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1.
2.
The structure of benthic phototrophic communities of 24 soda lakes of the southeastern Transbaikal Region was studied. The physicochemical properties of the lakes were determined. The results of enumeration of anoxygenic phototrophic bacteria (APB) belonging to various groups are presented. The influence of salinity on the structure of APB communities was investigated. The APB reaction to environmental conditions was determined. Massive development of phototrophic microorganisms in the form of mats and films was observed in the majority of the investigated lakes. The APB communities were characterized by a wide diversity and evenness of species composition. Purple sulfur bacteria of the families Ectothiorhodospiraceae and Chromatiaceae were predominant. Purple nonsulfur bacteria of the family Rhodobacteraceae, green filamentous bacteria Oscillochloris sp., and heliobacteria were also detected. According to preliminary data, no less than 15 species of APB occur in the studied lakes. Among them, three novel genera and four species have already been described. Identification of other isolates is still in progress. The lakes make an almost continuous series of fresh, brackish, and saline water bodies, varying in their degree of mineralization. It was demonstrated that the structure of APB communities was unaffected by changes in salinity from 5 to 40 g/l. At salt concentrations of lower than 5 g/l, the level of water mineralization became a limiting factor. Experiments with the isolated cultures showed that the APB were obligately dependent on the presence of carbonate ions in the medium. They were haloalkalitolerant or haloalkaliphilic. Thus, they are well adapted to the conditions of soda lakes with a low of moderate mineralization. It was demonstrated that soda lakes of the southeastern Transbaikal Region represent a special type of habitat which harbors a peculiar autochthonous microflora and differs from both highly mineralized soda lakes and shallow saline water bodies of the sea origin.  相似文献   

3.
The occurrence of dioic, hydroxy, branched, and unsaturated fatty acids in cyanobacteria of the genus Aphanizomenon growing in different freshwater lakes has been studied. Unusual dicarboxylic (from 4.52 to 7.14%) and other fatty acids were identified by gas chromatography/mass spectrometry (GC/MS).  相似文献   

4.
The genes encoding the key metabolic reactions are often used as functional markers for phylogenetic analysis and microbial ecology studies. The composition and structure of the genes encoding ribulose-1,5-bisphosphate carboxylase (RuBisCO) of various photoautotrophic bacteria, representatives of the order Chromatiales, including collection strains and the strains isolated from saline and soda lakes, were studied in detail. The green-like form I RuBisCO was detected in the majority of the studied strains. In some strains, the genes encoding both form I and form II RuBisCO were present, which has not been previously known for the representatives of this group of bacteria. Moreover, RuBisCO genes were used as functional markers to investigate the autotrophic microbial community inhabiting the upper horizons of bottom sediments of two saline soda lakes and two hypersaline neutral lakes of the Kulunda Steppe. In general, the diversity of autotrophic bacteria in the studied sediment horizons was low. In soda lakes, haloalkaliphilic cyanobacteria and sulfuroxidizing bacteria (SOB) of the genus Halorhodospira were predominant. In saline lakes, halophilic chemoautotrophic SOB Halothiobacillus and Thioalkalivibrio were found, as well as photoautotrophic bacteria of the genus Ectothiorhodosinus and cyanobacteria. Many phylotypes remained unidentified, which indicates the presence of groups of microorganisms with an unknown type of metabolism.  相似文献   

5.
The structure of benthic phototrophic communities of 24 soda lakes of the southeastern Transbaikal Region was studied. The physicochemical properties of the lakes were determined. The results of the cell count of anoxygenic phototrophic bacteria (APB) belonging to various groups are presented. The influence of salinity on the structure of APB communities was investigated. The APB reaction to environmental conditions was determined. Massive development of phototrophic microorganisms in the form of mats and films was observed in the majority of the investigated lakes. The APB communities were characterized by a wide diversity of species and evenness of species composition. Purple sulfur bacteria of the families Ectothiorhodospiraceae and Chromatiaceae were predominant. Purple nonsulfur bacteria of the family Rhodobacteraceae, green filamentous bacteria Oscillochloris sp., and heliobacteria were also detected. According to preliminary data, no less than 15 species of APB occur in the studied lakes. Among them, three novel genera and four species have already been described. Identification of other isolates is still in progress. The lakes make an almost continuous series of fresh, brackish, and saline water bodies, varying in their degree of mineralization. It was demonstrated that the structure of APB communities was unaffected by salinity ranging from 5 to 40 g/l. At salt concentrations of lower than 5 g/l, the level of water mineralization became a limiting factor. Experiments with the isolated cultures showed that the APB were obligately dependent on the presence of carbonate ions in the medium. They were haloalkalitolerant or haloalkaliphilic. Thus, they are well adapted to the conditions of soda lakes with a high mineralization. It was demonstrated that soda lakes of the southeastern Transbaikal Region represent a special type of habitat which harbors a peculiar autochthonous microflora and differs from both highly mineralized soda lakes and shallow saline water bodies of the sea origin.  相似文献   

