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Circadian clock-controlled gene expression in co-cultured, mat-forming cyanobacteria. Sci Rep 2020; 10:14095. [PMID: 32839512 PMCID: PMC7445270 DOI: 10.1038/s41598-020-69294-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Accepted: 05/11/2020] [Indexed: 11/08/2022] Open
Abstract
Natural coastal microbial mat communities are multi-species assemblages that experience fluctuating environmental conditions and are shaped by resource competition as well as by cooperation. Laboratory studies rarely address the natural complexity of microbial communities but are usually limited to homogeneous mono-cultures of key species grown in liquid media. The mat-forming filamentous cyanobacteria Lyngbya aestuarii and Coleofasciculus chthonoplastes were cultured under different conditions to investigate the expression of circadian clock genes and genes that are under their control. The cyanobacteria were grown in liquid medium or on a solid substrate (glass beads) as mono- or as co-cultures under a light-dark regime and subsequently transferred to continuous light. TaqMan-probe based qPCR assays were used to quantify the expression of the circadian clock genes kaiA, kaiB, and kaiC, and of four genes that are under control of the circadian clock: psbA, nifH, ftsZ, and prx. Expression of kaiABC was influenced by co-culturing the cyanobacteria and whether grown in liquid media or on a solid substrate. Free-running (i.e. under continuous light) expression cycle of the circadian clock genes was observed in L. aestuarii but not in C. chthonoplastes. In the former organism, maximum expression of psbA and nifH occurred temporally separated and independent of the light regime, although the peak shifted in time when the culture was transferred to continuous illumination. Although functionally similar, both species of cyanobacteria displayed different 24-h transcriptional patterns in response to the experimental treatments, suggesting that their circadian clocks have adapted to different life strategies adopted by these mat-forming cyanobacteria.
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2
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Glavaš N, Défarge C, Gautret P, Joulian C, Penhoud P, Motelica M, Kovač N. The structure and role of the "petola" microbial mat in sea salt production of the Sečovlje (Slovenia). THE SCIENCE OF THE TOTAL ENVIRONMENT 2018; 644:1254-1267. [PMID: 30743838 DOI: 10.1016/j.scitotenv.2018.07.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 06/03/2018] [Accepted: 07/01/2018] [Indexed: 06/09/2023]
Abstract
Microbial mats are commonly observed in estuaries and in salt marshes but they only rarely represent a significant surface involved in salt production. In the Sečovlje salt works in Northern Adriatic, a microbial mat known as the "petola" covers the bottom of salt crystallising pans, highly influencing salt composition and salt production processes. Throughout the year the petola is subjected to numerous co-varying factors that drive changes in its structure and the microbial community. Seasonal modifications were investigated via various methods (cryo-HRSEM, XRD, elemental analysis, carbohydrate content, bacterial community structure). This study provides knowledge on microbial mat compositional characteristics and functional roles in response to seasonal variation in environmental conditions. The in situ characterisation (close-to its natural hydrated state) of the three-dimensional microstructure provides precise information about dominating filamentous cyanobacterium Coleofasciculus chthonoplastes and extracellular polymer secretion (EPS) organisation. This is the first study to address how microbial mat composition and structure, especially 3D EPS network (and microbial diversity), affects the salt production processes within a hypersaline environment.
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Affiliation(s)
- Neli Glavaš
- SOLINE Pridelava soli d. o. o, Seča 115, 6320 Portorož, Slovenia; Marine Biology Station, National Institute of Biology, Fornače 41, 6330 Piran, Slovenia.
