Microbial Adhesion To Solvents Research Articles

Probing surface properties of lactic acid bacteria - Comparative modification by anhydride and aldehyde grafting

Surface of Lactobacillus crispatus DSM 20584 (LBC) and Lactobacillus rhamnosus GG (LGG) from stationary and exponential phase were chemically modified using hexanoic anhydride (HA) and octanal via grafting hydrophobic moieties onto the bacterial surface hydroxyl and amine groups. The physicochemical properties of the bacteria were measured using a range of surface-sensitive methods including x-ray photoelectron spectroscopy (XPS), zeta potential measurement, contact angle measurement (CAM) and microbial adhesion to solvents (MATS). Before modification, the surface of two strains was distinctly different, where LBC was covered by hydrophobic surface-layer proteins (SLPs) while LGG was hydrophilic with the rich presence of polysaccharides. Surface hydrophilic polymers rendered steric hindrance of LGG against autoaggregation, whereas LBC lacking polysaccharides showed strong autoaggregation. After HA and octanal modifications, the intrinsic surface differences between two strains were reduced according to the Principal Component Analysis (PCA). The enhancement of hydrophobicity by HA and octanal was most likely derived from the lowered Lewis acid-base characters via elimination of hydroxyl and amine groups. Chemical modification using the two treatments can be a useful tool to tune the surface of lactic acid bacteria, which might be further applied to other microorganisms, enabling applications such as altered bacterial adhesive behaviors and biofilm formation.

Adhesion of Oral Bacteria to Commercial d-PTFE Membranes: Polymer Microstructure Makes a Difference.

Bacterial contamination of the membranes used during guided bone regeneration directly influences the outcome of this procedure. In this study, we analyzed the early stages of bacterial adhesion on two commercial dense polytetrafluoroethylene (d-PTFE) membranes in order to identify microstructural features that led to different adhesion strengths. The microstructure was investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR). The surface properties were analyzed by atomic force microscopy (AFM), scanning electron microscopy (SEM), and surface free energy (SFE) measurements. Bacterial properties were determined using the microbial adhesion to solvents (MATS) assay, and bacterial surface free energy (SFE) was measured spectrophotometrically. The adhesion of four species of oral bacteria (Streptococcus mutans, Streptococcus oralis, Aggregatibacter actinomycetemcomitas, and Veilonella parvula) was studied on surfaces with or without the artificial saliva coating. The results indicated that the degree of crystallinity (78.6% vs. 34.2%, with average crystallite size 50.54 nm vs. 32.86 nm) is the principal feature promoting the adhesion strength, through lower nanoscale roughness and possibly higher surface stiffness. The spherical crystallites (“warts”), observed on the surface of the highly crystalline sample, were also identified as a contributor. All bacterial species adhered better to a highly crystalline membrane (around 1 log10CFU/mL difference), both with and without artificial saliva coating. Our results show that the changes in polymer microstructure result in different antimicrobial properties even for chemically identical PTFE membranes.

Revealing the effect of lipopeptide on improving the probiotics characteristics: Flavor and texture enhancer in the formulated yogurt

Probiotics are beneficial viable microorganisms that protects from pathogens, enhance immunity and health. In this study, a biosurfactant from marine sponge associated bacteria MS48 was used to effectively enhance the survival of starter cultures and thereby improving their functional properties. The biosurfactant MS48 was characterized as lipopeptide based upon the spectroscopic analysis. The GC-MS analysis showed the moiety as l-glutamic acid methyl ester with the mass of m/z 161.16. Probiotics supplemented with lipopeptide showed better survival in the stress tolerance assays includes acid, bile, heat, salt stress and other assays including auto-aggregation, hydrophobicity, microbial adhesion to solvents (MATS), and simulated gastric juice. Yogurt formulated using lipopeptide showed enhanced flavor components, stability, improved characteristics, EPS production, and lower syneresis than the control. Malonic acid, acidity regulator was detected in the mass spectrum of lipopeptide added yogurt. The texture analysis of the lipopeptide added yogurt showed improved textural and sensorial properties when compared to the control.

