Phototrophic biofilms and microbial mats from the marine littoral of the central Mediterranean

Phototrophic biofilm and microbial mat communities grow along the rocky coastline of the Maltese islands. During this study, phototrophs from the mediolittoral and supralittoral zones were studied over a two-year period and seasonal changes were observed. Attachment of pioneer microorganisms to the porous eroded limestone bedrock was facilitated via a gelatinous matrix composed of exopolymeric substances (EPS). In submerged areas, such as undisturbed rock pools, these progressively formed green or brown compact biofilms, some of which thickened over spring to form microbial mats via the production of more extensive EPS layers. Microbial mats gradually attained a lighter colouration due to the presence of ultraviolet (UV) screening pigments. In full summer, they were observed to shrink, detach from the exposed substrate, harden and progressively calcify. Biofilm microorganisms survived the harsh summer months in sheltered areas. The major biofilm formers were filamentous non-heterocytous cyanobacteria belonging to the Leptolyngbyaceae, Pseudanabaenaceae and Oscillatoriaceae. Their sheaths were thick, lamellated and often confluent. A higher biodiversity of phototrophs was observed in late autumn and winter, when tufts of heterocytous Calothrix sp. grew on thin compact biofilms of Nodosilinea sp., Toxifilum sp. and Phormidesmis spp., while Lyngbya spp. trichomes were surrounded by thick brown sheaths. Germlings of green and brown macroalgal species belonging to Ulva, Cladophora and Sphacelaria were embedded in biofilms and microbial mats and gradually grew to form extensive macroalgal covers submerged in rock pools. Erythrotrichia sp. filaments colonised the mediolittoral zone and were confined to areas that were exposed to wave action and submerged intermittently. Over summer, macroalgal coverage diminished and microalgal biofilms and microbial mats prevailed in rock pools.

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Axenic Biofilm Formation and Aggregation bySynechocystissp. Strain PCC 6803 Are Induced by Changes in Nutrient Concentration and Require Cell Surface Structures

Applied and Environmental Microbiology ◽

10.1128/aem.02192-18 ◽

2019 ◽

Vol 85 (7) ◽

Cited By ~ 11

Author(s):

Rey Allen ◽

Bruce E. Rittmann ◽

Roy Curtiss

Keyword(s):

Biofilm Formation ◽

Molecular Mechanisms ◽

Type Iv Pili ◽

Biofuel Production ◽

Oxygenic Photosynthesis ◽

Phototrophic Biofilm ◽

Bg11 Medium ◽

Phototrophic Biofilms ◽

Type Iv ◽

Cell Surface Structures

ABSTRACTPhototrophic biofilms are key to nutrient cycling in natural environments and bioremediation technologies, but few studies describe biofilm formation by pure (axenic) cultures of a phototrophic microbe. The cyanobacteriumSynechocystissp. strain PCC 6803 (hereSynechocystis) is a model microorganism for the study of oxygenic photosynthesis and biofuel production. We report here that wild-type (WT)Synechocystiscaused extensive biofilm formation in a 2,000-liter outdoor nonaxenic photobioreactor under conditions attributed to nutrient limitation. We developed a biofilm assay and found that axenicSynechocystisforms biofilms of cells and extracellular material but only when cells are induced by an environmental signal, such as a reduction in the concentration of growth medium BG11. Mutants lacking cell surface structures, namely type IV pili and the S-layer, do not form biofilms. To further characterize the molecular mechanisms of cell-cell binding bySynechocystis, we also developed a rapid (8-h) axenic aggregation assay. Mutants lacking type IV pili were unable to aggregate, but mutants lacking a homolog to Wza, a protein required for type 1 exopolysaccharide export inEscherichia coli, had a superbinding phenotype. In WT cultures, 1.2× BG11 medium induced aggregation to the same degree as 0.8× BG11 medium. Overall, our data support that Wza-dependent exopolysaccharide is essential to maintain stable, uniform suspensions of WTSynechocystiscells in unmodified growth medium and that this mechanism is counteracted in a pilus-dependent manner under altered BG11 concentrations.IMPORTANCEMicrobes can exist as suspensions of individual cells in liquids and also commonly form multicellular communities attached to surfaces. Surface-attached communities, called biofilms, can confer antibiotic resistance to pathogenic bacteria during infections and establish food webs for global nutrient cycling in the environment. Phototrophic biofilm formation is one of the earliest phenotypes visible in the fossil record, dating back over 3 billion years. Despite the importance and ubiquity of phototrophic biofilms, most of what we know about the molecular mechanisms, genetic regulation, and environmental signals of biofilm formation comes from studies of heterotrophic bacteria. We aim to help bridge this knowledge gap by developing new assays forSynechocystis, a phototrophic cyanobacterium used to study oxygenic photosynthesis and biofuel production. With the aid of these new assays, we contribute to the development ofSynechocystisas a model organism for the study of axenic phototrophic biofilm formation.

