Submit to Microorganisms Review for Microorganisms Propose a Special Issue

Journal Menu

Journal Browser

► Journal Browser

Microbial Films-the Interplay of Physics and Biology

Print Special Issue Flyer
Special Issue Editors
Special Issue Information
Keywords
Published Papers

A special issue of Microorganisms (ISSN 2076-2607). This special issue belongs to the section "Biofilm".

Deadline for manuscript submissions: closed (31 January 2022) | Viewed by 35937

Share This Special Issue

Special Issue Editor

Prof. Dr. Luis F. Melo

E-Mail Website
Guest Editor

Department of Chemical Engineering, Faculty of Engineering, University of Porto, 4200-465 Porto, Portugal
Interests: biofilms; biofouling in cooling and drinking water systems; mass transfer; biological reactors

Special Issue Information

Dear Colleagues,

Authors are invited to submit their experimental modelling/simulation and theoretical work focused on the physics of biofilms and its interaction with biological aspects, such as: (i) biofilm mechanical properties and their relation to microbial attachment, growth and matrix maturation; (ii) effects of the physics of the environment on biofilm development (interactions with suspended particles, impact of air/gas-liquid flows, hydrodynamic patterns/shear stress, temperature, etc.); (iii) experimental methodologies to assess/interpret biofilm behaviour based on the measurement of physical parameters (rheology, porosity, density, tortuosity, ...); (iv) physical methods for online monitoring of biofilm development at lab and industrial scale, diffusion-mass transfer around and inside biofilms; (v) nanostructured surfaces/topographies and microbial adhesion. Other topics are welcome provided they keep the focus on physical approaches and their impact on biofilm metabolism, structure and spatial distribution of biofilm components.

Prof. Luis F. Melo
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Microorganisms is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

biofilm physics
environmental physical effects on biofilm metabolism
biofilm detachment and removal - mechanical Issues
biofilm monitoring with physical methods
surface physical properties and microbial adhesion

Published Papers (10 papers)

Download All Papers

Research

Jump to: Review

10 pages, 412 KiB

Open AccessArticle

Hydrodynamic Effects on Biofilm Development and Recombinant Protein Expression

by Alexandra Soares, Luciana C. Gomes, Gabriel A. Monteiro and Filipe J. Mergulhão

Microorganisms 2022, 10(5), 931; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms10050931 - 29 Apr 2022

Cited by 4 | Viewed by 1554

Abstract

Hydrodynamics play an important role in the rate of cell attachment and nutrient and oxygen transfer, which can affect biofilm development and the level of recombinant protein production. In the present study, the effects of different flow conditions on the development of Escherichia coli biofilms and the expression of a model recombinant protein (enhanced green fluorescent protein, eGFP) were examined. Planktonic and biofilm cells were grown at two different flow rates in a recirculating flow cell system for 7 days: 255 and 128 L h⁻¹ (corresponding to a Reynolds number of 4600 and 2300, respectively). The fluorometric analysis showed that the specific eGFP production was higher in biofilms than in planktonic cells under both hydrodynamic conditions (3-fold higher for 255 L h⁻¹ and 2-fold higher for 128 L h⁻¹). In the biofilm cells, the percentage of eGFP-expressing cells was on average 52% higher at a flow rate of 255 L h⁻¹. Furthermore, a higher plasmid copy number (PCN) was obtained for the highest flow rate for both planktonic (244 PCN/cell versus 118 PCN/cell) and biofilm cells (43 PCN/cell versus 29 PCN/cell). The results suggested that higher flow velocities promoted eGFP expression in E. coli biofilms. Full article

(This article belongs to the Special Issue Microbial Films-the Interplay of Physics and Biology)

► Show Figures

Figure 1

12 pages, 3866 KiB

Open AccessArticle

Low-Field Nuclear Magnetic Resonance Characteristics of Biofilm Development Process

by Yajun Zhang, Yusheng Lin, Xin Lv, Aoshu Xu, Caihui Feng and Jun Lin

Microorganisms 2021, 9(12), 2466; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms9122466 - 29 Nov 2021

Cited by 1 | Viewed by 1202

Abstract

To in situ and noninvasively monitor the biofilm development process by low-field nuclear magnetic resonance (NMR), experiments should be made to determine the mechanisms responsible for the T₂ signals of biofilm growth. In this paper, biofilms were cultivated in both fluid media and saturated porous media. T₂ relaxation for each sample was measured to investigate the contribution of the related processes to T₂ relaxation signals. In addition, OD values of bacterial cell suspensions were measured to provide the relative number of bacterial cells. We also obtained SEM photos of the biofilms after vacuum freeze-drying the pure sand and the sand with biofilm formation to confirm the space within the biofilm matrix and identify the existence of biofilm formation. The T₂ relaxation distribution is strongly dependent on the density of the bacterial cells suspended in the fluid and the stage of biofilm development. The peak time and the peak percentage can be used as indicators of the biofilm growth states. Full article