| | - Christian Défarge
- Université d'Orléans, ISTO, UMR 7327, Polytech'Orléans, 8 rue Léonard de Vinci, 45072 Orléans Cedex 2, France; CNRS/INSU, ISTO, UMR 7327, 45071 Orléans, France; BRGM, ISTO, UMR 7327, BP 36009, 45060 Orléans, France
| | - Pascale Gautret
- Université d'Orléans, ISTO, UMR 7327, Polytech'Orléans, 8 rue Léonard de Vinci, 45072 Orléans Cedex 2, France; CNRS/INSU, ISTO, UMR 7327, 45071 Orléans, France; BRGM, ISTO, UMR 7327, BP 36009, 45060 Orléans, France
| | - Catherine Joulian
- BRGM, Geomicrobiology and Environmental Monitoring Unit, 3, Avenue Claude Guillemin, 45060 Orléans Cedex 02, France
| | - Philippe Penhoud
- Université d'Orléans, ISTO, UMR 7327, Polytech'Orléans, 8 rue Léonard de Vinci, 45072 Orléans Cedex 2, France; CNRS/INSU, ISTO, UMR 7327, 45071 Orléans, France; BRGM, ISTO, UMR 7327, BP 36009, 45060 Orléans, France
| | - Mikael Motelica
- Université d'Orléans, ISTO, UMR 7327, Polytech'Orléans, 8 rue Léonard de Vinci, 45072 Orléans Cedex 2, France; CNRS/INSU, ISTO, UMR 7327, 45071 Orléans, France; BRGM, ISTO, UMR 7327, BP 36009, 45060 Orléans, France
| | - Nives Kovač
- Marine Biology Station, National Institute of Biology, Fornače 41, 6330 Piran, Slovenia
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3
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Living Dendrolitic Microbial Mats in Hamelin Pool, Shark Bay, Western Australia. GEOSCIENCES 2018. [DOI: 10.3390/geosciences8060212] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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4
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Pan J, Cuadrado DG, Bournod CN. Diatom-driven recolonization of microbial mat-dominated siliciclastic tidal flat sediments. FEMS Microbiol Ecol 2017; 93:4107761. [DOI: 10.1093/femsec/fix111] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2016] [Accepted: 09/05/2017] [Indexed: 11/14/2022] Open
Affiliation(s)
- Jerónimo Pan
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Av. Rivadavia 1917, Buenos Aires (C1033AAJ), Argentina
- Instituto de Investigaciones Marinas y Costeras (IIMyC, CONICET/UNMdP), Rodriguez Peña 4046, Mar del Plata (7600), Buenos Aires, Argentina
- Instituto de Geología de Costas y del Cuaternario (IGCyC, UNMdP/CIC), Funes 3350, Mar del Plata (7600), Buenos Aires, Argentina
| | - Diana G. Cuadrado
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Av. Rivadavia 1917, Buenos Aires (C1033AAJ), Argentina
- Instituto Argentino de Oceanografía (IADO, CONICET/UNS), Florida 7500, Bahía Blanca (8000), Buenos Aires, Argentina
- Departamento de Geología, Universidad Nacional del Sur, San Juan 670, Bahía Blanca (8000), Buenos Aires, Argentina
| | - Constanza N. Bournod
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Av. Rivadavia 1917, Buenos Aires (C1033AAJ), Argentina
- Instituto Argentino de Oceanografía (IADO, CONICET/UNS), Florida 7500, Bahía Blanca (8000), Buenos Aires, Argentina
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5
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Lichtenberg M, Brodersen KE, Kühl M. Radiative Energy Budgets of Phototrophic Surface-Associated Microbial Communities and their Photosynthetic Efficiency Under Diffuse and Collimated Light. Front Microbiol 2017; 8:452. [PMID: 28400749 PMCID: PMC5368174 DOI: 10.3389/fmicb.2017.00452] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Accepted: 03/03/2017] [Indexed: 11/13/2022] Open
Abstract
