively discriminate against the normal chlorophyll a-associated apcE. Even short recovered sequences carry enough information for phylogenetic placement. Markers of chlorophyll f photosynthesis were found in metagenomic datasets from diverse environments around the globe, including cyanobacterial symbionts, hypersaline lakes, corals, and the Arctic/Antarctic regions. This additional information enabled higher phylogenetic resolution supporting the hypothesis that vertical descent, as opposed to horizontal gene transfer, is largely responsible for this phenotype’s distribution.
Zamzam N, Rakowski R, Kaucikas M, et al., 2020, Femtosecond visible transient absorption spectroscopy of chlorophyll f- containing Photosystem II, Proceedings of the National Academy of Sciences of USA, Vol: 117, Pages: 1-7, ISSN: 0027-8424
The recently discovered, chlorophyll-f-containing, far-red photosystem II (FR-PSII) supports far-red light photosynthesis. Participation and kinetics of spectrally shifted far-red pigments are directly observable and separated from that of bulk chlorophyll-a. We present an ultrafast transient absorption study of FR-PSII, investigating energy transfer and charge separation processes. Results show a rapid subpicosecond energy transfer from chlorophyll-a to the long-wavelength chlorophylls-f/d. The data demonstrate the decay of an ∼720-nm negative feature on the picosecond-to-nanosecond timescales, coinciding with charge separation, secondary electron transfer, and stimulated emission decay. An ∼675-nm bleach attributed to the loss of chl-a absorption due to the formation of a cation radical, PD1+•, is only fully developed in the nanosecond spectra, indicating an unusually delayed formation. A major spectral feature on the nanosecond timescale at 725 nm is attributed to an electrochromic blue shift of a FR-chlorophyll among the reaction center pigments. These time-resolved observations provide direct experimental support for the model of Nürnberg et al. [D. J. Nürnberg et al., Science 360, 1210–1213 (2018)], in which the primary electron donor is a FR-chlorophyll and the secondary donor is chlorophyll-a (PD1 of the central chlorophyll pair). Efficient charge separation also occurs using selective excitation of long-wavelength chlorophylls-f/d, and the localization of the excited state on P720* points to a smaller (entropic) energy loss compared to conventional PSII, where the excited state is shared over all of the chlorin pigments. This has important repercussions on understanding the overall energetics of excitation energy transfer and charge separation reactions in FR-PSII.
Judd M, Morton J, Nürnberg D, et al., 2020, The primary donor of far-red Photosystem II: Chl<sub>D1</sub> or P<sub>D2</sub>?
<jats:title>ABSTRACT</jats:title><jats:p>Far-red light (FRL) Photosystem II (PSII) isolated from <jats:italic>Chroococcidiopsis thermalis</jats:italic> is studied using parallel analyses of low-temperature absorption, circular dichroism (CD) and magnetic circular dichroism (MCD) spectroscopies in conjunction with fluorescence measurements. This extends earlier studies (Nurnberg <jats:italic>et al</jats:italic> 2018 Science 360 (2018) 1210-1213). We confirm that the chlorophyll absorbing at 726 nm is the primary electron donor. At 1.8 K efficient photochemistry occurs when exciting at 726 nm and shorter wavelengths; but not at wavelengths longer than 726 nm. The 726 nm absorption peak exhibits a 21 ± 4 cm<jats:sup>−1</jats:sup> electrochromic shift due to formation of the semiquinone anion, Q<jats:sub>A</jats:sub><jats:sup>•-</jats:sup>. Modelling indicates that no other FRL pigment is located among the 6 central reaction center chlorins: P<jats:sub>D1</jats:sub>, P<jats:sub>D2</jats:sub> Chl<jats:sub>D1</jats:sub>, Chl<jats:sub>D2</jats:sub>, Pheo<jats:sub>D1</jats:sub> and