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Temperature can fluctuate widely between different seasons, and this may greatly impact many biological processes. However, little is known about its influence on the functioning of benthic microbial communities. Here we investigated the nutrient accumulation capability of periphytic biofilm under temperature fluctuations (17-35°C). Periphytic biofilm maintained the same nutrient accumulation capacity after experiencing the 'warming-hot-cooling' temperature fluctuation under both lab and outdoor conditions as those without temperature disturbance. In response to temperature increase, both community composition and species richness changed greatly and the increase in biodiversity was identified as being the underlying mechanism boosting the sustainable function in nutrient accumulation, indicating zero net effects of community changes. These findings provide insights into the underlying mechanisms of how benthic microbial communities adapt to temperature fluctuations to maintain nutrient accumulation capacity and elucidate that periphytic biofilm plays important roles in influencing nutrient cycling in aquatic ecosystems under temperature changes such as seasonal fluctuations.

Microplastics (MPs) have been gaining the attention of environmental researchers since the 1960s anecdotal reports of plastic entanglement and ingestion by marine creatures. Due to their increasing accretion in aquatic environments, as well as resistance towards degradation, marine litter research has focused on microplastics more recently. In the present study, a relatively new method of biodegradation was implemented for the biodegradation of three structurally different MPs i.e. polypropylene (PP), polyethylene (PE) and polyethylene terephthalate (PET). Periphytic biofilm was used for this purpose in various backgrounds of carbon sources (glucose, peptone, and glucose and peptone). Biodegradation of MPs was estimated in terms of weight loss. It was observed that the addition of glucose enhanced the biodegradation of MPs by periphyton biofilm for all MPs (from 9.52%-18.02%, 5.95%-14.02% and 13.24-19.72% for PP, PE and PET respectively) after 60 days compared to natural biofilm alone. To the contrary, peptone, and glucose and peptone together, were inhibitory. Biodegradation was further confirmed by morphological changes observed using SEM, FTIR spectra and GPC lent further support to the results whereby new peaks appeared along with reduction in old peaks and decrease in peak intensities. MiSeq sequencing shows that Deinococcus-thermus > Proteobacteria > Cyanobacteria are the dominant phyla in natural biofilms, and their relative abundances increase after the addition of glucose. However, the abundances shifted to Deinococcus-thermus > Cyanobacteria > Firmicutes > Bacteroidetes, when the biofilms were treated with either peptone alone, or with glucose and peptone together. Therefore, the change in biodegradation capability might also be due to the change in the microbial community structures after addition of the C-sources. These experiments provide an innovative approach towards effective biodegradation of MPs using a relatively new environment-friendly method., Competing Interests: Declaration of competing interest The manuscript entitled “Periphytic Biofilm: an innovative approach for biodegradation of Microplastics”, the authors whose names are listed immediately below certify that they have NO affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers' bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Responses of microbial communities to nanotoxicity in aquatic ecosystems are largely unknown, particularly with respect to relationship between community dynamics and functions. Here, periphytic biofilms were selected as a model of species-rich microbial communities to elucidate their responses when exposed to titanium dioxide nanoparticles (TiO 2 -NPs). Especially, the relationships between the functions (e.g. organic matter and Cu 2+ removal) and community dynamics after long-term exposure to TiO 2 -NPs were assessed systematically. After 5days exposure to TiO 2 -NPs (5mgL -1 ), periphytic biofilms showed sustainable functions in pollutant removal and strong plasticity in defensing the toxic disturbance of TiO 2 -NPs, including photosynthesis and carbon metabolic diversity. The sustainable pollutant removal functions of periphytic biofilms were attributed to their functional redundancy. Specifically, periphytic biofilms altered their composition with cyanobacteria, Sphingobacteriia and Spirochaetes being the newly dominant taxa, and changed the carbon substrate utilization pattern to maintain high photosynthesis and metabolic rates. Moreover, extracellular polymeric substances (EPS) especially proteins were overproduced to bind the NPs and thereby reduce the nanotoxicity. The information obtained in this study may greatly help to understand the interactions between microbial community dynamics and function under NPs exposure conditions and functional redundancy is an important mechanism of periphytic biofilms to maintain sustainable functions., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Allelopathy among aquatic organisms, especially microorganisms, has received growing attention in recent years for its role in shaping interactions with bloom-forming algae. Many studies have shown that allelopathy occurs and increases under nutrient limiting conditions. However, to date there is no reported direct evidence to indicate that allelopathy occurs under the condition of constant high nutrient supply. Here we report the allelopathic action of periphytic biofilm on bloom-forming cyanobacteria (Microcystis aeruginosa), which was triggered by the stress of high nutrient conditions, and continues while nutrients are maintained at high levels (trophic state index at 159 and 171). The experimental evidence indicates that the electron transport from photosystem II (PS II) to photosystem I (PS I) in M. aeruginosa is interrupted by the identified allelochemicals, (9Z)-Octadec-9-enoic acid and (9Z)-Hexadec-9-enoic acid, leading to the failure of photosynthesis and the subsequent death of M. aeruginosa. Our findings indicate that the nutrient stress of constant high nutrient supply may be a newly recognized trigger causing allelopathy between microbial competitors, and therefore opening a new direction for the better management of ecological processes in cyanobacteria-dominated and hyper-eutrophic waters.

