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Ulf Karsten - One of the best experts on this subject based on the ideXlab platform.
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COLEOFASCICULUS GEN. NOV. (CYANOBACTERIA): MORPHOLOGICAL AND MOLECULAR CRITERIA FOR REVISION OF THE GENUS Microcoleus GOMONT(1).
Journal of phycology, 2008Co-Authors: Maria A. Siegesmund, Ulf Karsten, Jeffrey R. Johansen, Thomas FriedlAbstract:Species currently classified within the cyanobacterial genus Microcoleus were determined to fall into two distinct clades in a 16S rDNA phylogeny, one containing taxa within the Oscillatoriaceae, the other containing taxa within the Phormidiaceae. The two lineages were confirmed in an analysis of the 16S-23S internal transcribed spacer (ITS) region sequences and secondary structures. The type species for Microcoleus is M. vaginatus Gomont, and this taxon belongs in the Oscillatoriaceae. Consequently, Microcoleus taxa in the Phormidiaceae must be placed in separate genera, and we propose the new genus Coleofasciculus to contain marine taxa currently placed in Microcoleus. The type species for Coleofasciculus is the well-studied and widespread marine mat-forming species Microcoleus Chthonoplastes (Mert.) Zanardini ex Gomont. Other characters separating the two families include type of cell division and thylakoid structure.
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Isolate-specific effects of ultraviolet radiation on photosynthesis, growth and mycosporine-like amino acids in the microbial mat-forming cyanobacterium Microcoleus Chthonoplastes.
Planta, 2007Co-Authors: Bagmi Pattanaik, Michael Y. Roleda, Rhena Schumann, Ulf KarstenAbstract:Microcoleus Chthonoplastes constitutes one of the dominant microorganisms in intertidal microbial mat communities. In the laboratory, the effects of repeated daily exposure to ultraviolet radiation (16:8 light:dark cycle) was investigated in unicyanobacterial cultures isolated from three different localities (Baltic Sea = WW6; North Sea = STO and Brittany = BRE). Photosynthesis and growth were measured in time series (12–15 days) while UV-absorbing mycosporine-like amino acids (MAAs) and cellular integrity were determined after 12 and 3 days exposure to three radiation treatments [PAR (22 μmol photon m−2 s−1) = P; PAR + UV-A (8 W m−2) = PA; PAR + UV-A + UV-B (0.4 W m−2) = PAB]. Isolate-specific responses to UVR were observed. The proximate response to radiation stress after 1-day treatment showed that isolate WW6 was the most sensitive to UVR. However, repeated exposure to radiation stress indicated that photosynthetic efficiency (Fv/Fm) of WW6 acclimated to UVR. Conversely, although photosynthesis in STO exhibited lower reduction in Fv/Fm during the first day, the values declined over time. The BRE isolate was the most tolerant to radiation stress with the lowest reduction in Fv/Fm sustained over time. While photosynthetic efficiencies of different isolates were able to acclimate to UVR, growth did not. The discrepancy seems to be due to the higher cell density used for photosynthesis compared to the growth measurement. Apparently, the cell density used for photosynthesis was not high enough to offer self-shading protection because cellular damage was also observed in those filaments under UVR. Most likely, the UVR acclimation of photosynthesis reflects predominantly the performance of the surviving cells within the filaments. Different strategies were observed in MAAs synthesis. Total MAAs content in WW6 was not significantly different between all the radiation treatments. In contrast, the additional fluence of UV-A and UV-B significantly increased MAAs synthesis and accumulation in STO while only UV-B fluence significantly increased MAAs content in BRE. Regardless of the dynamic photosynthetic recovery process and potential UV-protective functions of MAAs, cellular investigation showed that UV-B significantly contributed to an increased cell mortality in single filaments. In their natural mat habitat, M. Chthonoplastes benefits from closely associated cyanobacteria which are highly UVR-tolerant due to the production of the extracellular UV-sunscreen scytonemin.