Pheo<jats:sub>D2</jats:sub>. Two of these chlorins, Chl<jats:sub>D1</jats:sub> and P<jats:sub>D2</jats:sub>, are located at a distance and orientation relative to Q<jats:sub>A</jats:sub><jats:sup>•-</jats:sup> so as to account for the observed electrochromic shift. Previously, Chl<jats:sub>D1</jats:sub> was taken as the most likely candidate for the primary donor based on spectroscopy, sequence analysis and mechanistic arguments. Here, a more detailed comparison of the spectroscopic data with exciton modelling of the electrochromic pattern indicates that P<jats:sub>D2</jats:sub> is at least as likely as Chl<jats:sub>D1</jats:sub> to be responsi
Chernev P, Fischer S, Hoffmann J, et al., 2020, Light-driven formation of high-valent manganese oxide by photosystem II supports evolutionary role in early bioenergetics
<jats:title>Abstract</jats:title><jats:p>Water oxidation and concomitant O<jats:sub>2</jats:sub>-formation by the Mn<jats:sub>4</jats:sub>Ca cluster of oxygenic photosynthesis has shaped the biosphere, atmosphere, and geosphere. It has been hypothesized that at an early stage of evolution, before photosynthetic water oxidation became prominent, photosynthetic formation of Mn oxides from dissolved Mn(2+) ions may have played a key role in bioenergetics and possibly facilitated early geological manganese deposits. The biochemical evidence for the ability of photosystems to form extended Mn oxide particles, lacking until now, is provided herein. We tracked the light-driven redox processes in spinach photosystem II (PSII) particles devoid of the Mn<jats:sub>4</jats:sub>Ca clusters by UV-vis and X-ray spectroscopy. We find that oxidation of aqueous Mn(2+) ions results in PSII-bound Mn(III,IV)-oxide nanoparticles of the birnessite type comprising 50-100 Mn ions per PSII. Having shown that even today’s photosystem-II can form birnessite-type oxide particles efficiently, we propose an evolutionary scenario, which involves Mn-oxide production by ancestral photosystems, later followed by down-sizing of protein-bound Mn-oxide nanoparticles to finally yield today’s Mn<jats:sub>4</jats:sub>CaO<jats:sub>5</jats:sub> cluster of photosynthetic water oxidation.</jats:p>
Alcorta J, Vergara-Barros P, Antonaru LA, et al., 2019, Fischerella thermalis: a model organism to study thermophilic diazotrophy, photosynthesis and multicellularity in cyanobacteria, Extremophiles, Vol: 23, Pages: 635-647, ISSN: 1431-0651
The true-branching cyanobacterium Fischerella thermalis (also known as Mastigocladus laminosus) is widely distributed in hot springs around the world. Morphologically, it has been described as early as 1837. However, its taxonomic placement remains controversial. F. thermalis belongs to the same genus as mesophilic Fischerella species but forms a monophyletic clade of thermophilic Fischerella strains and sequences from hot springs. Their recent divergence from freshwater or soil true-branching species and the ongoing process of specialization inside the thermal gradient make them an interesting evolutionary model to study. F. thermalis is one of the most complex prokaryotes. It forms a cellular network in which the main trichome and branches exchange metabolites and regulators via septal junctions. This species can adapt to a variety of environmental conditions, with its photosynthetic apparatus remaining active in a temperature range from 15 to 58 °C. Together with its nitrogen-fixing ability, this allows it to dominate in hot spring microbial mats and contribute significantly to the de novo carbon and nitrogen input. Here, we review the current knowledge on the taxonomy and distribution of F. thermalis, its morphological complexity, and its physiological adaptations to an extreme environment.
