Search Results (14)

Biofilms are structurally organized communities of microorganisms that adhere to a variety of surfaces. These communities produce protective matrices consisting of polymeric polysaccharides, proteins, nucleic acids, and/or lipids that promote shared resistance to various environmental threats, including chemical, antibiotic, and immune insults. While algal and bacterial biofilms are more apparent in the scientific zeitgeist, many fungal pathogens also form biofilms. These surprisingly common biofilms are morphologically distinct from the multicellular molds and mushrooms normally associated with fungi and are instead an assemblage of single-celled organisms. As a collection of yeast and filamentous cells cloaked in an extracellular matrix, fungal biofilms are an extreme threat to public health, especially in conjunction with surgical implants. The encapsulated yeast, Cryptococcus neoformans, is an opportunistic pathogen that causes both pulmonary and disseminated infections, particularly in immunocompromised individuals. However, there is an emerging trend of cryptococcosis among otherwise healthy individuals. C. neoformans forms biofilms in diverse environments, including within human hosts. Notably, biofilm association correlates with increased expression of multiple virulence factors and increased resistance to both host defenses and antifungal treatments. Thus, it is crucial to develop novel strategies to combat fungal biofilms. In this review, we discuss the development and treatment of fungal biofilms, with a particular focus on C. neoformans. Full article

Climate change and nutrient enrichment are increasing the frequency of algal blooms, with sometimes significant impacts on coastal ecosystems. Haslea ostrearia blooms have been documented in oyster ponds and are not harmful, yet their effects in open environments remain underexplored. Marennine, a blue pigment produced by H. ostrearia, can display a range of biological properties in laboratory conditions, including antibacterial and allelopathic properties. Other blue Haslea species, forming blooms, synthesize bioactive marennine-like pigments. This study aims to understand if and how these blooms could affect the underlying community of microorganisms living in the biofilms. Morphological and molecular techniques were used to assess community dynamics during bloom events. Our findings indicate that blue Haslea blooms do not significantly alter the diatom or bacterial populations. However, they are paired with enhanced alpha diversity in the microbial communities. These observations suggest a complex interaction between bloom events and microbial dynamics. Additionally, this study expands our understanding of the bioactive properties of marennine-like pigments and their ecological roles, suggesting new avenues for biotechnological applications. This work underscores the importance of further research into the environmental and biological implications of blue Haslea blooms. Full article

Currently, the water ecological environment is severely polluted and traditional bioreactors have issues with high energy consumption and greenhouse gas emissions. However, a promising solution is the bacterial–algal reactor, which is a green bioreactor that can simultaneously treat sewage and fix CO₂. The main configurations of bacterial–algal reactors, including several types, activated sludge, biofilm, batch biofilm–sludge reactor coupled with activated sludge method, and bacterial–algal open reactor, have been reviewed. The performance of these reactors in reducing pollutants and carbon emissions during wastewater treatment has been investigated. Additionally, the technical advantages of coupling a bacterial–algal symbiosis system with a conventional bioreactor have been analyzed. The interaction mechanism of the bacterial–algal system in various reactors has also been elaborated. The bacterial–algal reactor improves pollutant removal efficiency through assimilation and absorption of pollutants by microalgae, and reduces aeration by releasing oxygen through photosynthesis of microalgae. Finally, the existing problems in the practical application of bacterial–algal reactors have been summarized, and future research directions have been suggested, providing theoretical support for the future application of bacterial–algal reactors and directions for optimal design and development of bacterial–algal symbiotic reactors. Full article

