Microbial Community Structure Of Biofilms Research Articles

Response of submerged macrophytes and leaf biofilms to different concentrations of oxytetracycline and sulfadiazine

Oxytetracycline and sulfadiazine were widely used and they entered the environment through various channels such as domestic sewage, medical wastewater and agricultural wastewater, causing significant ecological risk. To determine the effects of different antibiotic concentrations on submerged macrophytes, Vallisneria natans was exposed to solutions containing different concentrations of oxytetracycline and sulfadiazine (0.1 mg/L、1 mg/L、10 mg/L、50 mg/L). After 20-days exposure, we found that 10 mg/L groups had a significant effect on Vallisneria natans. Under high antibiotic concentrations, the growth of Vallisneria natans was inhibited, chloroplasts were deformed, the chlorophyll content was reduced, and antioxidant enzyme activities, such as superoxide dismutase and glutathione, were increased. There was no significant difference between the control group and groups with low antibiotic concentrations (≤1 mg/L). The N-acyl-l-homoserine lactone concentration tended to increase with increasing antibiotic concentrations. The presence of antibiotics also affected the microbial community structure of biofilms on the submerged macrophytes. For example, the higher the concentration of antibiotics, the higher the proportion of Proteobacteria. These results suggest that high concentrations of oxytetracycline and sulfadiazine can disrupt homeostasis, induce effective Vallisneria natans defense mechanisms and alter biofilms in aquatic ecosystems.

New quorum quenching bacteria for controlling biofilm thickness in the membrane aerated biofilm reactor

The uncontrolled increase of biofilm thickness on the membrane surface directly affects substrate diffusion rate, pollutant removal efficiency, and microbial ecology of the membrane aerated biofilm reactor (MABR). This study aimed to control the biofilm growth using a promising antifouling strategy called quorum quenching (QQ). For this purpose, new QQ bacteria (Bacillus methylotrophicus BT1, Klebsiella pneumoniae BT2, Lysinibacillus fusiformis BT3, and Achromobacter xylosoxidans BT4) were isolated and immobilized to control the biofilm thickness on the membrane fibers in MABR. The Bacillus methylotrophicus BT1 with the highest QQ activity disrupted bacterial communication among microorganisms, provided a relatively thin and dense biofilm thickness (250 µm), and exhibited the best MABR performance. The amount of EPS secreted by the microorganisms significantly decreased due to the increase in the QQ activities of the QQ bacteria. A significant COD removal performance improvement of 74.5% compared to the control-MABR was achieved by MABR containing BT1. Microbial analysis revealed a change in the microbial community structure of biofilms in the MABRs containing different QQ bacteria. In conclusion, the newly isolated QQ bacteria effectively could be controlled biofilm formation on the membrane fibers in MABR systems, and the results obtained can form the basis for larger-scale studies.

Effects of sodium citrate on the structure and microbial community composition of an early-stage multispecies biofilm model

In recent years, most biofilm studies have focused on fundamental investigations using multispecies biofilm models developed preferentially in simulated naturally occurring low-nutrient medium than in artificial nutrient-rich medium. Because biofilm development under low-nutrient growth media is slow, natural media are often supplemented with an additional carbon source to increase the rate of biofilm formation. However, there are knowledge gaps in interpreting the effects of such supplementation on the resulting biofilm in terms of structure and microbial community composition. We investigated the effects of supplementation of a simulated freshwater medium with sodium citrate on the resulting structure, bacterial community composition, and microbial network interactions of an early-stage multispecies biofilm model. Qualitative and quantitative analyses of acquired confocal laser scanning microscopy data confirmed that sodium citrate supplementation distinctly increased biofilm biomass. Sequencing data revealed that the microbial community structure of biofilms grown in sodium citrate-supplemented conditions was characterized with increased relative abundance and dominance of Proteobacteria compared with that of biofilms grown in sodium citrate-free conditions. Our findings suggest that the supplementation of a low-nutrient medium with a carbon source in experiments involving multispecies biofilms may lead to structural and compositional biases of the microbial community, causing changes in biofilm phenotype.

