96 research outputs found

    Evaluation of phytotherapeutic activities and phytochemical content of Phormidium autumnale Gomont from natural freshwater sources

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    The information available on microalgae-sourced compounds, especially antibiotics and other bioactive compounds, and their potential commercial applications is still insufficient. In this study, antibacterial activity, metabolites, and molecular characterization of Phormidium autumnale, which was isolated from samples collected from different natural freshwater sources in Ankara, Turkey, were investigated. Sequencing results of 16s rDNA confirmed the molecular identification of P. autumnale by 99%. It was determined that the peak values of some phenolic compounds and cyclic peptides were consistent with the 1653-1389 cm(-1) band regions in the FTIR spectra of the species. The antibacterial activities of P. autumnale cyanobacteria (CBA) extracts that were obtained by using different solvents were tested on Escherichia coli, Staphylococcus epidermidis, methicillin-resistant (MR) Staphylococcus aureus, Streptococcus agalactiae, and Enterococcus faecalis by using a disc diffusion method. Also, the minimum inhibition concentration (MIC) and antimicrobial indexes of all extracts were determined. It was found that P. autumnale methanol extracts showed antibacterial activity on all test bacteria, whereas acetone extracts showed effects only on E. coli. For the inhibition of MR S. aureus, the control methanol extract was found to give very similar results to those exhibited by the control antibiotics, and the antimicrobial index results were determined to be 58.7-67.5%. According to the results of the analysis of methanol extract, gentisic acid, vanillic acid, 4-hydroxybenzoic acid, p-coumaric acid, and catechin (especially phenolic compounds) were determined to be the active compounds. It can be concluded that P. autumnale is an alternative to current commercial applications as an antibacterial agent in phytotherapy

    Characterising the benthic Phormidium autumnale-dominated biofilm community and anatoxin production throughout biofilm succession

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    There has been an increase in the prevalence and intensity of Phormidium autumnale-dominated benthic blooms in New Zealand over the last decade. This species produces the potent neurotoxins Anatoxin-a, Homoanatoxin-a and their derivatives, and consumption of P. autumnale biofilms has led to over 70 dog deaths since 2005. The mechanisms regulating the dominance and toxicity of P. autumnale are still unclear, as these blooms can reach high biomass in low nutrient conditions. Benthic biofilms are composed of multiple taxa and usually harbor a complex community of bacteria and other microbes, which can change over time and interact to facilitate biofilm development and metabolic processing. Prior to this thesis, the microbial composition of P. autumnale-dominated biofilms was unknown. This study provides insights into the relationships of this neurotoxic cyanobacterium with microbial components of the biofilm community. Benthic biofilms were sampled every two to four days for 32 days from three sites in the Hutt River (Wellington) following a high flow event. A combination of microscopy and molecular techniques (bacterial ARISA and Illumina™ sequencing) were used to identify the micro-algal and bacterial components of the biofilm throughout its development. Variation in total anatoxin production was measured using LC-MS and changes in toxic P. autumnale cell numbers were quantified using QPCR. A suite of environmental variables (point velocity, depth, flow, conductivity, temperature and nutrients) were also monitored throughout the study period. Three distinct phases of microbial succession were identified (early, mid and late) using non-metric multidimensional cluster analyses. The micro-algal community composition (including P. autumnale) shifted from early to mid-phase ca. 16 days after the flushing flow and from mid to late phase at ca. day 30. The ARISA and Illumina™ sequencing showed the bacterial community shifts occurred ca. 4 and 9 days before the respective micro-algal community shifts. These analyses indicate a close coupling of the micro-algal and bacterial communities and may suggest bacterial driven succession. However, bacteria are likely to depend on micro-algal by-products for nutrition from the mid-phases onward and assessment of the metabolic processes occurring within the biofilms is needed to clarify this. Phormidium autumnale was dominant in the biofilm from an early stage in development and grew exponentially despite an influx of diatoms at day 20. None of the environmental parameters measured could explain the temporal variation in micro-algal and bacterial communities, which suggested that intrinsic rather than extrinsic factors were more important in regulating succession. This further supports the hypothesis that biofilm microbes may facilitate P. autumnale dominance. There was a significant variation in anatoxins per cell over time (p = 0.034). Production of anatoxins was greatest in the mid-phase of succession (208 fg cell⁻¹), coinciding with an increase in diatom biomass, which could implicate anatoxins as allelopathic chemicals that alleviate the effects of competition on P. autumnale. Changes in proportions of the different anatoxin variants produced over time also aligned with the three successional phases in both the micro-algal and bacterial communities, providing further evidence of a relationship between anatoxin production and microbial biofilm components. Bacterial taxa of the Alphaproteobacteria were dominant within the early bacterial community, but were surpassed by the Betaproteobacteria and Flavobacteria in mid and late phases. Bacterial genera involved in exopolysaccharide production, alkaline phosphatase activity and biopolymer degradation were identified. These attributes are important in the formation, maintenance and break-down of biofilms and therefore strengthen the likelihood of linkages between the micro-algal and bacterial community. Further investigations into functional roles of the biofilm components are needed to infer relationships between P. autumnale and the bacterial community. A clear pattern of microbial succession is described here and linkages between the micro-algal and bacterial communities are evident. Future work should focus on the functional attributes of microbes occurring at different stages of succession to further understand how P. autumnale dominates these benthic communities

