Bacterial adhesion measurements on soft contact lenses using a Modified Vortex Device and a Modified Robbins Device

S. marcescens 8100 andP. aeruginosa 15442 were used to study bacterial adhesion to hydrogel contact lenses which had not been worn. Bacterial removal from unworn lens materials was assessed with a calibrated vortex device modified with a digital rpm readout and fitted with a test tube attachment (MVD). The MVD, which relies on a whirlpool-like force to remove the bacteria, showed that bacteria adhered to the same degree to etafilcon A, vifilcon A and polymacon lenses under standardized conditions. Tracking the isoenzyme patterns of these bacterial species over time showed instability ofS. marcescens upon repeated passage. This instability was not evident withP. aeruginosa. Bacterial adhesion ofP. aeruginosa 15442, to human worn and unworn etafilcon A materials was determined with a Modified Robbins Device. The MRD was closed off at both ends stopping medium and bacterial movement after 1 h of fluid flow over the lens surface. The results show that immediately following this 1-h period more bacteria adhere to unworn contact lenses than to worn lenses. However, bacterial counts were equivalent on worn and unworn lenses following 5 h of static incubation.     

The inhibitory activity of pomelo essential oil on the bacterial biofilms development on soft contact lenses

The aim of present study was to investigate the microbial colonization of worn contact lenses (CLs) and to evaluate the inhibitory effect of pomelo (Citrus maxima) peels essential oil on the biofilm development on unworn CLs. The essential oil was isolated by steam distillation and analyzed by gas chromatography coupled with mass spectrometry, twenty compounds being isolated. The antimicrobial activity of pomelo oil was tested against S. epidermidis and P. aeruginosa strains, known for their ability to develop biofilms on prosthetic devices, by qualitative screening methods and quantitative assay of the minimal inhibitory concentrations (MIC) in order to evaluate the antibiofilm activity. Our study revealed that all worn CLs where 100% colonized by staphylococci and Enterobacteriaceae strains. The pomelo essential oil inhibited the development of bacterial biofilms formed by Gram-positive and Gram-negative microorganisms on soft CLs, its antibiofilm activity being specific and dependent on different physical parameters (contact time and temperature). The architecture of bacterial biofilms developed on soft contact lenses was analyzed using confocal scanning laser microscopy (CSLM).     

A relatively small change in sodium chloride concentration has a strong effect on adhesion of ocular bacteria to contact lenses

Adhesion of bacteria to hydrogel lenses is thought to be an initial step of ocular colonization allowing evasion of normal host defences. The salt concentration of media is an important parameter controlling microbial adhesion. Salinity varies from 0·97% NaCl equivalents in the open eye to 0·89% in the closed eye state. In this study, the effect of sodium chloride in the concentration range of 0·8–1·0% (w/v) NaCl on adhesion of ocular bacteria to soft contact lenses was investigated using a static adhesion assay. Pseudomonas aeruginosa was found to adhere to lenses in significantly greater amounts than Serratia marcescens, Flavobacterium meningosepticum, Stenotrophomonas maltophilia and Staphylococcus intermedius . Increasing NaCl from 0·8% to 1·0% (w/v) increased adhesion of all bacteria tested. This adhesion was strong since the organisms could not be removed by washing in low ionic buffer. Adhesion of these organisms did not correlate with their cell surface properties as determined by bacterial adhesion to hydrocarbons (BATH) and retention on sepharose columns.     

Adhesion of Pseudomonas aeruginosa,Achromobacter xylosoxidans,Delftia acidovorans,Stenotrophomonas maltophilia to contact lenses under the influence of an artificial tear solution

Abstract

Corneal infection is a devastating sight-threatening complication that is associated with contact lens (CL) wear, commonly caused by Pseudomonas aeruginosa. Lately, Achromobacter xylosoxidans, Delftia acidovorans, and Stenotrophomonas maltophilia have been associated with corneal infection. This study investigated the adhesion of these emerging pathogens to CLs, under the influence of an artificial tear solution (ATS) containing a variety of components commonly found in human tears. Two different CL materials, etafilcon A and senofilcon A, either soaked in an ATS or phosphate buffered saline, were exposed to the bacteria. Bacterial adhesion was investigated using a radio-labeling technique (total counts) and plate count method (viable counts). The findings from this study revealed that in addition to P. aeruginosa, among the emerging pathogens evaluated, A. xylosoxidans showed an increased propensity for adherence to both CL materials and S. maltophilia showed lower viability. ATS influenced the viable counts more than the total counts on CLs.     

