Microbial Attachment Research Articles

The Potential of Frog Skin Peptides for Anti-Infective Therapies: The Case of Esculentin-1a(1-21)NH2.

Antimicrobial Peptides (AMPs) are the key effectors of the innate immunity and represent promising molecules for the development of new antibacterial drugs. However, to achieve this goal, some problems need to be overcome: (i) the cytotoxic effects at high concentrations; (ii) the poor biostability and (iii) the difficulty in reaching the target site. Frog skin is one of the richest natural storehouses of AMPs, and over the years, many peptides have been isolated from it, characterized and classified into several families encompassing temporins, brevinins, nigrocins and esculentins. In this review, we summarized how the isolation/characterization of peptides belonging to the esculentin-1 family drove us to the design of an analogue, i.e. esculentin-1a(1-21)NH2, with a powerful antimicrobial action and immunomodulatory properties. The peptide had a wide spectrum of activity, especially against the opportunistic Gram-negative bacterium Pseudomonas aeruginosa. We described the structural features and the in vitro/in vivo biological characterization of this peptide as well as the strategies used to improve its biological properties. Among them: (i) the design of a diastereomer carrying Damino acids in order to reduce the peptide's cytotoxicity and improve its half-life; (ii) the covalent conjugation of the peptide to gold nanoparticles or its encapsulation into poly(lactide- co-glycolide) nanoparticles; and (iii) the peptide immobilization to biomedical devices (such as silicon hydrogel contact lenses) to obtain an antibacterial surface able to reduce microbial growth and attachment. Summing up the best results obtained so far, this review traces all the steps that led these frog-skin AMPs to the direction of peptide-based drugs for clinical use.

Developing anti-biofouling and energy-efficient cation-exchange membranes using conductive polymers and nanomaterials

Membrane fouling, in particular biofouling is a major problem in membrane applications for water and wastewater treatment. In this study, cation-exchange membranes were modified with conductive polymer polyethyleneimine and nanomaterials such as titanium dioxide (TiO2) and graphene oxide (GO) to improve membrane anti-microbial properties and energy efficiency during electrodialysis. The anti-fouling potential was evaluated by quantitative measurement of biomass and biofilm accumulation on membrane surface with Escherichia coli (E. coli) as model microbes. Experimental results showed polyethyleneimine and nanomaterials coating changed membrane surface hydrophilicity and significantly improved anti-biofouling properties with an optimal nanomaterial dosage of 37.5 μg/mL of coating solution. Polyethyleneimine had limited effect on preventing microbial cell attachment, but demonstrated remarkable anti-biofilm growth by its cytotoxicity. Overall desalination performance of polyethyleneimine coated membrane was similar to unmodified membrane. GO coating significantly improved desalination efficiency because of its high conductivity and negative charge, while TiO2 coated membrane showed decreased overall desalination performance due to its reduced electrical conductivity.

An Insight Into Surface Topographical Parameters and Bacterial Adhesion: a Case Study of Listeria monocytogenes Scott a Attachment On 304 Stainless Steel

Bacterial attachment on surfaces is an important biological and industrial concern. Many parameters affect cell attachment behavior, including surface roughness and other topographical features. An understanding of these relationships is critical in the light of recent outbreaks caused by foodborne bacteria. Postharvest packing lines have been identified as a potential source of cross-contamination with pathogens, which can cause subsequent foodborne illness. The objective of this article is to evaluate the influence of surface topographical features on bacterial attachment at various processing temperatures to determine the extent of bacterial colonization. Type 304 stainless steel surfaces and pathogenic Listeria monocytogenes Scott A were used for a detailed investigation. Two commonly used surface types, extruded and ground, were evaluated to determine differences in bacterial attachment on the same type of material. Fifteen surface topography parameters at three processing temperatures were studied to evaluate possible correlations with microbial attachment on these surfaces. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, and confocal microscopy were used for both qualitative and quantitative analyses of surfaces. An analysis of variance and multivariate regression analysis were used to predict the attachment behavior of L. monocytogenes Scott A on stainless steel surfaces. Surface isotropy, average surface roughness, surface spacing, and processing temperatures were strongly correlated with bacterial attachment on 304 stainless steel material.

Plants and Associated Soil Microbiota Cooperatively Suppress Plant-Parasitic Nematodes.