In this study, an algal–bacterial symbiotic consortium was integrated with the sediment microbial fuel cell (SMFC) to construct an algal–bacterial cathode SMFC (AC-SMFC) for excess sewage sludge treatment and electricity generation. A bacterial cathode SMFC (BC-SMFC) and a static settling system (SS-system) were used as controls. Electrochemical analysis confirmed that the algal–bacterial biofilm on the cathode improved electricity production. The maximum power density of AC-SMFC was 75.21 mW/m², which was 65.70% higher than that of the BC-SMFC (45.39 mW/m²). After 60 days of treatment, AC-SMFC achieved much higher removal efficiencies of the total chemical oxygen demand (TCOD) (59.60%), suspended solids (SS) (62.42%), and volatile suspended solids (VSS) (71.44%) in the sediment, compared to BC-SMFC and the SS-system, exhibiting an effective degradation of the organic matter in the sediment sludge. Moreover, the lower concentration of total nitrogen (TN) and total phosphorus (TP) in the overlying water of AC-SMFC demonstrated that the algae on the cathode could inhibit the accumulation of nitrogen and phosphorus released from the sediments. The three-dimensional excitation–emission matrix (EEM) fluorescence spectroscopy revealed that the tryptophan protein and aromatic protein in the loosely bound extracellular polymeric substances (LB-EPS) of the sediment sludge in the AC-SMFC were significantly decreased. Additionally, the abundance of functional microbiota in the AC-SMFC increased, such as Trichococcus, Alphaproteobacteria, and Clostridia, which contributed to electricity generation and sludge degradation. The combined application of microalgae and the SMFC provided a promising approach for excess sludge reduction and energy recovery. Full article

Magnesium oxide nanoparticles (MgO NPs) have emerged as potential materials for various biomedical applications due to their unique physicochemical properties, including biodegradability, biocompatibility, cationic capacity, high stability and redox properties. MgO NPs have become an attractive platform to combat microbes and may be a promising alternative to overcome challenges associated with eliminating microbial biofilms and antibiotic resistance. Hence, due to the increasing use of MgO NPs in biomedicine, new synthetic strategies for MgO NPs are necessary. MgO NPs synthesised using green methods are non-toxic, eco-friendly and have high stability for a wide range of biological, medical and catalytic applications. This review presents the recent advances in biosynthesis strategies of MgO NPs by diverse bio-templates, such as plant, bacterial, fungal and algal extracts. Its photocatalytic properties show a suitable inhibitory function against pathogenic agents, such as microbial proliferation, biofilm formation and fungal growth. Furthermore, MgO NPs and relevant nanocomposites are comprehensively discussed regarding the mechanisms of their effect on microbes, biofilms and fungal strains, as well as challenges and future perspectives. Full article

Caves present unique habitats for the development of microbial communities due to their peculiar environmental conditions. In caves decorated with frescoes, the characterization of microbial biofilm is important to better preserve and safeguard such artworks. This study aims to investigate the microbial communities present in the Fornelle Cave (Calvi Risorta, Caserta, Italy) and their correlation with environmental parameters. The cave walls and the wall paintings have been altered by environmental conditions and microbial activity. We first used light microscopy and scanning electron microscopy (SEM) and X-ray diffraction to characterise the biofilm structure and the mineral composition of substrata, respectively. Then, using both culture-dependent (Sanger sequencing) and culture-independent (automated ribosomal intergenic spacer analysis, ARISA) molecular methods, we demonstrated that the taxonomic composition of biofilms was different across the three substrata analysed and, in some cases, positively correlated with some environmental parameters. We identified 47 taxa in the biofilm samples, specifically 8 bacterial, 18 cyanobacterial, 14 algal and 7 fungal taxa. Fungi showed the highest number of ARISA types on the tuff rock, while autotrophic organisms (cyanobacteria and algae) on the frescoes exposed to light. This study confirms that caves constitute a biodiversity-rich environment for microbial taxa and that, in the presence of wall paintings, taxonomic characterization is particularly important for conservation and restoration purposes. Full article

The “University of Coimbra-Alta and Sofia” area was awarded the UNESCO World Heritage Site distinction in 2013. The Old Cathedral of Coimbra, a 12th-century limestone monument located in this area, has been significantly impacted during the last 800 years by physical, chemical, and biological processes. This led to the significant deterioration of some of its structures and carvings, with loss of aesthetical, cultural, and historical values. For this work, deteriorated spots of the walls of three semi-open chapels from the cloister of the Cathedral were sampled to ascertain their bacterial and archaeal structural diversity. Based on Next-Generation Sequencing (NGS) result analysis, we report the presence of microbial populations that are well adapted to an ecosystem with harsh conditions and that can establish a diverse biofilm in most cases. While it was possible to determine dominant phylogenetic groups in Archaea and Bacteria domains, there was no clear connection between specific core microbiomes and the different deterioration patterns analyzed. The distribution of these archaeal and bacterial communities within the analyzed biodeterioration spots suggests they are more influenced by abiotic factors (i.e., water availability, salinity, etc.), although they influence (and are influenced by) the algal and fungal population composition in this ecosystem. This work provides valuable information that can assist in establishing future guidelines for the preservation and conservation of this kind of historic stone monuments. Full article

