Search Results (30)

The response of the desert cyanobacterium Chroococcidiopsis sp. CCMEE 010 was tested in Mars simulations to investigate the possibility of photosynthesis in near-surface protected niches. This cyanobacterium colonizes lithic niches enriched in far-red light (FRL) and depleted in visible light (VL) and is capable of far-red light photoacclimation (FaRLiP). Biofilms were grown under FRL and VL and exposed in a hydrated state to a low-pressure atmosphere, variable humidity, and UV irradiation, as occur on the Martian surface. VL biofilms showed a maximum quantum efficiency that dropped after 1 h, whereas a slow reduction occurred in FRL biofilms up to undetectable after 8 h, indicating that UV irradiation was the primary cause of photoinhibition. Post-exposure analyses showed that VL and FRL biofilms were dehydrated, suggesting that they entered a dried, dormant state and that top-layer cells shielded bottom-layer cells from UV radiation. After Mars simulations, the survivors (12% in VL biofilms and few cells in FRL biofilms) suggested that, during the evolution of Mars habitability, near-surface niches could have been colonized by phototrophs utilizing low-energy light. The biofilm UV resistance suggests that, during the loss of surface habitability on Mars, microbial life-forms might have survived surface conditions by taking refuge in near-surface protected niches. Full article

The surface adhesion and stiffness of underlying substrates mediate the geometry, mechanics, and self-organization of expanding bacterial colonies. Recent studies have qualitatively indicted that stiffness may impact bacterial attachment and accumulation, yet the variation in the cell-to-surface adhesion with substrate stiffness remains to be quantified. Here, by developing a cell-level force–distance spectroscopy (FDS) technique based on atomic force microscopy (AFM), we simultaneously quantify the cell–surface adhesion and stiffness of the underlying substrates to reveal the stiffness-dependent adhesion of the phototrophic bacterium Chromatium okenii. As the stiffness of the soft substrate, modeled using a low-melting-point (LMP) agarose pad, was varied between 20 kPa and 120 kPa by changing the agarose concentrations, we observed a progressive increase in the mean adhesion force by over an order of magnitude, from $0.21\pm 0.10$ nN to $2.42\pm 1.16$ nN. In contrast, passive polystyrene (PS) microparticles of comparable dimensions showed no perceptible change in their surface adhesion, confirming that the stiffness-dependent adhesive interaction of C. okenii is of a biological origin. Furthermore, for Escherichia coli, the cell–surface adhesion varied between $0.29\pm 0.17$ nN and $0.39\pm 0.20$ nN, showing a weak dependence on the substrate stiffness, thus suggesting that stiffness-modulated adhesion is a species-specific trait. Finally, by quantifying the adhesion of the C. okenii population across different timescales, we reported the emergent co-existence of weak and strongly adherent sub-populations, demonstrating diversification of the adherent phenotypes over the growth stages. Taken together, these findings suggest that bacteria, depending on the species and their physiological stage, may actively modulate cell-to-surface adhesion in response to the stiffness of soft surfaces. While the surface properties, for instance, hydrophobicity (or hydrophilicity), play a key role in mediating bacterial attachment, this work introduces substrate stiffness as a biophysical parameter that could reinforce or suppress effective surface interactions. Our results suggest how bacteria could leverage stiffness-dependent adhesion and the diversity therein as functional traits to modulate their initial attachment to, colonization of, and proliferation on soft substrates during the early stages of biofilm development. Full article

