Cyanobacterial Mats Research Articles

Potential of cyanobacterial biofilms in phosphate removal and biomass production

Four cyanobacterial biofilms, raised from cyanobacterial mats and dominated by Phormidium and Oscillatoria spp., were successfully grown attached to polyester mesh discs, and were tested for their probable application in PO43−-P removal from domestic sewage and other nutrient enriched wastewaters. Biofilm # 2, dominated by Phormidium fragile, best removed PO43−-P; nevertheless, some of it also grew outside the substrate making harvesting difficult. Other biofilms also efficiently removed PO43−-P from the medium in the following order: Biofilm # 1 > Biofilm # 3 > Biofilm # 4. Their growths were restricted to discs and are therefore better candidates as they can be efficiently harvested after PO43−-P removal. PO43−-P removal was primarily due to its uptake during growth of the biofilm rather than because of precipitation as pH of the medium remained <8.5. NO3−-N concentration in the medium determined PO43−-P removal efficiency of the test biofilms and therefore optimum N:P ratio is necessary for optimizing PO43−-P removal. The test biofilms could also efficiently remove NO3−-N from the medium.

The influence of seasonality on benthic primary production in a Red Sea coral reef

Northern Red Sea coral reefs experience pronounced seasonal variations in environmental factors such as water temperature, light intensity, and nutrient availability. This allows studying related effects on primary production by different functional groups. The present study therefore quantified primary production of all dominant benthic primary producers from a Jordanian fringing reef (29° 27′ 31″ N, 34° 58′ 26″ E) by measuring net photosynthesis (P n) and dark respiration (R) using stirred respirometry chamber incubations during all four seasons of 2013. Annual mean P n was highest for the macroalga Caulerpa (901 nmol O2 cm−2 h−1) and lowest for both the soft coral Sarcophyton and sedimentary microphytobenthos (212 and 223 nmol O2 cm−2 h−1, respectively). Sedimentary microphytobenthos exhibited the strongest response to seasonality with 5.7 times higher P n in spring than in winter. R was highest in hard corals among all groups in every season, likely due to nighttime calcification and heterotrophic activity. Gross photosynthesis-to-respiration ratios (P g:R) were highest for turf algae and macroalgae as well as cyanobacterial mats. While R was primarily positively related to PAR and temperature and P g:R to inorganic nutrients, few groups revealed significant relations between P n and environmental parameters. Seasonal budgets found daily gross primary production and respiration to be dominated by hard and soft corals. Total reef gross primary production was comparable between less oligotrophic spring and more oligotrophic summer. This indicates that processes such as heterotrophic feeding and microbial dinitrogen fixation may help the functional groups overcome potential nutrient limitation of primary production in summer.

Heavy Metal Concentrations in Cyanobacterial Mats and Underlying Sediments in Some Northern Western Desert Lakes of Egypt

Heavy Metal Concentrations in Cyanobacterial Mats and Underlying Sediments in Some Northern Western Desert Lakes of Egypt

Dolomitized cells within chert of the Permian Assistência Formation, Paraná Basin, Brazil

Dolomitic microscopic structures in the form of microspheres, “horseshoe- shaped” objects, and thin botryoidal crusts found within microfossiliferous chert within stromatolites of the Evaporite Bed (EB) of the Permian Assistência Formation, Irati Subgroup, Paraná Basin, Brazil, have been investigated by means of optical microscopy, X-ray fluorescence, scanning electron microscopy, Raman spectrometry and energy-dispersive X-ray spectrometry. The microspheres were identified as dolomitized coccoidal cyanobacteria based on similarity in size, spheroidal and paired hemispheroidal morphologies and colonial habit to co-occurring silicified organic-walled cyanobacteria embedded within the same microfabric and rock samples. The co-occurrence of dolomite, pyrite framboids, and abundant dispersed carbonaceous material and silicified cells is consistent with a hypersaline depositional environment with abundant cyanobacterial mats and elevated Mg2+/Ca2+ ratios and reducing conditions with active anoxic microbial processes near the water-(bio)sediment interface. The abundance of extracellular polymeric substances facilitated anoxic microbial processes (sulfate reduction), providing essential conditions for possible primary microbially induced dolomitization. In most of the dolomitized cells dolomite occurs only as an external layer; in fully dolomitized cells magnesium is richest in the outermost layer. Presumably, the dolomitization process was favored by the presence of anoxic microbial degraders and negatively charged functional groups at the surface of the cyanobacterial cells. Botryoidal dolomite rims of silica-filled fenestrae formed by a similar process and inherited the botryoidal morphology of the cell as originally lining the fenestrae. Silicification interrupted the dolomitization of the largely organic biosediment, mostly by permineralization, but locally by substitution, thereby preserving not only dolomitic microspheres, but also huge numbers of structurally well-preserved organic-walled cyanobacteria and portions of microbial mat. Clearly, dolomitization began very early in the microbial mats, prior to compaction of the sediment or full obliteration of cellular remains, followed very closely by silicification thereby impeding continued degradation and providing a window onto very well-preserved Permian microbial mats.

