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1.
In seawater, several trace metals with biological significance are highly complexed with organic matter. Marine cyanobacteria
are an important phytoplanktonic group, with the ability to release trace metal-binding compounds to the seawater medium,
which in turn modulates their bioavailability and influences their biogeochemical cycles. Such interactions may allow cyanobacteria
to more easily access less available trace metals essential for their metabolic processes, or, conversely, keep the toxic
forms of the trace metals from reaching intolerable levels. In this minireview, Cu and Fe interactions with cyanobacteria
received special attention, although other trace metals (Co, Pb, Zn, and Cd) are also covered. Recent research has shed light
on many aspects of trace metal–cyanobacteria ecology in seawater; nevertheless, the biochemical processes behind this dynamics
and the structure of the vast majority of the metal binding compounds remain unclear. 相似文献
2.
Sulfate inhibition of molybdenum-dependent nitrogen fixation by planktonic cyanobacteria under seawater conditions: a non-reversible effect 总被引:3,自引:0,他引:3
Marino Roxanne Howarth Robert W. Chan Francis Cole Jonathan J. Likens Gene E. 《Hydrobiologia》2003,500(1-3):277-293
The trace element molybdenum is a central component of several enzymes essential to bacterial nitrogen metabolism, including nitrogen fixation. Despite reasonably high dissolved concentrations (for a trace metal) of molybdenum in seawater, evidence suggests that its biological reactivity and availability are lower in seawater than in freshwater. We have previously argued that this difference is related to an inhibition in the uptake of molybdate (the thermodynamically stable form of molybdenum in oxic natural waters) by sulfate, a stereochemically similar ion. Low molybdenum availability may slow the growth rate of nitrogen-fixing cyanobacteria, and in combination with an ecological control such as grazing by zooplankton, keep fixation rates very low in even strongly nitrogen-limited coastal marine ecosystems. Here we present results from a seawater mesocosm experiment where the molybdenum concentration was increased 10-fold under highly nitrogen-limited conditions. The observed effects on nitrogen-fixing cyanobacterial abundance and nitrogen-fixation inputs were much smaller than expected. A follow-up experiment with sulfate and molybdenum additions to freshwater microcosms showed that sulfate (at seawater concentrations) greatly reduced nitrogen fixation by cyanobacteria and that additions of molybdenum to the levels present in the seawater mesocosm experiment only slightly reversed this effect. In light of these results, we re-evaluated our previous work on the uptake of radio-labeled molybdenum by lake plankton and by cultures of heterocystic cyanobacteria. Our new interpretation indicates that sulfate at saline estuarine levels (>8–10 mM) up to seawater (28 mM) concentrations does inhibit molybdenum assimilation. However, the maximum molybdenum uptake rate (V
max) was a function of the sulfate concentration, with lower V
max values at higher sulfate levels. This indicates that this inhibition is not fully reversed at some saturating level of molybdenum, as assumed in a simple competitive inhibition model. A multi-enzyme, mixed kinetics model with two or more uptake enzyme systems activated in response to the environmental sulfate and molybdate conditions may better explain the repressive effect of sulfate on Mo-mediated processes such as nitrogen fixation. 相似文献
3.
Marine pelagic N(2)-fixing bacteria have not, in general, been identified or quantified, since low or negligible rates of N(2) fixation have been recorded for seawater when blue-green algae (cyanobacteria) are absent. In the study reported here, marine N(2)-fixing bacteria were found in all samples of seawater collected and were analyzed by using a most-probable-number (MPN) method. Two different media were used which allowed growth of microaerophiles, as well as that of aerobes and facultative anaerobes. MPN values obtained for N(2)-fixing bacteria ranged from 0.4 to 1 x 10 per liter for water collected off the coast of Puerto Rico and from 2 to 5.5 x 10 per liter for Chesapeake Bay water. Over 100 strains of N(2)-fixing bacteria were isolated from the MPN tubes and classified, yielding four major groups of NaCl-requiring bacteria based on biochemical characteristics. Results of differential filtration studies indicate that N(2)-fixing bacteria may be associated with phytoplankton. In addition, when N(2)-fixing bacteria were inoculated into unfiltered seawater and incubated in situ, nitrogenase activity could be detected within 1 h. However, no nitrogenase activity was detected in uninoculated seawater or when bacteria were incubated in 0.2-mum-filtered (phytoplankton-free) seawater. The ability of these isolates to fix N(2) at ambient conditions in seawater and the large variety of N(2)-fixing bacteria isolated and identified lead to the conclusion that N(2) fixation in the ocean may occur to a greater degree than previously believed. 相似文献
4.