Fritsch VN, Vu VL, Busche T, et al., 2019, The MarR-type repressor MhqR confers quinone and antimicrobial resistance in staphylococcus aureus, Antioxidants and Redox Signaling, Vol: 31, Pages: 1235-1252, ISSN: 1523-0864
Aims: Quinone compounds are electron carriers and have antimicrobial and toxic properties due to their mode of actions as electrophiles and oxidants. However, the regulatory mechanism of quinone resistance is less well understood in the pathogen Staphylococcus aureus.Results: Methylhydroquinone (MHQ) caused a thiol-specific oxidative and electrophile stress response in the S. aureus transcriptome as revealed by the induction of the PerR, QsrR, CstR, CtsR, and HrcA regulons. The SACOL2531-29 operon was most strongly upregulated by MHQ and was renamed as mhqRED operon based on its homology to the Bacillus subtilis locus. Here, we characterized the MarR-type regulator MhqR (SACOL2531) as quinone-sensing repressor of the mhqRED operon, which confers quinone and antimicrobial resistance in S. aureus. The mhqRED operon responds specifically to MHQ and less pronounced to pyocyanin and ciprofloxacin, but not to reactive oxygen species (ROS), hypochlorous acid, or aldehydes. The MhqR repressor binds specifically to a 9–9 bp inverted repeat (MhqR operator) upstream of the mhqRED operon and is inactivated by MHQ in vitro, which does not involve a thiol-based mechanism. In phenotypic assays, the mhqR deletion mutant was resistant to MHQ and quinone-like antimicrobial compounds, including pyocyanin, ciprofloxacin, norfloxacin, and rifampicin. In addition, the mhqR mutant was sensitive to sublethal ROS and 24 h post-macrophage infections but acquired an improved survival under lethal ROS stress and after long-term infections.Innovation: Our results provide a link between quinone and antimicrobial resistance via the MhqR regulon of S. aureus.Conclusion: The MhqR regulon was identified as a novel resistance mechanism towards quinone-like antimicrobials and contributes to virulence of S. aureus under long-term infections.
Dau H, Nürnberg DJ, Burnap RL, 2019, Local Cycle of Photosynthesis and Quasi-Aerobic Respiration Facilitated by Manganese Oxides — A Hypothesis on the Evolution of Phototrophy, Oxygen Production and Reduction in Artificial and Natural Systems, Publisher: WORLD SCIENTIFIC, Pages: 367-395
Springstein BL, Nürnberg DJ, Woehle C, et al., 2019, Two novel heteropolymer-forming proteins maintain multicellular shape of the cyanobacterium<i>Anabaena</i>sp. PCC 7120
<jats:title>Abstract</jats:title><jats:p>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 – e.g. MreB and FtsZ in bacteria – or heteropolymers that are composed of two subunits, e.g. keratin and α/β tubulin in eukaryotes. Here, we describe two novel coiled-coil-rich proteins (CCRPs) in the filament forming cyanobacterium<jats:italic>Anabaena</jats:italic>sp. PCC 7120 (hereafter<jats:italic>Anabaena</jats:italic>) that assemble into a heteropolymer and function in the maintenance of the<jats:italic>Anabaena</jats:italic>multicellular shape (termed trichome). The two CCRPs – Alr4504 and Alr4505 (named ZicK and ZacK) – are strictly interdependent for the assembly of protein filaments<jats:italic>in vivo</jats:italic>and polymerize nucleotide-independently<jats:italic>in vitro</jats:italic>, 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<jats:italic>Anabaena</jats:italic>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<jats:italic>Anabaena</jats:italic>trichome and are likely essential for the manifestation of the multicellular shape in<jats:italic>Anabaena</jats:italic>. Our study reveals the presence of filament-forming IF-like proteins whose function is achieved through the fo
Zamzam N, Kaucikas M, Nurnberg D, et al., 2019, Femtosecond infrared spectroscopy of chlorophyll f-containing photosystem I, Physical Chemistry Chemical Physics, Vol: 21, Pages: 1224-1234, ISSN: 1463-9076