Toxicological data of some antibiotics and pesticides to fish, mosquitoes, cyanobacterial mats and to plants

This article provides toxicological data of antibiotics to fish and mosquito (El-Nahhal and El-dahdaouh, 2015) (doi: 10.5132/eec.2015.01.03 [1]), to cyanobacteria (El-Nahhal and Alshanti, 2015)(dx.doi.org/10.4172/2161-0525.1000274 [2]) and pesticides to plants (El-Nahhal and Hamdona, 2015) (doi.10.1186/s40064-015-1148-7 [3]). The data provided herein described the experimental procedure and calculation of the appropriate toxicity parameters, lethal concentrations (LC50) required to kill 50% of tested animal, percentage growth inhibition, relative toxicity (RT) and Mixture toxicity index. Moreover, the data enable the readers to perform future experiments and open future discussion with other authors elsewhere and generate future research guidelines which benefit the young scientific community around the globe in the field of mixture toxicity.

Annual Cycles of Two Cyanobacterial Mat Communities in Hydro-Terrestrial Habitats of the High Arctic.

Cyanobacteria form extensive macroscopic mats in shallow freshwater environments in the High Arctic and Antarctic. In these habitats, the communities are exposed to seasonal freezing and desiccation as well as to freeze-thawing and drying-rewetting cycles. Here, we characterized the annual cycles of two Phormidium communities in very shallow seepages located in central Svalbard. We observed the structure of the communities and the morphology, ultrastructure, metabolic activity, and viability of filaments and single cells. The communities overwintered as frozen mats, which were formed by long filaments enclosed in thick multilayered polysaccharide sheaths. No morphologically and/or ultrastructurally distinct spore-like cells were produced for surviving the winter, and the winter survival of the communities was not provided by a few resistant cells, which did not undergo visible morphological and ultrastructural transformations. Instead, a high proportion of cells in samples (85%) remained viable after prolonged freezing. The sheaths were the only morphological adaption, which seemed to protect the trichomes from damage due to freezing and freeze-associated dehydration. The cells in the overwintering communities were not dormant, as all viable cells rapidly resumed respiration after thawing, and their nucleoids were not condensed. During the whole vegetative season, defined by the presence of water in a liquid state, the communities were constantly metabolically active and contained <1% of dead and injured cells. The morphology and ultrastructure of the cells remained unaltered during observations throughout the year, except for light-induced changes in thylakoids. The dissemination events are likely to occur in spring as most of the trichomes were split into short fragments (hormogonia), a substantial proportion of which were released into the environment by gliding out of their sheaths, as well as by cracking and dissolving their sheaths. The short fragments subsequently grew longer and gradually produced new polysaccharide sheaths.

New multi-scale perspectives on the stromatolites of Shark Bay, Western Australia.