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Effects of salinity and ultraviolet radiation on the concentration of mycosporine-like amino acids in various isolates of the benthic cyanobacterium Microcoleus Chthonoplastes
Phycological Research, 2002Co-Authors: Ulf KarstenAbstract:SUMMARY The effects of salinity and ultraviolet B (UV-B) treat-ment on the intracellular mycosporine-like amino acid(MAA) concentration in three isolates of the benthiccyanobacterium Microcoleus Chthonoplastes from theBaltic Sea (WIS), Spain (EBD) and Australia (TOW)were compared. All strains contained shinorine and, inaddition, both EBD and TOW exhibited the unknownMAA-332, and WIS exhibited the unknown MAA-346.Salinity treatment led to MAA accumulation in TOWand WIS, but not in EBD. Whereas UV-B exposure wasaccompanied by a strong increase in MAA in EBD andTOW, WIS did not survive the treatment. All dataindicate isolate-specific MAA accumulation patternsunder different environmental conditions and can beexplained by ecotypic differentiation. A double func-tion of MAAs as organic osmolytes and photoprotect-ants seems possible. INTRODUCTION The filamentous cyanobacterium Microcoleus chthono-plastes Thuret is a common and dominant member ofmany microbial mat communities from all over theworld, preferentially growing in intertidal and hyper-saline habitats (Prufert-Bebout and Garcia-Pichel1994). In many such mats, the cyanobacterial layer isformed almost exclusively by this species. These micro-phytobenthic communities are often found in the toplayers of coastal sediments where they play an impor-tant ecological role as primary producers, as well as inthe stabilization of intertidal sediments (Paterson1994). In this environment, microbial mats are subjectedto tidal immersion/emersion cycles and under such condi-tions may experience strong fluctuations and wide rangesof salinity, as well as long intervals of exposure to elevatedsolar radiation (Karsten
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Seasonality in UV-absorbing compounds of cyanobacterial mat communities from an intertidal mangrove flat
Aquatic Microbial Ecology, 1998Co-Authors: Ulf Karsten, Josef Maier, Ferran Garcia-pichelAbstract:Biomass and the concentrations of the UV-absorbing compounds scytonemin, pterins and mycosporine-like amino acid compounds (MAAs) were determined in a seasonal study of a cyanobacterial mat growing on an intertidal mangrove sediment at Towra Point, Sydney, Australia. The community was dominated by the filamentous cyanobacteria Lyngbya cf. aestuarii and Microcoleus Chthonoplastes. While the first occurred as a thin compact layer on top of the mat without any obvious indcation of growth over the course of the study, the latter formed a layer underneath Lyngbya and showed an increase in the thickness of the layer after the summer period. The sheath pigment scytonemin was only formed by L. cf. aestuarii and represented at all sampling dates the quantitatively most important UV-absorbing compound, ranglng from 140 to 1300 mg m-'. The areal scytonemin content seemed to follow the seasonally fluctuating solar intensity In contrast, the areal contents of pterins and MAAs did not increase under elevated solar radiation conditions. The data indicate the importance and effectiveness of scytonemin deposition in the outer sheaths of L. cf. aestuarii as a sunscreen for the entire benthic community underneath.
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Growth and organic osmolytes of geographically different isolates of Microcoleus Chthonoplastes (cyanobacteria) from benthic microbial mats: Response to salinity change
Journal of Phycology, 1996Co-Authors: Ulf KarstenAbstract:The comparative growth and osmotic acclimation often culture strains of the marine benthic cyanobacterium Microcoleus Chthonoplastes Thuret isolated from microbial mats in Germany, Spain, Egypt, the United States, Mexico, Chile, and Australia were investigated in salinities ranging from freshwater to twice seawater. All isolates showed a broad growth versus salinity response consistent with the dominance of this species in intertidal and hypersaline microbial communities. Growth optima, salinity preferences, and maximum growth rates differed for each isolate and could be related to the habitat from which they were isolated. This is most obvious when comparing strains from brackish habitats with those from a hypersaline lake. While the former isolates exhibited sharply pronounced growth optima under hyposaline conditions, cultures from the hypersaline environment grew best in salinity more than double seawater. The major low-molecular weight organic compounds present in all M. Chthonoplastes strains were the carbohydrates glycosylglycerol and trehalose. This was proven by using 13C-nuclear magnetic resonance spectroscopy. Glycosylglycerol was synthesized and accumulated with increasing salinities, indicating its role as an osmolyte. In contrast, trehalose was present in relatively high concentrations under hyposaline conditions only. Differences in the patterns of growth versus salinity, as well as in those of osmotic acclimation among the M. Chthonoplastes isolates, point to the development of different physiological ecotypes within the species.