Agriculture delivers significant amounts of dissolved organic matter (DOM) to streams, thereby changing the composition and biodegradability of the aquatic DOM. This study focuses on the interactive effects of DOM quality and biofilm composition on the degradation of DOM in a laboratory flume experiment. Half of the flumes were exposed to light to stimulate algal growth, the other half was shaded. Leachates of deciduous leaves, maize leaves, and cow dung were added to the flumes in a single pulse and changes of DOC (dissolved organic carbon) and nutrient concentrations, DOM composition (absorbance and fluorescence data), chlorophyll-a concentrations, bacterial abundances, and enzymatic activities were recorded over a week. DOM was taken up with rates of 50, 109, and 136 µg DOC L⁻¹ h⁻¹ for dung, leaf, and maize leachates, respectively, in the light flumes and 37, 80, and 170 µg DOC L⁻¹ h⁻¹ in the dark flumes. DOC uptake correlated strongly with initial SRP (soluble reactive phosphorus) and DOC concentrations, but barely with DOM components and indices. Algae mostly stimulated the microbial DOC uptake, but the effects differed among differently aged biofilms. We developed a conceptual model of intrinsic (DOM quality) and external (environmental) controlling factors on DOM degradation, with the microbial community acting as biotic filter. Full article

The discharge of aquaculture wastewater and the excessive selenium in aquaculture effluent caused by selenium addition to aquatic feed are posing a serious risk for the marine environment. In this study, batch tests were carried out to investigate the feasibility of utilizing algal–bacterial biofilm for the treatment of selenium-rich aquaculture wastewater. The effects of four different types of commercial biofilm carriers on the attached growth of biofilms and the contaminant removal capacity were examined. The braided cotton biofilm carrier had the best performance on biofilm growth, while in an exponential growth period the dry weight density of the biofilm was above 2.0 g L⁻¹. By utilizing the braided cotton carrier with a hydraulic retention time (HRT) of 6 days, the removal rate of N and P from the raw aquaculture wastewater was 88.5 ± 6.2% and 99.8 ± 0.2%, respectively. After that, the effects of different initial wastewater load ratios (IWLR) and HRT on the effluent quality of the treatment process were studied. The decrease in IWLR and the extension of HRT could improve the treatment performance. The effluent N, P and Se concentrations in the group with 50% IWLR and 6-day HRT were 0.75 ± 0.10 mg L⁻¹, 0.015 ± 0.02 mg L⁻¹, 35.2 ± 3.2 μg L⁻¹, respectively, indicating an effective removal of the main contaminants. The algal–bacterial biofilm harvested from the batch test was rich in N, P and Se, where the Se content was 21.8 ± 3.4 mg kg⁻¹, which has the potential to be used as an Se-rich biofertilizer. Full article

The majority of studies on biofilms have focused on autotrophic and bacterial taxa, without considering the potential effects on biofilm grazers. In this work, we investigated the effects of realistic environmental concentrations of zirconium (Zr) on periphyton algal growth and micromeiofauna biodiversity. Glass slides were submerged in a pond for four weeks to colonize biofilms and exposed for four weeks in aquaria to targeted Zr concentrations of 0, 1, and 10 nM, which were monitored over time (average measured concentrations were 0.2 ± 0.1, 0.5 ± 0.3, and 2.9 ± 0.3 nM Zr). The four-week exposure to the highest concentration (3 nM) affected the micromeiofauna structure of biofilms and modified the autotrophic biofilm structure by increasing the proportion of green algae and decreasing the abundance of cyanobacteria and brown algae. Rotifers and the ciliate Aspidisca cicada appeared to be the most sensitive organisms among the observed micromeiofauna. A toxic effect of Zr on rotifers could explain such results. Indirect effects, such as reduced food availability given the reduced algal growth in the presence of Zr, could also play a role in the changes of micromeiofauna community structure. These results are among the few published data on the effects of Zr. Full article