(This article belongs to the Special Issue Microbial Films-the Interplay of Physics and Biology)

► Show Figures

Figure 1

14 pages, 5171 KiB

Open AccessArticle

Characterizing the Shearing Stresses within the CDC Biofilm Reactor Using Computational Fluid Dynamics

by Erick Johnson, Theodore Petersen and Darla M. Goeres

Microorganisms 2021, 9(8), 1709; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms9081709 - 11 Aug 2021

Cited by 7 | Viewed by 2881

Abstract

Shearing stresses are known to be a critical factor impacting the growth and physiology of biofilms, but the underlying fluid dynamics within biofilm reactors are rarely well characterized and not always considered when a researcher decides which biofilm reactor to use. The CDC biofilm reactor is referenced in validated Standard Test Methods and US EPA guidance documents. The driving fluid dynamics within the CDC biofilm reactor were investigated using computational fluid dynamics. An unsteady, three-dimensional model of the CDC reactor was simulated at a rotation rate of 125 RPM. The reactor showed turbulent structures, with shear stresses averaging near 0.365 ± 0.074 Pa across all 24 coupons. The pressure variation on the coupon surfaces was found to be larger, with a continuous 2–3 Pa amplitude, coinciding with the baffle passage. Computational fluid dynamics was shown to be a powerful tool for defining key fluid dynamic parameters at a high fidelity within the CDC biofilm reactor. The consistency of the shear stresses and pressures and the unsteadiness of the flow within the CDC reactor may help explain its reproducibility in laboratory studies. The computational model will enable researchers to make an informed decision whether the fluid dynamics present in the CDC biofilm reactor are appropriate for their research. Full article

(This article belongs to the Special Issue Microbial Films-the Interplay of Physics and Biology)

► Show Figures

Figure 1

11 pages, 1756 KiB

Open AccessArticle

Dental Biofilm and Saliva Microbiome and Its Interplay with Pediatric Allergies

by Nicole B. Arweiler, Vivien Rahmel, Bilal Alashkar Alhamwe, Fahd Alhamdan, Michael Zemlin, Sébastien Boutin, Alexander Dalpke and Harald Renz

Microorganisms 2021, 9(6), 1330; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms9061330 - 18 Jun 2021

Cited by 9 | Viewed by 3101

Abstract

Little is known about the interplay and contribution of oral microorganisms to allergic diseases, especially in children. The aim of the clinical study was to associate saliva and dental biofilm microbiome with allergic disease, in particular with allergic asthma. In a single-center study, allergic/asthmatic children (n = 15; AA-Chd; age 10.7 ± 2.9), atopic/allergic children (n = 16; AT/AL-Chd; 11.3 ± 2.9), and healthy controls (n = 15; CON-Chd; age 9.9 ± 2.2) were recruited. After removing adhering biofilms from teeth and collecting saliva, microbiome was analyzed by using a 16s-rRNA gene-based next-generation sequencing in these two mediums. Microbiome structure differed significantly between saliva and dental biofilms (β-diversity). Within the groups, the dental biofilm microbiome of AA-Chd and AT/AL-Chd showed a similar microbial fingerprint characterized by only a small number of taxa that were enriched or depleted (4) compared to the CON-Chd, while both diseased groups showed a stronger microbial shift compared to CON-Chd, revealing 14 taxa in AA-Chd and 15 taxa in AT/AL-Chd that were different. This could be the first note to the contribution of dental biofilm and its metabolic activity to allergic health or disease. Full article

(This article belongs to the Special Issue Microbial Films-the Interplay of Physics and Biology)

► Show Figures

Figure 1

13 pages, 1773 KiB

Open AccessArticle

Assessment of the Impact of Temperature on Biofilm Composition with a Laboratory Heat Exchanger Module

by Ingrid Pinel, Renata Biškauskaitė, Ema Pal’ová, Hans Vrouwenvelder and Mark van Loosdrecht

Microorganisms 2021, 9(6), 1185; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms9061185 - 31 May 2021