Ferran Garcia-pichel - One of the best experts on this subject based on the ideXlab platform.
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Long‐term compositional changes after transplant in a microbial mat cyanobacterial community revealed using a polyphasic approach
Environmental microbiology, 2001Co-Authors: Raeid M. M. Abed, Ferran Garcia-pichelAbstract:Using a polyphasic approach that included microscopy, cultivation and 16S rRNA-based cultivation-independent molecular fingerprinting, we compared the cyanobacterial composition of Solar Lake microbial mats and samples thereof transplanted and maintained in new settings for extended periods of time. Significant changes in community composition, with clear replacement of the dominant cyanobacterium, Microcoleus Chthonoplastes, were detected in all cases. The most dramatic shifts occurred in a sample kept in the laboratory for 3 years, which resulted in dominance by an Oscillatoria-like cyanobacterium whose 16S rRNA closely matched that of a morphologically similar isolate from mats in Mexico. Transfer of Solar Lake mat to an artificial experimental pond with incubation under seminatural conditions resulted in an increase in cyanobacterial diversity. Judging from the molecular signatures, two novel, previously unrecognized and phylogenetically well-delimited cyanobacterial populations became dominant. Through cultivation, one population was shown to correspond to a filamentous, non-heterocystous group of Cyanobacteria with very narrow trichomes (approximately equals 0.75-1.5 microm). The most dominant novel molecular signature, however, could not be identified by cultivation efforts or correlation with microscopy and, upon phylogenetic analyses, its 16S rRNA genes showed no particular close association to known cyanobacterial groups.
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Seasonality in UV-absorbing compounds of cyanobacterial mat communities from an intertidal mangrove flat
Aquatic Microbial Ecology, 1998Co-Authors: Ulf Karsten, Josef Maier, Ferran Garcia-pichelAbstract:Biomass and the concentrations of the UV-absorbing compounds scytonemin, pterins and mycosporine-like amino acid compounds (MAAs) were determined in a seasonal study of a cyanobacterial mat growing on an intertidal mangrove sediment at Towra Point, Sydney, Australia. The community was dominated by the filamentous cyanobacteria Lyngbya cf. aestuarii and Microcoleus Chthonoplastes. While the first occurred as a thin compact layer on top of the mat without any obvious indcation of growth over the course of the study, the latter formed a layer underneath Lyngbya and showed an increase in the thickness of the layer after the summer period. The sheath pigment scytonemin was only formed by L. cf. aestuarii and represented at all sampling dates the quantitatively most important UV-absorbing compound, ranglng from 140 to 1300 mg m-'. The areal scytonemin content seemed to follow the seasonally fluctuating solar intensity In contrast, the areal contents of pterins and MAAs did not increase under elevated solar radiation conditions. The data indicate the importance and effectiveness of scytonemin deposition in the outer sheaths of L. cf. aestuarii as a sunscreen for the entire benthic community underneath.
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Phenotypic and phylogenetic analyses show Microcoleus Chthonoplastes to be a cosmopolitan cyanobacterium
Applied and environmental microbiology, 1996Co-Authors: Ferran Garcia-pichel, Lee Prufert-bebout, Gerard MuyzerAbstract:We used micromanipulation to isolate from their environment representative samples of seven geographically distant field populations fitting the description of Microcoleus Chthonoplastes (a cyanobacterium) and obtained seven corresponding cultured strains. Samples of both field populations and cultures were phenotypically characterized by microscale techniques, and their partial 16S rRNA gene sequences were compared by denaturing gradient gel electrophoresis and in some cases by sequencing. All field populations and strains were phenotypically extremely coherent, and their 16S rRNA sequences were indistinguishable by DGGE. The sequences determined were identical or virtually identical. Thus, M. Chthonoplastes represents a single, well-delimited taxon with a truly cosmopolitan distribution. Comparison with three culture collection strains originally assigned to M. Chthonoplastes revealed that strain PCC 7420 belongs to the same tightly delimited group, both phenotypically and in 16S rRNA gene sequence, but that strains SAG 3192 and 10mfx do not.