Disease suppressive soils with specific suppression of soil-borne pathogens and parasites have been long studied and are most often of microbiological origin. As for the plant-parasitic nematodes (PPN), which represent a huge threat to agricultural crops and which successfully defy many conventional control methods, soil progression from conducive to suppressive state is accompanied by the enrichment of specific antagonistic microbial consortia. However, a few microbial groups have come to the fore in diminishing PPN in disease suppressive soils using culture-dependent methods. Studies with cultured strains resulted in understanding the mechanisms by which nematodes are antagonized by microorganisms. Recent culture-independent studies on the microbiome associated with soil, plant roots, and PPN contributed to a better understanding of the functional potential of disease suppressive microbial cohort. Plant root exudation is an important pathway determining host-microbe communication and plays a key role in selection and enrichment of a specific set of microbial antagonists in the rhizosphere as first line of defense against crop pathogens or parasites. Root exudates comprising primary metabolites such as amino acids, sugars, organic acids, and secondary metabolites can also cause modifications in the nematode surface and subsequently affect microbial attachment. A positive interaction between hosts and their beneficial root microbiota is correlated with a low nematode performance on the host. In this review, we first summarized the historical records of nematode-suppressive soils and then focused on more recent studies in this aspect, emphasizing the advances in studying nematode-microbe interactions over time. We highlighted nematode biocontrol mechanisms, especially parasitism, induced systemic resistance, and volatile organic compounds using microbial consortia, or bacterial strains of the genera Pasteuria, Bacillus, Pseudomonas, Rhizobium, Streptomyces, Arthrobacter, and Variovorax, or fungal isolates of Pochonia, Dactylella, Nematophthora, Purpureocillium, Trichoderma, Hirsutella, Arthrobotrys, and Mortierella. We discussed the importance of root exudates in plant communication with PPN and soil microorganisms, emphasizing their role in microbial attachment to the nematode surface and subsequent events of nematode parasitism. Comprehensive understanding of the plant-beneficial microbial consortia and the mechanisms underlying disease suppression may help to develop synthetic microbial communities for biocontrol of PPN, thereby reducing nematicides and fertilizers inputs.

Targeting Pathogenic Biofilms: Newly Developed Superhydrophobic Coating Favors a Host-Compatible Microbial Profile on the Titanium Surface.

Polymicrobial infections are one of the most common reasons for inflammation of surrounding tissues and failure of implanted biomaterials. Because microorganism adhesion is the first step for biofilm formation, physical-chemical modifications of biomaterials have been proposed to reduce the initial microbial attachment. Thus, the use of superhydrophobic coatings has emerged because of their anti-biofilm properties. However, these coatings on the titanium (Ti) surface have been developed mainly by dual-step surface modification techniques and have not been tested using polymicrobial biofilms. Therefore, we developed a one-step superhydrophobic coating on the Ti surface by using a low-pressure plasma technology to create a biocompatible coating that reduces polymicrobial biofilm adhesion and formation. The superhydrophobic coating on Ti was created by the glow discharge plasma using Ar, O2, and hexamethyldisiloxane gases, and after full physical, chemical, and biological characterizations, we evaluated its properties regarding oral biofilm inhibition. The newly developed coating presented an increased surface roughness and, consequently, superhydrophobicity (contact angle over 150°) and enhanced corrosion resistance (p < 0.05) of the Ti surface. Furthermore, proteomic analysis showed a unique pattern of protein adsorption on the superhydrophobic coating without drastically changing the biologic processes mediated by proteins. Additionally, superhydrophobic treatment did not present a cytotoxic effect on fibroblasts or reduction of proliferation; however, it significantly reduced (≈8-fold change) polymicrobial adhesion (bacterial and fungal) and biofilm formation in vitro. Interestingly, superhydrophobic coating shifted the microbiological profile of biofilms formed in situ in the oral cavity, reducing by up to ≈7 fold pathogens associated with the peri-implant disease. Thus, this new superhydrophobic coating developed by a one-step glow discharge plasma technique is a promising biocompatible strategy to drastically reduce microbial adhesion and biofilm formation on Ti-based biomedical implants.