Due to their large scale use, azo dyes are adversely affecting aquatic fauna and flora as well as humans. The persistent nature of sulphonated azo dyes makes them potential ecotoxic hazards. The aim of the present study was to employ a proficient, locally available biomaterial, viz. periphyton (i.e. epiphyton, epilithon or metaphyton), for removal of the azo dye, methyl orange (MO). Results showed that the periphytic biofilms are capable of completely removing comparatively high concentrations (up to 500 mg L -1 ) of MO from wastewater. The removal of MO occurs by a synergistic mechanism involving bioadsorption and biodegradation processes. The adsorption of MO by periphyton can be described by pseudo-second order kinetics. Elovich and intraparticle diffusion models as well as Langmuir equations fit well to the MO adsorption process. FTIR analysis of MO and its metabolites demonstrated biotransformation into simpler compounds within 72 h. GC-MS/MS analysis showed the conversion of MO into simpler compounds such as phenol, ethyl acetate and acetyl acetate. The results indicated that periphyton is a promising biomaterial for the complete removal of MO from wastewater and that the treatment process has the potential for in situ removal of MO at contaminated sites., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Sodium alginate (SA) is a naturally occurring, non-toxic, polysaccharide that is able to form gels after exposure to calcium. These gels have been used in food and biomedical industries. This is the first direct comparison of two different methods of calcium alginate film production, namely interfacial gelation (IFG) and dry cast gelation (DCG). IFG films were significantly thicker than DCG films, and were more extensively rehydrated in water and 0.1 M HCl than the DCG films. During rehydration in 0.1 M HCl almost all calcium ions were lost. Under scanning electron microscopy, IFG films appeared less dense than DCG films. IFG films were mechanically weaker than DCG films, and both types of film were weaker after rehydration in 0.1 M HCl compared with deionized water. Permeation of theophylline (TPL) was evaluated in-vitro; the diffusion coefficient ( D ) of the TPL was almost 90 times lower in DCG films than IFG films when both were rehydrated in water. Although the 0.1 M HCl rendered both gels more permeable to TPL, D of TPL was still about five times lower in DCG compared to IFG films. The evaluation of selected physico-chemical properties of films is important, since this information may inform the choice of gelation technique used to produce calcium alginate coatings on pharmaceutical products. [ABSTRACT FROM AUTHOR]

[Display omitted] • La loading to periphytic biofilm was mainly based on ligand exchange reactions. • La-loading achieved rapid initial P-entrapment. • AHLs stimulated periphytic biofilm growth and formation. • AHLs-stimulation enhanced steady and efficient P-entrapment. • Enhanced EPS production stimulated by AHLs can protect cells against La exposure. This study presents an approach for developing periphytic biofilm with N-acyl-homoserine-lactones (AHLs) stimulation and lanthanum (La, a rare earth element) loading, to achieve highly efficient and stable phosphorus (P) recovery from wastewater. AHLs stimulated biofilm growth and formation, also improved stable P entrapment by enhancing extracellular polymeric substance (EPS) production and optimizing P-entrapment bacterial communities. Periphytic biofilms loading La is based on ligand exchanges, and La loading achieved initial rapid P entrapment by surface adsorption. The combination of AHLs stimulation and La loading achieved 99.0% P entrapment. Interestingly, the enhanced EPS production stimulated by AHLs protected biofilms against La. Moreover, a method for P and La separately recovery from biofilms was developed, achieving 89–96% of P and 88–93% of La recovery. This study offers a promising biotechnology to reuse La from La-rich wastewater and recover P by biofilm doped with La, which results in a win–win situation for resource sustainability. [ABSTRACT FROM AUTHOR]

Endocrine-disrupting compounds (EDCs), as well as microplastics, have drawn global attention due to their presence in the aquatic ecosystem and persistence in wastewater treatment plants (WWTPs). In the present study, for simultaneous bio-removal of two EDCs, 17α-ethinylestradiol (EE2), bisphenol A (BPA), and a microplastic, polypropylene (PP) four kinds of periphytic biofilms were employed. Additionally, the effect of humic acid (HA) on the removal efficacy of these biofilms was evaluated. It was observed that EE2 and BPA (0.2 mg L−1 each) were completely (∼100%) removed within 36 days of treatment; and the biodegradation of EE2, BPA, and PP was significantly enhanced in the presence of HA. Biodegradation of EE2 and BPA was evaluated through Ultra-high performance liquid chromatography (UHPLC), and Gas chromatography coupled with tandem mass spectrometry (GC-MS/MS) was used to determine the mechanism of degradation. Gel permeation chromatography (GPC) and SEM had validated the biodegradation of PP (5.2–14.7%). MiSeqsequencing showed that the community structure of natural biofilm changed after the addition of HA, as well as after the addition of EDCs and PP. This change in community structure might be a key factor regarding variable biodegradation percentages. The present study revealed the potential of periphytic biofilms for the simultaneous removal of pollutants of different chemical natures, thus provides a promising new method for wastewater treatment applications. [Display omitted] • EDCs and microplastics were co-treated with immobilized periphytic biofilms. • Humic acid can substantially induce biodegradation potency of periphytic biofilms. • EDCs were completely whereas PP was partially degraded within 36 days with HA. • HA affects biodegradation potential as well as structure and abundance of biofilms. • Periphytic biofilms are a potent technology for simultaneous removal of pollutants. [ABSTRACT FROM AUTHOR]