The recent discovery of extremely red-shifted chlorophyll f pigments in both photosystem I (PSI) and photosystem II has led to the conclusion that chlorophyll f plays a role not only in the energy transfer, but also in the charge separation processes [Nürnberg et al., Science, 2018, 360, 1210–1213]. We have employed ultrafast transient infrared absorption spectroscopy to study the contribution of far-red light absorbing chlorophyll f to energy transfer and charge separation processes in far-red light-grown PSI (FRL-PSI) from the cyanobacterium Chroococcidiopsis thermalis PCC 7203. We compare the kinetics and spectra of FRL-grown PSI excited at 670 nm and 740 nm wavelengths to those of white light-grown PSI (WL-PSI) obtained at 675 nm excitation. We report a fast decay of excited state features of chlorophyll a and complete energy transfer from chlorophyll a to chlorophyll f in FRL-PSI upon 670 nm excitation, as indicated by a frequency shift in a carbonyl absorption band occurring within a 1 ps timescale. While the WL-PSI measurements support the assignment of initial charge separation to A−1+˙A0−˙ [Di Donato et al., Biochemistry, 2011, 50, 480–490] from the kinetics of a distinct cation feature at 1710 cm−1, in the case of FRL-PSI, small features at 1715 cm−1 from the chlorophyll cation are present from sub-ps delays instead, supporting the replacement of the A−1 pigment with chlorophyll f. Comparisons of nanosecond spectra show that charge separation proceeds with 740 nm excitation, which selectively excites chlorophyll f, and modifications in specific carbonyl absorption bands assigned to P700+˙ minus P700 and A1−˙ minus A1 indicate dielectric differences of FRL-PSI compared to WL-PSI in one or both of the two electron transfer branches of FRL-PSI.
Nuernberg DJ, Morton J, Santabarbara S, et al., 2018, Photochemistry beyond the red limit in chlorophyll f-containing photosystems, Science, Vol: 360, Pages: 1210-1213, ISSN: 0036-8075
Photosystems I and II convert solar energy into the chemical energy that powers life. Chlorophyll a photochemistry, using red light (680 to 700 nm), is near universal and is considered to define the energy “red limit” of oxygenic photosynthesis. We present biophysical studies on the photosystems from a cyanobacterium grown in far-red light (750 nm). The few long-wavelength chlorophylls present are well resolved from each other and from the majority pigment, chlorophyll a. Charge separation in photosystem I and II uses chlorophyll f at 745 nm and chlorophyll f (or d) at 727 nm, respectively. Each photosystem has a few even longer-wavelength chlorophylls f that collect light and pass excitation energy uphill to the photochemically active pigments. These photosystems function beyond the red limit using far-red pigments in only a few key positions.
Antonaru LA, Nuernberg DJ, 2017, Role of PatS and cell type on the heterocyst spacing pattern in a filamentous branching cyanobacterium, FEMS Microbiology Letters, Vol: 364, ISSN: 0378-1097
Cell differentiation is one of the marks of multicellular organisms. Terminally specialised nitrogen-fixing cells, termed heterocysts, evolved in filamentous cyanobacteria more than 2 Gya. The development of their spacing pattern has been thoroughly investigated in model organisms such as Anabaena sp. PCC 7120. This paper focuses on the more complex, branching cyanobacterium Mastigocladus laminosus (Stigonematales). Contrary to what has been previously published, a heterocyst spacing pattern is present in M. laminosus but it varies with the age of the culture and the morphology of the cells. Heterocysts in young, narrow trichomes were more widely spaced (∼14.8 cells) than those in old, wide trichomes (∼9.4 cells). Biochemical and transgenic experiments reveal that the heterocyst spacing pattern is affected by the heterocyst inhibitor PatS. Addition of the pentapeptide RGSGR (PatS-5) to the growth medium and overexpression of patS from Anabaena sp. PCC 7120 in M. laminosus resulted in the loss of heterocyst differentiation under nitrogen deprivation. Bioinformatics investigations indicated that putative PatS sequences within cyanobacteria are highly diverse, and fall into two main clades. Both are present in most branching cyanobacteria. Despite its more complex, branching phenotype, M. laminosus appears to use a PatS-based pathway for heterocyst differentiation, a property shared by Anabaena/Nostoc.