Adaptation and growth of Serratia marcescens in contact lens disinfectant solutions containing chlorhexidine gluconate.

Serratia marcescens (11 of 12 strains) demonstrated an ability to grow in certain chlorhexidine-based disinfecting solutions recommended for rigid gas-permeable contact lenses. For a representative strain, cells that were grown in nutrient-rich medium, washed, and inoculated into disinfecting solution went into a nonrecoverable phase within 24 h. However, after 4 days, cells that had the ability to grow in the disinfectant (doubling time, g = 5.7 h) emerged. Solutions supporting growth of S. marcescens were filter sterilized. These solutions, even after removal of the cells, showed bactericidal activity against Pseudomonas aeruginosa and a biphasic survival curve when rechallenged with S. marcescens. Adaptation to chlorhexidine by S. marcescens was not observed in solutions formulated with borate ions. For chlorhexidine-adapted cells, the MIC of chlorhexidine in saline was eightfold higher than that for unadapted cells. Cells adapted to chlorhexidine showed alterations in the proteins of the outer membrane and increased adherence to polyethylene. Cells adapted to chlorhexidine persisted or grew in several other contact lens solutions with different antimicrobial agents, including benzalkonium chloride.     

Dynamics of flagellum- and pilus-mediated association of Pseudomonas aeruginosa with contact lens surfaces

Flagella and pili are appendages that modulate attachment of Pseudomonas aeruginosa to solid surfaces. However, previous studies have mostly reported absolute attachment. Neither the dynamic roles of these appendages in surface association nor those of attachment phenotypes have been quantified. We used video microscopy to address this issue. Unworn, sterile, soft contact lenses were placed in a laminar-flow optical chamber. Initial lens association kinetics for P. aeruginosa strain PAK were assessed in addition to lens-surface association phenotypes. Comparisons were made to strains with mutations in flagellin (fliC) or pilin (pilA) or those in flagellum (motAB) or pilus (pilU) function. PAK and its mutants associated with the contact lens surface at a constant rate according to first-order kinetics. Nonswimming mutants associated ～30 to 40 times slower than the wild type. PAK and its pilA mutant associated at similar rates, but each ～4 times faster than the pilU mutant. Lens attachment by wild-type PAK induced multiple phenotypes (static, lateral, and rotational surface movement), each showing only minor detachment. Flagellin (fliC) and flagellar-motility (motAB) mutants did not exhibit surface rotation. Conversely, strains with mutations in pilin (pilA) and pilus retraction (pilU) lacked lateral-surface movement but displayed enhanced surface rotation. Slower surface association of swimming-incapable P. aeruginosa mutants was ascribed to lower convective-diffusion-arrival rates, not to an inability to adhere. Flagellum function (swimming) enhanced lens association, attachment, and rotation; hyperpiliation hindered lens association. P. aeruginosa bound through three different adhesion sites: flagellum, pili, and body. Reduction of bacterial attachment to contact lenses thus requires blockage of multiple adhesion phenotypes.     

Cell adhesion to fibronectin and tenascin: quantitative measurements of initial binding and subsequent strengthening response

Cell-substratum adhesion strengths have been quantified using fibroblasts and glioma cells binding to two extracellular matrix proteins, fibronectin and tenascin. A centrifugal force-based adhesion assay was used for the adhesive strength measurements, and the corresponding morphology of the adhesions was visualized by interference reflection microscopy. The initial adhesions as measured at 4 degrees C were on the order of 10(-5)dynes/cell and did not involve the cytoskeleton. Adhesion to fibronectin after 15 min at 37 degrees C were more than an order of magnitude stronger; the strengthening response required cytoskeletal involvement. By contrast to the marked strengthening of adhesion to FN, adhesion to TN was unchanged or weakened after 15 min at 37 degrees C. The absolute strength of adhesion achieved varied according to protein and cell type. When a mixed substratum of fibronectin and tenascin was tested, the presence of tenascin was found to reduce the level of the strengthening of cell adhesion normally observed at 37 degrees C on a substratum of fibronectin alone. Parallel analysis of corresponding interference reflection micrographs showed that differences in the area of cell surface within 10-15 nm of the substratum correlated closely with each of the changes in adhesion observed: after incubation for 15 min on fibronectin at 37 degrees C, glioma cells increased their surface area within close contact to the substrate by integral to 125- fold. Cells on tenascin did not increase their surface area of contact. The increased surface area of contact and the inhibitory activity of cytochalasin b suggest that the adhesive "strengthening" in the 15 min after initial binding brings additional adhesion molecules into the adhesive site and couples the actin cytoskeleton to the adhesion complex.     

