Roberto Rusconi

• PhD
• Professor (Associate) at Humanitas University, Milan, Italy

Introduction Periprosthetic joint infections (PJIs) occur at a rate of 1–2% in primary arthroplasties and 4% in revisions, posing a significant healthcare challenge. PJI diagnosis is hindered by absence of a universally accepted diagnostic standard. The primary outcome was to develop a predictive model to identify patients at risk of developing unf...

Macrophages play pivotal roles in the immune response, participating in both inflammatory and pro-healing processes. Like other cells, macrophages continually survey their microenvironment through mechanosensing, adapting their intracellular organization in response to mechanical signals. In this study, we elucidate how macrophages perceive the top...

Breast implants are extensively employed for both reconstructive and esthetic purposes. However, the safety of breast implants with textured surfaces has been questioned, owing to a potential correlation with anaplastic large-cell lymphoma and the recurrence of breast cancer. This study investigates the immune response elicited by different prosthe...

The recognition of microbe and extracellular matrix (ECM) is a recurring theme in the humoral innate immune system. Fluid-phase molecules of innate immunity share regulatory roles in ECM. On the other hand, ECM elements have immunological functions. Innate immunity is evolutionary and functionally connected to hemostasis. Staphylococcus aureus (S....

The incidence of periprosthetic joint infections (PJIs) is ~2% of total procedures and it is expected to rise due to an ageing population. Despite the large burden PJI has on both the individual and society, the immune response to the most commonly isolated pathogens, i.e., Staphylococcus aureus and Staphylococcus epidermidis, remains incompletely...

Bacteria often live surrounded by polymer solutions, such as in animal respiratory, gastrointestinal, and reproductive tracts. In these systems, polymer solutions are often exposed to fluid flow, and their complex rheology can affect the transport of chemical compounds and microorganisms. Recent studies have focused on the effect of polymer solutio...

Biofilm formation is the most successful survival strategy for bacterial communities. In the biofilm lifestyle, bacteria embed themselves in a self-secreted matrix of extracellular polymeric substances (EPS), which acts as a shield against mechanical and chemical insults. When ambient flow is present, this viscoelastic scaffold can take a streamlin...

Significance Streamers, filamentous bacterial biofilms formed in flowing systems, are ubiquitous in natural and artificial environments, where they cause clogging of devices and spreading of infections. Despite their impact, little is known about the nature and properties of streamers and their response to fluid flow. Here, we uncover the specific...

Biofilm formation is the most successful survival strategy for bacterial communities. In the biofilm lifestyle, bacteria embed themselves in a self-secreted matrix of extracellular polymeric substances (EPS), which acts as a shield against mechanical and chemical insults. When ambient flow is present, this viscoelastic scaffold can take a streamlin...

The spread of biofilms on medical implants represents one of the principal triggers of persistent and chronic infections in clinical settings, and it has been the subject of many studies in the past few years, with most of them focused on prosthetic joint infections. We review here recent works on biofilm formation and microbial colonization on a l...

Across diverse habitats, bacteria are mainly found as biofilms, surface-attached communities embedded in a self-secreted matrix of extracellular polymeric substances (EPS), which enhances bacterial resistance to antimicrobial treatment and mechanical stresses. In the presence of flow and geometric constraints such as corners or constrictions, biofi...

The colonization of surfaces by bacteria is a widespread phenomenon with consequences on environmental processes and human health. While much is known about the molecular mechanisms of surface colonization, the influence of the physical environment remains poorly understood. Here we show that the colonization of non-planar surfaces by motile bacter...

The colonization of solid surfaces by bacteria is a widespread phenomenon with major consequences on environmental processes, biotechnology and human health. While much is known about the molecular mechanisms of surface colonization, the influence of the physical environment remains poorly understood. Here we show that the magnitude and location of...

Microorganisms often live in habitats characterized by fluid flow, from lakes and oceans to soil and the human body. Bacteria and plankton experience a broad range of flows, from the chaotic motion characteristic of turbulence to smooth flows at boundaries and in confined environments. Flow creates forces and torques that affect the movement, behav...

In natural environments, microbes are typically non‐dividing and gauge when nutrients permit division. Current models are phenomenological and specific to nutrient‐rich, exponentially growing cells, thus cannot predict the first division under limiting nutrient availability. To assess this regime, we supplied starving Escherichia coli with glucose...