Photosynthetic performance of algal-bacterial biofilms from an Italian wastewater treatment plant was studied in a flow-lane photobioreactor at different irradiances, temperatures, and flow regime to evaluate the effects of these environmental parameters on biofilms’ functioning, in view of application of these communities in wastewater biological treatment. Pulse amplitude modulated fluorescence was used to estimate the effective quantum yield of PSII (ΔF/F_m’) of the light-acclimated biofilms and to perform rapid light curves (RLCs) for the determination of the photosynthetic parameters (rel.ETR_max, α, I_k). Chl a, ash free dry weight (AFDW), and dry weight (DW) were measured to assess phototrophic and whole biofilm biomass development over time. From the analysis of photosynthetic parameter variation with light intensity, temperature and flow rate, it was possible to identify the set of experimental values favoring biofilm photosynthetic activity. Biomass increased over time, especially at the highest irradiances, where substrata were fastly colonized and mature biofilms developed at all temperatures and flow conditions tested. Full article

Traditional aquaculture provides food for humans, but produces a large amount of wastewater, threatening global sustainability. The antibiotics abuse and the water replacement or treatment causes safety problems and increases the aquaculture cost. To overcome environmental and economic problems in the aquaculture industry, a lot of efforts have been devoted into the application of microalgae for wastewater remediation, biomass production, and water quality control. In this review, the systematic description of the technologies required for microalgae-assisted aquaculture and the recent progress were discussed. It deeply reviews the problems caused by the discharge of aquaculture wastewater and introduces the principles of microalgae-assisted aquaculture. Some interesting aspects, including nutrients assimilation mechanisms, algae cultivation systems (raceway pond and revolving algal biofilm), wastewater pretreatment, algal-bacterial cooperation, harvesting technologies (fungi-assisted harvesting and flotation), selection of algal species, and exploitation of value-added microalgae as aquaculture feed, were reviewed in this work. In view of the limitations of recent studies, to further reduce the negative effects of aquaculture wastewater on global sustainability, the future directions of microalgae-assisted aquaculture for industrial applications were suggested. Full article

Biofilms are important components of the mercury (Hg) biogeochemical cycle. However, Hg effects on biofilm communities are overlooked. Here, we present results of a pilot study on the chronic effects of Hg on biofilms, notably on the potential change of their taxonomic composition. Biofilms were cultivated in microcosms enriched with three different Hg concentrations (11 ± 2 pM, 121 ± 9 pM and 1454 ± 54 pM) for 55 days and examined for their accumulated Hg concentrations and composition. Bioaccumulated Hg concentrations were representative of those encountered in natural environments. Despite the lack of influence on the ash free dry weight and chlorophyll content, the surface coverage of the substrata of biofilms grown in Hg decreased. Algal community were strongly affected by Hg, with a decrease in their richness with Ochrophyta found as the most sensitive phyla. The diversity and richness of bacterial communities did not change upon cultivation in Hg but the presence of Proteobacteria increased with Hg, whereas Bacteroidetes, Actinobacteria, Verrumicrobia, and Cyanobacteria were negatively impacted. Overall, the above findings suggest that the examination of the algal community composition might be used as a potential biomonitoring tool to assess the impacts of environmental Hg concentrations on aquatic systems, which would merit further investigation. Full article

This study provides data to define an efficient biocide-free strategy based on zosteric acid to counteract biofilm formation on the membranes of submerged bioreactor system plants. 16S rRNA gene phylogenetic analysis showed that gammaproteobacteria was the prevalent taxa on fouled membranes of an Italian wastewater plant. Pseudomonas was the prevalent genus among the cultivable membrane-fouler bacteria and Pseudomonas putida was selected as the target microorganism to test the efficacy of the antifoulant. Zosteric acid was not a source of carbon and energy for P. putida cells and, at 200 mg/L, it caused a reduction of bacterial coverage by 80%. Biofilm experiments confirmed the compound caused a significant decrease in biomass (−97%) and thickness (−50%), and it induced a migration activity of the peritrichous flagellated P. putida over the polycarbonate surface not amenable to a biofilm phenotype. The low octanol-water partitioning coefficient and the high water solubility suggested a low bioaccumulation potential and the water compartment as its main environmental recipient and capacitor. Preliminary ecotoxicological tests did not highlight direct toxicity effects toward Daphnia magna. For green algae Pseudokirchneriella subcapitata an effect was observed at concentrations above 100 mg/L with a significant growth of protozoa that may be connected to a concurrent algal growth inhibition. Full article