《Harmful algae》2017
Cyanobacterial blooms are predicted to become more prominent in the future as a result of increasing seawater temperatures and the continued addition of nutrients to coastal waters. Many benthic marine cyanobacteria have potent chemical defenses that protect them from top down pressures and contribute to the persistence of blooms. Blooms of benthic cyanobacteria have been observed along the coast of Florida and within the Indian River Lagoon (IRL), a biodiverse estuary system that spans 250 km along Florida’s east coast. In this study, the cyanobacterial bloom progression at three sites within the central IRL was monitored over the course of two summers. The blooms consisted of four unique cyanobacterial species, including the recently described Okeania erythroflocculosa. The cyanobacteria produced a range of known bioactive compounds including malyngolide, lyngbyoic acid, microcolins A–B, and desacetylmicrocolin B. Ecologically-relevant assays showed that malyngolide inhibited the growth of marine fungi (Dendryphiella salina and Lindra thalassiae); microcolins A–B and desacetylmicrocolin B inhibited feeding by a generalist herbivore, the sea urchin Lytechinus variegatus; and lyngbyoic acid inhibited fungal growth and herbivore feeding. These chemical defenses likely contribute to the persistence of cyanobacterial blooms in the IRL during the summer growing period. 相似文献
5.
The photosynthetic picocyanobacteria and eukaryotic microorganisms that inhabit the open ocean must be able to supply iron
for their photosynthetic and respiratory needs from the subnanomolar concentrations available in seawater. Neither group appears
to produce siderophores, although some coastal cyanobacteria do. This is interpreted as an adaptation to the dilute oceanic
environment rather than a phylogenetic constraint, since there are cases in which related taxa from different environments
have the capacity to produce siderophores. Most photosynthetic marine microorganisms are presumably, however, capable of accessing
iron from strong chelates since the majority of dissolved iron in seawater is complexed by organic ligands, including siderophores.
Rather than direct internalization of siderophores and other iron chelates, marine organisms primarily appear to use uptake
pathways that involve a reduction step to free bound iron, closely coupled with transport into the cell. 相似文献
6.
Z. B. Namsaraev T. V. Kolganova E. O. Patutina D. D. Tsyrenova O. S. Samylina 《Microbiology》2018,87(4):583-590
Clone libraries and morphological analysis were used to investigate cyanobacterial diversity in the cyanobacterial mat and dry crust at the bottom of the shallow, saline, alkaline Lake Khilganta (Southern Siberia, Russia). Filamentous cyanobacteria belonging to Phormidium genus and Coleofasciculus chthonoplastes were found to predominate during the dry period (2006) and the wet periods (1995 and 2012), respectively. Community composition during the dry and wet periods differed significantly. While 11 operational taxonomic units of cyanobacteria were revealed, only 3 occurred during both dry and wet periods. Occurrence of cosmopolitan C. chthonoplastes, which is common in neutral saline environments, is not typical of a continental alkaline lake and may be explained by the similarity of the dominant ions composition in lake water and in seawater. 相似文献
7.