A recent field-intensive program in Shark Bay, Western Australia provides new multi-scale perspectives on the world’s most extensive modern stromatolite system. Mapping revealed a unique geographic distribution of morphologically distinct stromatolite structures, many of them previously undocumented. These distinctive structures combined with characteristic shelf physiography define eight ‘Stromatolite Provinces’. Morphological and molecular studies of microbial mat composition resulted in a revised growth model where coccoid cyanobacteria predominate in mat communities forming lithified discrete stromatolite buildups. This contradicts traditional views that stromatolites with the best lamination in Hamelin Pool are formed by filamentous cyanobacterial mats. Finally, analysis of internal fabrics of stromatolites revealed pervasive precipitation of microcrystalline carbonate (i.e. micrite) in microbial mats forming framework and cement that may be analogous to the micritic microstructures typical of Precambrian stromatolites. These discoveries represent fundamental advances in our knowledge of the Shark Bay microbial system, laying a foundation for detailed studies of stromatolite morphogenesis that will advance our understanding of benthic ecosystems on the early Earth.

Magnetic susceptibility as a biosignature in stromatolites

Microbialites have long been a focus of study in geobiology because they are macroscopic sedimentary records of the activities of microscopic organisms. However, abiotic processes can result in microbialite-like morphologies. Developing robust tools for substantiating the biogenicity of putative microbialites remains an important challenge.Here, we report a new potential biosignature based on the detrital magnetic mineral component present in nearly all sedimentary rocks. Detrital grains falling onto a hard, abiogenic, chemically precipitated structure would be expected to roll off surfaces at high incline angles. Thus, the distribution of grains in an abiogenic microbialite should exhibit a dependence on the dip angle along laminae. In contrast, a microbialite formed by the active trapping and binding of detrital grains by microorganisms could exhibit a distribution of detrital grains significantly less dependent on the dip angle of the laminae. However, given that most ancient stromatolites are micritic (composed of carbonate mud), tracking detrital grains vs. precipitated carbonate is not straightforward.Recent advances in our ability to measure miniscule magnetic fields open up the possibility to map magnetic susceptibility as a tracer of detrital grains in stromatolites. In abiogenic carbonate precipitation experiments, magnetic susceptibility fell to zero when the growth surface was inclined above 30° (the angle at which grains rolled off). In cyanobacterial mat experiments, even vertically inclined mats held magnetic material. The results indicate that cyanobacterial mats trap and bind small grains more readily than abiogenic carbonate precipitates alone. A variety of stromatolites of known and unknown biogenicity were then analyzed. Tested stromatolites span many different ages (Eocene to Holocene) and depositional environments (hot springs, lakes), and compositional forms (micritic, sparry crusts, etc.). The results were consistent with the laboratory results. The results of these experiments suggest that magnetic susceptibility shows promise as a new biosignature in the study of putative microbialites.

Recombination Does Not Hinder Formation or Detection of Ecological Species of Synechococcus Inhabiting a Hot Spring Cyanobacterial Mat.

Recent studies of bacterial speciation have claimed to support the biological species concept—that reduced recombination is required for bacterial populations to diverge into species. This conclusion has been reached from the discovery that ecologically distinct clades show lower rates of recombination than that which occurs among closest relatives. However, these previous studies did not attempt to determine whether the more-rapidly recombining close relatives within the clades studied may also have diversified ecologically, without benefit of sexual isolation. Here we have measured the impact of recombination on ecological diversification within and between two ecologically distinct clades (A and B') of Synechococcus in a hot spring microbial mat in Yellowstone National Park, using a cultivation-free, multi-locus approach. Bacterial artificial chromosome (BAC) libraries were constructed from mat samples collected at 60°C and 65°C. Analysis of multiple linked loci near Synechococcus 16S rRNA genes showed little evidence of recombination between the A and B' lineages, but a record of recombination was apparent within each lineage. Recombination and mutation rates within each lineage were of similar magnitude, but recombination had a somewhat greater impact on sequence diversity than mutation, as also seen in many other bacteria and archaea. Despite recombination within the A and B' lineages, there was evidence of ecological diversification within each lineage. The algorithm Ecotype Simulation identified sequence clusters consistent with ecologically distinct populations (ecotypes), and several hypothesized ecotypes were distinct in their habitat associations and in their adaptations to different microenvironments. We conclude that sexual isolation is more likely to follow ecological divergence than to precede it. Thus, an ecology-based model of speciation appears more appropriate than the biological species concept for bacterial and archaeal diversification.