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Plant Tissue Decay in Long-Term Experiments with Microbial Mats

Geosciences ◽

10.3390/geosciences8110387 ◽

2018 ◽

Vol 8 (11) ◽

pp. 387 ◽

Cited By ~ 4

Author(s):

Miguel Iniesto ◽

Candela Blanco-Moreno ◽

Aurora Villalba ◽

Ángela Buscalioni ◽

M. Guerrero ◽

...

Keyword(s):

Plant Tissue ◽

Microbial Mats ◽

Bacterial Biofilm ◽

Water Interface ◽

Fossil Plants ◽

Interface Control ◽

Exopolymeric Substances ◽

Long Term Experiments ◽

Mineralization Processes

The sequence of decay in fern pinnules was tracked using the species Davallia canariensis. Taphonomic alterations in the sediment–water interface (control tanks) and in subaqueous conditions with microbial mats were compared. The decay sequences were similar in control and mat tanks; in both cases, pinnules preserved the shape throughout the four-month experience. However, the quality and integrity of tissues were greater in mats. In control tanks, in which we detected anoxic and neutral acid conditions, the appearance of a fungal–bacterial biofilm promoted mechanical (cell breakage and tissue distortions) and geochemical changes (infrequent mineralizations) on the external and internal pinnule tissues. In mats, characterized by stable dissolved oxygen and basic pH, pinnules became progressively entombed. These settings, together with the products derived from mat metabolisms (exopolymeric substances, proteins, and rich-Ca nucleation), promoted the integrity of external and internal tissues, and favored massive and diverse mineralization processes. The experience validates that the patterns of taphonomic alterations may be applied in fossil plants.

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Axenic Biofilm Formation and Aggregation bySynechocystisPCC 6803 is Induced by Changes in Nutrient Concentration, and Requires Cell Surface Structures

10.1101/414151 ◽

2018 ◽

Cited By ~ 2

Author(s):

Rey Allen ◽

Bruce E. Rittmann ◽

Roy Curtiss

Keyword(s):

Cell Surface ◽

Biofilm Formation ◽

Molecular Mechanisms ◽

Type Iv Pili ◽

Surface Structures ◽

Biofuel Production ◽

Phototrophic Biofilm ◽

Phototrophic Biofilms ◽

Type Iv ◽

Cell Surface Structures

AbstractPhototrophic biofilms are key to nutrient cycling in natural environments and bioremediation technologies, but few studies describe biofilm formation by pure (axenic) cultures of a phototrophic microbe. The cyanobacteriumSynechocystissp. PCC 6803 (hereafterSynechocystis) is a model micro-organism for the study of oxygenic photosynthesis and biofuel production. We report here that wild-type (WT)Synechocystiscaused extensive biofilm formation in a 2000 liter outdoor non-axenic photobioreactor under conditions attributed to nutrient limitation. We developed a biofilm assay and found that axenicSynechocystisforms biofilms of cells and extracellular material, but only when induced by an environmental signal, such as by reducing the concentration of growth medium BG11. Mutants lacking cell surface structures, namely type IV pili and the S-layer, do not form biofilms.To further characterize the molecular mechanisms of cell-cell binding bySynechocystis, we also developed a rapid (8 hour) axenic aggregation assay. Mutants lacking Type IV pili were unable to aggregate, but mutants lacking a homolog to Wza, a protein required for Type 1 exopolysaccharide export inEscherichia coli, had a super-binding phenotype. In WT cultures, 1.2x BG11 induced aggregation to the same degree as 0.8x BG11. Overall, our data support that Wza-dependant exopolysaccharide is essential to maintain stable, uniform suspensions of WTSynechocystiscells in unmodified growth medium, and this mechanism is counter-acted in a pili-dependent manner under altered BG11 concentrations.ImportanceMicrobes can exist as suspensions of individual cells in liquids, and also commonly form multicellular communities attached to surfaces. Surface-attached communities, called biofilms, can confer antibiotic resistance to pathogenic bacteria during infections, and establish food webs for global nutrient cycling in the environment. Phototrophic biofilm formation is one of the earliest phenotypes visible in the fossil record, dating back over 3 billion years. Despite the importance and ubiquity of phototrophic biofilms, most of what we know about the molecular mechanisms, genetic regulation, and environmental signals of biofilm formation comes from studies of heterotrophic bacteria. We aim to help bridge this knowledge gap by developing new assays forSynechocystis, a phototrophic cyanobacterium used to study oxygenic phototsynthesis and biofuel production. With the aid of these new assays, we contribute to the development ofSynechocystisas a model organism for the study of axenic phototrophic biofilm formation.