Deterrence of Aspergillus Flavus Regrowth and Aflatoxin Accumulation on Shelled Corn Using Infrared Heat Treatments

HighlightsInfrared heating was used to deactivate Aspergillus flavus.Treating samples for 150 s at the 3.24 kW/m2 intensity resulted in complete deactivation of A. flavus.Adding a tempering step at 70°C for 4 h significantly increased deactivation of A. flavus.Corn treated at IR intensity =3.24 kW/m2 showed no potential for A. flavus regrowth or aflatoxin persistence.The study demonstrated a non-chemical approach to deactivate mycotoxigenic fungi on corn.Abstract.The objectives of this study were to determine the suitable combinations of infrared (IR) heating duration and intensity, followed by tempering treatments to maximize the deactivation of aflatoxin-producing mold spores, specifically Aspergillus flavus (A. flavus). Corn samples at moisture content of 24% wet basis were inoculated with spore suspension of A. flavus and incubated to allow microbial attachment on the kernels. Corn samples were then heated using IR energy and then tempered for 4 h. Following the treatments, the samples were placed in conditions favorable for mold regrowth. Treatments of non-tempered samples for 210 s at the lowest intensity (1.27 kW/m2) resulted in A. flavus load reductions of 5.9 Log CFU/g. Treatments of non-tempered samples at the medium (3.24 kW/m2) and highest intensity (6.9 kW/m2) for 210 s resulted in complete deactivation of A. flavus. No fungal regrowth or aflatoxin persistence was observed on samples treated for 210 s at the lowest, medium, and highest IR intensities. Keywords: Aflatoxins, Aspergillus flavus, Infrared heating, Shelled corn, Tempering.

Bacterial nanotubes mediate bacterial growth on periodic nano-pillars.

Surface topography designed to achieve spatial segregation has shown promise in delaying bacterial attachment and biofilm growth. However, the underlying mechanisms linking surface topography to the inhibition of microbial attachment and growth still remain unclear. Here, we investigated bacterial attachment, cell alignment and biofilm formation of Pseudomonas aeruginosa on periodic nano-pillar surfaces with different pillar spacing. Using fluorescence and scanning electron microscopy, bacteria were shown to align between the nanopillars. Threadlike structures ("bacterial nanotubes") protruded from the majority of bacterial cells and appeared to link cells directly with the nanopillars. Using ΔfliM and ΔpilA mutants lacking flagella or pili, respectively, we further demonstrated that cell alignment behavior within nano-pillars is independent of the flagella or pili. The presence of bacteria nanotubes was found in all cases, and is not linked to the expression of flagella or pili. We propose that bacterial nanotubes are produced to aid in cell-surface or cell-cell connections. Nano-pillars with smaller spacing appeared to enhance the extension and elongation of bacterial nanotube networks. Therefore, nano-pillars with narrow spacing can be easily overcome by nanotubes that connect isolated bacterial aggregates. Such nanotube networks may aid cell-cell communication, thereby promoting biofilm development.

Robust Low Friction Antibiotic Coating of Urethral Catheters Using a Catechol-Functionalized Polymeric Hydrogel Film

Indwelling urethral catheters are widely used in hospitalized patients however they are associated with bacterial infection and biofilm formation due to the suboptimal surface properties of the elastic materials used for the catheters. Although there are several antibacterial coating technologies to modify the surface properties of the catheter including hydrophilic polymeric coating, the risk of infection is still high given the absence of reactive functional groups on the surface of elastomers. In this study, we describe the use of catechol-functionalized hydrophilic polymers and explore strategies to create antibacterial hydrogel coatings. Three different types of catechol-functionalized polymers, chitosan, hyaluronic acid, and human serum albumin were synthesized and deposited using simple dip-coating method. All of the tested polymers could coat different types of elastomers widely used for urethral catheters independent to the surface properties, and the thickness of the coating could be controlled by the number of depositions. The coating formed stable water-containing lubricant surface beneficial as a physical repellant of microbial attachment. In addition, the coating could be combined with additional antibacterial agents such as silver nanoparticles to maximize the antibacterial effect on the surface of urethral catheter materials.

