Comparison Of Biofilms Research Articles

A comparison of biofilm and suspension methods in removing heavy metals (chromium) from industrial wastewater with Scenedesmus obliquus and Chlorella vulgaris

The study investigated the factors influencing chromium absorption by the microalgae species S. obliquus and C. vulgaris using an ANOVA approach. The analysis revealed significant independent effects of contact time, temperature, pH, density, algal species, and production methods, as well as notable interactions among these factors. Under standardized conditions of pH 7, 105 minutes of contact time, a temperature of 25°C, light intensity of 3500 lux, and a density of 60, S. obliquus showed the highest chromium absorption. The biofilm production method was consistently more effective than the suspension method for both species. At a pH of 5, C. vulgaris outperformed S. obliquus, achieving maximum absorption rates in both production methods. The study also found that higher temperatures facilitated increased chromium absorption, peaking at 27.5°C for suspension and 26.5°C for biofilm methods, with S. obliquus demonstrating superiority. Significant interactions resulted in the combination of the biofilm method and S. obliquus yielding the best absorption rates at specified conditions. Density trends indicated decreasing absorption rates for both microalgae at densities of 30 and 40, but S. obliquus later exhibited a reversal of this trend, unlike C. vulgaris. Contact time results indicated increased absorption from 60 to 115 minutes, but a decline afterwards, with S. obliquus again leading. The optimal conditions for chromium absorption were identified as pH 5, temperatures around 26–28°C, with particular density levels, highlighting the importance of production method in enhancing absorption rates for both microalgae species.

Characteristics and Comparison of Biofilm and Activated Sludge Sewage Treatment Technologies

Sewage treatment is a key environmental protection task and is of great significance to sustainable development. In this paper, biological filter method, rotating biological plate method, traditional push-flow activated sludge method and gradually reduced aeration method are selected to summarize and compare their principles, advantages and disadvantages, and removal objects. Biofilm method is similar to the principle of soil self-purification. It is a kind of aerobic biological treatment technology juxtaposed with activated sludge, and it is a fixed membrane process. The activated sludge is similar to the self-purification principle of water. It is an aerobic biological treatment method for sewage, removing dissolved and colloidal biochemical organic matter from the effluent, as well as suspended solids and other substances that can be adsorbed by activated sludge. It also removes some of the phosphorus and nitrogen. Both methods belong to wastewater biological treatment of suspended microorganisms in the water. They have their advantages, disadvantages and applicable conditions, so there is no competition between the two methods.

Autoinducer 2 (AI-2) Production by Nontypeable Haemophilus influenzae 86-028NP Promotes Expression of a Predicted Glycosyltransferase That Is a Determinant of Biofilm Maturation, Prevention of Dispersal, and Persistence In Vivo.

Nontypeable Haemophilus influenzae (NTHi) is an extremely common human pathobiont that persists on the airway mucosal surface within biofilm communities, and our previous work has shown that NTHi biofilm maturation is coordinated by the production and uptake of autoinducer 2 (AI-2) quorum signals. To directly test roles for AI-2 in maturation and maintenance of NTHi biofilms, we generated an NTHi 86-028NP mutant in which luxS transcription was under the control of the xylA promoter (NTHi 86-028NP luxS xylA::luxS), rendering AI-2 production inducible by xylose. Comparison of biofilms under inducing and noninducing conditions revealed a biofilm defect in the absence of xylose, whereas biofilm maturation increased following xylose induction. The removal of xylose resulted in the interruption of luxS expression and biofilm dispersal. Measurement of luxS transcript levels by real-time reverse transcription-PCR (RT-PCR) showed that luxS expression peaked as biofilms matured and waned before dispersal. Transcript profiling revealed significant changes following the induction of luxS, including increased transcript levels for a predicted family 8 glycosyltransferase (NTHI1750; designated gstA); this result was confirmed by real-time RT-PCR. An isogenic NTHi 86-028NP gstA mutant had a biofilm defect, including decreased levels of sialylated matrix and significantly altered biofilm structure. In experimental chinchilla infections, we observed a significant decrease in the number of bacteria in the biofilm population (but not in effusions) for NTHi 86-028NP gstA compared to the parental strain. Therefore, we conclude that AI-2 promotes NTHi biofilm maturation and the maintenance of biofilm integrity, due at least in part to the expression of a probable glycosyltransferase that is potentially involved in the synthesis of the biofilm matrix.