6.
The taxonomy of the genus Monoraphidium is unclear due in part to the absence of morphological features to clearly distinguish one species from another. Phytoplankton samples collected from lakes in the Arrowwood National Refuge in eastern North Dakota were found to contain several morphological species of Monoraphidium. Eighteen Monoraphidium isolates were examined with light microscopy and six morphological species were identified. PCR–RFLP of the 18S rDNA was used to type the isolates. Following digestion by Hae III and Taq I, the 18S rDNA PCR–RFLP patterns indicated 10 different types. Presently, the 18S rDNA product is being sequenced for each of the 10 types. By examining morphological characters and 18S rDNA sequences, congruence between morphology and sequence data may be compared. Also, because there is a lack of morphological characters defining Monoraphidium species, diversity within the 18S rDNA sequences may aid in the taxonomy of the genus and its place within the Chlorococcales. Supported by National Science Foundation Grants MCB‐0084188 and DBI‐0070387.  相似文献   

7.
In the last decades, numerous exotic species of microalgae have been found in the continental waters of Europe. In three natural shallow lakes located in the southwest of France, several planktonic species typically encountered in tropical areas were observed during 2006 and 2007. The most representative taxa were Planktolyngbya microspira Kom. & Cronb. P. circumcreta (G. S. West) Anagn. & Kom., Cyanodictyon tropicale Senna, Delazari & Sant’Anna and Staurastrum excavatum var. planctonicum Krieg. These species had so far only been reported from African lakes and other tropical areas, but in this study they accounted for up to 58 and 12% of the total abundance and biomass, respectively, during spring and summer. Some of these lakes were studied in the 1970s and only exotic desmids were reported; but at that time, the three cited cyanobacteria were not described yet. Waterfowl are considered as the main dispersers because they migrate over long distances, transporting algae on the feet and feathers or in the digestive tract. In fact, the Aquitaine Region is one of the main bird migration corridors in Europe. Survival of cyanobacteria, diatoms and desmids carried by birds could be possible due to resting stages, sheaths investments or vegetative cells. In addition, global warming may have contributed to the success of these tropical species in temperate lakes. Indeed, minimal temperatures have increased significantly in the Aquitaine region over the last 30 years and could have played a key role in algal survival through winter.  相似文献   

8.
With climate change and re-oligotrophication of lakes due to restoration efforts, the relative importance of benthic cyanobacteria is increasing, but they are much less studied than their planktonic counterparts. Following a major water level rise event that inundated massive reed stands in Lake Kinneret, Israel, we discovered the appearance of a vast abundance of Gloeotrichia pisum (cyanobacteria). This provided an opportunity to investigate the biology and ecology of a benthic epiphytic colonial cyanobacterium, proliferating under altered environmental conditions, with possible toxin production potential and as a model for an invasive epiphyte. The species was identified by its typical morphology, and by sequencing its 16S rRNA gene and the intragenic space. We report on the abundance and spatial distribution of the detected colonies, their morphological characteristics, and pigment composition. High phycoerythrin content provides a brownish color and supports growth at low light levels. Genomic community composition analysis revealed that G. pisum colonies host a diverse microbial community of microalgae, cyanobacteria, bacteria, and archaea with a conserved and characteristic taxonomic composition. The Synechococcales order showed high relative abundance in the colony, as well as other prokaryotes producing secondary metabolites, such as the rhodopsin producer Pseudorhodobacter. The microbial consortium in the colonies performed nitrogen fixation. The diazotroph's phylogenetic relations were demonstrated. Tests for the presence of cyanotoxins (microcystin and cylindrospermopsin) proved negative. This study is the first documentation of this genus in Israel, providing insights into the invasive nature of G. pisum and the ecological implications of its appearance in a lake ecosystem.  相似文献   