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Phenotypic and Phylogenetic Analyses ShowMicrocoleus ChthonoplastesTo Be a Cosmopolitan Cyanobacterium
1996Co-Authors: Ferran Garcia-pichel, Lee Prufert-bebout, Andgerard Muyzer, Max PlanckAbstract:We used micromanipulation to isolate from their environment representative samples of seven geographically distant field populations fitting the description of Microcoleus Chthonoplastes (a cyanobacterium) and obtained seven corresponding cultured strains. Samples of both field populations and cultures were phenotypically characterized by microscale techniques, and their partial 16S rRNA gene sequences were compared by denaturing gradient gel electrophoresis and in some cases by sequencing. Allfield populations and strains were phenotypically extremely coherent, and their 16S rRNA sequences were indistinguishable by DGGE. The sequences determined were identical or virtually identical. Thus, M. Chthonoplastes represents a single, welldelimited taxon with a truly cosmopolitan distribution. Comparison with three culture collection strains originally assigned to M. Chthonoplastes revealed that strain PCC 7420 belongs to the same tightly delimited group, both phenotypically and in 16S rRNA gene sequence, but that strains SAG 3192 and 10mfx do not.
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Field and cultivated Microcoleus Chthonoplastes : The search for clues to its prevalence in marine microbial mats
Microbial Mats, 1994Co-Authors: Lee Prufert-bebout, Ferran Garcia-pichelAbstract:The cyanobacterial species “Microcoleus Chthonoplastes” is defined by the presence of many typically oscillatorian filaments with tapered, conically shaped terminal cells within a common sheath both in the botanical (Geitler 1932) and, more recently in the bacteriological literature (Castenholz 1988). The significant and often dominant ecological role of Microcoleus species in the formation and stabilization of intertidal and hypersaline microbial mat systems around the world is well recognized. However, it is not known if geographically disjunct populations referred to as “Microcoleus Chthonoplastes” on the basis of gross morphological traits alone constitute a close genetic unit, or are in fact examples of evolutionary convergence driven by the adaptive advantages of a “Microcoleus-like” morphology in benthic marine environments. What adaptive advantages this morphology may confer has been difficult to ascertain since these features, most notably the defining features of bundle formation, and presence of conically-shaped terminal cells, are not observed in currently available cultures.
Jonathan P Zehr - One of the best experts on this subject based on the ideXlab platform.
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determination of nitrogen fixing phylotypes in lyngbya sp and Microcoleus Chthonoplastes cyanobacterial mats from guerrero negro baja california mexico
Applied and Environmental Microbiology, 2004Co-Authors: Enoma O Omoregie, Lori L Crumbliss, Brad M Bebout, Jonathan P ZehrAbstract:In many environments, biological nitrogen fixation can alleviate nitrogen limitation. The high rates of N2 fixation often observed in cyanobacterial mats suggest that N2 fixation may be an important source of N. In this study, organisms expressing nifH were identified in a Lyngbya sp.- and two Microcoleus Chthonoplastes-dominated cyanobacterial mats. The pattern of nitrogenase activity was determined for the Lyngbya sp. mat and a Microcoleus Chthonoplastes mat sampled directly in Guerrero Negro, Mexico. Their maximum rates were 23 and 15 μmol of C2H4 m−2 h−1, respectively. The second Microcoleus mat, which was maintained in a greenhouse facility, had a maximum rate of 40 μmol of C2H4 m−2 h−1. The overall diel pattern of nitrogenase activity in the three mats was similar, with the highest rates of activity occurring during the dark period. Analysis of nifH transcripts by reverse transcription-PCR revealed that several different organisms were expressing nifH during the dark period. nifH phylotypes recovered from these mats were similar to sequences from the unicellular cyanobacterial genera Halothece, Myxosarcina, and Synechocystis, the filamentous cyanobacterial genera Plectonema and Phormidium, and several bacterial nifH groups. The results of this study indicate that several different organisms, some of which were not previously known to fix nitrogen, are likely to be responsible for the observed dark-period nitrogenase activity in these cyanobacterial mats.
