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HYPOTHESIS: The ability exhibited by insect wings to resist microbial infestation is a unique feature developed over 400 million years of evolution in response to lifestyle and environmental pressures. The self-cleaning and antimicrobial properties of insect wings may be attributed to the unique combination of nanoscale structures found on the wing surface. EXPERIMENTS: In this study, we characterised the wetting characteristics of superhydrophobic damselfly Calopteryx haemorrhoidalis wings. We revealed the details of air entrapment at the micro- and nano scales on damselfly wing surfaces using a combination of spectroscopic and electron microscopic techniques. Cryo-focused-ion-beam scanning electron microscopy was used to directly observe fungal spores and conidia that were unable to cross the air-liquid interface. By contrast, bacterial cells were able to cross the air-water interface to be ruptured upon attachment to the nanopillar surface. The robustness of the air entrapment, and thus the wing antifungal behaviour, was demonstrated after 1-week of water immersion. A newly developed wetting model confirmed the strict Cassie-Baxter wetting regime when damselfly wings are immersed in water. FINDINGS: We provide evidence that the surface nanopillar topography serves to resist both fungal and bacterial attachment via a dual action: repulsion of fungal conidia while simultaneously killing bacterial cells upon direct contact. These findings will play an important role in guiding the fabrication of biomimetic, anti-fouling surfaces that exhibit both bactericidal and anti-fungal properties.

International audience; A whitish Gram-negative, motile, aerobic bacterium designated H 14T was isolated from seawater collected in Port Phillip Bay, Melbourne, at St. Kilda beach. Analysis of 16S rRNA gene sequences revealed that the organism belonged to the Roseobacter lineage of the class Alphaproteobacteria forming a distinct evolutionary lineage on the genus level. Strain H 14T was weakly related to Nautella, Ruegeria and Pseudoruegeria (family Rhodobacteraceae). Strain H 14T did not degrade gelatin, casein, chitin, agar and starch, did not produce any carotenoids, did not have Bacteriochlorophyll a, and had limited ability to utilise carbon sources. Strain H 14T grew at 1-8% of NaCl with the temperature range of 5-35 degrees C. Phosphatidylglycerol was the major phospholipid (90%); phosphatidylcholine (7.9%) and phosphatidylethanolamine (2%), were present in minor quantities. The predominant fatty acids were C18:0 (3.8%), C18:1omega9 (5.1%) and C18:1omega7 (82.4%). The DNA base composition for strain H 14T was 59.1 mol% G+C. Based on the results of physiological, biochemical, chemotaxonomic and phylogenetic investigations, new genus Celeribacter gen. nov., with a new species Celeribacter neptunius sp. nov. is proposed. The type strain is H 14T (= KMM 6012T = CIP 109922T).

International audience; A pale yellowish pigmented non motile strain 022-2-26T was isolated from a starfish Stellaster equestris. Gram-negative, short rod-shaped, nonmotile bacterium was chemoorganotrophic, alkalitolerant, and mesophilic. The type strain 022-2-26T contained MK-6 as the predominant menaquinone. The major cellular fatty acids were iso-15:0, iso-15:1, 15:0, iso-15:0-2OH and iso-17:0-3OH (together representing 86.4% of the total fatty acids). The DNA base composition was 30.1 mol% GC. A 16S rRNA gene sequence of the type strain 022-2-26T was determined and phylogenetic analyses revealed that 022-2-26T formed a robust clade (confirmed by neighbor-joining, parsimony and maximum-likelihood algorithms and 95% of bootstrap replication) with species of the genus Winogradskyella. The closest related species was Winogradskyella poriferorum UST030701-295T showing a similarity of 96% (59 differences between sequences). On the basis of the phenotypic, chemotaxonomic characteristics and phylogenetic evidence, it is suggested that the bacteria be classified as a novel species, Winogradskyella exilia sp. nov. The type strain is 022-2-26T (KMM 6013T = CIP 109976T).

