Bacterial biofilms are formed by communities that are embedded in a self-produced matrix of extracellular polymeric substances (EPS). Importantly, bacteria in biofilms exhibit a set of 'emergent properties' that differ substantially from free-living bacterial cells. In this Review, we consider the fundamental role of the biofilm matrix in establishing the emergent properties of biofilms, describing how the characteristic features of biofilms - such as social cooperation, resource capture and enhanced survival of exposure to antimicrobials - all rely on the structural and functional properties of the matrix. Finally, we highlight the value of an ecological perspective in the study of the emergent properties of biofilms, which enables an appreciation of the ecological success of biofilms as habitat formers and, more generally, as a bacterial lifestyle.

Biofilms: an emergent form of bacterial life.

In the last few decades, pharmaceuticals, credited with saving millions of lives, have emerged as a new class of environmental contaminant. These compounds can have both chronic and acute harmful effects on natural flora and fauna. The presence of pharmaceutical contaminants in ground waters, surface waters (lakes, rivers, and streams), sea water, wastewater treatment plants (influents and effluents), soils, and sludges has been well doccumented. A range of methods including oxidation, photolysis, UV-degradation, nanofiltration, reverse osmosis, and adsorption has been used for their remediation from aqueous systems. Many methods have been commercially limited by toxic sludge generation, incomplete removal, high capital and operating costs, and the need for skilled operating and maintenance personnel. Adsorption technologies are a low-cost alternative, easily used in developing countries where there is a dearth of advanced technologies, skilled personnel, and available capital, and adsorption appears to be the most broadly feasible pharmaceutical removal method. Adsorption remediation methods are easily integrated with wastewater treatment plants (WWTPs). Herein, we have reviewed the literature (1990-2018) illustrating the rising environmental pharmaceutical contamination concerns as well as remediation efforts emphasizing adsorption.

Pharmaceuticals of Emerging Concern in Aquatic Systems: Chemistry, Occurrence, Effects, and Removal Methods.

Graphene-based materials are gaining heightened attention as novel materials for environmental applications The unique physicochemical properties of graphene, notably its exceptionally high surface area, electron mobility, thermal conductivity, and mechanical strength, can lead to novel or improved technologies to address the pressing global environmental challenges This critical review assesses the recent developments in the use of graphene-based materials as sorbent or photocatalytic materials for environmental decontamination, as building blocks for next generation water treatment and desalination membranes, and as electrode materials for contaminant monitoring or removal The most promising areas of research are highlighted, with a discussion of the main challenges that we need to overcome in order to fully realize the exceptional properties of graphene in environmental applications

Environmental applications of graphene-based nanomaterials.

Composite Photocatalysts Nan Zhang,†,‡ Min-Quan Yang,†,‡ Siqi Liu,†,‡ Yugang Sun,* and Yi-Jun Xu*,†,‡ †State Key Laboratory of Photocatalysis on Energy and Environment, College of Chemistry, Fuzhou University, Fuzhou 350002, P.R. China ‡College of Chemistry, New Campus, Fuzhou University, Fuzhou 350108, P.R. China Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, United States

Waltzing with the Versatile Platform of Graphene to Synthesize Composite Photocatalysts.

Polymer-matrix nanocomposite membranes for water treatment

Principle and applications of microbubble and nanobubble technology for water treatment

https://dr.ntu.edu.sg/bitstream/10356/106348/1/fuel%20last%20revision.pdf

Bioconversion of food waste to energy : a review

Graphene oxide–CdS composite with high photocatalytic degradation and disinfection activities under visible light irradiation

https://dr.ntu.edu.sg/bitstream/10356/106226/1/Accepted%20Manuscript%20version.pdf

The Effect of pH on Solubilization of Organic Matter and Microbial Community Structures in Sludge Fermentation

Recent reports exploring the role of gradients of quorum sensing (QS) signals in functional activated sludge have raised the question of whether shared systems of signalling synthesis and degradation, or quorum quenching (QQ), across the community inform of the means by which QS biology regulate floccular and granular biofilm assembly. In this study, we aimed to explore the species origin and interactive role of QS and QQ activities in such highly diverse microbial biofilm communities. Here, such aims were addressed systematically by a comprehensive multi-pronged RNA-sequencing, microbiological and analytical chemistry experimental approach, using two related but independently evolved floccular and granular sludge communities. Our data revealed a distinct difference between the QS and QQ potentials of the two communities, with different species largely displaying either QS or QQ functions. The floccular sludge community showed a high rate of QQ activity, and this rate was dependent on the acyl chain length demonstrating specificity of degradation. When the floccular biomass was transformed into the granular sludge, the QQ activity of the community was reduced by 30%. N-acyl homoserine lactones with four to eight carbons on the acyl chain accumulated at the granular stage, and their concentrations were at least threefold higher than those of the floccular stage. These findings corroborated meta-community analysis where a major shift in the dominant species from potential signal quenchers to producers was observed during the transition from flocs to granules, indicating the role of species composition and associated signalling activities in coordinating community behaviours. This study suggests that QQ has an important function in regulating community level QS signalling, and provides a mechanistic insight into the role of QS biology in complex community assembly. Researchers in Singapore have shed new light on the regulation of signaling between species of bacteria within microbial communities such as biofilms. Biofilms consist of diverse species of bacteria, which communicate via a signaling mechanism called quorum sensing (QS) to regulate gene expression and optimize community behaviors. Different species share signaling molecules, meaning they can communicate with each other to form granular (well-ordered) biofilms. Staffan Kjelleberg and co-workers at Nanyang Technological University found that more community members exhibited ‘quorum quenching’ (QQ) activity — the enzymatic degradation of signals — in floccular (unstructured) sludge than in granular sludge. They conclude that, by degrading particular signaling molecules, QQ activity inhibits granular biofilm formation. The study highlights the importance of signaling and quenching in determining biofilm stability and suggests that community QS activity reflects a shared contribution by different species.

/pdf/community-quorum-sensing-signalling-and-quenching-microbial-7wxahyz69o.pdf

Wun Jern Ng

Papers

Principle and applications of microbubble and nanobubble technology for water treatment

Bioconversion of food waste to energy : a review

Graphene oxide–CdS composite with high photocatalytic degradation and disinfection activities under visible light irradiation

The Effect of pH on Solubilization of Organic Matter and Microbial Community Structures in Sludge Fermentation

Community quorum sensing signalling and quenching: microbial granular biofilm assembly