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In natural environments, microbes are typically non-dividing. Such quiescent cells manage fleeting nutrients and gauge when intra- and extracellular resources permit division. Quantitative prediction of the division event as a function of nutritional status is currently achieved through phenomenological models for nutrient-rich, exponentially growi...

Bacteria often adhere to surfaces, where they form communities known as biofilms. Recently, it has been shown that biofilm formation initiates with the microscopically heterogeneous deposition of a skeleton of extracellular polymeric substances (EPS) by individual cells crawling on the surface, followed by growth of the biofilm into a surface-cover...

The development of strategies to reduce the load of unwanted bacteria is a fundamental challenge in industrial processing, environmental sciences and medical applications. Here, we report a new method to sequester motile bacteria from a liquid, based on passive, deployable micro-traps that confine bacteria using micro-funnels that open into trappin...

Aerotaxis, the directed migration along oxygen gradients, allows many microorganisms to locate favorable oxygen concentrations. Despite oxygen’s fundamental role for life, even key aspects of aerotaxis remain poorly understood. In Bacillus subtilis, for example, there is conflicting evidence of whether migration occurs to the maximal oxygen concent...

Quorum sensing (QS) is a population-density dependent chemical process that enables bacteria to communicate based on the production, secretion and sensing of small inducer molecules. While recombinant constructs have been widely used to decipher the molecular details of QS, how those findings translate to natural QS systems has remained an open que...

The advent of microscale technologies such as microfluidics has revolutionized many areas of biology, yet has only recently begun to impact the field of bacterial biofilms. By enabling accurate control and manipulation of physical and chemical conditions, these new microscale approaches afford the ability to include important features of natural an...

Dense suspensions of motile bacteria, possibly including the human gut microbiome, exhibit collective dynamics akin to those observed in classic, high Reynolds number turbulence with important implications for chemical and biological transport, yet this analogy has remained primarily qualitative. Here, we present experiments in which a dense suspen...

How microorganisms interact with their environment and with their conspecifics depends strongly on their mechanical properties , on the hydrodynamic signatures they generate while swimming and on fluid flows in their environment. The rich fluid-structure interaction between flagella – the appendages microorganisms use for propulsion – and the surro...

Fluid flow, ubiquitous in natural and man-made environments, has the potential to profoundly impact the transport of microorganisms, including phytoplankton in aquatic habitats and bioreactors. Yet, the effect of ambient flow on the swimming behaviour of phytoplankton has remained poorly understood, largely owing to the difficulty of observing cell...

Microbes often live in moving fluids. Despite the multitude of implications that flow has on microbial ecology and environmental microbiology, only recently have experimental tools and conceptual frameworks from fluid physics been applied systematically to further our knowledge of the behavior of microbes in flow. This nascent research field, which...

Bacteria are the smallest and most abundant form of life. They have traditionally been considered as primarily planktonic organisms, swimming or floating in a liquid medium, and this view has shaped many of the approaches to microbial processes, including for example the design of most antibiotics. However, over the last few decades it has become c...

In many environments, bacteria favor a sessile, surface-attached community lifestyle. These communities, termed biofilms, are ubiquitous among many species of bacteria. In some cases, biofilms form under flow conditions. Flow chambers, and in particular microfluidic channels, can be used to observe biofilm development and physiological effects whil...

Microfluidics has significantly contributed to the expansion of the frontiers of microbial ecology over the past decade by allowing researchers to observe the behaviors of microbes in highly controlled microenvironments, across scales from a single cell to mixed communities. Spatially and temporally varying distributions of organisms and chemical c...

Bacteria often live in dynamic fluid environments, and flow can affect fundamental microbial processes such as nutrient uptake and infection. However, little is known about the consequences of the forces and torques associated with fluid flow on bacteria. Through microfluidic experiments, we show that fluid shear produces strong spatial heterogenei...

Diseases are an emerging threat to ocean ecosystems. Coral reefs, in particular, are experiencing a worldwide decline because of disease and bleaching, which have been exacerbated by rising seawater temperatures. Yet, the ecological mechanisms behind most coral diseases remain unidentified. Here, we demonstrate that a coral pathogen, Vibrio coralli...