Cited by 10 | Viewed by 2934

Abstract

Temperature change over the length of heat exchangers might be an important factor affecting biofouling. This research aimed at assessing the impact of temperature on biofilm accumulation and composition with respect to bacterial community and extracellular polymeric substances. Two identical laboratory-scale plate heat exchanger modules were developed and tested. Tap water supplemented with nutrients was fed to the two modules to enhance biofilm formation. One “reference” module was kept at 20.0 ± 1.4 °C and one “heated” module was operated with a counter-flow hot water stream resulting in a bulk water gradient from 20 to 27 °C. Biofilms were grown during 40 days, sampled, and characterized using 16S rRNA gene amplicon sequencing, EPS extraction, FTIR, protein and polysaccharide quantifications. The experiments were performed in consecutive triplicate. Monitoring of heat transfer resistance in the heated module displayed a replicable biofilm growth profile. The module was shown suitable to study the impact of temperature on biofouling formation. Biofilm analyses revealed: (i) comparable amounts of biofilms and EPS yield in the reference and heated modules, (ii) a significantly different protein to polysaccharide ratio in the EPS of the reference (5.4 ± 1.0%) and heated modules (7.8 ± 2.1%), caused by a relatively lower extracellular sugar production at elevated temperatures, and (iii) a strong shift in bacterial community composition with increasing temperature. The outcomes of the study, therefore, suggest that heat induces a change in biofilm bacterial community members and EPS composition, which should be taken into consideration when investigating heat exchanger biofouling and cleaning strategies. Research potential and optimization of the heat exchanger modules are discussed. Full article

(This article belongs to the Special Issue Microbial Films-the Interplay of Physics and Biology)

► Show Figures

Figure 1

14 pages, 2057 KiB

Open AccessArticle

The Effects of Chemical and Mechanical Stresses on Bacillus cereus and Pseudomonas fluorescens Single- and Dual-Species Biofilm Removal

by Inês B. Gomes, Madalena Lemos, Susana Fernandes, Anabela Borges, Lúcia C. Simões and Manuel Simões

Microorganisms 2021, 9(6), 1174; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms9061174 - 29 May 2021

Cited by 11 | Viewed by 3044

Abstract

Biofilm control is mainly based on chemical disinfection, without a clear understanding of the role of the biocides and process conditions on biofilm removal. This study aims to understand the effects of a biocide (benzyldimethyldodecyl ammonium chloride—BDMDAC) and mechanical treatment (an increase of [...] Read more.

τ_{w}

) on single- and dual-species biofilms formed by Bacillus cereus and Pseudomonas fluorescens on high-density polyethene (HDPE). BDMDAC effects were initially assessed on bacterial physicochemical properties and initial adhesion ability. Then, mature biofilms were formed on a rotating cylinder reactor (RCR) for 7 days to assess the effects of chemical and mechanical treatments, and the combination of both on biofilm removal. The results demonstrated that the initial adhesion does not predict the formation of mature biofilms. It was observed that the dual-species biofilms were the most susceptible to BDMDAC exposure. The exposure to increasing

τ_{w}

emphasised the mechanical stability of biofilms, as lower values of

τ_{w}

(1.66 Pa) caused high biofilm erosion and higher

τ_{w}

values (17.7 Pa) seem to compress the remaining biofilm. In general, the combination of BDMDAC and the mechanical treatment was synergic in increasing biofilm removal. However, these were insufficient to cause total biofilm removal (100%; an average standard deviation of 11% for the method accuracy should be considered) from HDPE. Full article

(This article belongs to the Special Issue Microbial Films-the Interplay of Physics and Biology)

► Show Figures

Figure 1

17 pages, 11986 KiB

Open AccessArticle

Unveiling the Antifouling Performance of Different Marine Surfaces and Their Effect on the Development and Structure of Cyanobacterial Biofilms

by Sara I. Faria, Rita Teixeira-Santos, Maria J. Romeu, João Morais, Ed de Jong, Jelmer Sjollema, Vítor Vasconcelos and Filipe J. Mergulhão

Microorganisms 2021, 9(5), 1102; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms9051102 - 20 May 2021

Cited by 18 | Viewed by 3055

Abstract

Since biofilm formation by microfoulers significantly contributes to the fouling process, it is important to evaluate the performance of marine surfaces to prevent biofilm formation, as well as understand their interactions with microfoulers and how these affect biofilm development and structure. In this study, the long-term performance of five surface materials—glass, perspex, polystyrene, epoxy-coated glass, and a silicone hydrogel coating—in inhibiting biofilm formation by cyanobacteria was evaluated. For this purpose, cyanobacterial biofilms were developed under controlled hydrodynamic conditions typically found in marine environments, and the biofilm cell number, wet weight, chlorophyll a content, and biofilm thickness and structure were assessed after 49 days. In order to obtain more insight into the effect of surface properties on biofilm formation, they were characterized concerning their hydrophobicity and roughness. Results demonstrated that silicone hydrogel surfaces were effective in inhibiting cyanobacterial biofilm formation. In fact, biofilms formed on these surfaces showed a lower number of biofilm cells, chlorophyll a content, biofilm thickness, and percentage and size of biofilm empty spaces compared to remaining surfaces. Additionally, our results demonstrated that the surface properties, together with the features of the fouling microorganisms, have a considerable impact on marine biofouling potential. Full article