Lactobacillus acidophilus ve Lactobacillus rhamnosus için Nerium oleander L. Ekstraktının Prebiyotik Olarak Kullanım Olanaklarının Araştırılması

The use of microorganisms that support human health and stimulate the immune system is gaining more importance. It is thought that probiotic bacterial strains, representing a significant portion of these microorganisms, may be treated in different disease groups. For instance, prevention of gastrointestinal diseases, ulcerative colitis, diarrhea, necrotizing enterocolitis, inflammatory bowel diseases, constipation, urogenital system health, rotavirus diarrhea as well as colon cancer can be prevented using probiotics. The probiotic bacterial strains, have basic needs such as bacterial auto-aggregation and cell surface hydrophobicity. Due to the phytochemicals contained in the Nerium oleander L., this plant has been used as medicinal plants. Such plants, when ingested, contact with the human gastrointestinal microbiome, so beneficial microorganisms can be affected. Thus, present study aimed to investigate the effects of Nerium oleander L. extract on two of the most studied and very well-known probiotic bacteria, Lactobacillus acidophilus and Lactobacillus rhamnosus. Nerium oleander L. was extracted using ethanol. Probiotics were grown in the presence of this extract. Surface hydrophobicity of probiotics grown in the presence of plant extract was assessed by Microbial Adhesion to Solvents (MATS) Assay, and auto-aggregation was performed. Auto-aggregation and surface hydrophobicity properties of these bacteria can be modulated by this plant, due to its phytochemicals. Auto-aggregation, as well as surface hydrophobicity were increased or decreased dependent on the dose as the plant extract The combinations of this plant and a probiotic strain could be next generation functional food, defined as food ingredient that has positive health benefits to the human.

Antibacterial Properties of Polyphenols: Characterization and QSAR (Quantitative Structure-Activity Relationship) Models.

Besides their established antioxidant activity, many phenolic compounds may exhibit significant antibacterial activity. Here, the effect of a large dataset of 35 polyphenols on the growth of 6 foodborne pathogenic or food-spoiling bacterial strains, three Gram-positive ones (Staphylococcus aureus, Bacillus subtilis, and Listeria monocytogenes) and three Gram-negative ones (Escherichia coli, Pseudomonas aeruginosa, and Salmonella Enteritidis), have been characterized. As expected, the effects of phenolic compounds were highly heterogeneous ranging from bacterial growth stimulation to antibacterial activity and depended on bacterial strains. The effect on bacterial growth of each of the polyphenols was expressed as relative Bacterial Load Difference (BLD) between a culture with and without (control) polyphenols at a 1 g L−1 concentration after 24 h incubation at 37°C. Reliable Quantitative Structure-Activity Relationship (QSAR) models were developed (regardless of polyphenol class or the mechanism of action involved) to predict BLD for E. coli, S. Enteritidis, S. aureus, and B. subtilis, unlike for L. monocytogenes and P. aeruginosa. L. monocytogenes was generally sensitive to polyphenols whereas P. aeruginosa was not. No satisfactory models predicting the BLD of P. aeruginosa and L. monocytogenes were obtained due to their specific and quite constant behavior toward polyphenols. The main descriptors involved in reliable QSAR models were the lipophilicity and the electronic and charge properties of the polyphenols. The models developed for the two Gram-negative bacteria (E. coli, S. Enteritidis) were comparable suggesting similar mechanisms of toxic action. This was not clearly observed for the two Gram-positive bacteria (S. aureus and B. subtilis). Interestingly, a preliminary evaluation by Microbial Adhesion To Solvents (MATS) measurements of surface properties of the two Gram-negative bacteria for which QSAR models were based on similar physico-chemical descriptors, revealed that MATS results were also quite similar. Moreover, the MATS results of the two Gram-positive bacterial strains S. aureus and B. subtilis for which QSARs were not based on similar physico-chemical descriptors also strongly differed. These observations suggest that the antibacterial activity of most of polyphenols likely depends on interactions between polyphenols and bacterial cells surface, although the surface properties of the bacterial strains should be further investigated with other techniques than MATS.