Rapid Reactivation of Cyanobacterial Photosynthesis and Migration upon Rehydration of Desiccated Marine Microbial Mats.

Desiccated cyanobacterial mats are the dominant biological feature in the Earth’s arid zones. While the response of desiccated cyanobacteria to rehydration is well-documented for terrestrial systems, information about the response in marine systems is lacking. We used high temporal resolution hyperspectral imaging, liquid chromatography, pulse-amplitude fluorometry, oxygen microsensors, and confocal laser microscopy to study this response in a desiccated microbial mat from Exmouth Gulf, Australia. During the initial 15 min after rehydration chlorophyll a concentrations increased 2–5 fold and cyanobacterial photosynthesis was re-established. Although the mechanism behind this rapid increase of chlorophyll a remains unknown, we hypothesize that it involves resynthesis from a precursor stored in desiccated cyanobacteria. The subsequent phase (15 min–48 h) involved migration of the reactivated cyanobacteria toward the mat surface, which led, together with a gradual increase in chlorophyll a, to a further increase in photosynthesis. We conclude that the response involving an increase in chlorophyll a and recovery of photosynthetic activity within minutes after rehydration is common for cyanobacteria from desiccated mats of both terrestrial and marine origin. However, the response of upward migration and its triggering factor appear to be mat-specific and likely linked to other factors.

Fatty Acid Profiles, Pigments and Biochemical Contents of Cyanobacterial Mat in Some Lakes of North Western Desert, Egypt

Fatty Acid Profiles, Pigments and Biochemical Contents of Cyanobacterial Mat in Some Lakes of North Western Desert, Egypt

Chemical Composition and Antimicrobial Activities of Cyanobacterial Mats from Hyper Saline Lakes, Northern Western Desert, Egypt

Chemical Composition and Antimicrobial Activities of Cyanobacterial Mats from Hyper Saline Lakes, Northern Western Desert, Egypt

PUNCTUATED GROWTH OF MICROBIAL CONES WITHIN EARLY CAMBRIAN ONCOIDS, BAYAN GOL FORMATION, WESTERN MONGOLIA

Abstract Oxygen bubbles produced during photosynthesis internally deform filamentous cyanobacterial mats, producing distinctive fenestral patterns. Similar textures preserved in ancient microbialites are useful biosignatures when filaments are no longer preserved, but have typically been observed within stromatolites. This study describes bubble-associated fenestrae within oncoids from the early Cambrian Bayan Gol Formation of Mongolia. Fenestrae appear in mm-scale micritic laminae which contain dense accumulations of large (10 × 300 μm) filamentous Girvanella microfossils. Many laminae are not spherical, often occurring with one flat side opposite a conical peak. Up to six generations of conical geometry are present, with each cone rotated with respect to the previous peak. We hypothesize that the oncoids experienced intermittent disturbances followed by periods of stasis and vertical growth. During resting periods, we hypothesize that flat areas formed the oncoid resting base and peaked areas the top. T...

Multi-species biofilms in ecology, medicine, and biotechnology

The structure, composition, and developmental patterns of multi-species biofilms are analyzed, as well as the mechanisms of interaction of their microbial components. The main methodological approaches used for analysis of multi-species biofilms, including omics technologies, are characterized. Environmental communities (cyanobacterial mats and methanotrophic communities), as well as typical multi-species communities of medical importance (oral cavity, skin, and gut microbiomes) are described. A special section deals with the role of multi-species biofilms in such biotechnological processes as wastewater treatment, heavy metal removal, corrosion control, and environmental bioremediation.

Cyanobacterial reuse of extracellular organic carbon in microbial mats.