Nieves-Morión M, Lechno-Yossef S, López-Igual R, et al., 2017, Specific glucoside transporters influence septal structure and function in the filamentous, heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120, Journal of Bacteriology, Vol: 199, ISSN: 1098-5530
When deprived of combined nitrogen, some filamentous cyanobacteria contain two cell types: vegetative cells that fix CO2 through oxygenic photosynthesis and heterocysts that are specialized in N2 fixation. In the diazotrophic filament, the vegetative cells provide the heterocysts with reduced carbon (mainly in the form of sucrose) and heterocysts provide the vegetative cells with combined nitrogen. Septal junctions traverse peptidoglycan through structures known as nanopores and appear to mediate intercellular molecular transfer that can be traced with fluorescent markers, including the sucrose analog esculin (a coumarin glucoside) that is incorporated into the cells. Uptake of esculin by the model heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120 was inhibited by the α-glucosides sucrose and maltose. Analysis of Anabaena mutants identified components of three glucoside transporters that move esculin into the cells: GlsC (Alr4781) and GlsP (All0261) are an ATP-binding subunit and a permease subunit of two different ABC transporters, respectively, and HepP (All1711) is a major facilitator superfamily (MFS) protein that was shown previously to be involved in formation of the heterocyst envelope. Transfer of fluorescent markers (especially calcein) between vegetative cells of Anabaena was impaired by mutation of glucoside transporter genes. GlsP and HepP interact in bacterial two-hybrid assays with the septal junction-related protein SepJ, and GlsC was found to be necessary for the formation of a normal number of septal peptidoglycan nanopores and for normal subcellular localization of SepJ. Therefore, beyond their possible role in nutrient uptake in Anabaena, glucoside transporters influence the structure and function of septal junctions.
Kaucikas M, Nurnberg D, Dorhliac G, et al., 2017, Femtosecond visible transient absorption spectroscopy ofChlorophyll f-containing Photosystem I, Biophysical Journal, Vol: 112, Pages: 234-249, ISSN: 1542-0086
Photosystem I (PSI) from Chroococcidiopsis thermalis PCC 7203 grown under far-red light (FRL; >725 nm) contains both chlorophyll a and a small proportion of chlorophyll f. Here, we investigated excitation energy transfer and charge separation using this FRL-grown form of PSI (FRL-PSI). We compared femtosecond transient visible absorption changes of normal, white-light (WL)-grown PSI (WL-PSI) with those of FRL-PSI using excitation at 670 nm, 700 nm, and (in the case of FRL-PSI) 740 nm. The possibility that chlorophyll f participates in energy transfer or charge separation is discussed on the basis of spectral assignments. With selective pumping of chlorophyll f at 740 nm, we observe a final ∼150 ps decay assigned to trapping by charge separation, and the amplitude of the resulting P700+•A1−• charge-separated state indicates that the yield is directly comparable to that of WL-PSI. The kinetics shows a rapid 2 ps time constant for almost complete transfer to chlorophyll f if chlorophyll a is pumped with a wavelength of 670 nm or 700 nm. Although the physical role of chlorophyll f is best supported as a low-energy radiative trap, the physical location should be close to or potentially within the charge-separating pigments to allow efficient transfer for charge separation on the 150 ps timescale. Target models can be developed that include a branching in the formation of the charge separation for either WL-PSI or FRL-PSI.
Lea-Smith DJ, Ortiz-Suarez ML, Lenn T, et al., 2016, Hydrocarbons are essential for optimal cell size, division, and growth of cyanobacteria, Plant Physiology, Vol: 172, Pages: 1928-1940, ISSN: 0032-0889
Cyanobacteria are intricately organized, incorporating an array of internal thylakoid membranes, the site of photosynthesis, into cells no larger than other bacteria. They also synthesize C15-C19 alkanes and alkenes, which results in substantial production of hydrocarbons in the environment. All sequenced cyanobacteria encode hydrocarbon biosynthesis pathways, suggesting an important, undefined physiological role for these compounds. Here, we demonstrate that hydrocarbon-deficient mutants of Synechococcus sp. PCC 7002 and Synechocystis sp. PCC 6803 exhibit significant phenotypic differences from wild type, including enlarged cell size, reduced growth, and increased division defects. Photosynthetic rates were similar between strains, although a minor reduction in energy transfer between the soluble light harvesting phycobilisome complex and membrane-bound photosystems was observed. Hydrocarbons were shown to accumulate in thylakoid and cytoplasmic membranes. Modeling of membranes suggests these compounds aggregate in the center of the lipid bilayer, potentially promoting membrane flexibility and facilitating curvature. In vivo measurements confirmed that Synechococcus sp. PCC 7002 mutants lacking hydrocarbons exhibit reduced thylakoid membrane curvature compared to wild type. We propose that hydrocarbons may have a role in inducing the flexibility in membranes required for optimal cell division, size, and growth, and efficient association of soluble and membrane bound proteins. The recent identification of C15-C17 alkanes and alkenes in microalgal species suggests hydrocarbons may serve a similar function in a broad range of photosynthetic organisms.