(This article belongs to the Special Issue Microbial Films-the Interplay of Physics and Biology)

► Show Figures

Figure 1

Review

Jump to: Research

34 pages, 1955 KiB

Open AccessReview

A Selection of Platforms to Evaluate Surface Adhesion and Biofilm Formation in Controlled Hydrodynamic Conditions

by Luciana C. Gomes and Filipe J. M. Mergulhão

Microorganisms 2021, 9(9), 1993; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms9091993 - 21 Sep 2021

Cited by 20 | Viewed by 3749

Abstract

The early colonization of surfaces and subsequent biofilm development have severe impacts in environmental, industrial, and biomedical settings since they entail high costs and health risks. To develop more effective biofilm control strategies, there is a need to obtain laboratory biofilms that resemble those found in natural or man-made settings. Since microbial adhesion and biofilm formation are strongly affected by hydrodynamics, the knowledge of flow characteristics in different marine, food processing, and medical device locations is essential. Once the hydrodynamic conditions are known, platforms for cell adhesion and biofilm formation should be selected and operated, in order to obtain reproducible biofilms that mimic those found in target scenarios. This review focuses on the most widely used platforms that enable the study of initial microbial adhesion and biofilm formation under controlled hydrodynamic conditions—modified Robbins devices, flow chambers, rotating biofilm devices, microplates, and microfluidic devices—and where numerical simulations have been used to define relevant flow characteristics, namely the shear stress and shear rate. Full article

(This article belongs to the Special Issue Microbial Films-the Interplay of Physics and Biology)

► Show Figures

Figure 1

23 pages, 814 KiB

Open AccessReview

Legionella and Biofilms—Integrated Surveillance to Bridge Science and Real-Field Demands

by Ana Pereira, Ana Rosa Silva and Luis F. Melo

Microorganisms 2021, 9(6), 1212; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms9061212 - 03 Jun 2021

Cited by 14 | Viewed by 4984

Abstract

Legionella is responsible for the life-threatening pneumonia commonly known as Legionnaires’ disease or legionellosis. Legionellosis is known to be preventable if proper measures are put into practice. Despite the efforts to improve preventive approaches, Legionella control remains one of the most challenging issues in the water treatment industry. Legionellosis incidence is on the rise and is expected to keep increasing as global challenges become a reality. This puts great emphasis on prevention, which must be grounded in strengthened Legionella management practices. Herein, an overview of field-based studies (the system as a test rig) is provided to unravel the common roots of research and the main contributions to Legionella’s understanding. The perpetuation of a water-focused monitoring approach and the importance of protozoa and biofilms will then be discussed as bottom-line questions for reliable Legionella real-field surveillance. Finally, an integrated monitoring model is proposed to study and control Legionella in water systems by combining discrete and continuous information about water and biofilm. Although the successful implementation of such a model requires a broader discussion across the scientific community and practitioners, this might be a starting point to build more consistent Legionella management strategies that can effectively mitigate legionellosis risks by reinforcing a pro-active Legionella prevention philosophy. Full article

(This article belongs to the Special Issue Microbial Films-the Interplay of Physics and Biology)

► Show Figures

Figure 1

34 pages, 1652 KiB

Open AccessReview

Targeting Biofilms Therapy: Current Research Strategies and Development Hurdles

by Yu Jiang, Mengxin Geng and Liping Bai

Microorganisms 2020, 8(8), 1222; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms8081222 - 11 Aug 2020

Cited by 81 | Viewed by 7573

Abstract

Biofilms are aggregate of microorganisms in which cells are frequently embedded within a self-produced matrix of extracellular polymeric substance (EPS) and adhere to each other and/or to a surface. The development of biofilm affords pathogens significantly increased tolerances to antibiotics and antimicrobials. Up to 80% of human bacterial infections are biofilm-associated. Dispersal of biofilms can turn microbial cells into their more vulnerable planktonic phenotype and improve the therapeutic effect of antimicrobials. In this review, we focus on multiple therapeutic strategies that are currently being developed to target important structural and functional characteristics and drug resistance mechanisms of biofilms. We thoroughly discuss the current biofilm targeting strategies from four major aspects—targeting EPS, dispersal molecules, targeting quorum sensing, and targeting dormant cells. We explain each aspect with examples and discuss the main hurdles in the development of biofilm dispersal agents in order to provide a rationale for multi-targeted therapy strategies that target the complicated biofilms. Biofilm dispersal is a promising research direction to treat biofilm-associated infections in the future, and more in vivo experiments should be performed to ensure the efficacy of these therapeutic agents before being used in clinic. Full article

(This article belongs to the Special Issue Microbial Films-the Interplay of Physics and Biology)

► Show Figures