A deletion of pslAB in the WT PAO1 background reduces total biomass in an in vitro biofilm model. Crystal violet assays were used to quantify the total biomass for air-liquid interface biofilms grown in 96 well plates for 24, 48, and 72-hour biofilms. The total biomass for ΔpslAB was reduced relative to WT PAO1 for all time points measured. Althoug...

Lectin staining reveals patterns of Psl distribution in 24-hour biofilms. Fluorescently labeled HHA stained Psl in WT PAO1, ΔpelA, ΔalgD, PBAD-psl, and CF127 biofilms [54]. Both PA14 and ΔpslAB lack Psl in the matrix and did not bind HHA. Psl was distributed as a localized, fibrous material associated with WT PAO1 and PBAD-psl biofilms, while in Δp...

Psl protects 24-hour biofilms from cationic antimicrobial peptides. WT PAO1, WT PA14, ΔpslAB, ΔpelA, ΔalgD, PBAD-psl, and CF127 biofilms were grown for 24, 48, 72 hours in microtiter plates. After a 2-hour treatment with 32 µg/ml of colistin (A) or polymyxin B (B), cell viability was measure and reported at CFU (log10). Psl-mediated protection was...

Psl protects 24-hour biofilms from cationic antimicrobial peptides. WT PAO1, WT PA14, ΔpslAB, ΔpelA, ΔalgD, PBAD-psl, and CF127 biofilms were grown for 24, 48, 72 hours in microtiter plates. After a 2-hour treatment with 650 µg/ml of tobramycin (A) or 50 µg/ml ciprofloxacin (B), cell viability was measure and reported at CFU (log10). Psl-mediated p...

Biofilms treated with water only did not contribute to cell death in microfluidic channel. To serve as a control, biofilms grown in microfluidic channels were treated with sterile water only and monitored for cell death for 2 hours. Images of WT PAO1 and mutant strain ΔpslAB stained with Syto 9 (live cells) and propidium iodide (dead cells) were ac...

Description of the strains and antibiotics used in this study. (DOCX)

Polymyxin B interaction with the extracellular matrix in planktonic cells. Images of over-producing Psl (PBAD-psl) and Psl deficient (ΔpslAB) cells after a 2-hour challenge with fluorescent polymyxin B. Polymyxin B accumulates in the EPS of Psl over-expressing cells, but appears to bind directly to the cell surface in the Psl deletion strain. Scale...

Biomass before and after treatment with colistin. 3-D projection of confocal images of WT PAO1 and mutant strain ΔpslAB were acquired and compared before (at 24 hours) and after treatment (at 26 hours) with 20 µg/ml colistin. Cells were stained with Syto9 (Molecular Probes) and counted in the series of xyz images. Scale bars represent 25 µm. (TIF)

Psl increases MBC-B for E. coli and S. aureus. MBC-B assay reveals an increase in tolerance toward colistin for E. coli and PBAD-psl biofilms (A). Tolerance is also observed toward tobramycin for S. aureus and PBAD-psl biofilms, but to a lesser extent (B). (TIF)

Bacteria within biofilms secrete and surround themselves with an extracellular matrix, which serves as a first line of defense against antibiotic attack. Polysaccharides constitute major elements of the biofilm matrix and are implied in surface adhesion and biofilm organization, but their contributions to the resistance properties of biofilms remai...

We demonstrate a novel pattern that results in bacterial biofilms as a result of the competition between hydrodynamic forces and adhesion forces. After the passage of an air plug, the break up of the residual thin liquid film scrapes and rearranges bacteria on the surface, such that a Swiss cheese pattern of holes is left in the residual biofilm.

The diversity of the morphologies, propulsion mechanisms, flow environments, and behaviors of planktonic microorganisms has long provided inspiration for fluid physicists, with further intrigue provided by the counterintuitive hydrodynamics of their viscous world. Motivation for studying the fluid dynamics of microplankton abounds, as microorganism...

Bacteria often exhibit directed motility (``taxis'') in response to gradients of dissolved resources, like nutrients or oxygen. While we have a detailed understanding of chemotaxis in quiescent environments, it has been largely overlooked how this behavior is affected by fluid flow, despite the ubiquity of flow in bacterial habitats. Here we presen...