Refereed/Peer-reviewed Liquid metals (LMs) have emerged as novel materials for biomedical applications. Here, the interactions taking place between cells and LMs are reported, presenting a unique opportunity to explore and understand the LM-biological interface. Several high-resolution imaging techniques are used to characterize the interaction between droplets of gallium LM and bacterial, fungal, and mammalian cells. Adhesive interactions between cells and LM droplets are observed, causing deformation of the LM droplet surface, resulting in surface wrinkling and in some cases, breakage of the native oxide layer present on the LM droplet surface. In many instances, the cell wall deforms to intimately contact the LM droplets. Single-cell force spectroscopy is performed to quantify the adhesion forces between cells and LM and characterize the nature of the adhesion. It is proposed that the flexible nature of the cell enables multiple adhesion sites with the LM droplets, imparting tensile forces on the LM droplet surface, which results in surface wrinkling on the LM droplets due to their liquid nature. Molecular dynamics simulations also suggest that flexible biomolecules on the cell surface can disrupt the Ga2O3 layer formed at the LM droplet surface. This study reveals a unique biointerfacial interaction and provides insights into the mechanisms involved.

Dragonflies have gained much attention due to their sophisticated wing surface structure, and their associated superhydrophobic, self-cleaning and bactericidal properties. In this work, we compared and contrasted the chemical composition and surface morphology of the wing membranes of four species of dragonfly and damselfly from the Odonata family collected in 1970s (Diplacodes melanopsis and Xanthagrion erythroneurum) and 2011 (Diplacodes bipunctata, and Ischnura heterosticta). Diplacodes species are dragonflies, whilst Xanthagrion and Ischnura are damselflies. Fourier-transform infrared spectroscopy data obtained from the Australian Synchrotron were used to classify the fundamental components of all four of the insect species' wings. The spectra of all species were dominated by C H stretching, amide I and amide II and O-H stretch absorbance indicating the presence of a similar membrane composition of chitin, protein and wax in all four species. Although the samples were collected 40 years apart, there was no evidence of degradation having taken place during this time. Despite the overall similarities in spectral profile, species-specific differences were observed, most notably in the intensity of the vCH(2) peaks, which in part reflected the amount of waxes present on the wings, which appeared to be different between individual species. The surface topography also contained minor differences in the diameter and the spacial distribution of its nanopillars. It is postulated that the differences in surface wettability of the wings could be attributed to these minor differences in surface chemistry and surface topography. For example, X. erythroneurum presented the highest water contact angle (WCA) of 160 degrees whilst the D. melanopsis wings exhibited the lowest WCA (138), and the wettability of their wings was found to directly correlate with the intensity of hydrocarbon peaks found in their respective IR specta. Refereed/Peer-reviewed

Numerous natural surfaces possess superhydrophobicity and self-cleaning properties that would be extremely beneficial when applied in industry. Dragonfly wings are one example of such surfaces, and while their general surface structure is known, their precise chemical composition is not. Here, the epicuticular lipids of dragonfly wing membranes were characterized to investigate their significance in contributing to self-cleaning and superhydrophobic properties. After just 10 s of lipid extraction using chloroform, the water contact angles exhibited by the wings decreased below the accepted threshold for superhydrophobicity (150 degrees). Infrared spectra collected at the Australian Synchrotron contained characteristic absorption bands of amide, ester and aliphatic hydrocarbons moieties on the wing surfaces, the latter of which was decreased post-extraction with chloroform. GC-MS data analysis revealed that the epicuticular wax components were dominated by n-alkanes with even-numbered carbons, especially n-hexacosane, and palmitic acid. SEM and AFM data analysis conducted on the untreated and chloroform-extracted wing surfaces demonstrated that surface topography changed after extraction; the surface nanostructure was progressively lost with extended extraction times. The data presented here indicate that epicuticular lipids contribute not only to self-cleaning and superhydrophobic properties through their inherent hydrophobic nature, but also by forming the physical structure of the wing surface. This knowledge will be extremely valuable for reconstruction of dragonfly wing structures as a biomimetic template. Refereed/Peer-reviewed