9.
Predators strongly influence species assemblages and shape morphological defenses of prey. Interestingly, adaptations that constitute effective defenses against one type of predator may render the prey susceptible to other types of predators. Hence, prey may evolve different strategies to escape predation, which may facilitate adaptive radiation of prey organisms. Larvae of different species in the dragonfly genus Leucorrhinia have various morphological defenses. We studied the distribution of these larvae in relation to the presence of predatory fish. In addition, we examined the variation in morphological defenses within species with respect to the occurrence of fish. We found that well-defended species, those with more and longer spines, were more closely associated with habitats inhabited by predatory fish and that species with weakly developed morphological defenses were more abundant in habitats without fish. The species predominantly connected to lakes with or without fish, respectively, were not restricted to a single clade in the phylogeny of the genus. Our data is suggestive of phenotypic plasticity in morphological defense in three of the studied species since these species showed longer spines in lakes with fish. We suggest that adaptive phenotypic plasticity may have broadened the range of habitats accessible to Leucorrhinia. It may have facilitated colonization of new habitats with different types of predators, and ultimately, speciation through adaptive radiation.  相似文献   

10.
Twelve populations of filamentous, heterocytous scytonematoid cyanobacteria from subaerophytic (mainly epiphytic) habitats in subtropical and tropical Brazil (São Paulo) were studied. The populations form a uniform cluster, which differs from the traditional scytonematoid genera genetically and by several indistinct, but typical morphological characters (fasciculation of filaments, rare false branching). Two strains were isolated in monospecific cultures. Molecular analyses were performed on these strains from natural populations taken from bromeliad leaves and iron water pipes. Because the results from 16S rRNA gene sequencing indicated the separate position of this cyanobacterium at the generic level, a new genus, Brasilonema, is proposed with the type species Brasilonema bromeliae. The new genus is described using combined molecular and cytomorphological criteria, in accordance with the nomenclatorial recommendations of both the Bacteriological Code and the Botanical Code of Nomenclature (cf. Oren 2004 ). The ultrastructure of the type species was studied, and vacuole‐like structures in the cells were explained. The genus Brasilonema is commonly distributed, particularly in subaerophytic habitats from southeastern Brazil. The type species (B. bromeliae) has a rather curious ecology, living epiphytically (in phytothelmes) inside the vase‐shaped leaf rosettes of bromeliads.  相似文献   

11.
The structural features of a cyanobacterial mat from Lake Khilganta (Southeastern Transbaikal Region) developing at different values of salinity and pH were determined based on our long-term investigation of the natural community, as well as results obtained during experimentation with its laboratory analogue. At water mineralization of 40–50 g/l, Microcoleus chthonoplastes and Phormidium molle play a key role in the formation of the cyanobacterial mat. As water mineralization increases, the diversity of cyanobacteria in the natural mat increases as well, reaches its maximum at 80 g/l NaCl, and decreases at 100 g/l. In the laboratory community, Nodularia sp. prevailed. It was able to form matlike structures within a broad pH range and at a salinity of up to 50 g/l NaCl. As the water mineralization level increased up to 100 g/l or higher, a replacement of the dominant complexes occurred both in the laboratory and natural communities: cyanobacterial species were substituted with green algae.  相似文献   

12.
Radioisotopic measurements of the methane consumption by mud samples taken from nine Southern Transbaikal soda lakes (pH 9.5–10.6) showed an intense oxidation of methane in the muds of Lakes Khuzhirta, Bulamai Nur, Gorbunka, and Suduntuiskii Torom, with the maximum oxidation rate in the mud of Lake Khuzhirta (33.2 nmol/(ml day)). The incorporation rate of the radioactive label from14CH4 into14CO2 was higher than into acid-stable metabolites. Optimum pH values for methane oxidation in water samples were 7–8, whereas mud samples exhibited two peaks of methane oxidation activity (at pH 8.15–9.4 and 5.8–6.0). The majority of samples could oxidize ammonium to nitrites; the oxidation was inhibited by methane. The PCR amplification analysis of samples revealed the presence of genes encoding soluble and paniculate methane monooxygenase and methanol dehydrogenase. Three alkaliphilic methanotrophic bacteria of morphotype I were isolated from mud samples in pure cultures, one of which, B5, was able to oxidize ammonium to nitrites at pH 7–11. The data obtained suggest that methanotrophs are widely spread in the soda lakes of Southern Transbaikal, where they can actively oxidize methane and ammonium.  相似文献   