Thermomineral springs are unique aquatic habitats characterized by high temperatures or mineral-rich water and often host specialized microbial communities. In Serbia, these springs represent an important but under-researched ecological resource whose diverse physicochemical properties are shaped by their geological context. In this study, the physical and chemical properties of Serbian thermomineral springs and their relationship with phototrophic communities in different substrates are investigated. Phototrophic biofilms were categorized into fully submerged and splash zone biofilms, with the former showing higher primary production. Cyanobacteria, Chlorophyta, and Bacillariophyta were recorded, with Bacillariophyta being the predominant division in terms of diversity, followed by Cyanobacteria. Among Cyanobacteria, coccoid forms like Aphanocapsa, Chroococcus, Gloeocapsa and Synechococcus dominated splash zones, while trichal forms such as Leptolyngbya, Oscillatoria and Pseudanabaena were abundant in submerged biofilms, forming thick mats. Unique cyanobacterial taxa, including Desertifilum, Elainella, Geitlerinema, Nodosilinea and Wilmottia, were identified through molecular analysis, underscoring the springs’ potential as habitats for specialized phototrophs. Diatom communities, dominated by Nitzschia and Navicula, exhibited site-specific species influenced by microenvironmental parameters. Statistical analysis revealed ammonia, total nitrogen, and organic carbon as key factors shaping community composition. This study enhances the understanding of these ecosystems, emphasizing their conservation importance and potential for biotechnological applications. Full article

The role of biofilms in the formation of ooids is a focal point of current research. This study synthesizes macroscopic data with microscopic observations to analyze the depositional environment and genesis of oolitic limestone within the Xuzhuang Formation at the Nangao section. Notably, cerebroid ooids with unique cortical morphologies have been discovered. Within the nucleus, cortex, and the lumps among the ooids, a high-density preservation of Girvanella has been identified. Clotted micrite structures have also been observed within the filler content. The findings suggest that phototrophic biofilms have facilitated the formation of oolitic limestone in this profile, offering direct evidence for the connection between the festooned cortical morphologies and biofilms. This study further questions the interpretation of clotted micrite structures as sponge remains. These insights significantly enhance our understanding of the causal factors behind ooid formation. Full article

Cyanobacteria are promising organisms for the sustainable production of various biotechnological interesting products. Due to their energy production via photosynthesis, the cultivation of cyanobacteria expands the CO₂ cycle. Most cyanobacteria form biofilms on surfaces in their natural environment by surrounding the cells with a self-produced matrix of extracellular polymeric substances (EPS) that hold the cells together. These special growth properties need special reactors for cultivation. By immobilizing cyanobacteria on carriers, systems currently established in industry could also be used for biofilm formers. Various artificial carriers for immobilized growth of cyanobacteria and microalgae have already been described in the literature. However, the use of waste materials or natural biodegradable carriers would be more sustainable and is, therefore, the focus of this study. Dried Luffa cylindrica, zeolite, and corn stalks were investigated for their use as carriers for cyanobacteria. L. cylindrica was shown to be an excellent natural carrier for (i) Anabaena cylindrica, (ii) Nostoc muscorum 1453-12a, and (iii) Nostoc muscorum 1453-12b. Higher or at least similar growth rates were achieved when cyanobacteria were cultivated with L. cylindrica compared to submerged cultivation. Additionally, the production of EPS and C-phycocyanin was increased at least 1.4 fold in all strains by culturing on L. cylindrica. The improved growth could be explained on the one hand by the high surface area of L. cylindrica and its properties, and, on the other hand, by the release of growth-promoting nutrients from L. cylindrica to the medium. Full article

Green microalgae, including those from the genus Lobosphaera, are exploited in various fields of biotechnology to obtain valuable fatty acids (e.g., arachidonic acid (C20:4, ARA)) for the production of infant formulae, food and feed additives. In nature, microalgae frequently exist in naturally immobilized state (as biofilms) with a limited cell division rate and increased stress resilience. In the fields of biotechnology, immobilization of microalgae on artificial cell carriers simplifies biomass harvesting and increases culture robustness and productivity. The choice of a suitable cell carrier is central to biotechnology involving immobilized cultures. Cell carriers based on the natural amine-containing polymer chitosan and synthetic polyethylenimine (PEI) are promising candidates for immobilization of phototrophic microorganisms. This is the first report on the effects of immobilization on PEI and chitosan on the accumulation and composition of polyunsaturated fatty acids, including ARA, in Lobosphaera sp. IPPAS C-2047. Immobilization on PEI increased the ARA percentage in the total fatty acids and ARA accumulation by 72% and 81% compared to the suspended cells cultured in complete or nitrogen-deprived medium 14 days, respectively. Immobilization of Lobosphaera sp. on the chitosan-based carrier reduced the ARA percentage but increased oleic and α-linoleic acid percentages. The mechanisms of the effects of immobilization on the fatty acid profiles of the microalgae are discussed. Full article