In this review we attempt to clarify the notion of what is meant by the term antibacterial surfaces and categorise the approaches that are commonly used in the design of antibacterial surfaces. Application of surface coatings and the modification of the surface chemistry of substrata are generally considered to be a chemical approach to surface modification (as are surface polymerisation, functionalisation, and derivatisation), whereas, modification of the surface architecture of a substrate can be considered a physical approach. Here, the antifouling and bactericidal effects of antibacterial surfaces are briefly discussed. Finally, several recent efforts to design a new generation of antibacterial surfaces, which are based on mimicking the surface nanotopography of natural surfaces, are considered. Refereed/Peer-reviewed

Self-cleaning surfaces found in nature show great potential for application in many fields, ranging from industry to medicine. The ability for a surface to self-clean is intimately related to the wetting properties of the surface; for a surface to possess self-cleaning ability it must exhibit extremely high water contact angles and low water adhesion. While investigating the self-cleaning properties of damselfly wings, significant spatial variations in surface wettability were observed. Within an area of 100 mu m x 100 mu m of the wing surface the water contact angle was found to vary up to 17.8 degrees, while remaining consistently superhydrophobic. The contributions of both surface chemistry and topography to the hydrophobicity of the wings were assessed in an effort to explain these variations. Synchrotron-sourced Fourier-transform infrared microspectroscopy revealed that some of the major components of the wing were aliphatic hydrocarbons and esters, which are attributable to epicuticular lipids. The wing topography, as determined by optical profilometry and atomic force microscopy (AFM), also showed only minor levels of heterogeneity arising from irregular ordering of surface nanostructures. The measured contact angle of a single droplet of water was also found to decrease over time as it evaporated, reaching a minimum of 107 degrees. This is well below the threshold value for superhydrophobicity (i.e., 150 degrees), demonstrating that when the surface is in contact with water for a prolonged period, the damselfly wings lose their superhydrophobicity and subsequently their ability to self-clean. This decrease in hydrophobicity over time can be attributed to the surface undergoing a transition from the Cassie Baxter wettability state toward the Wenzel wettability state. Refereed/Peer-reviewed

Natural superhydrophobic surfaces are often thought to have antibiofouling potential due to their self‐cleaning properties. However, when incubated on cicada wings, Pseudomonas aeruginosa cells are not repelled; instead they are penetrated by the nanopillar arrays present on the wing surface, resulting in bacterial cell death. Cicada wings are effective antibacterial, as opposed to antibiofouling, surfaces. Refereed/Peer-reviewed

The molecular organization of the epicuticle (the outermost layer) of insect wings is vital in the formation of the nanoscale surface patterns that are responsible for bestowing remarkable functional properties. Using a combination of spectroscopic and chromatographic techniques, including Synchrotron-sourced Fourier-transform infrared microspectroscopy (FTIR), x-ray photoelectron spectroscopy (XPS) depth profiling and gas chromatography-mass spectrometry (GCMS), we have identified the chemical components that constitute the nanoscale structures on the surface of the wings of the dragonfly, Hemianax papuensis. The major components were identified to be fatty acids, predominantly hexadecanoic acid and octadecanoic acid, and n-alkanes with even numbered carbon chains ranging from C-14 to C-30. The data obtained from XPS depth profiling, in conjunction with that obtained from GCMS analyses, enabled the location of particular classes of compounds to different regions within the epicuticle. Hexadecanoic acid was found to be a major component of the outer region of the epicuticle, which forms the surface nanostructures, and was also detected in deeper layers along with octadecanoic acid. Aliphatic compounds were detected throughout the epicuticle, and these appeared to form a third discrete layer that was separate from both the inner and outer epicuticles, which has never previously been reported. Refereed/Peer-reviewed

Black silicon is a synthetic nanomaterial that contains high aspect ratio nanoprotrusions on its surface, produced through a simple reactive-ion etching technique for use in photovoltaic applications. Surfaces with high aspect-ratio nanofeatures are also common in the natural world, for example, the wings of the dragonfly Diplacodes bipunctata. Here we show that the nanoprotrusions on the surfaces of both black silicon and D. bipunctata wings form hierarchical structures through the formation of clusters of adjacent nanoprotrusions. These structures generate a mechanical bactericidal effect, independent of chemical composition. Both surfaces are highly bactericidal against all tested Gram-negative and Gram-positive bacteria, and endospores, and exhibit estimated average killing rates of up to ~450,000 cells min−1 cm−2. This represents the first reported physical bactericidal activity of black silicon or indeed for any hydrophilic surface. This biomimetic analogue represents an excellent prospect for the development of a new generation of mechano-responsive, antibacterial nanomaterials., The topographical features of insect wings result in some interesting surface properties, including hydrophobicity and antibacterial activity. Here the authors identify the surface of black silicon as a mimic of dragonfly wings and show that it too possesses antibacterial activity.