Bacterial colonization of rigid gas permeable and hydrogel contact lenses by Staphylococcus aureus

Staphylococcus aureus ATCC 6538 and a clinical isolate of S. aureus from a bacterial keratitis patient were examined for their ability to adhere to etafilcon A, polymacon, silafocon, and pauflufocon A, B and C contact lenses. Both isolates adhered more to the rigid gas permeable (RGP) materials than to the hydrogel lenses tested (P < 0.05). S. aureus ATCC 6538 adhered to the etafilcon A material to a greater extent than did the clinical isolate (P < 0.05). there were no statistically significant differences in the recovery of staphylococci from unworn lens materials when surface area, composition and ionicity were evaluated for either the hydrogel or rgp lenses tested against lenses of a similar type. however, differences were observed when hydrogel lenses were evaluated against rgp lenses (P < 0.05). these differences may be related to water content. Journal of Industrial Microbiology & Biotechnology (2000) 24, 113–115. Received 12 August 1999/ Accepted in revised form 02 November 1999     

Observation of soft contact lens disinfection with fluorescent metabolic stains

A rapid fluorescent staining method using a tetrazolium dye and propidium iodide for the in-use assessment of disinfection of Pseudomonas aeruginosa biofilms on soft contact lenses showed that 11 to 13% of cells on lenses remained actively respiring and recoverable by culture methods after 30 min of exposure to 3% hydrogen peroxide.     

Swarming of Pseudomonas aeruginosa is dependent on cell-to-cell signaling and requires flagella and pili

We describe swarming in Pseudomonas aeruginosa as a third mode of surface translocation in addition to the previously described swimming and twitching motilities. Swarming in P. aeruginosa is induced on semisolid surfaces (0.5 to 0.7% agar) under conditions of nitrogen limitation and in response to certain amino acids. Glutamate, aspartate, histidine, or proline, when provided as the sole source of nitrogen, induced swarming, while arginine, asparagine, and glutamine, among other amino acids, did not sustain swarming. Cells from the edge of the swarm were about twice as long as cells from the swarm center. In both instances, bacteria possessing two polar flagella were observed by light and electron microscopy. While a fliC mutant of P. aeruginosa displayed slightly diminished swarming, a pilR and a pilA mutant, both deficient in type IV pili, were unable to swarm. Furthermore, cells with mutations in the las cell-to-cell signaling system showed diminished swarming behavior, while rhl mutants were completely unable to swarm. Evidence is presented for rhamnolipids being the actual surfactant involved in swarming motility, which explains the involvement of the cell-to-cell signaling circuitry of P. aeruginosa in this type of surface motility.     

Role of E-Cadherin in Membrane-Cortex Interaction Probed by Nanotube Extrusion

This study aims to define the role of E-cadherin (Ecad) engagement in cell-cell contact during membrane-cortex interaction. As a tool, we used a hydrodynamic membrane tube extrusion technique to characterize the mechanical interaction between the plasma membrane and the underlying cortical cytoskeleton. Cells were anchored on 4.5 μm beads coated with polylysine (PL) to obtain nonspecific cell adhesion or with an antibody against Ecad to mimic specific Ecad-mediated cell adhesion. We investigated tube length dynamics L(t) over time and through successive extrusions applied to the cell at regular time intervals. A constant slow velocity was observed for the first extrusion, for PL-attached cells. Subsequent extrusions had two phases: an initial high-velocity regime followed by a low-velocity regime. Successive extrusions gradually weakened the binding of the membrane around the tube neck to the underlying cortical cytoskeleton. Cells specifically attached via Ecad first exhibited a very low extrusion velocity regime followed by a faster extrusion regime similar to nonspecific extrusion. This indicates that Ecad strengthens the membrane-cortical cytoskeleton interaction, but only in a restricted area corresponding to the site of contact between the cell and the bead. Occasional giant “cortex” tubes were extruded with specifically anchored cells, demonstrating that the cortex remained tightly bound to the membrane through Ecad-mediated adhesion at the contact site.     