The imbalance of inorganic nutrients in micro-polluted source water poses a huge threat to aquatic environments and human health. To pretreat micro-polluted source water, some biological reactors have been conducted at lab-scale. However, using phototrophic biofilms to pretreat micro-polluted source water at pilot-scale has yet to be explored, and the effects of light on the practical operation of phototrophic biofilms are poorly understood. In this study, the potential of pretreating micro-polluted source water by phototrophic biofilms was explored. The high light intensity (4500 lx, 60.75 μmol/m²/s) promoted the growth of phototrophic biofilms and the secretion of extracellular polymeric substance. The removal efficiency of inorganic nitrogen and total phosphorus in synthetic micro-polluted water was 56.82% and 40.90%, respectively. When interacting with actual micro-polluted source water, the nutrients in the actual micro-polluted source water were reduced by the stable pilot-scale phototrophic biofilms. The final concentration of effluent nutrients was lower than the Grade II surface water quality standard in China. Therefore, using phototrophic biofilms as a pretreatment facility in water treatment plants is a promising solution to this issue. Full article

Unique natural objects, such as the caves of the Gobustan National Historical and Artistic Preserve, are also of great cultural and historical value due to rock art and sites of ancient people. A favorable microclimate makes these habitats convenient for colonization by microbiota, including phototrophs. In arid regions with intense seasonal fluctuations of microclimatic parameters, the conditions for survival are the least favorable; therefore, it becomes especially important to determine the composition of communities that are the most adapted to specific conditions. This work aimed to identify the biodiversity of communities of caves and grottoes of the Gobustan Reserve. The studies were carried out in July 2019. Samples were analyzed for cyanobacteria and algae by microscopy and cultivation methods, microfungi were isolated by soil dilution, and the fouling glass method was also used. In total, 29 taxa of cyanobacteria and algae, 18 taxa of fungi, and 3 species of mosses were identified. The studied habitats were dominated by the algae Chlorella vulgaris, Aphanocapsa sp., and Stichococcus bacillaris; the subdominants were Jaaginema subtilissimum, Leptolyngbya tenuis, Chlorococcum minutum, and Humidophila contenta. Microfungi had the highest occurrence of Aspergillus niger, Aureobasidium pullulans, Alternaria alternata, and Talaromyces ruber. It was noted that cyanobacteria dominated in morphologically differentiated biofilms and green algae on the rocks. The greatest number of microfungi was found in the aphotic zone and bryophyte tufts. The dominance of green algae is atypical for most caves of other regions and may be associated with intense lighting of habitats. The absence of protonema is a consequence of the aridity and low moisture content of the substrates. Full article

Microbial biofilms have co-evolved with grazing animals, such as gastropods, to develop mutually beneficial relationships. Although microbial biofilms demonstrate resilience and resistance to chemical exposure, pre-existing relationships can be negatively affected by chemical input. In this study, we determined how the grazer, Littorina littorea (common periwinkle sea snail), and a biological surfactant (rhamnolipid) interact on a phototrophic marine biofilm. Biofilms were cultured in 32 twenty-liter buckets at the Queen’s University Marine Laboratory in Portaferry, Northern Ireland on clay tiles that were either exposed to 150 ppm of a rhamnolipid solution or that had no chemical exposure. L. littorea were added into half of the buckets, and biofilms were developed over 14 days. Biofilms exposed to grazing alone demonstrated high tolerance to the disturbance, while those growing on rhamnolipid-exposed substrate demonstrated resistance but experienced slight declines in carbon and stoichiometric ratios. However, when exposed to both, biofilms had significant decreases in stoichiometry and declined in productivity and respiration. This is problematic, as continuing marine pollution increases the likelihood that biofilms will be exposed to combinations of stressors and disturbances. Loss of biofilm productivity within these areas could lead to the loss of an important food source and nutrient cycler within the marine ecosystem. Full article