13.
The SSU (16S) rRNA gene was used to investigate the phylogeny of the cyanobacterial genus Lyngbya as well as examined for its capacity to discriminate between different marine species of Lyngbya. We show that Lyngbya forms a polyphyletic genus composed of a marine lineage and a halophilic/brackish/freshwater lineage. In addition, we found morphological and genetic evidence that Lyngbya spp. often grow in association with other microorganisms, in particular smaller filamentous cyanobacteria such as Oscillatoria, and propose that these associated microorganisms have led to extensive phylogenetic confusion in identification of Lyngbya spp. At the species level, the phylogenetic diversity obtained from the comparison of 16S rRNA genes exceeded morphological diversity in Lyngbya. However, the expectation that this improved phylogeny would be useful to species and subspecies identification was eliminated by the fact that phylogenetic species did not correlate in any respect with the species obtained from current taxonomic systems. In addition, phylogenetic identification was adversely affected by the presence of multiple gene copies within individual Lyngbya colonies. Analysis of clonal Lyngbya cultures and multiple displacement amplified (MDA) single‐cell genomes revealed that Lyngbya genomes contain two 16S rRNA gene copies, and that these typically are of variable sequence. Furthermore, intragenomic and interspecies 16S rRNA gene heterogeneity was approximately of the same magnitude. Hence, the intragenomic heterogeneity of the 16S rRNA gene overestimates the microdiversity of different strains and does not accurately reflect speciation within cyanobacteria, including the genus Lyngbya.  相似文献   

14.
Toxic cyanobacteria (blue-green algae) in Finnish fresh and coastal waters   总被引:5,自引:5,他引:0  
A survey of the occurrence of toxic blooms of cyanobacteria in Finnish fresh and coastal waters was made during 1985 and 1986. Toxicity of the freeze-dried water bloom samples was tested by mouse-bioassay (i.p.). Forty-four per cent (83/188) of the bloom samples were found to be lethally toxic. Hepatotoxic blooms (54) were almost twice as common as neurotoxic ones (29). Anabaena was the most frequently found genus in toxic and non-toxic blooms and it was present in all neurotoxic samples. Statistical associations were found between hepatotoxicity and incidence of Microcystis aeruginosa, M. viridis, M. wesenbergii, Anabaena flos-aquae and Anabaena spiroides. Neurotoxicity was statistically associated with Anabaena lemmermannii, Anabaena flos-aquae and Gomphosphaeria naegeliana. Isolation of strains of cyanobacteria confirmed the occurrence of hepatotoxic and neurotoxic strains of Anabaena, as well as hepatotoxic strains of Microcystis and Oscillatoria species.Toxic blooms caused cattle poisonings at three different lakes during the study period. Toxic blooms also occurred in drinking water sources. Our study shows that toxic cyanobacteria are more common in Finnish lakes than would be expected on the basis of animal poisonings. The results of this study show the existence of toxic cyanobacteria in Finnish water supplies and the need for their continued study as agents of water based disease.  相似文献   

15.
The morphology and ultrastructure of associative microsymbiont complexes (AMC) isolated from the ferns Azolla pinnata and Azolla sp. and the apogeotropic roots of the cycad Cycas revoluta were studied. The composition of the AMC obtained includes the cyanobionts (symbiotic cyanobacteria) and satellite bacteria (SB). It was found that two types of cyanobacteria that substantially differ in their morphological organization are likely present as cyanobionts in the coralloids of C. revoluta. The isolated cyanobiont strains exhibited the morphological traits and regularities of development typical of the genus Nostoc; they were characterized by the ability of their cells to divide in mutually perpendicular planes. When isolating AMC from different morphological zones of C. revoluta apogeotropic roots, SB growth was revealed only around the pieces corresponding to the coralloid apical zone. No AMC components were revealed around the segments of the basal growth zone. Pure cyanobiont cultures were obtained from the AMC of C. revoluta coralloids. The AMC isolated from the ferns A. pinnata and Azolla sp. are characterized by obligate mutual dependence of the partners (the cyanobiont and SB).  相似文献   

16.
The genus Microcystis (cyanobacteria) includes toxic and bloom-forming morphotypes which are usually arranged into species based on morphological features. Immunofluorescence assays using polyclonal and preadsorbed antibodies, as well as FITC-labebd lectins were used to characterize three morphospecies of Microcystis (M. viridis, M. wesenbergii, and M. aeruginosa) from natural populations (several lakes/reservoirs in Denmark and Spain) and laboratory clones. The cell probes used were unaffected by the different phases of the cell division cycle, growth phase, or environmental factors, such as culture medium, light, or temperature. Anhbody and lectin binding patterns were specific to each clone. In nature, the cell probes were useful tools to characterize Microcystis populations. Antibodies and lectins revealed geographic differentiation within the same morphospecies. Differentiation was moderate among nearby locales and intensified among areas distant from one another. Microcystis aeruginosa from Spain has very different cell surface antigens and lectin binding sites than M. aeruginosa from Denmark. A taxonomy of Microcystis based on cell probes reveals some discrepancies with classical morphospecies. The binding affinities were more closely related to the geographic origin of the tested material than to the morphospecies identification. Different morphospecies from the same lake in some cases were more similar than the same morphospecies from different lakes. Microcystis viridis and M. aeruginosa from Danish lakes appeared to be closely related species, whereas M. wesenbergii emerged as a different species.  相似文献   