Explaining the nearly ubiquitous absence of nitrogen fixation by planktonic organisms in strongly nitrogen-limited estuaries presents a major challenge to aquatic ecologists. In freshwater lakes of moderate productivity, nitrogen limitation is seldom maintained for long since heterocystic, nitrogen-fixing cyanobacteria bloom, fix nitrogen, and alleviate the nitrogen limitation. In marked contrast to lakes, this behavior occurs in only a few estuaries worldwide. Primary production is limited by nitrogen in most temperate estuaries, yet no measurable planktonic nitrogen fixation occurs. In this paper, we present the hypothesis that the absence of planktonic nitrogen fixers from most estuaries is due to an interaction of bottom-up and top-down controls. The availability of Mo, a trace metal required for nitrogen fixation, is lower in estuaries than in freshwater lakes. This is not an absolute physiological constraint against the occurrence of nitrogen-fixing organisms, but the lower Mo availability may slow the growth rate of these organisms. The slower growth rate makes nitrogen-fixing cyanobacteria in estuaries more sensitive to mortality from grazing by zooplankton and benthic organisms.We use a simple, mechanistically based simulation model to explore this hypothesis. The model correctly predicts the timing of the formation of heterocystic, cyanobacterial blooms in freshwater lakes and the magnitude of the rate of nitrogen fixation. The model also correctly predicts that high zooplankton biomasses in freshwaters can partially suppress blooms of nitrogen-fixing cyanobacteria, even in strongly nitrogen-limited lakes. Further, the model indicates that a relatively small and environmentally realistic decrease in Mo availability, such as that which may occur in seawater compared to freshwaters due to sulfate inhibition of Mo assimilation, can suppress blooms of heterocystic cyanobacteria and prevent planktonic nitrogen fixation. For example, the model predicts that at a zooplankton biomass of 0.2 mg l–1, cyanobacteria will bloom and fix nitrogen in lakes but not in estuaries of full-strength seawater salinity because of the lower Mo availability. Thus, the model provides strong support for our hypothesis that bottom-up and top-down controls may interact to cause the absence of planktonic nitrogen fixation in most estuaries. The model also provides a basis for further exploration of this hypothesis in individual estuarine systems and correctly predicts that planktonic nitrogen fixation can occur in low salinity estuaries, such as the Baltic Sea, where Mo availability is greater than in higher salinity estuaries. 相似文献
8.
Venigalla Purnachandra Rao Ernst Hegner Syed Wajih Ahmad Naqvi Pratima Mohan Kessarkar Syed Masood Ahmad Datta Suryanarayana Raju 《Palaeogeography, Palaeoclimatology, Palaeoecology》2008,260(3-4):347-358
Phosphorites from the Murray Ridge, NW Arabian Sea comprise nodules, bioclasts, and bone fragments. The nodules are made up of a homogeneous, light-colored phosphate nucleus consisting of Rivulariacean filamentous cyanobacteria and a thin dark-grey colored phosphate cortex showing abundant microbial filaments and microborings. The bioclasts comprise of 14–14.5 Ma old planktonic foraminifers, accepted as the time of deposition. Spherical to ovoid-shaped apatite microparticles resembling fossil bacteria are distinct components in the bioclasts. Bone fragments exhibit apatite fillings. The nodules and bone fragments consist entirely of carbonate fluorapatite (CFA) with low Al, K, and Th concentrations suggesting absence of continental detritus. Shale-normalized REE patterns of the samples support a seawater-derived composition. The highly uniform initial Nd values of − 4.8 to − 5.1 are interpreted as the seawater value at the onset of phosphatization 14 Ma ago. In contrast, 87Sr/86Sr ratios show a large range of 0.709055 to 0.709124 corresponding to unusually young stratigraphic ages of 1 to 3 Ma. The data are interpreted as evidence for post-depositional Sr exchange of the recrystallizing phosphorites with fluids isotopically not much different from modern seawater. It is concluded that the phosphorites formed under oxic, shallow-water conditions where microbial populations assimilated phosphorus primarily from seawater and mediated precipitation of CFA during early diagenesis at the sediment–water interface on different substrates. 相似文献
9.
Biofuel-bioenergy production has generated intensive interest due to increased concern regarding limited petroleum-based fuel supplies and their contribution to atmospheric CO2 levels. Biofuel research is not just a matter of finding the right type of biomass and converting it to fuel, but it must also be economically sustainable on large-scale. Several aspects of cyanobacteria and microalgae such as oxygenic photosynthesis, high per-acre productivity, non-food based feedstock, growth on non-productive and non-arable land, utilization of wide variety of water sources (fresh, brackish, seawater and wastewater) and production of valuable co-products along with biofuels have combined to capture the interest of researchers and entrepreneurs. Currently, worldwide biofuels mainly in focus include biohydrogen, bioethanol, biodiesel and biogas. This review focuses on cultivation and harvesting of cyanobacteria and microalgae, possible biofuels and co-products, challenges for cyanobacterial and microalgal biofuels and the approaches of genetic engineering and modifications to increase biofuel production. 相似文献
10.