Show caves have different grades of colonization by phototrophic biofilms. They may receive a varied number of visits, from a few thousand to hundreds of thousands of visitors annually. Among them, Tesoro Cave, Rincon de la Victoria, Spain, showed severe anthropic alterations, including artificial lighting. The most noticeable effect of the lighting was the growth of a dense phototrophic community of cyanobacteria, algae and bryophytes on the speleothems, walls and ground. The biofilms were dominated by the cyanobacterium Phormidium sp., the chlorophyte Myrmecia israelensis, and the rhodophyte Cyanidium sp. In many cases, the biofilms also showed an abundance of the bryophyte Eucladium verticillatum. Other cyanobacteria observed in different biofilms along the cave were: Chroococcidiopsis sp., Synechocystis sp. and Nostoc cf. edaphicum, the green microalgae Pseudococcomyxa simplex, Chlorella sp. and the diatom Diadesmis contenta. Preliminary cleaning tests on selected areas showed the effectiveness of hydrogen peroxide and sodium hypochlorite. A physicochemical treatment involving the mechanical removal of the thickest layers of biofilms was followed by chemical treatments. In total, 94% of the surface was cleaned with hydrogen peroxide, with a subsequent treatment with sodium hypochlorite in only 1% of cases. The remaining 5% was cleaned with sodium hypochlorite in areas where the biofilms were entrapped into a calcite layer and in sandy surfaces with little physical compaction. The green biofilms from the entire cave were successfully cleaned. Full article

European caves contain some of the world’s greatest Paleolithic paintings, and their conservation is at risk due to the use of artificial lighting. Both lighting and high CO₂ promotes the growth of phototrophic organisms on walls, speleothems and ground sediments. In addition, the combined effect of increases in CO₂, vapor concentration and temperature variations induced by visitors can directly affect the development of corrosion processes on the cave rock surfaces. An early detection of the occurrence of phototrophic biofilms on Paleolithic paintings is of the utmost importance, as well as knowing the microorganisms involved in the colonization of rocks and walls. Knowledge of the colonizing species and their ecology will allow the adoption of control measures. However, this is not always possible due to the limited amount of biomass available for molecular analyses. Here, we present an alternative approach to study faint green biofilms of Chlorophyta in the initial stage of colonization on the Polychrome Panel in El Castillo Cave, Cantabria, Spain. The study of the biofilms collected on the rock art panel and in the ground sediments revealed that the lighting of the cave promoted the development of the green algae Jenufa and Coccomyxa, as well as of complex prokaryotic and eukaryotic communities, including amoebae, their endoparasites and associated bacteria and fungi. The enrichment method used is proposed as a tool to overcome technical constraints in characterizing biofilms in the early stages, allowing a preliminary characterization before deciding for direct or indirect interventions in the cave. Full article

The removal of biological colonization on building materials of cultural heritage is a difficult challenge, as the treatment must completely eliminate the biological patina without altering the treated substrate and possibly delaying new colonization. With the aim of searching for systems to minimize the biocide impact on the substrate, the environment and the operators, different alginate–oxidizing biocide hydrogels were previously tested and optimized in the laboratory and here selected for application in situ. The churches “San Pietro Barisano” and “Madonna dei Derelitti”, located in the Sassi of Matera (UNESCO World Heritage Site in Basilicata region, Italy), were chosen as case studies. They differ in terms of both the environmental conditions and the microorganisms responsible for colonization. Colorimetric measurements and microscopic investigation proved the efficacy of biocide hydrogels in removing biopatinas and in restoring the original chromaticity of the selected treated surfaces of both sites. After the biocidal treatments, new protective acrylic coatings were applied to prevent recolonization and minimize the loss of material grains. Samples collected, immediately after and two years later, established the absence of biological colonization, demonstrating the long-term efficacy of the proposed restoration protocol. Full article