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Linking decay of microbial mats and dolomite formation in the sabkhas of Qatar

10.5194/egusphere-egu2020-12203 ◽

2020 ◽

Author(s):

Zach Diloreto ◽

Maria Dittrich ◽

Tomaso Bontognali ◽

Hamad Al Saad Al Kuwari ◽

Judith A. McKenzie

Keyword(s):

Low Temperature ◽

Functional Groups ◽

Intertidal Zone ◽

Microbial Mats ◽

Microbial Mat ◽

Exopolymeric Substances ◽

Elevated Salinity ◽

Nucleation Sites ◽

Upper Intertidal ◽

Dolomite Formation

<p>The sabkhas of Qatar are excellent environments to examine the mechanisms of low-temperature dolomite precipitation. The detailed microbial and geochemical analysis of the dynamics in environmental conditions in two microbial mats over two years provide a unique opportunity to gain insights in low-temperature dolomite formation in modern time. The compositions of extracted exopolymeric substances (EPS) &#160;in two microbial mats, one within the lower intertidal zone and one within the upper intertidal zone exhibit an increase in the concentration of carboxylic functional groups during periods of elevated salinity. We interpret it as an indicator for dolomite formation since carboxylic functional groups are suggested to be the primary drivers for low-temperature dolomite as nucleation sites and inhibitors of Mg complexes. Notably, the increase in the concentration of the carboxylic group is associated with an increase in salinity in sabkha which happened periodically.</p><p>These fluctuations have been accompanied by the changes in the community from cyanobacterial dominated mat to one dominated by heterotrophs. During these periodical events, when a growing microbial mat turned into degrading microbial mat, we observed low-temperature dolomite formation. Such events occur in other modern dolomite forming environments and possibly in ancient sequences. Our work observed dynamical changes both in microbial mats, exopolymeric substances composition, geochemical gradients and accompanied low-temperature dolomite formation over several seasons. Our findings proving evidence that EPS degradation within microbial mats is a key mechanism in the formation of modern and most probable, ancient low-temperature dolomite with implications for those formed in ancient sequences.</p>

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Role of Cyanobacterial Exopolysaccharides in Phototrophic Biofilms and in Complex Microbial Mats

Life ◽

10.3390/life5021218 ◽

2015 ◽

Vol 5 (2) ◽

pp. 1218-1238 ◽

Cited By ~ 136

Author(s):

Federico Rossi ◽

Roberto De Philippis

Keyword(s):

Microbial Mats ◽

Phototrophic Biofilms

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Interaction between CO2-consuming autotrophy and CO2-producing heterotrophy in non-axenic phototrophic biofilms

PLoS ONE ◽

10.1371/journal.pone.0253224 ◽

2021 ◽

Vol 16 (6) ◽

pp. e0253224

Author(s):

Patrick Ronan ◽

Otini Kroukamp ◽

Steven N. Liss ◽

Gideon Wolfaardt

Keyword(s):

Organic Carbon ◽

Sodium Acetate ◽

Carbon Sources ◽

Algal Growth ◽

Biofilm Growth ◽

Phototrophic Biofilm ◽

Phototrophic Biofilms ◽

Carbon Amendment ◽

Autotrophic Metabolism ◽

Research Questions

As the effects of climate change become increasingly evident, the need for effective CO2 management is clear. Microalgae are well-suited for CO2 sequestration, given their ability to rapidly uptake and fix CO2. They also readily assimilate inorganic nutrients and produce a biomass with inherent commercial value, leading to a paradigm in which CO2-sequestration, enhanced wastewater treatment, and biomass generation could be effectively combined. Natural non-axenic phototrophic cultures comprising both autotrophic and heterotrophic fractions are particularly attractive in this endeavour, given their increased robustness and innate O2-CO2 exchange. In this study, the interplay between CO2-consuming autotrophy and CO2-producing heterotrophy in a non-axenic phototrophic biofilm was examined. When the biofilm was cultivated under autotrophic conditions (i.e. no organic carbon), it grew autotrophically and exhibited CO2 uptake. After amending its growth medium with organic carbon (0.25 g/L glucose and 0.28 g/L sodium acetate), the biofilm rapidly toggled from net-autotrophic to net-heterotrophic growth, reaching a CO2 production rate of 60 μmol/h after 31 hours. When the organic carbon sources were provided at a lower concentration (0.125 g/L glucose and 0.14 g/L sodium acetate), the biofilm exhibited distinct, longitudinally discrete regions of heterotrophic and autotrophic metabolism in the proximal and distal halves of the biofilm respectively, within 4 hours of carbon amendment. Interestingly, this upstream and downstream partitioning of heterotrophic and autotrophic metabolism appeared to be reversible, as the position of these regions began to flip once the direction of medium flow (and hence nutrient availability) was reversed. The insight generated here can inform new and important research questions and contribute to efforts aimed at scaling and industrializing algal growth systems, where the ability to understand, predict, and optimize biofilm growth and activity is critical.