Cyanobacterial organic matter excretion is crucial to carbon cycling in many microbial communities, but the nature and bioavailability of this C depend on unknown physiological functions. Cyanobacteria-dominated hypersaline laminated mats are a useful model ecosystem for the study of C flow in complex communities, as they use photosynthesis to sustain a more or less closed system. Although such mats have a large C reservoir in the extracellular polymeric substances (EPSs), the production and degradation of organic carbon is not well defined. To identify extracellular processes in cyanobacterial mats, we examined mats collected from Elkhorn Slough (ES) at Monterey Bay, California, for glycosyl and protein composition of the EPS. We found a prevalence of simple glucose polysaccharides containing either α or β (1,4) linkages, indicating distinct sources of glucose with differing enzymatic accessibility. Using proteomics, we identified cyanobacterial extracellular enzymes, and also detected activities that indicate a capacity for EPS degradation. In a less complex system, we characterized the EPS of a cyanobacterial isolate from ES, ESFC-1, and found the extracellular composition of biofilms produced by this unicyanobacterial culture were similar to that of natural mats. By tracing isotopically labeled EPS into single cells of ESFC-1, we demonstrated rapid incorporation of extracellular-derived carbon. Taken together, these results indicate cyanobacteria reuse excess organic carbon, constituting a dynamic pool of extracellular resources in these mats.

The Co-Evolution of Fe-Oxides, Ti-Oxides, and Other Microbially Induced Mineral Precipitates In Sandy Sediments: Understanding the Role of Cyanobacteria In Weathering and Early Diagenesis

Abstract Changes in composition during the transition from sediment to rock are usually attributed to long, complicated histories and atmospheric influences, while the contribution of benthic mat-building cyanobacteria is not typically considered. Here the goal is to understand the influence of cyanobacterial mats on mineral weathering in postdepositional settings of sandy, shallow subaquatic environments. Laboratory incubation experiments were done using ilmenite sands and ilmenite-enriched quartz sands colonized by cyanobacterial mats for five months at three temperatures: 25°C and 37°C, representative of postdepositional weathering regimes, and 70°C corresponding to early diagenesis. As a comparative control to represent abiotic processes, ilmenite sands and ilmenite-enriched quartz sands were also subjected to the same conditions without cyanobacterial colonization. The precipitation of minerals on cyanobacterial cells and extracellular polymeric substances (EPS) as well as the phase changes in natural ilmenites (FeTiO3) were documented to determine if cyanobacteria influence mineral reaction pathways. The precipitates, ilmenite grains, and permineralized cells were analyzed using complementary techniques of scanning electron microscopy (SEM), X-ray diffraction (XRD), and micro-Raman spectroscopy. The results of this study show that a variety of pure and mixed mineral phases precipitate under postdepositional conditions (T ≤ 70°C) in wet, sandy environments with or without cyanobacteria. Akaganeite, anatase, ankerite, lepidocrocite, gibbsite, kaolinite, and natrojarosite formed exclusively in the samples incubated with cyanobacteria. In the samples incubated with cyanobacteria, more mineral phases formed at 37°C, suggesting that cyanobacteria play a greater role in weathering than in early diagenesis. Sulfate phases that formed in the presence of cyanobacteria differed in chemical composition from the abiotic precipitates as Na, Al, Mg, and Si were incorporated into the structures of newly formed biotic phases. Understanding the possible fate of these precursor mineral phases will help redefine geochemical biosignatures that can be used for the detection of ancient microbial life in sedimentary rocks on Earth as well as for future missions exploring life on other planets.

Filamentous anoxygenic phototrophic bacteria from cyanobacterial mats of Alla hot springs (Barguzin Valley, Russia).

Alkaline hydrotherms of the Baikal rift zone are unique systems to study the diversity of thermophilic bacteria. In this study, we present data on the phototrophic bacterial community of cyanobacterial mats from the alkaline Alla hot spring. Using a clonal analysis approach, this study evaluated the species diversity, the proportion of oxygenic and anoxygenic phototrophs and their distribution between various areas of the spring. Novel group-specific PCR primers were designed and applied to detect representatives of the Chloroflexus and Roseiflexus genera in mat samples. For the first time, the presence of Roseiflexus-like bacteria was detected in the Baikal rift zone.

Ecological connectivity shapes quasispecies structure of RNA viruses in an Antarctic lake.