Freshwater and terrigenous suspended material inputs were studied in Longoni Bay, an area of the lagoon of Mayotte (Comoro,
Indian Ocean) that is unaffected by the influence of the most populated area of the island. The influence of terrigenous material
on the lagoon waters was limited to the coastal zone and resulted in the increase of inorganic nitrogen and silica. The response
of the bacteria was an increase of their cell volume; that of the phytoplankton was an increase of cyanobacteria numbers and
chlorophyll a related to ammonia. Ammonification was apparently enhanced in freshwater whereas nitrification was enhanced
in seawater. The high nitrate and silicate content of the reef zone were explained neither by river or rainfall inputs nor
by enrichments by ocean waters. The hypothesis of the participation of marine groundwater discharges to this enrichment was
examined and found to be supported by the range of concentrations in the reef zone and because enrichment did not concern
ammonia and nitrite but only nitrate and silicate and occurred during the wet period when the aquifer is fed by abundant rainfall.
The response of bacteria to the characteristics of the reef zone was an increase in biomass and a lower level of heterotrophic
activity related to nitrate concentration. The changes observed during the wet period confirmed that the nitrogen increase
was linked to the terrigenous material, and possibly to discharge of groundwater, and yielded a lower number of bacteria but
increased biomass, and despite a drop in large phytoplankton numbers, a strong increase in chlorophyll a related in part to
small cyanobacteria. This enrichment is high enough to place the Mayotte Lagoon among the richest high island lagoons, with
regard to nitrogen and chlorophyll a.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
11.
12.
R. RIDING 《Geobiology》2006,4(4):299-316
Photosynthetic uptake of inorganic carbon can raise the pH adjacent to cyanobacterial cells, promoting CaCO3 precipitation. This effect is enhanced by CO2 concentrating mechanisms that actively transport into cells for carbon fixation. CO2 concentrating mechanisms presumably developed in response to atmospheric decrease in CO2 and increase in O2 over geological timescales. In present‐day cyanobacteria, CO2 concentrating mechanisms are induced when the atmospheric partial pressure of CO2 (pCO2) falls below ~0.4%. Reduction in pCO2 during the Proterozoic may have had two successive effects on cyanobacterial calcification. First, fall in pCO2 below ~1% (33 times present atmospheric level, PAL) resulted in lower dissolved inorganic carbon (DIC) concentrations that reduced pH buffering sufficiently for isolated CaCO3 crystals to begin to nucleate adjacent to cyanobacterial cells. As a result, blooms of planktic cyanobacteria induced precipitated ‘whitings’ of carbonate mud in the water column whose sedimentary accumulation began to dominate carbonate platforms ~1400–1300 Ma. Second, fall in pCO2 below ~0.4% (10 PAL) induced CO2‐concentrating mechanisms that further increased pH rise adjacent to cells and promoted in vivo cyanobacterial sheath calcification. Crossing of this second threshold is indicated in the fossil record by the appearance of Girvanella 750–700 Ma. Coeval acquisition of CO2 concentrating mechanisms by planktic cyanobacteria further stimulated whiting production. These inferences, that pCO2 fell below ~1%~1400–1300 Ma and below ~0.4% 750–700 Ma, are consistent with empirical and modelled palaeo‐atmosphere estimates. Development of CO2 concentrating mechanisms was probably temporarily slowed by global cooling ~700–570 Ma that favoured diffusive entry of CO2 into cells. Lower levels of temperature and DIC at this time would have reduced seawater carbonate saturation state, also hindering cyanobacterial calcification. It is suggested that as Earth emerged from ‘Snowball’ glaciations in the late Neoproterozoic, global warming and O2 rise reactivated the development of CO2 concentrating mechanisms. At the same time, rising levels of temperature, calcium ions and DIC increased seawater carbonate saturation state, stimulating widespread cyanobacterial in vivo sheath calcification in the Early Cambrian. This biocalcification event promoted rapid widespread development of calcified cyanobacterial reefs and transformed benthic microbial carbonate fabrics. 相似文献
13.