Seasonality combined with the orientation of surfaces influences the microbial community structure of biofilms in the deep Mediterranean Sea

Seasonality combined with the orientation of surfaces influences the microbial community structure of biofilms in the deep Mediterranean Sea

Seasonality combined with the orientation of surfaces influences the microbial community structure of biofilms in the deep Mediterranean Sea

Attachment to surfaces represents an important life strategy for microbial communities as indicated by the rapid colonization of biotic and abiotic surfaces in marine waters. However, little attention has been paid to the development of biofilm-associated microbial communities and the environmental parameters influencing biofilm development in the deep sea. In this study, a deep-sea experimental setup was used to follow the development of the microbial community colonizing solid surfaces deployed at 4500 m depth at the deepest point of the Mediterranean Sea. The experiment was performed during summer (May to October 2007) and winter (October 2007–May 2008), each lasting for 155 d. The phylogenetic composition of the biofilm community was determined by tag sequencing of the 16S rRNA gene. We investigated whether the composition of the deep-sea microbial biofilms is influenced by seasonality. Based on tag sequencing, operational taxonomic units were identified and diversity indices calculated. Seasonality combined with the orientation of the solid surface on which the biofilms were growing was the main factor influencing the structure of the microbial community. The most abundant phyla of deep-sea biofilm communities attached to the solid surfaces were Gammaproteobacteria (range: 10.8%–92.6%), Alphaproteobacteria (range: 34.9%–92.6%) and Betaproteobacteria (range: 0.3%–2.1%), irrespective of the variables (surface, orientation, season). Flavobacteria and Epsilonbacteria show a clear preference with respect to the orientation of the deployed surfaces during the winter, however, they were essentially absent at the surfaces during the summer. Some bacterial classes such as Campylobacterales and Rhodobacterales showed distinct preferences for specific seasons or orientation of the substrate. Taken together, we conclude that even on deep-sea biofilms, there is to some extent seasonality detectable in the composition of the surface associated prokaryotic community, despite the fact that the deep-sea is, in terms of physico-chemical parameters, a fairly stable environment.

Allelopathic effects of harmful algal extracts and exudates on biofilms on leaves of Vallisneria natans

This study investigated the allelopathic effects of Microcystis aeruginosa (M. aeruginosa) extracts and exudates on the physiological responses, photosynthetic activity, and microbial structure of biofilms on leaves of Vallisneria natans (V. natans). By measuring physiological and photosynthetic indices, the results showed that M. aeruginosa allelochemicals inhibited photosynthesis, oxidative stress and antioxidant system stress response in the biofilms of V. natans leaves. Multifractal analysis found that the surface topography of V. natans leaves was altered due to the allelochemicals found in M. aeruginosa. Microbial diversity on the leaves was analyzed using high-throughput sequencing, and the results showed that M. aeruginosa exudates had a stronger effects on the microbial community structure of biofilms compared to extracts. These findings highlight how cyanobacterial allelochemicals induce negative effects on submerged macrophytes.

Low-temperature anaerobic digestion enhanced by bioelectrochemical systems equipped with graphene/PPy- and MnO2 nanoparticles/PPy-modified electrodes

Bioelectrochemical systems (BESs) with graphene (Gr)/polypyrrole (PPy)- and MnO2 nanoparticles (NPs)/PPy-modified electrodes were developed to enhance low-temperature anaerobic digestion (LTAD) of low-strength wastewater. At 20 °C, the chemical oxygen demand removal efficiencies and CH4 yield of the BESs with Gr/PPy (R2) and MnO2 NPs/PPy (R3)-modified electrodes were 12.7% and 25.6%, and 43.9% and 66.3%, respectively, higher than those of the control (R1, without modification). Although the performance of all reactors decreased as temperature dropping to 12 °C, the CH4 yield rates of R2 and R3 were still 22.8% and 39.0% higher than that of R1. Further analysis indicated that the modified electrodes might stimulate the metabolic activity of the anaerobic digester sludge. Scanning electron microscopy observation showed that the modified electrodes had higher specific surface area, favoring the attachment and formation of dense biofilms on the surface of electrodes. 16S rRNA gene-sequencing results demonstrated that H2-consuming methanogens dominated in the BESs and the influence of Gr/PPy and MnO2 NPs/PPy differed on the microbial community structure of biofilms. These findings justify the wider use of Gr and MnO2 NPs in electrode modification to assist LTAD using BESs.