We investigated the radiative energy budgets of a heterogeneous photosynthetic coral reef sediment and a compact uniform cyanobacterial biofilm on top of coastal sediment. By combining electrochemical, thermocouple and fiber-optic microsensor measurements of O2, temperature and light, we could calculate the proportion of the absorbed light energy that was either dissipated as heat or conserved by photosynthesis. We show, across a range of different incident light regimes, that such radiative energy budgets are highly dominated by heat dissipation constituting up to 99.5% of the absorbed light energy. Highest photosynthetic energy conservation efficiency was found in the coral sediment under low light conditions and amounted to 18.1% of the absorbed light energy. Additionally, the effect of light directionality, i.e., diffuse or collimated light, on energy conversion efficiency was tested on the two surface-associated systems. The effects of light directionality on the radiative energy budgets of these phototrophic communities were not unanimous but, resulted in local spatial differences in heat-transfer, gross photosynthesis, and light distribution. The light acclimation index, Ek, i.e., the irradiance at the onset of saturation of photosynthesis, was >2 times higher in the coral sediment compared to the biofilm and changed the pattern of photosynthetic energy conservation under light-limiting conditions. At moderate to high incident irradiances, the photosynthetic conservation of absorbed energy was highest in collimated light; a tendency that changed in the biofilm under sub-saturating incident irradiances, where higher photosynthetic efficiencies were observed under diffuse light. The aim was to investigate how the physical structure and light propagation affected energy budgets and light utilization efficiencies in loosely organized vs. compact phototrophic sediment under diffuse and collimated light. Our results suggest that the optical properties and the structural organization of phytoelements are important traits affecting the photosynthetic efficiency of biofilms and sediments.
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Affiliation(s)
- Mads Lichtenberg
- Marine Biological Section, Department of Biology, University of Copenhagen Helsingør, Denmark
| | - Kasper E Brodersen
- Marine Biological Section, Department of Biology, University of Copenhagen Helsingør, Denmark
| | - Michael Kühl
- Marine Biological Section, Department of Biology, University of CopenhagenHelsingør, Denmark; Climate Change Cluster, University of Technology SydneyUltimo, NSW, Australia
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6
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Wong HL, Smith DL, Visscher PT, Burns BP. Niche differentiation of bacterial communities at a millimeter scale in Shark Bay microbial mats. Sci Rep 2015; 5:15607. [PMID: 26499760 PMCID: PMC4620479 DOI: 10.1038/srep15607] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Accepted: 09/28/2015] [Indexed: 02/01/2023] Open
Abstract
Modern microbial mats can provide key insights into early Earth ecosystems, and Shark Bay, Australia, holds one of the best examples of these systems. Identifying the spatial distribution of microorganisms with mat depth facilitates a greater understanding of specific niches and potentially novel microbial interactions. High throughput sequencing coupled with elemental analyses and biogeochemical measurements of two distinct mat types (smooth and pustular) at a millimeter scale were undertaken in the present study. A total of 8,263,982 16S rRNA gene sequences were obtained, which were affiliated to 58 bacterial and candidate phyla. The surface of both mats were dominated by Cyanobacteria, accompanied with known or putative members of Alphaproteobacteria and Bacteroidetes. The deeper anoxic layers of smooth mats were dominated by Chloroflexi, while Alphaproteobacteria dominated the lower layers of pustular mats. In situ microelectrode measurements revealed smooth mats have a steeper profile of O2 and H2S concentrations, as well as higher oxygen production, consumption, and sulfate reduction rates. Specific elements (Mo, Mg, Mn, Fe, V, P) could be correlated with specific mat types and putative phylogenetic groups. Models are proposed for these systems suggesting putative surface anoxic niches, differential nitrogen fixing niches, and those coupled with methane metabolism.