    Arctic ecosystems – relations between cyanobacterial assemblages and vegetation (Spitsbergen)

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    The paper describes cyanobacterial assemblages in relation to mosses and vascular plants forming mosaic communities in Arctic tundra. The study area is located in the north of the Hornsund fjord. In the selected 14 type of habitats, the study analyzed the quantitative and qualitative share of cyanobacteria, mosses and vascular plants. Due to their similarity in cyanobacterial assemblages and their relations to vegetation, they were divided into 10 groups. Each group was characterized by a particular combination of species with a distinguishing cyanobacteria dominant species and mosses and vascular plants. The significant role of cyanobacteria crusts and mats in the formation of the Spitsbergen tundra suggests they should be included in the descriptions of communities present in the region

    Multiple adaptations to polar and alpine environments within cyanobacteria:a phylogenomic and Bayesian approach

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    Cyanobacteria are major primary producers in the polar and alpine regions contributing significantly to nitrogen and carbon cycles in the cryosphere. Recent advancements in environmental sequencing techniques have revealed great molecular diversity of microorganisms in cold environments. However, there are no comprehensive phylogenetic analyses including the entire known diversity of cyanobacteria from these extreme environments. We present here a global phylogenetic analysis of cyanobacteria including an extensive dataset comprised of available SSU rRNA gene sequences of cyanobacteria from polar and high altitude environments. Furthermore, we used a large-scale multi-gene (135 proteins and two ribosomal RNAs) genome constraint including 57 cyanobacterial genomes. Our analyses produced the first phylogeny of cold cyanobacteria exhibiting robust deep branching relationships implementing a phylogenomic approach. We recovered several clades common to Arctic, Antarctic and alpine sites suggesting that the traits necessary for survival in the cold have been acquired by a range of different mechanisms in all major cyanobacteria lineages. Bayesian ancestral state reconstruction revealed that twenty clades each have common ancestors with high probabilities of being capable of surviving in cold environments

    Hypolithic Microbial Community of Quartz Pavement in the High-Altitude Tundra of Central Tibet

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    The hypolithic microbial community associated with quartz pavement at a high-altitude tundra location in central Tibet is described. A small-scale ecological survey indicated that 36% of quartz rocks were colonized. Community profiling using terminal restriction fragment length polymorphism revealed no significant difference in community structure among a number of colonized rocks. Real-time quantitative PCR and phylogenetic analysis of environmental phylotypes obtained from clone libraries were used to elucidate community structure across all domains. The hypolithon was dominated by cyanobacterial phylotypes (73%) with relatively low frequencies of other bacterial phylotypes, largely represented by the chloroflexi, actinobacteria, and bacteriodetes. Unidentified crenarchaeal phylotypes accounted for 4% of recoverable phylotypes, while algae, fungi, and mosses were indicated by a small fraction of recoverable phylotypes