SELEKSI ISOLAT BAKTERI ASAM LAKTAT ASAL TEMPE DAN TAPE SEBAGAI KANDIDAT PROBIOTIK

Lactic acid bacteria (LAB) have been isolated from Indonesian fermented foods such as tempe and tape. Some lactic acid bacteria are known to have health benefits and as probiotics. The objective of this study was to evaluate the probiotic potential of lactic acid bacteria isolated from tempe and tape. LAB isolated from tape were evaluated for their tolerance towards low pH (pH 2.0) and 0.5% bile salt. LAB isolated from tape and tempe resistant to low pH and bile salt were then evaluated for their antimicrobial activities against pathogenic bacteria (E. coli ATCC 25922, S. typhimurium ATCC 14028, L. monocytoge-nes ATCC 7644, S. aureus ATCC 25923 and B. cereus ATCC 11778). The isolates were also tested for their adherence properties, consisting of hidrophobicity test using microbial adhesion to solvents (MATS) assay, autoaggregation as well as coaggregation between LAB and pathogens. The results of this study indicated that three isolates from tape (L. fermentum 1 BK2-5, L. fermentum 2 BK2-7, P. acidilactici NG6-4) showed good tolerance to pH 2.0 and 0.5% bile salt. L. fermentum S21209 isolated from tempe showed the strongest antimicrobial activity against the five pathogens tested. Based on the adhesion to xylene, L. fermentum 1 BK 2-5 was categorized as strong hydrophobic, followed by L. fermentum S21209 and L. fermentum TS4-5. Meanwhile, L. fermentum TS 4-5, L. fermentum S21209, L. fermentum 1 BK 2-5 and P. pentose-ceus 1 W2SR04 have the highest autoaggregation ability. L. fermentum S21209 also had the highest co-aggregation ability to the five pathogenic bacteria tested. The ability of LAB to coaggregate with all pathogens tested correlated with their strong antimicrobial properties. Based on the resistance toward low pH and bile salt, antimicrobial activity and adherence properties, L. fermentum S21209 from tempe and L. fermentum 1 BK 2-5 from tape are the most potential as probiotic candidates.

English

Bacillus cereus is a foodborne pathogen that often persists on food processing surfaces due the formation of spores and biofilms. Spores of 12 selected B. cereus strains from genotypes that recurred in a pasteurized milk processing line were investigated in this study, for their surface and biofilm characteristics. The main objective was to have an insight into their persistence strategies. Spore surface hydrophobicity and acid-base properties, were assessed using the microbial adhesion to solvents (MATS) method. To determine how hydrophobicity was affected by cleaning procedures, this property was measured when spores were submitted to alkali or acidic stresses mimicking those of cleaning-in-place (CIP) procedures. Biofilms formation on stainless steel coupons by pH-treated spores was investigated in three culture media and imaged by using environmental scanning electron microscopy (ESEM). Results showed that spores were either hydrophilic or moderately hydrophobic. Alkali-stress reduced spore surface hydrophobicity, whereas acidic shock increased it. More limited hydrophobicity changes following alkaline stress suggest alkali adaptation of spores. In addition, spores submitted to pH-stresses produced specific biofilm features on stainless steel as shown by ESEM imaging. Alkali tolerance and the biofilm lifestyle are strategies that permit B. cereus recurrent genotypes to persist in the milk processing line. Overall, this study gives an insight into hydrophobicity and specific biofilm features of B. cereus spores submitted to chemical cleaning. Key words: Bacillus cereus, biofilms, spores, hydrophobicity, CIP-like stress, dairy industry, environmental scanning electron microscopy (ESEM).

Cell surface characterization of some oleaginous green algae

This study reports a comprehensive set of experimentally measured surface properties of six oleaginous green microalgae. The results showed that the hydrophobic character of the six microalgae, determined by the contact angle method, was more accurate than by using the microbial adhesion to solvents (MATS) method. However, they both indicated that all studied microalgae presented an electron donor parameter. Due to the abundant surface carboxyl, phosphoryl, and hydroxyl groups, all microalgae presented a negatively charged surface. Monoraphidium dybowoskii XJ-377 was the most hydrophobic strain with a negative ΔG coh and the lowest surface free energy. Kirchneriella dianae XJ-93 had the lowest total surface functional group concentration and the lowest surface area, which can lower the harvesting cost. Overall, cellular surface properties should be evaluated and considered in oleaginous microalgal screening and identification in addition to the biomass and oil production normally considered.