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comparison of diazotroph community structure in lyngbya sp and Microcoleus Chthonoplastes dominated microbial mats from guerrero negro baja mexico
FEMS Microbiology Ecology, 2004Co-Authors: Enoma O Omoregie, Lori L Crumbliss, Brad M Bebout, Jonathan P ZehrAbstract:The nitrogenase activity and phylogenetic diversity of nitrogen fixing microorganisms in several different cyanobacterial mat types from Guerrero Negro, Baja California, Mexico were investigated by acetylene reduction assay, and by amplification and sequencing of the nitrogenase nifH gene. Acetylene reduction assays performed on a Lyngbya sp. and two Microcoleus Chthonoplastes dominated microbial mats showed a typical diel pattern of nitrogenase activity in these mats. The highest rates of activity were found at night, with 40 and 37 μmol C2H4 m−2 h−1 measured in the Microcoleus mats, and 9 μmol C2H4 m−2 h−1 in the Lyngbya mat. Nitrogenase sequences were obtained that clustered with sequences from cyanobacteria, γ-Proteobacteria, and cluster 3 of nifH. In addition, novel and divergent sequences were also recovered. The composition of nifH sequence types recovered differed between the Lyngbya and Microcoleus mats. Interestingly, nifH sequences belonging to filamentous cyanobacteria were absent in most mat samples even though both mats were dominated by filamentous cyanobacteria. nifH sequences clustering with those of unicellular cyanobacteria were found, some of which were virtually identical to the nifH sequence from Halothece sp. MPI96P605, which had previously been isolated from the mat. In manipulation experiments, the Lyngbya and Microcoleus mats were allowed to re-colonize a cleared surface. In these developing mats, nifH sequences not previously observed in the mats were discovered. Our results showed that organisms capable of N2 fixation were present in N2 fixing mats, that the composition of the N2 fixing communities differs between mats, and that filamentous cyanobacterial diazotrophs may not have a large role in the early stages of mat development.
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Diversity of Heterotrophic Nitrogen Fixation Genes in a Marine Cyanobacterial Mat
Applied and environmental microbiology, 1995Co-Authors: Jonathan P Zehr, Mark T. Mellon, S. T. Braun, W Litaker, T Steppe, H W PaerlAbstract:The diversity of nitrogenase genes in a marine cyanobacterial mat was investigated through amplification of a fragment of nifH, which encodes the Fe protein of the nitrogenase complex. The amplified nifH products were characterized by DNA sequencing and were compared with the sequences of nitrogenase genes from cultivated organisms. Phylogenetic analysis showed that similar organisms clustered together, with the exception that anaerobic bacteria clustered together, even though they represented firmicutes, (delta)-proteobacteria, and (gamma)-proteobacteria. Mat nifH sequences were most closely related to those of the anaerobes, with a few being most closely related to the cluster of (gamma)-proteobacteria containing Klebsiella and Azotobacter species. No cyanobacterial nifH sequences were found from the mat collected in November when Microcoleus Chthonoplastes was the dominant cyanobacterium, but sequences closely related to the cyanobacterium Lyngbya lagerheimeii were found during summer, when a Lyngbya strain was dominant. The results indicate that there is a high diversity of heterotrophic nitrogen-fixing organisms in marine cyanobacterial mats.
Isabel Esteve - One of the best experts on this subject based on the ideXlab platform.
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Characterization of an oil-degrading Microcoleus consortium by means of confocal scanning microscopy, scanning electron microscopy and transmission electron microscopy
Scanning, 2006Co-Authors: Elia Diestra, Antonio Solé, Mercedes Martí, Tirso García De Oteyza, Joan O. Grimalt, Isabel EsteveAbstract:A consortium of microorganisms with the capacity to degrade crude oil has been characterized by means of confocal laser scanning microscopy (CLSM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The analysis using CLSM shows that Microcoleus Chthonoplastes is the dominant organism in the consortium. This cyanobacterium forms long filaments that group together in bundles inside a mucopolysaccharide sheath. Scanning electron microscopy and transmission electron microscopy have allowed us to demonstrate that this cyanobacterium forms a consortium primarily with three morphotypes of the heterotrophic microorganisms found in the Microcoleus Chthonoplastes sheath. The optimal growth of Microcoleus consortium was obtained in presence of light and crude oil, and under anaerobic conditions. When grown in agar plate, only one type of colony (green and filamentous) was observed.