The deformation of a flexible filament held fixed at one end in a nonuniform viscous flow with curved streamlines is considered, with a focus on the filament dynamics and steady-state shape. Our motivation arises from recent microfluidic experiments on biofilm formation: in a channel with bends, thread-like structures, or streamers, were observed,...

Although ubiquitous, the processes by which bacteria colonize surfaces remain poorly understood. Here we report results for the influence of the wall shear stress on the early-stage adhesion of Pseudomonas aeruginosa PA14 on glass and polydimethylsiloxane surfaces. We use image analysis to measure the residence time of each adhering bacterium under...

In most environments, such as natural aquatic systems, bacteria are found predominantly in self-organized sessile communities known as biofilms. In the presence of a significant flow, mature multispecies biofilms often develop into long filamentous structures called streamers, which can greatly influence ecosystem processes by increasing transient...

In recent microfluidic experiments with solutions of bacteria we observed the formation of biofilms in the form of thread-like structures, called ‘streamers’, which float in the middle plane of the channel and are connected to the side walls at the inner corners. Motivated by this observation, we discuss here the pressure-driven low-Reynolds-number...

We show that thermophoresis, i.e., mass flow driven by thermal gradients, can be used to drive particle motion in microfluidic devices exploiting suitable temperature control strategies. Due to its high sensitivity to particle/solvent interfacial properties, this method presents several advantages in terms of selectivity compared to standard partic...

We show that a large set of nanofluid thermal conductivity data falls within the upper and lower Maxwell bounds for homogeneous systems. This indicates that the thermal conductivity of nanofluids is largely dependent on whether the nanoparticles stay dispersed in the base fluid, form large aggregates, or assume a percolating fractal configuration....

Bacterial biofilms have an enormous impact on medicine, industry and ecology. These microbial communities are generally considered to adhere to surfaces or interfaces. Nevertheless, suspended filamentous biofilms, or streamers, are frequently observed in natural ecosystems where they play crucial roles by enhancing transport of nutrients and retent...

For many physical, chemical and biological measurements, temperature is a crucial parameter to control. In particular, the recent development of microreactors and chip-based technologies requires integrated thermostatic systems. However, the requirements of disposability and visual inspection of a device under a microscope cannot accommodate equipm...

We exploit the recent developments of microfluidic technologies to investigate the collective shear-induced diffusion in suspensions of micron-sized particles. Whereas spherical particles do not diffuse on the time scale of our experiments, the results with platelike clay particles show a strong cross-stream shear-induced diffusivity at low volume...

Measuring the concentration profiles induced by gravity settling is known to be an efficient route to obtain the equation of state of a colloidal suspension, to inspect the fine details of the phase diagram and to provide clues on the nature of metastable phases. Here we show that a careful analysis of the transient settling profiles may add valuab...

Transient hot-wire data on thermal conductivity of suspensions of silica and perfluorinated particles show agreement with the mean-field theory of Maxwell but not with the recently postulated microconvection mechanism. The influence of interfacial thermal resistance, convective effects at microscales, and the possibility of thermal conductivity enh...

A large variety of engaging phenomena, ranging from crystallization in protein solutions to the formation of colloidal gels and glasses via depletion forces, stems from the occurrence of very short-ranged attractive forces. From depolarized light scattering measurements of equilibrium sedimentation profiles, we obtain an accurate description of the...

Numerical simulation has been used to investigate the effects of natural convection on measurements of the thermal conductivity of fluids by transient hot-wire methods. Comparison of the numerical data with the experimental results obtained with a custom-built setup exploiting a short-wire geometry allows fixing an operationally useful time scale,...

The authors show that the thermal conductivity and diffusivity of colloidal particle dispersions can be rapidly obtained with high accuracy and reproducibility by exploiting a noninvasive, all-optical thermal lensing method. Applications of this technique to model suspensions of spherical monodisperse particles suggest that classical models for the...

By performing measurements on a large class of macromolecular and colloidal systems, we show that thermophoresis (particle drift induced by thermal gradients) in aqueous solvents displays a distinctive universal dependence on temperature. For systems of particles interacting via temperature-independent forces, this behavior is strictly related to t...

We show that thermophoresis (particle drift driven by thermal gradients) in aqueous solutions can be measured by using an all-optical thermal-lensing setup, where a temperature gradient is set by a near-infrared laser beam with no need of light-absorbing dyes. After discussing the principles of the method, we study by numerical simulation the natur...