Enhancement of biological nitrogen removal performance using novel carriers based on the recycling of waste materials

This study aims to enhance biological nitrogen removal performance by the innovative carbon-based carriers. The new carriers were produced based on recycling waste materials. In these carriers, the advantages of the hybrid system and physicochemical properties of activated carbon were integrated to promote microbial attachment. To verify the performance of the new carriers compared to the conventional moving carriers, the experiments were conducted in two parallel laboratory-scale sequencing batch reactors under various operating conditions. The analysis revealed that the specific surface area of the new carrier with a total pore volume of 0.0015cm3/gr was 10.9 times the specific surface area of a conventional carrier. Further, the comparative results indicated that the new highly porous carriers made a major contribution to increasing the attached active biomass up to 20.2%. From the data analysis (DO, ORP, and pH), it was also confirmed that the new carriers had a positive effect on the creation of a greater anoxic zone within the biofilm. Consequently, the simultaneous nitrification-denitrification and total nitrogen removal efficiencies enhanced significantly up to 14.3% and 16.8%, respectively. From the environmental and economic viewpoints, the benefits of the novel carrier showed that it is a practical alternative for the conventional carrier providing a cost-effective wastewater treatment technology.

Enhancement of power generation with concomitant removal of toluene from artificial groundwater using a mini microbial fuel cell with a packed-composite anode

Composite beads are packed in the anode chamber of a microbial fuel cell (MFC), providing more area for microbial attachment and growth, increasing the efficiency of removal of toluene from toluene-contaminated groundwater. The composite beads were fabricated by integrating carbon coke (CC) with a relatively large specific surface area to which microorganisms easily adhere with conductive carbon black (CCB), which has low electrical resistance. Since the advantages of both are complementary, the power generation of MFC is improved. The single layer-packed anode MFC (SP-MFC) completely degraded 200 mg L−1 of toluene - 2.3 times faster than the non-packed anode MFC (NP-MFC). The high power density (44.9 mW m-3) and oxidation peak (1 mA), with low internal resistance (207 Ω) revealed that SP effectively improved the power generation efficiency. A composition ratio (CRCCB:CC) of composite beads of one to two yielded the best performance with a removal efficiency of 100 % – 76 % faster than CC. The closed circuit voltage of CR1:2 MFC reached 340 mV, which was 16 times that of CC; the power density and oxidation peak reached 103 mW m-3 and 1.38 mA, respectively. Therefore, CR1:2 effectively increased the overall removal efficiency and power generation of the MFC.

Identification and characterization of core sludge and biofilm microbiota in anaerobic membrane bioreactors

An analysis of sludge (i.e., 63 samples) and biofilm (i.e., 79 samples) sampled from 13 anaerobic membrane bioreactors (AnMBR) was conducted. Predominant microbial community identification and multivariate analysis indicate that these reactors showed different microbial community structure, but these differences had no impact on the overall AnMBR performance. Instead, core microbial genera which occurred in ≥90% of sludge (20 genera) and biofilm (12 genera) samples could potentially account for the AnMBR performance. A further calculation on net growth rate (NGR) of core genera in sludge suggested distribution into two main groups (i.e., I: low relative abundance and NGR, II: high relative abundance or high NGR). Consistent positive correlations between bacterial genera were observed among those that exhibited either high relative abundance or high NGR. The anaerobic microbial consortium in both sludge and biofilm were largely affected by stochastic dispersal and migration processes (i.e., neutral assembly). However, Acinetobacter spp. and Methanobacterium spp. occurred consistently in higher frequency in the biofilm but in lower occurrence frequency in the AnMBR permeate. Findings from this study suggest first, specific core microorganisms exist in the sludge regardless of the operating conditions of the AnMBRs, and second, prevention of biofoulant layer on anaerobic membranes can be devised by minimizing attachment of microbes on surfaces in a non-selective manner.

Recombinant fibrolytic feed enzymes and ammonia fibre expansion (AFEX) pretreatment of crop residues to improve fibre degradability in cattle