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Affiliation(s)
- Hon Lun Wong
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, Australia
- Australian Centre for Astrobiology, University of New South Wales Sydney, Australia
| | - Daniela-Lee Smith
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, Australia
- Australian Centre for Astrobiology, University of New South Wales Sydney, Australia
| | - Pieter T. Visscher
- Department of Marine Sciences, University of Connecticut, USA
- Australian Centre for Astrobiology, University of New South Wales Sydney, Australia
| | - Brendan P. Burns
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, Australia
- Australian Centre for Astrobiology, University of New South Wales Sydney, Australia
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7
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McKew BA, Taylor JD, McGenity TJ, Underwood GJC. Resistance and resilience of benthic biofilm communities from a temperate saltmarsh to desiccation and rewetting. ISME JOURNAL 2010; 5:30-41. [PMID: 20596071 DOI: 10.1038/ismej.2010.91] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Periods of desiccation and rewetting are regular, yet stressful events encountered by saltmarsh microbial communities. To examine the resistance and resilience of microbial biofilms to such stresses, sediments from saltmarsh creeks were allowed to desiccate for 23 days, followed by rewetting for 4 days, whereas control sediments were maintained under a natural tidal cycle. In the top 2 mm of the dry sediments, salinity increased steadily from 36 to 231 over 23 days, and returned to seawater salinity on rewetting. After 3 days, desiccated sediments had a lower chlorophyll a (Chl a) fluorescence signal as benthic diatoms ceased to migrate to the surface, with a recovery in cell migration and Chl a fluorescence on rewetting. Extracellular β-glucosidase and aminopeptidase activities decreased within the first week of drying, but increased sharply on rewetting. The bacterial community in the desiccating sediment changed significantly from the controls after 14 days of desiccation (salinity 144). Rewetting did not cause a return to the original community composition, but led to a further change. Pyrosequencing analysis of 16S rRNA genes amplified from the sediment revealed diverse microbial responses, for example desiccation enabled haloversatile Marinobacter species to increase their relative abundance, and thus take advantage of rewetting to grow rapidly and dominate the community. A temporal sequence of effects of desiccation and rewetting were thus observed, but the most notable feature was the overall resistance and resilience of the microbial community.
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Affiliation(s)
- Boyd A McKew
- Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, UK.
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8
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Kohls K, Abed RMM, Polerecky L, Weber M, de Beer D. Halotaxis of cyanobacteria in an intertidal hypersaline microbial mat. Environ Microbiol 2009; 12:567-75. [PMID: 19919535 DOI: 10.1111/j.1462-2920.2009.02095.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
An intertidal hypersaline cyanobacterial mat from Abu Dhabi (United Arab Emirates) exhibited a reversible change in its surface colour within several hours upon changes in salinity of the overlying water. The mat surface was orange-reddish at salinities above 15% and turned dark green at lower salinities. We investigated this phenomenon using a polyphasic approach that included denaturing gradient gel electrophoresis, microscopy, high-performance liquid chromatography, hyperspectral imaging, absorption spectroscopy, oxygen microsensor measurements and modelling of salinity dynamics. Filaments of Microcoleus chthonoplastes, identified based on 16S rRNA sequencing and morphology, were found to migrate up and down when salinity was decreased below or increased above 15%, respectively, causing the colour change of the mat uppermost layer. Migration occurred in light and in the dark, and could be induced by different salts, not only NaCl. The influence of salinity-dependent and independent physico-chemical parameters, such as water activity, oxygen solubility, H2S, gravity and light, was excluded, indicating that the observed migration was due to a direct response to salt stress. We propose to term this salinity-driven cyanobacterial migration as 'halotaxis', a process that might play a vital role in the survival of cyanobacteria in environments exposed to continuous salinity fluctuations such as intertidal flats.
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Affiliation(s)
- Katharina Kohls
- Max Planck Institute for Marine Microbiology, Celsiusstrasse 1, 28359 Bremen, Germany.