RNA viruses exist as complex mixtures of genotypes, known as quasispecies, where the evolution potential resides in the whole community of related genotypes. Quasispecies structure and dynamics have been studied in detail for virus infecting animals and plants but remain unexplored for those infecting micro-organisms in environmental samples. We report the first metagenomic study of RNA viruses in an Antarctic lake (Lake Limnopolar, Livingston Island). Similar to low-latitude aquatic environments, this lake harbours an RNA virome dominated by positive single-strand RNA viruses from the order Picornavirales probably infecting micro-organisms. Antarctic picorna-like virus 1 (APLV1), one of the most abundant viruses in the lake, does not incorporate any mutation in the consensus sequence from 2006 to 2010 and shows stable quasispecies with low-complexity indexes. By contrast, APLV2-APLV3 are detected in the lake water exclusively in summer samples and are major constituents of surrounding cyanobacterial mats. Their quasispecies exhibit low complexity in cyanobacterial mat, but their run-off-mediated transfer to the lake results in a remarkable increase of complexity that may reflect the convergence of different viral quasispecies from the catchment area or replication in a more diverse host community. This is the first example of viral quasispecies from natural aquatic ecosystems and points to ecological connectivity as a modulating factor of quasispecies complexity.

Draft genome of Kocuria polaris CMS 76or(T) isolated from cyanobacterial mats, McMurdo Dry Valley, Antarctica: an insight into CspA family of proteins from Kocuria polaris CMS 76or(T).

Kocuria polaris strain CMS 76or(T) is a gram-positive, orange-pigmented bacterium isolated from a cyanobacterial mat sample from a pond located in McMurdo Dry Valley, Antarctica. It is psychrotolerant, orange pigmented, hydrolyses starch and Tween 80 and reduces nitrate. We report the 3.78-Mb genome of K. polaris strain CMS 76or(T), containing 3416 coding sequences, including one each for 5S rRNA, 23S rRNA, 16S rRNA and 47 tRNA genes, and the G+C content of DNA is 72.8%. An investigation of Csp family of proteins from K. polaris strain CMS 76or(T) indicated that it contains three different proteins of CspA (peg.319, peg.2255 and 2832) and the length varied from 67 to 69 amino acids. The three different proteins contain all the signature amino acids and two RNA binding regions that are characteristic of CspA proteins. Further, the CspA from K. polaris strain CMS 76or(T) was different from CspA of four other species of the genus Kocuria, Cryobacterium roopkundense and E. coli indirectly suggesting the role of CspA of K. polaris strain CMS 76or(T) in psychrotolerant growth of the bacterium.

Spirochaeta sinaica sp. nov., a halophilic spirochaete isolated from a cyanobacterial mat.

A strain of free-living obligately anaerobic, halophilic spirochaete, SLT, was isolated from a sample of a cyanobacterial mat of the hypersaline Solar Lake, Sinai shore. The strain had motile helical cells, 0.35-0.40 × 6-10 μm. Strain SLT exhibited high resistance to NaCl among known halophilic spirochaetes growing at NaCl concentrations from 2 to 12% (optimum growth at 7%). The strain grew at temperatures from 10 to 32 °C (optimum at 28 °C) and pH from 6 to 8.5 (optimum at pH 7.0-7.5). Carbohydrates, but not alcohols, organic acids or nitrogenous compounds (peptone, yeast extract and amino acids), were used as energy substrates for growth. Ethanol, acetate, lactate, H2 and CO2 were the products of glucose fermentation. Sulfide was produced in the presence of S0 or thiosulfate in the medium. The DNA G+C content was 44.7 mol%. Based on 16S rRNA gene sequence analysis, strain SLT clustered within the genus Spirochaeta, exhibiting 94.2 and 93.7% similarity with its closest relatives, Spirochaeta bajacaliforniensis DSM 160554T and Spirochaeta smaragdinae DSM 11293T, respectively; similarity with other species did not exceed 86%. The phenotypic and chemotaxonomic characteristics of the strain, as well as the results of phylogenetic analysis support the classification of strain SLT as representing a novel species of the genus Spirochaeta, for which the name Spirochaeta sinaica sp. nov. is proposed. The type strain is SLT ( = DSM 14994 = NIQEM U 783).