Structure and antimicrobial activity relationship of royalisin, an antimicrobial peptide from royal jelly of Apis mellifera

Royalisin is a 5.5-kDa antibacterial peptide isolated from the royal jelly of the honeybee (Apis mellifera). The antimicrobial activity of royalisin against fungi, Gram-positive and Gram-negative bacteria has been revealed. Compared with another insect antibacterial peptide, there is an extra stretch of 11 amino acid residues at the C-terminus of royalisin. In this study, a recombinant shortened form of royalisin named as royalisin-D, was constructed without the 11 amino acid residues at the C-terminal of royalisin and linked to the C-terminal of oleosin by an inteinS fragment. The recombinant protein was overexpressed in Escherichia coli, purified by artificial oil body system and subsequently released through self-splicing of inteinS induced by the changes of temperature. The antibacterial activity of royalisin-D was compared with royalisin via minimal inhibitory concentration (MIC) assay, minimal bactericidal concentration (MBC) assay, microbial adhesion to solvents (MATS) methods, and cell membrane permeability. Furthermore, the recombinant royalisin and royalisin-D have also been treated with the reducing agent of disulfide bonds, dithiothreitol (DTT), to investigate the importance of the intra-disulfide bond in royalisin. In our results, royalisin-D exhibited similar antimicrobial activity to royalisin. Royalisin and royalisin D lost their antimicrobial activities when the intra-disulfide bonds were reduced by DDT. The intra-disulfide bond plays a more important role than the extra stretch of 11 amino acid residues at the C-terminus of royalisin in terms of the antimicrobial properties of the native royalisin.

In vitro evaluation of the mucin-adhesion ability and probiotic potential of Lactobacillus mucosae LM1.

In this report, we characterized the probiotic potential of Lactobacillus mucosae LM1, focusing on its in vitro mucin-adhesion abilities. Screening assays were used to evaluate LM1. Previous studies on Lact.mucosae species have been performed, but few have examined the ability of this species to adhere to and colonize the intestinal mucosa. Thus, adhesion, aggregation and pathogen inhibition assays of LM1 along with microbial adhesion to solvents (MATS) assay were carried out in comparison with another putative probiotic, Lactobacillus johnsonii PF01, and the commercial strain, Lactobacillus rhamnosus GG. Based on MATS assay, the cell surfaces of the lactobacilli strains were found to be hydrophobic and highly electron-donating, but the average hydropathy (GRAVY) index of predicted surface-exposed proteins in the LM1 genome indicated that most were hydrophilic. LM1 showed the highest adhesion, aggregation and hydrophobicity among the strains tested and significantly inhibited the adhesion of Escherichia coli K88 and Salmonella enterica serovar Typhimurium KCCM 40253. Correlations among adhesion, aggregation and hydrophobicity, as well as between coaggregation and displacement of E.coli, were observed. Increased adhesion may not always correlate with increased pathogen inhibition due to various strain-specific mechanisms. Nevertheless, LM1 has promising probiotic properties that can be explored further using a genomics approach. Our data on adhesion of LM1 strain showed a significant correlation between adhesion, hydrophobicity of cell surface and autoaggregation. This study gives basic knowledge for the elucidation of the adhesion mechanism of Lactobacillus sp. and prediction of its adherence in specific host models.

Study of the Adhesion of Clinical Strains of <i>Staphylococcus aureus</i> on an Abiotic Surface Using the Biofilm Ring Test®

Four methicillin-sensitive (MSSA) and 4 methicillin-resistant (MRSA) strains of Staphylococcus aureus were collected and isolated at the Laboratory of Bacteriology of the Provincial General Reference Hospital of Kinshasa in the Democratic Republic of Congo. The microbial adhesion to solvents (MATS) test showed that the MRSA strains had a less hydrophobic membrane than the MSSA strains. Using the Biofilm Ring Test? (BFRT?) to investigate on the adhesion of these bacterial strains to smooth surfaces, we observed that the MSSA strains adhered more rapidly than the MRSA strains. The biomass of the produced biofilm measured by the Crystal violet staining method (CVSM) was more important with MSSA than with MRSA strains. Ethylene glycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA) inhibited the adhesion and the formation of a biofilm by MRSA strains; this inhibition was reversed by calcium, magnesium and manganese. The MRSA strains adhered less to silicon tubing and the adhesion was inhibited by EGTA in 2 of the 4 MRSA strains and none of the MSSA strains. In conclusion, the MSSA and MRSA strains adhered on an abiotic surface and formed a biofilm at distinct rates and with different sensitivities to ions. The results also confirm the utility as well as the limits of the BFRT? to study the adhesion of bacteria on a surface.