Lampenflora, a complex phototrophic community that develops near artificial light in show caves, is recognized as a major concern for cave management and its regular monitoring has become necessity. For the purpose of this work, the monitoring was performed in one of the most visited show caves in Serbia—Resavska Cave, directly before and after the main season in 2021 in March and November. Lampenflora was localized and developed mainly near the artificial light, but further parts of the cave were not affected by it. Different sampling sites (twelve in total) regarding the type of artificial light and the type of biofilm were chosen for the lampenflora sampling. Two biofilm types were recognized in situ: the epilithic/endolithic ones which were dominated by algae and/or Cyanobacteria and the moss-dominated biofilms. An analysis of the phototrophic microorganisms revealed the presence of Cyanobacteria, Chlorophyta and Bacillariophyta. The highest diversity was found among the Cyanobacteria where the genera Aphanocapsa, Eucapsis, Gloeocapsa and Leptolyngbya were recorded during both of the samplings, Nostoc and Synechocystis were recorded in March, while Hassalia, Oscillatoria and Pseudocapsa were only recorded in November. Chlorophyta were represented by Chlorella, Desmococcus, Klebsormidium, Mesotaenium and Stichococcus in March, and they were represented by same taxa except for Klebsormidium in November. Humidophila was the most widespread diatom in the fresh biofilm samples. Aside from there being higher a level of diversity of it, Cyanobacteria were sporadically found in the samples except on two sampling sites where Aphanocapsa cf. muscicola and Hassalia sp. were abundant. Chlorophyta dominated the samples, which is in accordance with many other studies. The ecological parameters—temperature, relative air humidity, light intensity, substratum moisture and substratum pH were also determined and related to a degree of colonization and the community composition. Full article

Cyanobacteria are ubiquitous phototrophic prokaryotes that find a wide range of applications in industry due to their broad product spectrum. In this context, the application of cyanobacteria as biofertilizers and thus as an alternative to artificial fertilizers has emerged in recent decades. The benefit is mostly based on the ability of cyanobacteria to fix elemental nitrogen and make it available to the plants in a usable form. However, the positive effects of co-cultivating plants with cyanobacteria are not limited to the provision of nitrogen. Cyanobacteria produce numerous secondary metabolites that can be useful for plants, for example, they can have growth-promoting effects or increase resistance to plant diseases. The effects of biotic and abiotic stress can as well be reduced by many secondary metabolites. Furthermore, the biofilms formed by the cyanobacteria can lead to improved soil conditions, such as increased water retention capacity. To exchange the substances mentioned, cyanobacteria form symbioses with plants, whereby the strength of the symbiosis depends on both partners, and not every plant can form symbiosis with every cyanobacterium. Not only the plants in symbiosis benefit from the cyanobacteria, but also vice versa. This review summarizes the beneficial effects of cyanobacterial co-cultivation on plants, highlighting the substances exchanged and the strength of cyanobacterial symbioses with plants. A detailed explanation of the mechanism of nitrogen fixation in cyanobacterial heterocysts is given. Finally, a summary of possible applications of co-cultivation in the (agrar-)industry is given. Full article

Phototrophic biofilms, in particular terrestrial cyanobacteria, offer a variety of biotechnologically interesting products such as natural dyes, antibiotics or dietary supplements. However, phototrophic biofilms are difficult to cultivate in submerged bioreactors. A new generation of biofilm photobioreactors imitates the natural habitat resulting in higher productivity. In this work, an aerosol-based photobioreactor is presented that was characterized for the cultivation of phototrophic biofilms. Experiments and simulation of aerosol distribution showed a uniform aerosol supply to biofilms. Compared to previous prototypes, the growth of the terrestrial cyanobacterium Nostoc sp. could be almost tripled. Different surfaces for biofilm growth were investigated regarding hydrophobicity, contact angle, light- and temperature distribution. Further, the results were successfully simulated. Finally, the growth of Nostoc sp. was investigated on different surfaces and the biofilm thickness was measured noninvasively using optical coherence tomography. It could be shown that the cultivation surface had no influence on biomass production, but did affect biofilm thickness. Full article