Response of the microbial community structure of biofilms to ferric iron in microbial fuel cells

Ferric iron can affect the current generation of microbial electrochemical system (MES); however, how it influences microbial biofilm formation and metabolic activity has not been reported. Here, we describe the response of microbial electrode biofilm communities to insoluble ferric iron (Fe3+) at different concentrations in microbial fuel cells (MFCs). Insoluble ferric iron (200μM) improved electrochemical activity of the MFCs microbial biofilms during start-up and resulted in a higher maximum power density of 0.95W/m2, compared with the control (0.76W/m2), 500μM Fe3+ (0.83W/m2), 1000μM Fe3+ (0.73W/m2), and 2000μM Fe3+ (0.59W/m2) treatments. Illumina Hiseq sequencing of 16S rRNA gene amplicons indicated that the predominant populations in the anode biofilms of the MFCs belonged to Geobacter, with relative abundance of 66–75%. Microbial cathode biofilm communities were more susceptible to Fe3+, as an obvious shift in the cathode biofilm community structures occurred as Fe3+ concentration was increased. The most predominant populations in the MFC cathode biofilms without Fe3+ and with 200μM Fe3+ were affiliated with Thauera (46% and 35%), whereas no absolutely predominant populations were present in the MFC cathode biofilm with 1000μM Fe3+. The results demonstrate that a low concentration of Fe3+ facilitated the power output of MFCs and shaped community structures of the electrode biofilm.

Characterisation of the physical composition and microbial community structure of biofilms within a model full-scale drinking water distribution system.

Within drinking water distribution systems (DWDS), microorganisms form multi-species biofilms on internal pipe surfaces. A matrix of extracellular polymeric substances (EPS) is produced by the attached community and provides structure and stability for the biofilm. If the EPS adhesive strength deteriorates or is overcome by external shear forces, biofilm is mobilised into the water potentially leading to degradation of water quality. However, little is known about the EPS within DWDS biofilms or how this is influenced by community composition or environmental parameters, because of the complications in obtaining biofilm samples and the difficulties in analysing EPS. Additionally, although biofilms may contain various microbial groups, research commonly focuses solely upon bacteria. This research applies an EPS analysis method based upon fluorescent confocal laser scanning microscopy (CLSM) in combination with digital image analysis (DIA), to concurrently characterize cells and EPS (carbohydrates and proteins) within drinking water biofilms from a full-scale DWDS experimental pipe loop facility with representative hydraulic conditions. Application of the EPS analysis method, alongside DNA fingerprinting of bacterial, archaeal and fungal communities, was demonstrated for biofilms sampled from different positions around the pipeline, after 28 days growth within the DWDS experimental facility. The volume of EPS was 4.9 times greater than that of the cells within biofilms, with carbohydrates present as the dominant component. Additionally, the greatest proportion of EPS was located above that of the cells. Fungi and archaea were established as important components of the biofilm community, although bacteria were more diverse. Moreover, biofilms from different positions were similar with respect to community structure and the quantity, composition and three-dimensional distribution of cells and EPS, indicating that active colonisation of the pipe wall is an important driver in material accumulation within the DWDS.

In situ environment rather than substrate type dictates microbial community structure of biofilms in a cold seep system.

Using microscopic and molecular techniques combined with computational analysis, this study examined the structure and composition of microbial communities in biofilms that formed on different artificial substrates in a brine pool and on a seep vent of a cold seep in the Red Sea to test our hypothesis that initiation of the biofilm formation and spreading mode of microbial structures differs between the cold seep and the other aquatic environments. Biofilms on different substrates at two deployment sites differed morphologically, with the vent biofilms having higher microbial abundance and better structural features than the pool biofilms. Microbes in the pool biofilms were more taxonomically diverse and mainly composed of various sulfate-reducing bacteria whereas the vent biofilms were exclusively dominated by sulfur-oxidizing Thiomicrospira. These results suggest that the redox environments at the deployment sites might have exerted a strong selection on microbes in the biofilms at two sites whereas the types of substrates had limited effects on the biofilm development.