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The biomass dynamics of cyanobacteria in an annual cycle determined by confocal laser scanning microscopy
Scanning, 2006Co-Authors: Antonio Solé, Núria Gaju, Isabel EsteveAbstract:We recently published a method for estimating cyanobacteria biomass in delta microbial mats from the Ebro river using confocal laser scanning microscopy (CLSM). The present paper uses this method for identifying differentgroups of cyanobacteria and for determining their biomass dynamics..Microcoleus Chthonoplastes and the Lyngbya-Oscillatoria were the most important contributors to the cyanobacterial biomass throughout the study. Biomass values ranged from 1.29 to 6.55 mgC/cm 2 sediment for Microcoleus Chthonoplastes, and from 128 μgC/cm 2 to 3.16 mgC/cm 2 sediment for Lyngbya-Oscillatoria. This technique is useful for determining biomass and for studying filamentous cyanobacteria as well as ramified eukaryotic cells. Confocal serial sections through the samples can be obtained. Two-dimensional images from the samples can be used to calculate the biomass of individual cells.
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A comparative study of cyanobacterial diversity in polluted and unpolluted microbial mats by means CLSM
Ophelia, 2004Co-Authors: Elia Diestra, Antonio Solé, Isabel EsteveAbstract:Abstract This paper is a summary of the results obtained from a study of the diversity of cyanobacteria in oil polluted and unpolluted natural environments. Our work group identified the different genera of cyanobacteria by means of CLSM, as this technique is specifically appropriate for studying the diversity of these microorganisms in stratified bentonic environments (microbial mats). The cyanobacteria identified in pristine ecosystems show that the most abundant cyanobacteria correspond to the genera: Microcoleus Chthonoplastes, Oscillatona sp., Lyngbya sp., Leptolyngbya sp., and Limnothrix sp. Phormidium sp.and Pseudanabaena sp. were also identified, although they were less abundant. On the other hand, in the ecosystems heavily polluted with oil (Etang de Berre) neither Microcoleus Chthonoplastes nor Oscillatoria sp. were detected, although the other genera mentioned were. With respect to coccoid cyanobacteria, the most abundant groups in the Ebro delta were Gloeocapsa sp. and Synechocystis sp. and al...
Raeid M. M. Abed - One of the best experts on this subject based on the ideXlab platform.
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Abundance and diversity of aerobic heterotrophic microorganisms and their interaction with cyanobacteria in the oxic layer of an intertidal hypersaline cyanobacterial mat
FEMS Microbiology Ecology, 2018Co-Authors: Raeid M. M. Abed, Katharina Kohls, Julie Leloup, Dirk De BeerAbstract:Aerobic heterotrophic microorganisms (AH) play a significant role in carbon cycling in cyanobacterial mats; however, little is known about their abundance, diversity and interaction with cyanobacteria. Using catalyzed reporter deposition fluorescence in situ hybridization (CARD-FISH), bacterial counts in the mat's oxic layer reached a mean of 2.23 +/- 0.4 x 10(10) cells g(-1). Cultivation of AH yielded strains belonging to Actinobacteria, Bacteroidetes, Firmicutes, Gammaproteobacteria and Haloarchaea. 16S rRNA bacterial sequences retrieved from the mat's oxic layer were related to Bacteroidetes, Chloroflexi and Proteobacteria, whereas archaeal sequences belonged to Crenarchaeota and Haloarchaea. Monocultures of cyanobacteria from the same mat were associated with different AH, although Bacteroidetes were found in most cultures. CARD-FISH showed that Bacteroidetes- and Chloroflexi-related bacteria were closely associated with filaments of Microcoleus Chthonoplastes. The growth of an axenic culture of M. Chthonoplastes PCC7420 was stimulated on the addition of a filtrate obtained from a non-axenic Microcoleus culture and containing only AH and released substances. In contrast, a similar filtrate from a non-axenic Cyanothece-related culture killed Cyanothece PCC 7418. We conclude that a diverse community of AH exist in close association with cyanobacteria in microbial mats and the interactions between AH and cyanobacteria are species-specific and involve the release of substances.