The nanopattern on the surface of Clanger cicada (Psaltoda claripennis) wings represents the first example of a new class of biomaterials that can kill bacteria on contact based solely on its physical surface structure. As such, they provide a model for the development of novel functional surfaces that possess an increased resistance to bacterial contamination and infection. Their effectiveness against a wide spectrum of bacteria, however, is yet to be established. Here, the bactericidal properties of the wings were tested against several bacterial species, possessing a range of combinations of morphology and cell wall type. The tested species were primarily pathogens, and included Bacillus subtilis, Branhamella catarrhalis, Escherichia coli, Planococcus maritimus, Pseudomonas aeruginosa, Pseudomonas fluorescens, and Staphylococcus aureus. The wings were found to consistently kill Gram-negative cells (i.e., B. catarrhalis, E. coli, P. aeruginosa, and P. fluorescens), while Gram-positive cells (B. subtilis, P. maritimus, and S. aureus) remained resistant. The morphology of the cells did not appear to play any role in determining cell susceptibility. The bactericidal activity of the wing was also found to be quite efficient; 6.1 +/- 1.5 x 10(6) P. aeruginosa cells in suspension were inactivated per square centimeter of wing surface after 30-min incubation. These findings demonstrate the potential for the development of selective bactericidal surfaces incorporating cicada wing nanopatterns into the design. Refereed/Peer-reviewed

The wings of some insects, such as cicadae, have been reported to possess a number of interesting and unusual qualities such as superhydrophobicity, anisotropic wetting and antibacterial properties. Here, the chemical composition of the wings of the Clanger cicada (Psaltoda claripennis) were characterized using infrared (IR) microspectroscopy. In addition, the data generated from two separate synchrotron IR facilities, the Australian Synchrotron Infrared Microspectroscopy beamline (AS-IRM) and the Synchrotron Radiation Center (SRC), University of Wisconsin-Madison, IRENI beamline, were analysed and compared. Characteristic peaks in the IR spectra of the wings were assigned primarily to aliphatic hydrocarbon and amide functionalities, which were considered to be an indication of the presence of waxy and proteinaceous components, respectively, in good agreement with the literature. Chemical distribution maps showed that, while the protein component was homogeneously distributed, a significant degree of heterogeneity was observed in the distribution of the waxy component, which may contribute to the self-cleaning and aerodynamic properties of the cicada wing. When comparing the data generated from the two beamlines, it was determined that the SRC IRENI beamline was capable of producing higher-spatial-resolution distribution images in a shorter time than was achievable at the AS-IRM beamline, but that spectral noise levels per pixel were considerably lower on the AS-IRM beamline, resulting in more favourable data where the detection of weak absorbances is required. The data generated by the two complementary synchrotron IR methods on the chemical composition of cicada wings will be immensely useful in understanding their unusual properties with a view to reproducing their characteristics in, for example, industry applications.

The nanoarchitecture and surface roughness of metallic thin films prepared by magnetron sputtering were analyzed to determine the topographical statistics that give the optimum description of their nanoarchitechture. Nanoscale topographical profiles were generated by performing atomic force microscopy (AFM) scans of 1 mu m x 1 mu m areas of titanium and silver films of three different thicknesses (3 nm, 12 nm, and 150 nm). Of the titanium films, the 150-nm film had the highest average roughness (Ra = 2.63 nm), more than four times that of the 3-nm and 12-nm titanium films. When silver films were coated on top of 150-nm titanium films, the average roughness increased further; the 3-nm (Ra = 4.96 nm) and 150-nm (Ra = 4.65 nm) silver films average roughnesses were approximately twice that of the 150-nm titanium film. For topographical analysis, seven statistical parameters were calculated. These parameters included commonly used roughness measurements, as well as some less commonly used measurements, in order to determine which combination of parameters gave the best overall description of the nanoarchitecture of the films presented. Skewness (Rskw), surface area increase (Rsa), and peak counts (Rpc) provided the best description of horizontal surface dimensions, and in conjunction with vertical descriptors Ra and Rq gave the best characterization of surface architecture. The five roughness parameters Ra, Rq, Rskw, Rsa, and Rpc are proposed as a new standard for describing surface nanoarchitecture. Refereed/Peer-reviewed