Cyanobacteria and Photosynthetic Species as Part of the Microbial Community Structure of Biofilms in Copahue Geothermal Springs (Neuquén, Argentina)

Copahue is a geothermal field located in the Northwest corner of Neuquén province in Argentina. It is dominated by the still active Copahue volcano. In the area there are many acidic pools, hot springs and solfataras with different temperature and pH conditions that influence their microbial diversity. On the surrounding rocks and the borders of the pools, where water movements and thermal activity are less intense, many biofilms can be found. They have different aspects and structure, and they present less extreme temperature and pH conditions than the ponds and hot springs. Biofilms are a different ecological niche and they have different microbial community structure. In this study carried out by molecular ecology techniques, mainly 16S and 18S rRNA sequencing, we report a strong presence of cyanobacterias, cloroflexi and eukaryotes, not detected in previous biodiversity studies done on water samples. Almost no acidophilic bacteria were found, with the exception of members of genusThiomonas, also found in the acidic pools. Archaea were detected only in one of the biofilms and the structure of that community seems to be similar to those found in water samples, with many uncultured species mainly related to orderSulfolobales. The aim of this study is to assess microbial community diversity in the biofilms present in this acidic geothermal area, with particular emphasis on detection of cyanobacterias and eukaryotes with potential biotechnological applications like production of alternative energy sources, synthesis and accumulation of biomolecules with antiviral or antibiotic activities or potential ability to bioremediate contaminated areas.

Phylogenetic analysis of nitrate- and sulfate-reducing bacteria in a hydrogen-fed biofilm

Using two membrane biofilm reactors in which hydrogen (H₂) was the only exogenous electron donor, we studied the microbial community structure of biofilms composed primarily of denitrifying bacteria (DB) and sulfate-reducing bacteria (SRB). In steady-state EDvSS, H₂ availability was restricted and varied. In steady-state EAvSS, the input nitrate (NO₃⁻) concentration was varied relative to a fixed sulfate (SO₄²⁻) concentration. SRB co-existed with DB, even when SO₄²⁻ reduction was absent due to restricted H₂ availability. UniFrac and principal coordinate analysis indicated that H₂ availability and electron-acceptor loadings framed the microbial community structure, with H₂ availability having a greater impact. In EDvSS, restricted H₂ availability favored heterotrophic DB (i.e. Burkholderiales) compared with autotrophic DB (e.g. Hydrogenophilales and Rhodocyclales). In EAvSS, SO₄²⁻ reduction lowered the relative abundance of some DB (e.g. Hydrogenophilales), and the biofilm was colonized by Desulfovibrionales and Bacteroidales. Reinforcing the impact of H₂ availability, EAvSS showed a higher microbial diversity and more even distribution among microbial groups than did EDvSS. Thus, the biofilm community in a H₂-fed biofilm with DB and SRB became more heterotrophic when the H₂ availability was constrained, while low NO₃⁻ loading allowed more SO₄²⁻ reduction, causing a shift to more SRB.

Microbial composition of biofilms in a brewery investigated by fatty acid analysis, fluorescence in situ hybridisation and isolation techniques.

Biofilms associated with brewery plants can harbour spoiling microorganisms that potentially damage the final product. Most beer-spoiling microorganisms are thought to depend on numerous interactions with the accompanying microbiota. However, there is no information on the microbial community structure of biofilms from bottling plants. The conveyors that transport the bottles to and from the plant are known as potential sources of microbial contamination of beer. Consequently, the material buildup from two conveyors was analysed using a cultivation/isolation approach, and the culture-independent techniques of whole cell fatty acid analysis and fluorescence in situ hybridisation (FISH). Heterogeneous communities were present at both conveyors. Although characteristic fatty acids for Eukarya were present, FISH-signals for Eukarya were extremely low. The Proteobacteria, in particular the Gammaproteobacteria, were abundant at both sample sites. Bacterial isolates were obtained for every dominating group detected by FISH: the Alphaproteobacteria, Betaproteobacteria and Gammaproteobacteria, the Xanthomonadaceae, the Actinobacteria, the Bacteroidetes and the Firmicutes.