Mariscal V, Nürnberg DJ, Herrero A, et al., 2016, Overexpression of SepJ alters septal morphology and heterocyst pattern regulated by diffusible signals in Anabaena., Molecular Microbiology, Vol: 101, Pages: 968-981, ISSN: 0950-382X
Filamentous, N2 -fixing, heterocyst-forming cyanobacteria grow as chains of cells that are connected by septal junctions. In the model organism Anabaena sp. strain PCC 7120, the septal protein SepJ is required for filament integrity, normal intercellular molecular exchange, heterocyst differentiation, and diazotrophic growth. An Anabaena strain overexpressing SepJ made wider septa between vegetative cells than the wild type, which correlated with a more spread location of SepJ in the septa as observed with a SepJ-GFP fusion, and contained an increased number of nanopores, the septal peptidoglycan perforations that likely accommodate septal junctions. The septa between heterocysts and vegetative cells, which are narrow in wild-type Anabaena, were notably enlarged in the SepJ-overexpressing mutant. Intercellular molecular exchange tested with fluorescent tracers was increased for the SepJ-overexpressing strain specifically in the case of calcein transfer between vegetative cells and heterocysts. These results support an association between calcein transfer, SepJ-related septal junctions, and septal peptidoglycan nanopores. Under nitrogen deprivation, the SepJ-overexpressing strain produced an increased number of contiguous heterocysts but a decreased percentage of total heterocysts. These effects were lost or altered in patS and hetN mutant backgrounds, supporting a role of SepJ in the intercellular transfer of regulatory signals for heterocyst differentiation.
Klemke F, Nürnberg DJ, Ziegler K, et al., 2016, CphA2 is a novel type of cyanophycin synthetase in N2-fixing cyanobacteria, Microbiology, Vol: 162, Pages: 526-536, ISSN: 1350-0872
Schuergers N, Nuernberg DJ, Wallner T, et al., 2015, PilB localization correlates with the direction of twitching motility in the cyanobacterium Synechocystis sp PCC 6803, MICROBIOLOGY-SGM, Vol: 161, Pages: 960-966, ISSN: 1350-0872
Nuernberg DJ, Mariscal V, Bornikoel J, et al., 2015, Intercellular Diffusion of a Fluorescent Sucrose Analog via the Septal Junctions in a Filamentous Cyanobacterium, MBIO, Vol: 6, ISSN: 2150-7511
Klemke F, Beyer G, Sawade L, et al., 2014, All1371 is a polyphosphate-dependent glucokinase in Anabaena sp PCC 7120, MICROBIOLOGY-SGM, Vol: 160, Pages: 2807-2819, ISSN: 1350-0872
Mullineaux CW, Nuernberg DJ, 2014, Tracing the path of a prokaryotic paracrine signal, MOLECULAR MICROBIOLOGY, Vol: 94, Pages: 1208-1212, ISSN: 0950-382X
Corrales-Guerrero L, Mariscal V, Nuernberg DJ, et al., 2014, Subcellular Localization and Clues for the Function of the HetN Factor Influencing Heterocyst Distribution in Anabaena sp Strain PCC 7120, JOURNAL OF BACTERIOLOGY, Vol: 196, Pages: 3452-3460, ISSN: 0021-9193
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