Initial adhesion of Listeria monocytogenes to solid surfaces under liquid flow

Some strains of the food borne pathogen Listeria monocytogenes persist in food processing environments. The exact reason behind this phenomenon is not known, but strain differences in the ability to adhere to solid surfaces could offer an explanation. In the present work, initial adhesion of nine strains of L. monocytogenes was investigated under liquid flow at two levels of shear stress on six different surfaces using a flow chamber set-up with microscopy measurements. The surfaces tested were glass and PVC, and glass coated with beef extract, casein, and homogenised and unhomogenised milk. In addition, the effect of prior environmental stress (5% NaCl, low nutrient availability) on initial adhesion was investigated. The hydrophobicity of the investigated surfaces was determined by contact angle measurements and the surface properties of the investigated L. monocytogenes strains were determined using Microbial Adhesion To Solvents (MATS). All surfaces with the exception of PVC were found to be hydrophilic. Strain differences were found to significantly influence the initial adhesion rate (IAR) of all nine strains to all the surfaces (p<0.05) at both low and high shear stress. Furthermore, there was a significant effect of the surfaces tested (p<0.05) in the adhesion ability of almost all strains. The IAR was affected by flow rate (shear stress) as seen by a decrease in adhesion at high shear stress for most strains. A significant effect of interactions between strain-surface and strain-shear stress (p<0.001) was observed but not of interactions between surface-shear stress. No correlation between surface hydrophobicity and IAR was observed. Addition of 5% NaCl during propagation resulted in a decrease in IAR whilst propagation in low nutrient media caused an increase indicating a general change in surface characteristics under these conditions. Known persisting strains did not display general better adherence.

Growth of a tropical marine yeast Yarrowia lipolytica NCIM 3589 on bromoalkanes: relevance of cell size and cell surface properties

Yarrowia lipolytica 3589, a tropical marine yeast, grew aerobically on a broad range of bromoalkanes varying in carbon chain length and differing in degree and position of bromide group. Amongst the bromoalkanes studied, viz. 2-bromopropane (2-BP), 1-bromobutane (1-BB), 1,5-dibromopentane (1,5-DBP) and 1-bromodecane (1-BD), the best utilized was 1-BD, with a maximal growth rate (μ(max) ) of 0.055 h⁻¹ and an affinity ratio (μ(max) /K(s) ) of 0.022. Utilization of these bromoalkanes as growth substrates was associated with a concomitant release of bromide (8202.9 µm) and cell mass (36 × 10⁹ cells/ml), occurring maximally on 1-BD. Adherence of yeast cells to these hydrophobic bromoalkanes was observed microscopically, with an increase in cell size and surface hydrophobicity. The maximal cell diameter was for 1-BD (4.66 µm), resulting in an increase in the calculated cell surface area (68.19 µm²) and sedimentation velocity (1.31 µm/s). Cell surface hydrophobicity values by microbial adhesion to solvents (MATS) analysis for yeasts grown on bromoalkanes and glucose were significantly high, i.e. >80%. Similarly, water contact angles also indicate that the cell surface of yeast cells grown in glucose possess a relatively more hydrophilic cell surface (θ = 49.1°), whereas cells grown in 1-BD possess a more hydrophobic cell surface (θ = 90.7°). No significant change in emulsification activity or surface tension was detected in the cell-free supernatant. Thus adherence to the bromoalkane droplets by an increase in cell size and surface hydrophobicity leading to debromination of the substrate might be the strategy employed in bromoalkane utilization and growth by Y. lipolytica 3589.

Quantification of acid–base interactions based on contact angle measurement allows XDLVO predictions to attachment of Campylobacter jejuni but not Salmonella

Acid–base (AB) interactions play the most important role in bacterial attachment to surfaces and can be quantified based on electron donor/electron acceptor data from contact angle measurement (CAM) according to the extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory. It follows that the XDLVO theory could fail to explain attachment numbers if differences in AB interactions between strains are not apparent by CAM. This study aimed to investigate the validity of the above assumptions by comparing empirical data on attachment of six bacterial strains (three strains of Campylobacter jejuni and three strains of Salmonella) to stainless steel and XDLVO theory predictions. A significant difference (P<0.05) in AB interactions, apparent by CAM, between C. jejuni strains allowed prediction of attachment of this species by the XDLVO theory. However, the theory failed to explain the attachment numbers for Salmonella due to similar AB interactions, as established by CAM, between the three Salmonella strains. Qualitative analysis of AB interactions by microbial adhesion to solvents (MATS) revealed a significant difference (P<0.05) in electron donor property between the three Salmonella strains suggesting that these strains may differ with respect to AB interactions. No significant correlation with respect to electron donor property (P=0.502, r2=12%) was apparent between CAM and MATS. These data suggest that CAM may not always reflect exactly AB interactions and that the difference in the outcomes from MATS and CAM should be considered when the XDLVO theory is used to predict bacterial attachment to surfaces.