A E Allen M G Booth M E Frischer P G Verity J P Zehr S Zani 《Applied and environmental microbiology》2001,67(11):5343-5348
A PCR approach was used to construct a database of nasA genes (called narB genes in cyanobacteria) and to detect the genetic potential for heterotrophic bacterial nitrate utilization in marine environments. A nasA-specific PCR primer set that could be used to selectively amplify the nasA gene from heterotrophic bacteria was designed. Using seawater DNA extracts obtained from microbial communities in the South Atlantic Bight, the Barents Sea, and the North Pacific Gyre, we PCR amplified and sequenced nasA genes. Our results indicate that several groups of heterotrophic bacterial nasA genes are common and widely distributed in oceanic environments. 相似文献
14.
15.
Cyanobacterial community structure as seen from RNA polymerase gene sequence analysis. 总被引:15,自引:10,他引:5
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B Palenik 《Applied microbiology》1994,60(9):3212-3219
PCR was used to amplify DNA-dependent RNA polymerase gene sequences specifically from the cyanobacterial population in a seawater sample from the Sargasso Sea. Sequencing and analysis of the cloned fragments suggest that the population in the sample consisted of two distinct clusters of Prochlorococcus-like cyanobacteria and four clusters of Synechococcus-like cyanobacteria. The diversity within these clusters was significantly different, however. Clones within each Synechococcus-like cluster were 99 to 100% identical, while each Prochlorococcus-like cluster was only 91% identical at the nucleotide level. One Prochlorococcus-like cluster was significantly more closely related to a Mediterranean Sea (surface) Prochlorococcus isolate than to the other cluster, showing the highly divergent nature of this group even in one sample. The approach described here can be used as a general method for examining cyanobacterial diversity, while an oligotrophic ocean ecosystem such as the Sargasso Sea may be an ideal model for examining diversity in relation to environmental parameters. 相似文献
16.
Lytic viral production and lysogeny were investigated in cyanobacteria and heterotrophic bacteria during a bloom of Synechococcus spp. in a pristine fjord in British Columbia, Canada. Triplicate seawater samples were incubated with and without mitomycin C and the abundances of heterotrophic bacteria, cyanobacteria, total viruses and infectious cyanophage were followed over 24 h. Addition of mitomycin C led to increases in total viral abundance as well as the abundance of cyanophages infecting Synechococcus strain DC2. Given typical estimates of burst size, these increases were consistent with 80% of the heterotrophic bacteria and 0.6% of Synechococcus cells being inducible by the addition of mitomycin C. This is the highest percentage of lysogens reported for a natural microbial community and demonstrates induction in a marine Synechococcus population. It is likely that the cyanophage production following the addition of mitomycin C was much higher than that titered against a single strain of Synechococcus; hence this estimate is a minimum. In untreated seawater samples, lytic viral production was estimated to remove ca. 27% of the gross heterotrophic bacterial production, and a minimum of 1.0% of the gross cyanobacterial production. Our results demonstrate very high levels of lysogeny in the heterotrophic bacterial community, outside of an oligotrophic environment, and the presence of inducible lysogens in Synechococcus spp. during a naturally occurring bloom. These data emphasize the need for further examination of the factors influencing lytic and lysogenic viral infection in natural microbial communities. 相似文献
17.
Up-to-date methods for isolation of cyanobacteria from soil samples, removal of accompanying microflora, obtaining axenic strains, and conditions and media for subsequent cultivation are reviewed. Characterization of soil as a specific habitat for cyanobacteria is provided. Comparative analysis of pH and elemental composition of the liquid phase of most soil types with the media for cultivating cyanobacteria is carried out. The functional role of the major components required for the cultivation of cyanobacteria is described. The problems associated with isolation, purification, and cultivation of soil cyanobacteria, as well as the relevant solutions, are discussed. 相似文献
18.