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The Response of Extracellular Polymeric Substances Production by Phototrophic Biofilms to a Sequential Disturbance Strongly Depends on Environmental Conditions

Frontiers in Microbiology ◽

10.3389/fmicb.2021.742027 ◽

2021 ◽

Vol 12 ◽

Author(s):

Emilie Loustau ◽

Joséphine Leflaive ◽

Claire Boscus ◽

Quentin Amalric ◽

Jessica Ferriol ◽

...

Keyword(s):

Light Intensity ◽

Green Alga ◽

Environmental Conditions ◽

Extracellular Polymeric Substances ◽

Multiple Stressors ◽

Light Condition ◽

Biofilm Growth ◽

Algal Strain ◽

Phototrophic Biofilm ◽

Phototrophic Biofilms

Phototrophic biofilms are exposed to multiple stressors that can affect them both directly and indirectly. By modifying either the composition of the community or the physiology of the microorganisms, press stressors may indirectly impact the ability of the biofilms to cope with disturbances. Extracellular polymeric substances (EPS) produced by the biofilm are known to play an important role in its resilience to various stresses. The aim of this study was to decipher to what extent slight modifications of environmental conditions could alter the resilience of phototrophic biofilm EPS to a realistic sequential disturbance (4-day copper exposure followed by a 14-day dry period). By using very simplified biofilms with a single algal strain, we focused solely on physiological effects. The biofilms, composed by the non-axenic strains of a green alga (Uronema confervicolum) or a diatom (Nitzschia palea) were grown in artificial channels in six different conditions of light intensity, temperature and phosphorous concentration. EPS quantity (total organic carbon) and quality (ratio protein/polysaccharide, PN/PS) were measured before and at the end of the disturbance, and after a 14-day rewetting period. The diatom biofilm accumulated more biomass at the highest temperature, with lower EPS content and lower PN/PS ratio while green alga biofilm accumulated more biomass at the highest light condition with lower EPS content and lower PN/PS ratio. Temperature, light intensity, and P concentration significantly modified the resistance and/or recovery of EPS quality and quantity, differently for the two biofilms. An increase in light intensity, which had effect neither on the diatom biofilm growth nor on EPS production before disturbance, increased the resistance of EPS quantity and the resilience of EPS quality. These results emphasize the importance of considering the modulation of community resilience ability by environmental conditions, which remains scarce in the literature.

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An importance of soil humidification in forming of avifauna of arboreal plantation in the Biosphere reserve «Askania Nova» (un-reproductive period)

Ecology and Noospherology ◽

10.15421/031614 ◽

2016 ◽

Vol 27 (3-4) ◽

pp. 55-69

Author(s):

M. A. Listopadsky

Keyword(s):

Soil Moisture ◽

Influence Factors ◽

Data Communication ◽

Biosphere Reserve ◽

Reproductive Period ◽

Defined Contribution ◽

Separate Species ◽

Steppe Birds ◽

Reserve Forest ◽

Autumn And Winter

With gradient analysis investigated the role of soil moisture in the formation of the modern population of birds in the reserve forest plantations. Soil moisture was divided into seven grades. For this purpose used grass cover and the coefficient of local moistening. His proposed PhD L. P. Travleev. This method allows knowing the degree of influence of soil moisture at the birds. We analyzed birds species composition, population, placement in space and power of influence factors (soil moisture). Investigations were carried out on the territory of the Biosphere Reserve «Askania Nova». We studied the birds which live in the reserve at the end of the summer, autumn and winter. This happened from 2006 to 2013 years. Specially was studied as permanently specific form of birds is found in a particular humidity. The degree of coupling was studied using the amount of information that transmits to the local bird humidification. For 68 species of birds are the options of the population density, coefficient koligatsii and data communication with the seven variants of soil moisture. For all kinds of set information «price» of each option dampening that contributes to the formation of a particular community of birds. Thus, the defined contribution to the formation of soil moisture forest bird communities. Species representation and density gradient within the test moisture is not in direct linear relationship from moisture and ranges from 11 (very coldly) to 50 species (moist soil). The density of the community varies from 0,5 birds / hectare (very dry) to 269 birds / hectare (fresh soil). The strongest link between the information and the formation of moisture gradient structure avifauna is typical in a fresh soil – bird on the edge, and wet – forest representatives. These types of humidification function is performed starting in the formation of two major blocks dendrophilous community. The steppe birds give way to forest representatives when the soil slightly moist. The main conclusion of our study includes the following: than wetter the soil the more species of birds lives in the forest; some graduation humidity are the most important for separate species of birds; it is very important for birds, there are places where one can drink water. Further invasive alien species can occur where the soil is moist. Forest with dry soil is already fully occupied by birds.

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