Performance comparison of biofilm and suspended sludge from a sequencing batch biofilm reactor treating mariculture wastewater under oxytetracycline stress

ABSTRACTThe performance, extracellular polymeric substances (EPS) and microbial community of a sequencing batch biofilm reactor (SBBR) were investigated in treating mariculture wastewater under oxytetracycline stress. The chemical oxygen demand and –N removal efficiencies of the SBBR decreased with the increase of oxytetracycline concentration, and no obvious –N and –N accumulation in the effluent appeared at less than 10 mg L−1 oxytetracycline. The specific oxygen utilization rate of the suspended sludge was more than that of the biofilm at different oxytetracycline concentrations. The specific ammonium oxidation rate (SAOR) of the biofilm was more easily affected by oxytetracycline than that of the suspended sludge, whereas the effect of oxytetracycline on the specific nitrite oxidation rate (SNOR) of the biofilm was less than that of the suspended sludge. The specific nitrate reduction rate of both the biofilm and suspended sludge was higher than the sum of the SAOR and SNOR at different oxytetracycline concentrations. The protein and polysaccharide contents in the EPS of the biofilm and suspended sludge increased with the increase of oxytetracycline concentration. The appearance of oxytetracycline in the influent could affect the chemical composition of the loosely bound EPS and tightly bound EPS. The amino, carboxyl and hydroxyl groups might be involved with interaction between EPS and oxytetracycline. The denaturing gradient gel electrophoresis profiles indicated that the variation of oxytetracycline concentration in the influent could affect the microbial communities of both the biofilm and suspended sludge.

Reconstruction of biofilm images: combining local and global structural parameters

Digitized images can be used for quantitative comparison of biofilms grown under different conditions. Using biofilm image reconstruction, it was previously found that biofilms with a completely different look can have nearly identical structural parameters and that the most commonly utilized global structural parameters were not sufficient to uniquely define these biofilms. Here, additional local and global parameters are introduced to show that these parameters considerably increase the reliability of the image reconstruction process. Assessment using human evaluators indicated that the correct identification rate of the reconstructed images increased from 50% to 72% with the introduction of the new parameters into the reconstruction procedure. An expanded set of parameters especially improved the identification of biofilm structures with internal orientational features and of structures in which colony sizes and spatial locations varied. Hence, the newly introduced structural parameter sets helped to better classify the biofilms by incorporating finer local structural details into the reconstruction process.

Evaluating the influence of novel cyanobacterial biofilmed biofertilizers on soil fertility and plant nutrition in wheat

Microbial inoculants suffer from the major problem of poor survival in rhizospheric soil and their plant growth-promoting abilities are dependent upon their competence in this niche. An interesting observation regarding the biofilms, which urged us to evaluate them with crop, was the increased nitrogen-fixing potential or ARA (Acetylene Reduction Activity), even after 10 and 24 weeks of incubation under laboratory conditions. Our present investigation was therefore aimed toward evaluating novel biofilmed preparations developed using cyanobacterium Anabaena torulosa as a matrix for agriculturally useful bacteria (Azotobacter, Mesorhizobium, Serratia and Pseudomonas) in wheat crop. The performance of such phototroph–heterotroph biofilmed preparations was evaluated using individual cyanobacterium, available bacterial inoculants and dual cultures of the partners. Comparison of biofilms was undertaken using RP (Rock phosphate) for phosphate solubilizers –Serratia, Pseudomonas and their combinations only. Nitrogen-fixers –Azotobacter, Mesorhizobium and their combinations, including biofilmed preparations were compared using SSP (single super phosphate) as phosphate source. An enhancement in ARA in the range of 40–50% was recorded in the treatments inoculated with biofilms even after 14 weeks of inoculation, as compared to 4 weeks old samples. The performance of Anabaena–Serratia biofilm and dual culture inoculant, in the presence of RP was most promising, as they exhibited highest ARA even at harvest stage. Anabaena–Pseudomonas biofilm showed highest P uptake, illustrating the interrelationships of nitrogen fixation with increased P uptake by plant. The observations highlighted the synergism among the partners, which emphasizes the need for evaluation at field level for their promise as a green technology for agriculture.

Comparison of biofilm and attachment mechanisms of a phytopathological and clinical isolate of Klebsiella pneumoniae Subsp. pneumoniae.

Some bacterial species can colonize humans and plants. It is almost impossible to prevent the contact of clinically pathogenic bacteria with food crops, and if they can persist there, they can reenter the human food chain and cause disease. On the leaf surface, microorganisms are exposed to a number of stress factors. It is unclear how they survive in such different environments. By increasing adhesion to diverse substrates, minimizing environmental differences, and providing protection against defence mechanisms, biofilms could provide part of the answer. Klebsiella pneumoniae subsp. pneumoniae is clinically important and also associated with fruit diseases, such as “pineapple fruit collapse.” We aimed to characterize biofilm formation and adhesion mechanisms of this species isolated from pineapple in comparison with a clinical isolate. No differences were found between the two isolates quantitatively or qualitatively. Both tested positive for capsule formation and were hydrophobic, but neither produced adherence fibres, which might account for their relatively weak adhesion compared to the positive control Staphylococcus epidermidis ATCC 35984. Both produced biofilms on glass and polystyrene, more consistently at 40°C than 35°C, confirmed by atomic force and high-vacuum scanning electron microscopy. Biofilm formation was maintained in an acidic environment, which may be relevant phytopathologically.