Corneal Cell Adhesion to Contact Lens Hydrogel Materials Enhanced via Tear Film Protein Deposition

Tear film protein deposition on contact lens hydrogels has been well characterized from the perspective of bacterial adhesion and viability. However, the effect of protein deposition on lens interactions with the corneal epithelium remains largely unexplored. The current study employs a live cell rheometer to quantify human corneal epithelial cell adhesion to soft contact lenses fouled with the tear film protein lysozyme. PureVision balafilcon A and AirOptix lotrafilcon B lenses were soaked for five days in either phosphate buffered saline (PBS), borate buffered saline (BBS), or Sensitive Eyes Plus Saline Solution (Sensitive Eyes), either pure or in the presence of lysozyme. Treated contact lenses were then contacted to a live monolayer of corneal epithelial cells for two hours, after which the contact lens was sheared laterally. The apparent cell monolayer relaxation modulus was then used to quantify the extent of cell adhesion to the contact lens surface. For both lens types, lysozyme increased corneal cell adhesion to the contact lens, with the apparent cell monolayer relaxation modulus increasing up to an order of magnitude in the presence of protein. The magnitude of this increase depended on the identity of the soaking solution: lenses soaked in borate-buffered solutions (BBS, Sensitive Eyes) exhibited a much greater increase in cell attachment upon protein addition than those soaked in PBS. Significantly, all measurements were conducted while subjecting the cells to moderate surface pressures and shear rates, similar to those experienced by corneal cells in vivo.     

Utilization of Organic Liquid Fertilizer in Microalgae Cultivation for Biodiesel Production

The utilization of organic liquid fertilizer PAL-1 as the culture medium of the microalga Chlorella vulgaris was investigated for the purpose of biodiesel production. Cell growth and lipid accumulation in PAL-1 were evaluated and compared with those in the artificial medium BG-11. Cells showed mixotrophic growth when utilizing the organic liquid fertilizer PAL-1. The rates of cell growth (0.143 d^-1) and N consumption (14.9 mg/L/d) in PAL-1 were almost the same as those in BG-11, under the presence of 2% CO₂-enriched aeration and light irradiation. Lipid synthesis was triggered in PAL-1 on day 4, when nitrogen was completely consumed, and the lipid content reached up to 48% thereafter. Lipid productivity could be enhanced using repeated-batch cultivation in which cells were exposed to N limitation repeatedly, and thus lipid synthesis was induced while maintaining a sufficiently high cell density.     

Colonization of hydrophilic contact lenses by yeast

The growth of six strains of yeast was analyzed in vitro in order to assess their capacity for colonizing (adhesion and invasion) hydrophilic contact lenses. Lenses with different water content were cultured in two culture media for 3, 7, 14, and 21 days. Only strain 93150 of Candida albicans could adhere to and invade the polymers. Specifically, fungal growth was observed in cultures with Sabourauds broth. The degree of yeast colonization of contact lenses was significantly related to the species, the strain, and the culture medium in which the yeast and lenses were cultured. The results here obtained were compared with those reported for the filamentous fungus Aspergillus niger 2700. For both microorganisms, the strain and the medium in which the lenses and microorganism were cultured influenced the colonization, but the percentage of colonized lenses, the degree of colonization, and the density and size of the internalized colonies were always noticeably lower for C. albicans 93150. Colonization by A. niger 2700 was also related to the type of material of the lenses and the incubation period. For both microorganisms, when the strain is right and the growth and development are correct, colonization of hydrophilic contact lenses occurs.     

Ultrasonic model and system for measurement of corneal biomechanical properties and validation on phantoms

Non-invasive measurement of biomechanical properties of corneas may provide important information for ocular disease management and therapeutic procedures. An ultrasonic non-destructive evaluation method with a wave propagation model was developed to determine corneal biomechanical properties in vivo. In this study, we tested the feasibility of the approach in differentiating the mechanical properties of soft contact lenses as corneal phantoms. Three material types of soft contact lenses (six samples in each group) were measured using a broadband ultrasound transducer. The ultrasonic reflections from the contact lenses were recorded by a 500MHz/8-bit digitizer, and displayed and processed by a PC. A reference signal was recorded to compute the normalized power spectra using Fast Fourier Transformation. An inverse algorithm based on least-squares minimization was used to reconstruct three parameters of the contact lenses: density, thickness, and elastic constants lambda+2micro. The thickness of each sample was verified using an electronic thickness gauge, and the averaged density for each type of lenses was verified using Archimedes' principle and manufacturer's report. Our results demonstrated that the ultrasonic system was able to differentiate the elastic properties of the three types of the soft contact lenses with statistical significance (P-value<0.001). The reconstructed thicknesses and densities agreed well with the independent measurements. Our studies on corneal phantoms indicated that the ultrasonic system was sensitive and accurate in measuring the material properties of cornea-like structures. It is important to optimize the system for in vivo measurements.     