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9
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Fourçans A, Ranchou-Peyruse A, Caumette P, Duran R. Molecular analysis of the spatio-temporal distribution of sulfate-reducing bacteria (SRB) in Camargue (France) hypersaline microbial mat. MICROBIAL ECOLOGY 2008; 56:90-100. [PMID: 17952491 DOI: 10.1007/s00248-007-9327-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2007] [Revised: 08/24/2007] [Accepted: 09/25/2007] [Indexed: 05/25/2023]
Abstract
The spatio-temporal distribution of sulfate-reducing bacteria (SRB) in the microbial mat of Camargue (Salins-de-Giraud, France) was investigated by molecular approaches at both microscale spatial resolution and different taxonomic organization levels. The vertical distribution of the SRB populations was correlated with oxygen and sulfide microgradient fluctuations. Comparisons of Terminal restriction fragment length polymorphism (T-RFLP) fingerprints showed distinct locations of some operational taxonomic units at daytime and at night (4:00 or 15:00 hours) revealing important differences on the structures of the bacterial communities. When oxygen penetrates the mat, SRB migration was observed either downward to reach deeper anoxic zones to escape oxygen or upward to reach oxic surface zones. When no migration was observed, both metabolism switches and aggregate formations were suspected. These behaviors allowed the aerotolerant SRB to deal with oxygen. The analysis of the Desulfococcus-Desulfonema-Desulfosarcina T-RFLP profiles revealed up-migrating populations related to both Desulfonema sp. and Desulfosarcina variabilis. T-RFLP profiles combined with 16S ribosomal ribonucleic acid gene library analysis of the Desulfobacter group revealed two distinct populations: a population related to the recently described Desulfotignum genus migrating upward during the night and a population of a new species of the Desulfobacter uniformly located throughout the mat independent of the period. Thus, the identification of the new oxygen-tolerant SRB will provide the basis for understanding the physiological adaptations to oxygen.
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Affiliation(s)
- Aude Fourçans
- Laboratoire de Génomique des Archaea, Institut de Génétique et Microbiologie, UMR CNRS 8621, Université Paris Sud XI, Bât 400, 91405 Orsay Cedex, France
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10
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Gupta S, Agrawal SC. Motility in Oscillatoria salina as affected by different factors. Folia Microbiol (Praha) 2007; 51:565-71. [PMID: 17455793 DOI: 10.1007/bf02931621] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
All 3-10-d-old Oscillatoria salina filaments glide with the speed of 323-330 microm/min (BG 11 medium, pH 7.5, 21 +/- 2 degrees C, continuous light intensity of approximately 30 micromol m(-2) s(-1)) in a culture chamber. However, a time bound progressive decrease in gliding speed and in percentage of gliding filaments occurred, depending upon the severity of different stress factors studied, viz. water stress (2-8% agarized media, liquid media with 0.2-1 mol/L NaCl, blot-dryness of filaments for > or = 5 min), temperature shock (5, 40 degrees C for > or = 5 min; 35 degrees C for > or = 15 min), darkness and low light intensity (2, 10 micromol m(-2) s(-1)), UV exposure (0.96-3.84 kJ/m2), pH extremes (< or = 6.5 and > or = 9.5), lack of all nutrients from liquid medium (double distilled water), presence of 'heavy' metals (1, 25 ppm Fe, Cu, Zn, Ni, Co, Hg) or organic substances in liquid medium (25, 250 ppm 2,4-D, captan, urea, DDT, thiourea). This feature of the alga (i.e. reduction in speed and percentage of gliding filaments depending upon severity of stress conditions) may thus be suggested to be used in assessing water quality.
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Affiliation(s)
- S Gupta
- Department of Botany, University of Allahabad, India
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11
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Fourçans A, Solé A, Diestra E, Ranchou-Peyruse A, Esteve I, Caumette P, Duran R. Vertical migration of phototrophic bacterial populations in a hypersaline microbial mat from Salins-de-Giraud (Camargue, France). FEMS Microbiol Ecol 2006; 57:367-77. [PMID: 16907751 DOI: 10.1111/j.1574-6941.2006.00124.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
The spatio-temporal distribution of phototrophic communities of the hypersaline photosynthetic Camarguc microbial mat (Salins-de-Giraud, France) was investigated over a diel cycle by combining microscopic and molecular approaches. Microcoleus chthonoplastes and Halomicronema excentricum, the dominant cyanobacteria of this oxyphotrophic community, were observed with confocal laser scanning microscopy to determine their biomass profiles. Both bacteria have similar vertical distributions, varying from a homogenous distribution through the mat during the night, to a specific localization in the upper oxic zone of 1.5 mm during the day. Terminal restriction fragment length polymorphism of PCR-amplified pufM gene fragments revealed three groups of anoxyphototrophic populations, which varied according to the two opposite periods of the diel cycle under study. They were either specifically detected in only one period, or homogenously distributed through the mat in all periods, or located in specific zones of the mat depending on the period considered. Oxygen concentrations, pH and biomass of the major filamentous cyanobacteria were the determinative factors in the distribution of these anoxyphototrophs across the mat. Thus, vertical migration, cell-cell aggregate formation and metabolic switches were the most evident defence of the photosynthetic populations against the adverse effects of sulfide and oxygen fluxes during a diel cycle.