Substratum surface roughness is known to be one of the key factors in determining the extent of bacterial colonization. Understanding the way by which the substratum topography, especially at the nanoscale, mediates bacterial attachment remains ambiguous at best, despite the volume of work available on the topic. This is because the vast majority of bacterial attachment studies do not perform comprehensive topographical characterization analyses, and typically consider roughness parameters that describe only one aspect of the surface topography. The most commonly reported surface roughness parameters are average and root mean square (RMS) roughness (R-a and R-q respectively), which are both measures of the typical height variation of the surface. They offer no insights into the spatial distribution or shape of the surface features. Here, a brief overview of the current state of research on topography-mediated bacterial adhesion is presented, as well as an outline of the suite of roughness characterization parameters that are available for the comprehensive description of the surface architecture of a substratum. Finally, a set of topographical parameters is proposed as a new standard for surface roughness characterization in bacterial adhesion studies to improve the likelihood of identifying direct relationships between substratum topography and the extent of bacterial adhesion. Refereed/Peer-reviewed

Atomic force microscopy (AFM) is a technique that has long been employed in materials science, but is now increasingly being used in the biological sciences. AFM provides excellent topographical information on prokaryotic and eukaryotic cell surfaces, and the extracellular material produced by the cells. It helps to generate important data on the mechanical properties of cells, such as hardness and elasticity. AFM can also be used to measure the strength of adhesion, attraction, and repulsion forces between cells and surfaces or even between individual molecules. Additionally, by combining AFM with other complementary techniques such as fluorescence microscopy or Raman spectroscopy, the chemistry of given surface structures can be identified. This review aims to provide an update on the AFM techniques currently used in cell biology studies, along with a description of the range of recently developed research methodologies in which AFM plays a key role. Refereed/Peer-reviewed

The physicochemical and bactericidal properties of thin silver films have been analysed. Silver films of 3 and 150 nm thicknesses were fabricated using a magnetron sputtering thin-film deposition system. X-ray photoelectron and energy dispersive X-ray spectroscopy and atomic force microscopy analyses confirmed that the resulting surfaces were homogeneous, and that silver was the most abundant element present on both surfaces, being 45 and 53 at.% on the 3- and 150-nm films, respectively. Inductively coupled plasma time of flight mass spectroscopy (ICP-TOF-MS) was used to measure the concentration of silver ions released from these films. Concentrations of 0.9 and 5.2 ppb were detected for the 3- and 150-nm films, respectively. The surface wettability of the films remained nearly identical for both film thicknesses, displaying a static water contact angle of 95A degrees, while the surface free energy of the 150-nm film was found to be slightly greater than that of the 3-nm film, being 28.8 and 23.9 mN m(-1), respectively. The two silver film thicknesses exhibited statistically significant differences in surface topographic profiles on the nanoscopic scale, with R (a), R (q) and R (max) values of 1.4, 1.8 and 15.4 nm for the 3-nm film and 0.8, 1.2 and 10.7 nm for the 150-nm film over a 5 x 5 mu m scanning area. Confocal scanning laser microscopy and scanning electron microscopy revealed that the bactericidal activity of the 3-nm silver film was not significant, whereas the nanoscopically smoother 150-nm silver film exhibited appreciable bactericidal activity towards Pseudomonas aeruginosa ATCC 9027 cells and Staphylococcus aureus CIP 65.8 cells, obtaining up to 75% and 27% sterilisation effect, respectively. Refereed/Peer-reviewed