Low digestibility of crop residues limits their use as animal feeds. The study examined the potential of Ammonia Fibre Expansion (AFEX) technology and dietary supplementation of a preselected recombinant xylanase to improve the in situ degradability of four crop residues for ruminants. AFEX pretreatment uses anhydrous ammonia, moisture, moderate temperature, and a short period of high pressure and results in partial lignin solubilization and hemicellulose hydrolysis, and increased surface area of substrate for microbial attachment. In situ neutral detergent fibre degradabilities of untreated (control) and AFEX pretreated crop residues (barley straw, corn stover, rice straw, and wheat straw) were determined in 8 heifers using a 2-period cross-over design with two dietary treatments (without and with XYL10C; 1,4-β-xylanase; recombinant enzyme from glycoside hydrolase family 10 produced by Aspergillus niger). The enzyme was diluted in water and applied to the barley straw (6.6 × 104 IU enzyme/kg straw dry matter) component of the basal diet (30 g/100 g diet dry matter) and to the control and AFEX crop residues incubated in situ. There were no interactions between enzyme and crop residues for A, B, or A + B fractions, indicating no enzyme × substrate specificity. Averaged across crop residues, enzyme slightly decreased the A fraction (P < 0.001) and slightly increased the B fraction (P = 0.02), such that there was no overall effect on A + B (P = 0.21). However, there were significant interactions between enzyme and AFEX for kd (P = 0.026); enzyme had no effect on control crop residues but it increased kd of AFEX residues by 12% (0.0323 vs. 0.0361 /h). As a result, xylanase supplementation increased the effective rumen degradability of crop residues by about 3%, but only when they were pretreated with AFEX (interaction, P ≤ 0.098). AFEX greatly increased effective ruminal degradability (+ 28 to + 126% depending upon the crop residue; P < 0.001), mainly by increasing the B fraction and decreasing the undigested fibre fraction, indicating increased accessibility of substrate to rumen microbial enzymes. The study demonstrates the tremendous potential of AFEX treatment to improve the feeding value of crop residues. Enzyme XYL10C was more effective for AFEX crop residues, possibly due to increased accessibility to substrate, suggesting that this enzyme may be more effective for less lignified and pretreated feeds.

The viscosity behaviors of bacterial suspensions or extracellular polymeric substances and their effects on aerobic granular sludge.

Although the viscosity behavior of bacteria and extracellular polymeric substances (EPS) in flocculent activated sludge (FAS) and aerobic granular sludge (AGS) has been investigated, no studies have explored the role of viscosity in microbial attachment in pure culture. This study investigated the viscosity behavior of bacteria and EPS. The results showed that bacteria and their EPS exhibited non-Newtonian fluid and shear-thinning behavior. The viscosity of bacteria and EPS was 1.55-3.80cP and 1.10-2.40cP, respectively, while the attachment of bacteria (optical density at 600nm) was 0.1426-3.1015. Bacteria with high attachment secreted EPS with a higher viscosity (2.40cP), whereas those with weak attachment expressed EPS with a lower viscosity (1.10cP). Viscosity and microbial attachment or extracellular polysaccharide (PS) content were significantly positively correlated. PS content was the source of bacterial viscosity, and β-polysaccharide played a more important role in viscosity and microbial attachment than α-polysaccharide. Thus, viscosity plays a critical role in microbial attachment, and high viscosity and PS content result in high microbial attachment, which is beneficial to the granulation process of AGS.

Liquid hot water pretreatment to enhance the anaerobic digestion of wheat straw—effects of temperature and retention time

Wheat straw is an abundant agricultural waste that is rich in lignocellulose. However, its waxy surface, highly crystallized structure, and limited surface area make it difficult to be hydrolyzed and used efficiently by microorganisms. Liquid hot water (LHW) pretreatment was studied to explore the feasibility of improving the methane yield of wheat straw in anaerobic digestion (AD). The results showed that the crosslinking structure of wheat straw was broken by LHW pretreatment. Some pores and cracks appeared on the surface of the pretreated wheat straw, increasing the microbial attachment sites. Under different hydrothermal temperatures (150-225 °C) and retention times (5-60 min), the degradation of hemicellulose ranged from 27.69 to 99.07%. The maximum methane yield (201.81 mL CH4/g volatile solids) was achieved after LHW pretreatment at 175 °C for 30 min, which was a 62.9% increase compared with non-treated straw. LHW at high temperatures such as 225 °C was not suitable for the AD of wheat straw. Methane yield results were fitted with the first-order and modified Gompertz equations to evaluate the hydrolysis rate and inhibitory effects of the pretreated materials in AD.