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The direct role of aerobic heterotrophic bacteria associated with cyanobacteria in the degradation of oil compounds
International Biodeterioration & Biodegradation, 2005Co-Authors: Raeid M. M. Abed, Jürgen KösterAbstract:This study aimed at evaluating the role of cyanobacteria and their associated aerobic heterotrophic bacteria in biodegradation of petroleum compounds. We investigated the potential of ten non-axenic typical mat-forming cyanobacterial strains to degrade phenanthrene, pristane, n-octadecane, and dibenzothiophene. Five strains (Aphanothece halophyletica, Dactyolococcopsis salina, Halothece strain EPUS, Oscillatoria strain OSC, and Synechocystis strain UNIGA) were able to degrade n-alkanes. In case of the other five strains (Microcoleus Chthonoplastes, Oscillatoria sp. MPI 95 OS 01, Halothece strain EPUG, Halomicronema exentricum, and Phormidium strain UNITF) alkanes were not significantly affected. Moderate changes in the concentration of the aromatic compounds were observed for three isolates only. In follow-up experiments with Oscillatoria strain OSC, we demonstrated that the cyanobacteria-associated aerobic heterotrophic bacteria were responsible for the observed biodegradation. The cyanobacteria themselves apparently do not degrade petroleum compounds, but more likely play a significant, indirect role in biodegradation by supporting the growth and activity of the actual degraders.
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long term compositional changes after transplant in a microbial mat cyanobacterial community revealed using a polyphasic approach
Environmental Microbiology, 2001Co-Authors: Raeid M. M. Abed, Ferran GarciapichelAbstract:Using a polyphasic approach that included microscopy, cultivation and 16S rRNA-based cultivation-independent molecular fingerprinting, we compared the cyanobacterial composition of Solar Lake microbial mats and samples thereof transplanted and maintained in new settings for extended periods of time. Significant changes in community composition, with clear replacement of the dominant cyanobacterium, Microcoleus Chthonoplastes, were detected in all cases. The most dramatic shifts occurred in a sample kept in the laboratory for 3 years, which resulted in dominance by an Oscillatoria-like cyanobacterium whose 16S rRNA closely matched that of a morphologically similar isolate from mats in Mexico. Transfer of Solar Lake mat to an artificial experimental pond with incubation under seminatural conditions resulted in an increase in cyanobacterial diversity. Judging from the molecular signatures, two novel, previously unrecognized and phylogenetically well-delimited cyanobacterial populations became dominant. Through cultivation, one population was shown to correspond to a filamentous, non-heterocystous group of Cyanobacteria with very narrow trichomes (approximately equals 0.75-1.5 microm). The most dominant novel molecular signature, however, could not be identified by cultivation efforts or correlation with microscopy and, upon phylogenetic analyses, its 16S rRNA genes showed no particular close association to known cyanobacterial groups.
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Long‐term compositional changes after transplant in a microbial mat cyanobacterial community revealed using a polyphasic approach
Environmental microbiology, 2001Co-Authors: Raeid M. M. Abed, Ferran Garcia-pichelAbstract:Using a polyphasic approach that included microscopy, cultivation and 16S rRNA-based cultivation-independent molecular fingerprinting, we compared the cyanobacterial composition of Solar Lake microbial mats and samples thereof transplanted and maintained in new settings for extended periods of time. Significant changes in community composition, with clear replacement of the dominant cyanobacterium, Microcoleus Chthonoplastes, were detected in all cases. The most dramatic shifts occurred in a sample kept in the laboratory for 3 years, which resulted in dominance by an Oscillatoria-like cyanobacterium whose 16S rRNA closely matched that of a morphologically similar isolate from mats in Mexico. Transfer of Solar Lake mat to an artificial experimental pond with incubation under seminatural conditions resulted in an increase in cyanobacterial diversity. Judging from the molecular signatures, two novel, previously unrecognized and phylogenetically well-delimited cyanobacterial populations became dominant. Through cultivation, one population was shown to correspond to a filamentous, non-heterocystous group of Cyanobacteria with very narrow trichomes (approximately equals 0.75-1.5 microm). The most dominant novel molecular signature, however, could not be identified by cultivation efforts or correlation with microscopy and, upon phylogenetic analyses, its 16S rRNA genes showed no particular close association to known cyanobacterial groups.