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Affiliation(s)
- Aude Fourçans
- Laboratoire d'Ecologie Moléculaire EA 3525, Université de Pau et des Pays de l'Adour, avenue de l'Université, BP 1155, Pau Cedex, France
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12
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Seong-Joo L, Golubic S. Multi-trichomous cyanobacterial microfossils from the Mesoproterozoic Gaoyuzhuang Formation, China: paleoecological and taxonomic implications. LETHAIA 1998; 31:169-184. [PMID: 11542928 DOI: 10.1111/j.1502-3931.1998.tb00505.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Populations of the multi-trichomous microbial fossil Eoschizothrix composita n.gen. et sp. are preserved in growth position in silicified stratiform stromatolites of the Gaoyuzhuang Formation, Hebei Province, northern China. The microbial fossils consist predominantly of preserved sheaths, although several specimens retain shriveled remains of trichomes within sheaths. Comparisons with modern morphological counterparts, including shape, growth habit and orientation, degradational sequences, and habitat, support the interpretation of the multi-trichomous microfossils as cyanobacteria, which acted as frame-builders of ancient stromatolites. The distribution and orientation of multi-trichomous microfossils within a synsedimentary context reveal their behavioral responses to sedimentation regime. Horizontally spread, interwoven mats formed during periods of sedimentary stasis. During periods of rapid sediment influx, the filaments assumed an upright orientation, possibly to avoid accumulating particles. This is the first record of fossil stromatolite-building multi-trichomous cyanobacterial which underscores early morphological and functional diversification in cyanobacterial evolution.
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Affiliation(s)
- L Seong-Joo
- Biological Science Center, Boston University, MA 02215, USA
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13
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Stal LJ. Physiological ecology of cyanobacteria in microbial mats and other communities. THE NEW PHYTOLOGIST 1995; 131:1-32. [PMID: 33863161 DOI: 10.1111/j.1469-8137.1995.tb03051.x] [Citation(s) in RCA: 141] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
In this review some aspects of the physiological ecology of cyanobacteria are discussed by taking a microbial mat as an example. The majority of microbial mats are built and dominated by cyarsobacteria which are primary producers at the basis of the microbial foodweb in microbial mats. These micro-scale ecosystems are characterized by steep and fluctuating physico-chemical gradients of which those of light, oxygen and sulphide are the most conspicuous. Light is strongly attenuated in the sediment, and owing to constant sedimentation, the mat-forming cyanobacteria have to move upwards towards the light. However, at the sediment surface, light intensity, particularly in the u.v. part of the spectrum, is often deleterious. The gliding movement of the cyanobacteria, with photo- and chemotaxis, allows the organism to position itself in a thin layer at optimal conditions. The organic matter produced by cyanobacterial photosynthesis is decomposed by the ruicrobial community. Sulphate-reducing bacteria are important in the end-oxidation of the organic matter. These organisms are obligate anaerobes and produce sulphide. Gradients of sulphide and oxygen move up and down in the sediment as a response to diurnal variations of light intensity. Cyanobacteria, therefore, are sometimes exposed to large concentrations of the extremely toxic sulphide. Some species are capable of sulphide-dependent anoxygenic photosynthesis. Other cyanobacteria show increased rates of oxygenic photosynthesis in the presence of sulphide and have mechanisms to oxidize sulphide while avoiding sulphide toxicity. Iron might play an important role in this process. Under anoxic conditions in the dark, mat-forming cyanobacteria switch to fermentative metabolism. Many species are also capable of fermentative reduction of elemental sulphur to sulphide. The gradients of sulphide and oxygen are of particular importance for nitrogen fixation. Very few microbial mats are formed by heterocystous cyanobacteria, which are best adapted to diazntrophic growth. However, these organisms probably cannot tolerate greater concentrations of sulphide or anoxic conditions or both. Under such conditions non-heterocystous cyanobacteria become dominant as diazotrophs. These organisms avoid conditions of oxygen supersaturation. In the ecosystem, nitrogen fixation and photosynthesis might be separated temporally as well as spatially. In addition, non-heterocystous diazotrophic cyanobacteria have mechanisms at the subcellular level to protect the oxygen-sensitive nitrogenase from inaction. CONTENTS Summary 1 I. Introduction 2 II. Microbial mats 3 III. Cyanobacteria in light gradients 7 IV. Dark metabolism 10 V. Interactions with sulphide 13 VI. Nitrogen fixation 16 VII. References 28.