Activated platelets form protected zones of adhesion on fibrinogen and fibronectin-coated surfaces

Leukocytes form zones of close apposition when they adhere to ligand- coated surfaces. Because plasma proteins are excluded from these contact zones, we have termed them protected zones of adhesion. To determine whether platelets form similar protected zones of adhesion, gel-filtered platelets stimulated with thrombin or ADP were allowed to adhere to fibrinogen- or fibronectin-coated surfaces. The protein- coated surfaces with platelets attached were stained with either fluorochrome-conjugated goat anti-human fibrinogen or anti-human fibronectin antibodies, or with rhodamine-conjugated polyethylene glycol polymers. Fluorescence microscopy revealed that F(ab')2 anti- fibrinogen (100 kD) did not penetrate into the contact zones between stimulated platelets and the underlying fibrinogen-coated surface, while Fab antifibrinogen (50 kD) and 10 kD polyethylene glycol readily penetrated and stained the substrate beneath the platelets. Thrombin- or ADP-stimulated platelets also formed protected zones of adhesion on fibronectin-coated surfaces. F(ab')2 anti-fibronectin and 10 kD polyethylene glycol were excluded from these adhesion zones, indicating that they are much less permeable than those formed by platelets on fibrinogen-coated surfaces. The permeability properties of protected zones of adhesion formed by stimulated platelets on surfaces coated with both fibrinogen and fibronectin were similar to the zones of adhesion formed on fibronectin alone. mAb 7E3, directed against the alpha IIb beta 3 integrin blocked the formation of protected adhesion zones between thrombin-stimulated platelets and fibrinogen or fibronectin coated surfaces. mAb C13 is directed against the alpha 5 beta 1 integrin on platelets. Stimulated platelets treated with this mAb formed protected zones of adhesion on surfaces coated with fibronectin. These protected zones were impermeable to F(ab')2 antifibronectin but were permeable to 10 kD polyethylene glycol. These results show that activated platelets form protected zones of adhesion and that the size of molecules excluded from these zones depends upon the composition of the matrix proteins to which the platelets adhere. They also show that formation of protected zones of adhesion by platelets requires alpha IIb beta 3 integrins while the permeability properties of these zones of adhesion are regulated by both alpha IIb beta 3 and alpha 5 beta 1 integrins.     

INDUCTION OF SPECIFIC PROTEINS IN EUKARYOTIC ALGAE GROWN UNDER IRON-, PHOSPHORUS-, OR NITROGEN-DEFICIENT CONDITIONS1

What limits phytoplankton growth in nature? The answer is elusive because of methodological problems associated with bottle incubations and nutrient addition experiments. We are investigating the possibility that antibodies to proteins repressed by a specific nutrient can be used as probes to indicate which nutrient limits photosynthetic carbon fixation in the ocean. The diatom Phaeodactylum tricornutum Bohlin and the chlorophyte Dunaliella tertiolecta Butcher were grown in batch cultures in artificial seawater and f/2 nutrient lacking either phosphorus, iron, or nitrogen. Chlorosis was induced by nutrient limitation in both species with the exception of phosphorus-limited D. tertiolecta. The synthesis and appearance of specific proteins were followed by labeling with ¹⁴C-bicarbonate. Nutrient limitation in general leads to a decrease in the quantum efficiency of photosystem II, suggesting that deficiency of any nutrient affects the photosynthetic apparatus to some degree: however, the effect of nitrogen and iron limitation on quantum efficiency is more severe than that of phosphorus. A crude fractionation of the soluble and membrane proteins demonstrated that the large proteins induced under limitation by phosphorus and iron were associated with the membranes. However, small iron-repressible proteins were located in the soluble fraction. Isolation with anion-exchange chromatography and N-terminal sequencing of iron-repressible, 23-kDa Proteins from D. tertiolecta, P. tricornutum, and Chaetoceros gracilis revealed that these small soluble proteins have strong homology with the N-terminal sequence of flavodoxins from Azotobacter and Clostridium. The identity of the flavodoxin from D. tertiolecta was confirmed by immunodetection using antiflavodoxin raised against Chlorella. Flavodoxin was detected only under iron deprivation and was absent from nitrogen-and phosphorus-limited algae. Flavodoxin is a prime candidate for a molecular probe of iron limitation in the ocean. The requirements to confirm its utility in nature are discussed.     