Biodegradable plastics from linier low-density polyethylene and polysaccharide: The influence of polysaccharide and acetic acid

Global problems associated with conventional, non-biodegradable plastics have urged the society to use more eco-friendly biodegradable plastics. In this study, linear low-density polyethylene (LLDPE) was co-compounded with cassava-based thermoplastic starch (TPS) to prepare biodegradable plastics (i.e. plastics that can be degraded by microbes), in which three different LLDPE/TPS ratios were studied. Acetic acid was used to hydrolyze the polysaccharides by breaking the branched amylopectin that causes the TPS-containing composites brittle and stiff. The biodegradation properties of the LLDPE/TPS composites were determined by observing the level of microbial growth on the sample surface after incubation with potato dextrose agar medium that was inoculated with Penicillium sp. and Aspergillus niger . Burial test in a humid composting medium was also performed to validate the biodegradation properties. The mass change (%) was calculated in relative to the initial mass before burial test. The physical properties (tensile strength and elongation at break) of the bioplastics were determined using universal testing machine before and after burial treatment. The morphology of the sample surface was evaluated using scanning electron microscopy. The results showed that the microbial growth increases with increasing TPS content. Negative mass changes were observed on all samples that contain TPS, with increase in the magnitude with increasing TPS content. The tensile strength tends to increase in the first 28 days of burial period in a composting medium then decreases and plateaus, while the elongation at break decreases with increasing burial period. Moreover, samples that contain acetic acid showed less microbial attachment and less biodegradation compared to samples that does not contain acetic acid.

Application of Novel 3,4-Dihydroxyphenylalanine-Containing Antimicrobial Polymers for the Prevention of Uropathogen Attachment to Urinary Biomaterials.

Introduction and Objective: Urinary catheters and stents are frequently prone to catheter-associated urinary tract infections (CAUTI) through biofilm formation. Several strategies have been evaluated in search of a stent coating to reliably prevent adherence of bacteria and biofilm. Previous in vivo and in vitro research with methoxylated polyethylene glycol 3,4-dihydroxyphenylalanine (DOPA) copolymer as a candidate coating showed promising results to reduce the bacterial attachment. We aimed to further enhance this antimicrobial activity by adding antimicrobial agents to newly synthesized DOPA-based copolymers. Materials and Methods: Building on our previous experience, novel copolymers were engineered based on DOPA. Quaternary ammonium groups and silver particles were added by cross-linking to increase the antimicrobial activity through both kill-by-contact and planktonic killing. After coating polyurethane sheets and measuring contact angles, all candidate coatings were challenged in vitro with an Escherichia coli culture. The most promising coatings were then further evaluated against a panel of seven clinically relevant uropathogens and planktonic killing, and microbial attachment was determined. Results: Initially, seven coatings were developed, referred to as Surphys 093-099. The most significant increase in contact angle was identified in Surphys-095 and -098. Surphys coatings S-094, S-095, and S-098 were cross-linked with silver and exhibited profound antimicrobial properties when challenged with E. coli. Further testing demonstrated S-095 to have antimicrobial efficacy against gram-positive and gram-negative bacteria at different silver-loading concentrations. The final coating, consisting of a 2 mg/mL solution of S-095 cross-linked with 0.25 mg/mL AgNO3, appeared to be highly bactericidal showing a ≥99.9% bacterial killing effect while remaining below cytotoxicity levels. Conclusions: We were able to engineer DOPA-based copolymers and add quaternary ammonium and silver particles, thus increasing the bactericidal properties of the coating. These coatings have exhibited a biologically significant ability to prevent uropathogens from attaching to biomaterials and represent a realistic opportunity to combat CAUTI.

Application of New Biomedical Materials in Orthodontic Appliances.

This review article describes the application and characteristics of certain biomedical materials in orthodontic appliances. The elastic recoil of shape memory polymers, determination of the forces and moments experienced by the brackets and eventually by the tooth, reduction in treatment time by employing self-healing smart brackets and decreased enamel lost during debonding due to usage of biomimetic adhesives such as dihydroxyphenylalanine (DOPA) is discussed. Increased plaque retention and microbial attachment around brackets and teeth is of profound concern and by utilisation of hydrophobic properties of self-cleaning materials, this can be reduced significantly. Implantation of bioresorbable temporary anchorage devices, which resorb once their purpose is accomplished and increasing the concentration of fluoride in the oral environment to counter the deleterious consequences of orthodontic treatment such as white spot lesions and caries, are also discussed briefly.