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Affiliation(s)
- Lucas J Stal
- Laboratory for Microbiology, University of Amsterdam, Nieuwe Achtergracht 127, NL-1018 WS Amsterdam, The Netherlands
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14
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Jørgensen BB, Cohen Y, Revsbech NP. Photosynthetic Potential and Light-Dependent Oxygen Consumption in a Benthic Cyanobacterial Mat. Appl Environ Microbiol 1988; 54:176-182. [PMID: 16347523 PMCID: PMC202418 DOI: 10.1128/aem.54.1.176-182.1988] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The potential to carry out oxygenic photosynthesis after prolonged burial below the photic zone was studied at 0.1-mm depth intervals in the thick, laminated
Microcoleus chthonoplastes
mats growing in Solar Lake, Sinai. The buried mat community lost about 20% of its photosynthetic potential with depth per annual layer down to 8- to 10-year-old layers at a 14-mm depth. In some of the older layers, below a 30-mm depth, light-dependent oxygen consumption which increased with increasing light intensity was observed. Possible mechanisms for this phenomenon are (i) pseudocyclic electron transport (Mehler reaction), (ii) interactions between respiratory electron transport and photosynthetic electron transport, (iii) photorespiration, and (iv) photooxidation.
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15
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Richardson LL, Castenholz RW. Diel Vertical Movements of the Cyanobacterium
Oscillatoria terebriformis
in a Sulfide-Rich Hot Spring Microbial Mat. Appl Environ Microbiol 1987; 53:2142-50. [PMID: 16347435 PMCID: PMC204072 DOI: 10.1128/aem.53.9.2142-2150.1987] [Citation(s) in RCA: 59] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Oscillatoria terebriformis,
a thermophilic cyanobacterium, carried out a diel vertical movement pattern in Hunter's Hot Springs, Oreg. Throughout most daylight hours, populations of
O. terebriformis
covered the surface of microbial mats in the hot spring outflows below an upper temperature limit of 54°C. Upon darkness trichomes moved downward by gliding motility into the substrate to a depth of 0.5 to 1.0 mm, where the population remained until dawn. At dawn the population rapidly returned to the top of the mats. Field studies with microelectrodes showed that the dense population of
O. terebriformis
moved each night across an oxygen-sulfide interface, entering a microenvironment which was anaerobic and reducing, a dramatic contrast to the daytime environment at the mat surface where oxygenic photosynthesis resulted in supersaturated O
2
. Laboratory experiments on motility with the use of sulfide gradients produced in agar revealed a negative response to sulfide at concentrations similar to those found in the natural mats. The motility response may help explain the presence of
O. terebriformis
below the mat surface at night. The movement back to the surface at dawn appears to be due to a combination of phototaxis, photokinesis, and the onset of oxygenic photosynthesis which consumes sulfide.
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Affiliation(s)
- L L Richardson
- Department of Biology, University of Oregon, Eugene, Oregon 97403
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