Human IgA inhibits adherence of Acanthamoeba polyphaga to epithelial cells and contact lenses

Specific anti-Acanthamoeba IgA antibodies have been detected in the serum and tears of patients and healthy individuals. However, the role of human secretory IgA antibodies in inhibiting the adherence of Acanthamoeba had not been previously investigated. Therefore, the purpose of this study was to purify secretory IgA from human colostrum and analyze its effect on the adherence of Acanthamoeba trophozoites to contact lenses and Madin-Darby canine kidney (MDCK) cells. IgA antibodies to Acanthamoeba polyphaga in colostrum of healthy women as well as in saliva and serum of healthy subjects were analyzed by ELISA and Western blot analysis. In serum, saliva, and colostrum, we detected IgA antibodies that recognized several antigens of A. polyphaga. In addition, colostrum and IgA antibodies purified from it inhibited adherence of A. polyphaga trophozoites to contact lenses and MDCK cells. These results suggest that IgA antibodies may participate in the resistance to the amoebic infection, probably by inhibiting the adherence of the trophozoites to contact lenses and corneal epithelial cells.     

Type IV pili are involved in plant–microbe and fungus–microbe interactions

Adherence of bacteria to eukaryotic cells is essential for the initiation of infection in many animal and human pathogens, e.g. Neisseria gonorrhoeae and Pseudomonas aeruginosa . Adhesion-mediating type IV pili, filamentous surface appendages formed by pilin subunits, are crucial virulence factors. Here, we report that type IV pilus-dependent adhesion is also involved in plant–bacteria and fungus–bacteria interactions. Nitrogen-fixing, endophytic bacteria, Azoarcus sp., can infect the roots of rice and spread systemically into the shoot without causing symptoms of plant disease. Formation of pili on solid media was dependent on the pilAB locus. PilA encodes an unusually short (6.4 kDa) putative pilin precursor showing 100% homology to the conserved N-terminus of the Pseudomonas aeruginosa type IV pilin. PilB encodes for a 14.2 kDa polypeptide showing similarity to FimF, a component of type I fimbriae of Escherichia coli . It was found to be extruded beyond the cell surface by immunofluorescence studies, and it may, therefore, be part of a pilus assembly complex or the pilus itself. Both genes are involved in the establishment of bacteria on the root surface of rice seedlings, as detected by fluorescence microscopy. Moreover, both genes are necessary for bacterial adhesion to the mycelium of an ascomycete, which was isolated from the same rhizosphere as the bacteria. In co-culture with the fungus, Azoarcus sp. forms complex intracytoplasmic membranes, diazosomes, which are related to efficient nitrogen fixation. Adhesion to the mycelium appears to be crucial for this process, as diazosomes were absent and nitrogen fixation rates were decreased in pilAB mutants in co-culture.     

Real-time monitoring of hematopoietic cell interaction with fibronectin fragment

Real-time cell analysis (RTCA) system based on measurement of electrical microimpedance has been introduced to monitor adherent cell cultures. We describe its use for real-time analysis of hematopoietic cell adhesion to bone marrow stroma proteins. Cells growing in suspension do not generate any significant change in the microimpedance signal until the surface with embedded microelectrodes is coated with a cell-binding protein. We show that in this case, the microimpedance signal specifically reflects cell binding to the coated surface. The optimized method was used to monitor the effect of two histone deacetylase inhibitors, suberoylanilide hydroxamic acid (SAHA) and tubastatin A, on JURL-MK1 cell adhesion to cell-binding fragment of fibronectin (FNF). Both compounds were used in non-toxic concentrations and induced an increase in the cell adhesivity. The kinetics of this increase was markedly slower for SAHA although tubulin hyperacetylation occurred rapidly for any of the two drugs. The strengthening of cell binding to FNF was paralleled with a decrease of Lyn kinase activity monitored using an anti-phospho-Src family antibody. The inhibition of Src kinase activity with PP2 accordingly enhanced JURL-MK1 cell interaction with FNF. Actin filaments were present at the proximity of the plasma membrane and in numerous membrane protrusions. In some cells, F-actin formed clusters at membrane regions interacting with the coated surface and these clusters colocalized with active Lyn kinase. Our results indicate that the role of Src kinases in the regulation of hematopoetic cell adhesion signaling is similar to that of c-Src in adherent cells.