Making quantitative sense of electromicrobial production

The integration of electrochemical and microbial processes offers a unique opportunity to displace fossil carbon with CO2 and renewable energy as the primary feedstocks for carbon-based chemicals. Yet, it is unclear which strategy for CO2 activation and electron transfer to microbes has the capacity to transform the chemical industry. Here, we systematically survey experimental data for microbial growth on compounds that can be produced electrochemically, either directly or indirectly. We show that only a few strategies can support efficient electromicrobial production, where formate and methanol seem the best electron mediators in terms of energetic efficiency of feedstock bioconversion under both anaerobic and aerobic conditions. We further show that direct attachment of microbes to the cathode is highly constrained due to an inherent discrepancy between the rates of the electrochemical and biological processes. Our quantitative perspective provides a data-driven roadmap towards an economically and environmentally viable realization of electromicrobial production.

Ease of biofilm accumulation, and efficacy of sanitizing treatments in removing the biofilms formed, on coupons made of materials commonly used in blueberry packing environment

Biofilm-forming ability of six two-strain mixtures of fecal coliforms, isolated from six different fresh market blueberry packing lines in Georgia, was assessed at 10 °C for 7 days on coupons made of materials commonly used for fresh market blueberry packing lines, lugs and clamshells. These materials included stainless steel, rubber, polyvinyl chloride, polypropylene, polyurethane, high-density polyethylene and polyethylene terephthalate. Coupons with developed biofilms were treated for 1 min at room temperature with four different sanitizers commonly used by blueberry packers in Georgia, including 5 ppm chlorine dioxide, 3 ppm ozonated water, 200 ppm quaternary ammonium compound or 200 ppm sodium hypochlorite. Residual biofilms on treated coupons were subsequently quantified using the crystal violet binding assay. On average, the amount of biofilm mass was significantly greater (P ≤ 0.05) on polypropylene, compared to the other coupons used in the study. Biofilms formed on polyvinyl chloride and rubber coupons were statisically similar (P > 0.05), but were significantly lower than those on polypropylene and polyurethane coupons and significantly higher than those on high-density polyethylene, stainless steel and polyethylene terephthalate coupons. Ozonated water had significantly higher efficiency in biofilm removal than the quaternary ammonium compound which had significantly higher efficiency than chlorine dioxide, followed by sodium hypochlorite. On average, significantly more residual biofilm mass was found on rubber coupons after the sanitizing treatments. The amounts of residual biofilms on polypropylene, polyvinyl chloride and high-density polyethylene coupons were statistically similar, but were significantly higher than those on polyurethane and stainless steel coupons. The evaluated sanitizers had different efficacies in biofilm removal. The type of coupon materials used in the study played a significant role in biofilm accumulation and removal. These results emphazise the importance of selecting proper chemical sanitizers (with high efficacies in microbial inactivation and biofilm removal) and surface materials (with low tendency in attracting microbial attachments) for fresh market blueberry packing lines because these decisions may affect the hygiene conditions of fresh market blueberry packing lines as well as the microbial quality of the fruits.

Bacterial-nanostructure interactions: The role of cell elasticity and adhesion forces

The attachment of single-celled organisms, namely bacteria and fungi, to abiotic surfaces is of great interest to both the scientific and medical communities. This is because the interaction of such cells has important implications in a range of areas, including biofilm formation, biofouling, antimicrobial surface technologies, and bio-nanotechnologies, as well as infection development, control, and mitigation. While central to many biological phenomena, the factors which govern microbial surface attachment are still not fully understood. This lack of understanding is a direct consequence of the complex nature of cell-surface interactions, which can involve both specific and non-specific interactions. For applications involving micro- and nano-structured surfaces, developing an understanding of such phenomenon is further complicated by the diverse nature of surface architectures, surface chemistry, variation in cellular physiology, and the intended technological output. These factors are extremely important to understand in the emerging field of antibacterial nanostructured surfaces. The aim of this perspective is to re-frame the discussion surrounding the mechanism of nanostructured-microbial surface interactions. Broadly, the article reviews our current understanding of these phenomena, while highlighting the knowledge gaps surrounding the adhesive forces which govern bacterial-nanostructure interactions and the role of cell membrane rigidity in modulating surface activity. The roles of surface charge, cell rigidity, and cell-surface adhesion force in bacterial-surface adsorption are discussed in detail. Presently, most studies have overlooked these areas, which has left many questions unanswered. Further, this perspective article highlights the numerous experimental issues and misinterpretations which surround current studies of antibacterial nanostructured surfaces.