17.
The Oocystaceae family is generally considered to contain common freshwater eukaryotic microalgae, and few are reported living in semi‐saline habitats. Our latest ecological survey in Qinghai Lake and Angzicuo Lake, both large, closed, high‐altitude, semi‐saline lakes located on the Qinghai‐Tibet plateau in China, revealed Oocystaceae species as a dominant group among plankton. Since limited knowledge exists about semi‐saline species in the Oocystaceae family, a taxonomical study was carried out using morphological and phylogenetic methods. Using this approach, four new strains of Oocystaceae were identified and successfully cultured in the lab. Molecular results correlated with morphological characters and resolved these species into at least three genera. A new genus, Euchlorocystis, with type species Euchlorocystis subsalina, is described here as having the distinctive morphology of multiple pyrenoids per chloroplast among Oocystaceae, and an independent phylogenetic position at the base of the Oocystaceae. Similarly, the genus Densicystis, with type species Densicystis glomerata, is newly proposed here as having a unique colony morphology of dozens or hundreds of little cells tightly embedded in ellipsoid to round mucilage masses. Oocystis marina, originally described from the Baltic Sea, was also identified in Qinghai Lake and Angzicuo Lake and phylogenetically positioned in the semi‐saline clade of the Oocystaceae. The result that a marine species was detected in the closed inland lakes implies a further need to reevaluate the origins of these species.  相似文献   

18.
Cyanobacterial blooms in eutrophic lakes are severe environmental problems worldwide. To characterize the spatiotemporal heterogeneity of cyanobacterial blooms, a high-throughput method is necessary for the specific detection of cyanobacteria. In this study, the cyanobacterial composition of three eutrophic waters in China (Taihu Lake, Dongqian Lake, and Dongzhen Reservoir) was determined by pyrosequencing the cpcBA intergenic spacer (cpcBA-IGS) of cyanobacteria. A total of 2585 OTUs were obtained from the normalized cpcBA-IGS sequence dataset at a distance of 0.05. The 238 most abundant OTUs contained 92% of the total sequences and were classified into six cyanobacterial groups. The water samples of Taihu Lake were dominated by Microcystis, mixed Nostocales species, Synechococcus, and unclassified cyanobacteria. Besides, all the samples from Taihu Lake were clustered together in the dendrogram based on shared abundant OTUs. The cyanobacterial diversity in Dongqian Lake was dramatically decreased after sediment dredging and Synechococcus became exclusively dominant in this lake. The genus Synechococcus was also dominant in the surface water of Dongzhen Reservoir, while phylogenetically diverse cyanobacteria coexisted at a depth of 10 m in this reservoir. In summary, targeted deep sequencing based on cpcBA-IGS revealed a large diversity of bloom-forming cyanobacteria in eutrophic lakes and spatiotemporal changes in the composition of cyanobacterial communities. The genus Microcystis was the most abundant bloom-forming cyanobacteria in eutrophic lakes, while Synechococcus could be exclusively dominant under appropriate environmental conditions.  相似文献   

19.
Epipelic cyanobacteria were studied in bottom sediments from ponds and lakes in the United Kingdom and the Czech Republic, covering a trophic gradient from deep, oligotrophic, glacial lakes to shallow, eutrophic, urban manmade ponds. Although many planktic species were observed, the most frequently occurring cyanobacteria were the motile filamentous genera Oscillatoria, Phormidium, Pseudanabaena and Komvophoron. These genera represent autochtonous epipelic assemblages, occurring in upper surface layers of the sediments throughout the year and exhibiting seasonal variation in their abundancy. The occurrence of individual Komvophoron species was influenced by sediment quality, particularly the proportions of fine mud and organic detritus. A new species Komvophoron hindakii sp. nov. is described. Morphological features, autecology and occurrence of all the Komvophoron-like morphospecies found are discussed.  相似文献   

20.
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   

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