Quantitative real-time PCR detection of toxic Nodularia cyanobacteria in the Baltic Sea 总被引:1,自引:0,他引:1
Koskenniemi K Lyra C Rajaniemi-Wacklin P Jokela J Sivonen K 《Applied and environmental microbiology》2007,73(7):2173-2179
A specific quantitative real-time PCR (qPCR) method was developed for the quantification of hepatotoxin nodularin-producing Nodularia, one of the main bloom-forming cyanobacteria in the Baltic Sea. Specific PCR primers were designed for subunit F of the nodularin synthetase gene (ndaF), which encodes the NdaF subunit of the nodularin synthetase gene complex needed for nodularin production. The qPCR method was applied to water samples (a total of 120 samples) collected from the Baltic Sea in July 2004. As few as 30 ndaF gene copies ml(-1) of seawater could be detected, and thus, the method was very sensitive. The ndaF gene copy numbers and nodularin concentrations were shown to correlate in the Baltic seawater, indicating the constant production of nodularin by Nodularia. This qPCR method for the ndaF gene can be used for detailed studies of Nodularia blooms and their formation. ndaF gene copies and nodularin were detected mostly in the surface water but also in deeper water layers (down to 30 m). Toxic Nodularia blooms are not only horizontally but also vertically widely distributed, and thus, the Baltic fauna is extensively exposed to nodularin. 相似文献
19.
Invasive and alien cyanobacteria are considered as a serious threat to aquatic ecosystems due to their ability to produce cyanotoxins and outcompeting native species. Among cyanobacteria, Nostocales is a group with strong competitive advantages including the production of resting cells, ability to fix nitrogen or high affinity to phosphorus. A species Chrysosporum bergii has broadened its original distribution from brackish and seawater habitats of Caspian and Aral Seas to northern regions of Europe. The aim of our study was to expand the knowledge on the distribution of C. bergii, its preferred habitats in the invaded areas and examine whether the biomass of C. bergii is related with biomass of other alien or native cyanobacteria. We examined the phytoplankton community composition and the abiotic factors in randomly selected lakes of western Poland. For the first time, we showed that it occurs widely in lakes of this region. However, it occurred in one third of the investigated lakes and its contribution to total phytoplankton biomass was low. It occurred more frequently in shallow lakes with low conductivity and dissolved phosphorus, yet with higher total phosphorus concentration. The most remarkable finding was a negative relationship of C. bergii biomass with the biomass of native A. gracile, but a positive relationship with an invasive cyanobacterium C. raciborskii. This result suggests that these alien species occur under similar environmental conditions in Polish lakes. Moreover, the morphological features of C. bergii in Poland were similar to those of Anabaena bergii var. limnetica Couté et Preisig from Lithuania and Anabaena bergii from Czech Republic. 相似文献
20.
The intracellular concentrations of the monovalent inorganic cations K+ and Na+, low molecular weight carbohydrates and quaternary ammonium compounds have been determined for 4 strains of cyanobacteria (Aphanothece halophytica, Coccochloris elabens, Dactylococcopsis salina and Synechocystis DUN52) originally isolated from hypersaline habitats (i.e. habitats with a salinity greater than that of seawater) over a range of external salt concentration (from 50% to 400% seawater). Intracellular cation levels (Na+ and K+) were determined to be within the range 80–320 mmol · dm-3 (cell volume), showing only minor changes in response to salinity. Intracellular carbohydrates were found to comprise a negligible component of the intracellular osmotic potential [at 2–19 mmol · dm-3 (cell volume)], throughout the salinity range. Quaternary ammonium compounds, however, were recorded in osmotically significant quantities [up to 1,640 mmol · dm-3 (cell volume)] in these strains, showing major variation in response to salinity. Thus Synechocystis DUN 52 showed an increase in quaternary ammonium compounds in the oder of 1,200 mmol · dm-3 between 50% and 400% seawater medium, accounting for a significant proportion of the change in external osmotic potential.Examination of intact cells and cell extracts using 13C and 1H nuclear magnetic resonance (NMR) spectroscopy confirmed the presence of the quaternary ammonium compound glycine betaine as the major osmoticum in the 4 strains; no other compounds were detected during NMR assays. These results suggest a common mechanism of osmotic adjustment, involving quaternary ammonium compounds, in cyanobacteria from hypersaline environments. 相似文献