Comparison of biofilm forming ability between wild-type and lipopolysaccharide deficient mutant strains of Bradyrhizobium japonicum

Comparison of biofilm forming ability between wild-type and lipopolysaccharide deficient mutant strains of Bradyrhizobium japonicum

In vitrobiofilm model for studying tongue flora and malodour

To develop a perfusion biofilm system to model tongue biofilm microflora and their physiological response to sulfur-containing substrates (S-substrates) in terms of volatile sulfide compound (VSC) production. Tongue-scrape inocula were used to establish in vitro perfusion biofilms which were examined in terms of ecological composition using culture-dependent and independent (PCR-DGGE) approaches. VSC-specific activity of cells was measured by a cell suspension assay, using a portable industrial sulfide monitor which was also used to monitor VSC production from biofilms in situ. Quasi steady states were achieved by 48 h and continued to 96 h. The mean (+/-SEM) growth rate for 72-h biofilms (n=4) was micro=0.014 h(-1) (+/-0.005 h(-1)). Comparison of biofilms, perfusate and original inoculum showed their ecological composition to be similar (Pearson coefficient>0.64). Perfusate and biofilm cells derived from the same condition (co-sampled) were equivalent with regard to VSC-specific activities which were up-regulated in the presence of S-substrates. The model maintained a stable tongue microcosm suitable for studying VSC production; biofilm growth in the presence of S-substrates up-regulated VSC activity. The method is apt for studying ecological and physiological aspects of oral biofilms and could be useful for screening inhibitory agents.

A comparison of biofilms from macrophytes and rocks for taste and odour producers in the St. Lawrence River

Given their widespread and prolific annual development in the St. Lawrence River (SLR), macrophytes (i.e. submerged aquatic plants) represent large surface areas for biofilm growth and potentially important sites for associated production of taste and odour (T&O) compounds. We therefore evaluated the importance of submerged macrophytes and their associated biofilms for production of T&O compounds, 2-methylisoborneol (MIB) and geosmin (GM), compared with biofilms from adjacent rocks. We also tested the hypothesis that production of these compounds would differ between macrophyte species, based on the premise that they are not inert substrates but directly influence the communities that colonise their surfaces. Samples collected from transects across the SLR between Kingston and Cornwall, ON were dominated by the flat-bladed Vallisneria spp., and the leafed Myriophyllum spicatum, Elodea canadensis, Chara spp., Potamgeton spp., and Ceratophyllum spp. Overall, MIB and GM levels in biofilms ranged widely between samples. Expressed per g dry weight of biofilm, median levels from macrophyte were 50 (range 1-5000) ng MIB g(-1) and 10 (<1 to 580) ng GM g(-1) compared with 50 (range 5-970) ng MIB g(-1) and 160 (1-1600) ng GM g(-1) from rocks. Based on non-parametric statistical analysis, levels of GM were higher on a g dry weight basis in biofilms from rocks than macrophytes (P = 0.02), but MIB levels were similar (P = 0.94). However, when normalised for differences in substrate surface area (i.e. ng cm(-2)), levels of both MIB and GM were higher in biofilms from rocks than from macrophytes (P < 0.01). There were no discernable differences in MIB and GM concentrations from biofilms of different macrophytes based on either g dry weight sample or surface area (P > 0.05). Overlying water (OLW) concentrations ranged between 2-45 ng L(-1) for MIB and 5-30 ng L(-1) for GM and were not correlated with levels in adjacent biofilms. However, OLW concentrations peaked in shallow, low energy embayments consistent with enhanced production and release of MIB and GM in nearshore areas. The results support our previous work showing the importance of biofilms on various surfaces (rocks, macrophytes and zebra mussels) for MIB and GM production in the SLR, but suggest that inert surfaces like rocks are more productive sites per unit surface area than macrophytes.

Evaluation of multiple-species biofilm and floc processes using a simplified aggregate model

A simplified model of microbial aggregates is developed to evaluate how the key features of aggregation affect the stability of nitrification in multiple-species biofilms and flocs. The foundation of the model is a layered system in which each layer contains a different type of biomass, includes mass-transport resistance for all substrates (i.e., COD, NH4+, and O2), and included formation and consumption of soluble microbial products. The model describes how the outer biofilm layer of heterotrophs protects the inner layers of nitrifiers and inert biomass from detachment, so that an inner layer can have a low specific detachment-loss rate. This protecting function is not important for suspended flocs, because the entire floc is wasted. Comparison of biofilm and suspended flocs shows that the protecting function of the biofilms provides greater nitrification stability. The model also demonstrates that extensive heterotrophic growth induced by high organic loading can cause a deterioration of nitrification when the dissolved oxygen is depleted in the inner layer of the aggregate. Although it is based on a simplified spatial distribution, the aggregate model identifies key differences among biofilm, floc, and dispersed-growth processes.