Surface properties of Lactobacillus and Leuconostoc isolates from homemade cheeses showing auto-aggregation ability

Ten lactobacilli and one leuconostoc showing auto-aggregation ability were isolated from artisanal cheeses. Furthermore, non-aggregation strains were isolated from the same cheese sample, if existed. The analysis of factor(s) possibly involved in auto-aggregation was performed. The pretreatment of cells with proteinase K resulted in the disappearance of auto-aggregation ability. Moreover, cells also lost aggregation ability after three-times, successive washing in distilled water. Testing the ability of strain Lactobacillus paracasei subsp. paracasei BGSJ2-8 and its aggregation-deficient derivative BGSJ2-81 to co-aggregate with Listeria innocua ATCC33090, Escherichia coli ATCC25922 or Salmonella typhimurium TR251 showed that strain BGSJ2-8 co-aggregated with these strains, but derivative BGSJ2-81 was not. However, the treatment of L. paracasei subsp. paracasei BGSJ2-8 with proteinase K prior to co-aggregation tests resulted in losing co-aggregation ability. Surface properties of selected strains were analyzed by MATS (microbial adhesion to solvents) method. It was noticed that the strains with auto-aggregation ability were highly hydrophobic in comparison with aggregation-deficient ones. Comparative analyses of the surface features of strain L. paracasei subsp. paracasei BGSJ2-8 and its derivative BGSJ2-81 revealed notable difference.

Influence of cell surface characteristics on adhesion of Saccharomyces cerevisiae to the biomaterial hydroxylapatite

The influence of the physicochemical properties of biomaterials on microbial cell adhesion is well known, with the extent of adhesion depending on hydrophobicity, surface charge, specific functional groups and acid-base properties. Regarding yeasts, the effect of cell surfaces is often overlooked, despite the fact that generalisations may not be made between closely related strains. The current investigation compared adhesion of three industrially relevant strains of Saccharomyces cerevisiae (M-type, NCYC 1681 and ALY, strains used in production of Scotch whisky, ale and lager, respectively) to the biomaterial hydroxylapatite (HAP). Adhesion of the whisky yeast was greatest, followed by the ale strain, while adhesion of the lager strain was approximately 10-times less. According to microbial adhesion to solvents (MATS) analysis, the ale strain was hydrophobic while the whisky and lager strains were moderately hydrophilic. This contrasted with analyses of water contact angles where all strains were characterised as hydrophilic. All yeast strains were electron donating, with low electron accepting potential, as indicated by both surface energy and MATS analysis. Overall, there was a linear correlation between adhesion to HAP and the overall surface free energy of the yeasts. This is the first time that the relationship between yeast cell surface energy and adherence to a biomaterial has been described.

An investigation of microbial adhesion to natural and synthetic polysaccharide-based films and its relationship with the surface energy components

In recent years, polysaccharide-based films have been developed for many applications. Some of these are in the pharmaceutical industry, where the adhesion of microorganisms to surfaces is a concern. After adhesion of a microorganism to a solid surface has taken place, the subsequent biofilm formed can act as a vehicle for spreading infections. The aim of this study is to compare the bacterial adhesion of E. coli and S. aureus from a contaminated solid model (Tryptone Soya Agar) to a range of polysaccharide-based films. These polysaccharide-based films consist of different natural starches (potato, cassava, wheat, pea and rice) and synthetic polymers hydroxyl-propyl cellulose (HPC) and carboxyl methyl cellulose (CMC)). The surface energy parameters of the films were calculated from the contact angle measurements by the sessile drop method. Apolar and polar liquids (water, formamide and hexadecane) and the Lifshitz-Van der Waals/acid-base (LW/AB) approach were used according to the method of Van Oss, Chaundhury and Good. The surface properties of the films were also correlated to the microbial adhesion. This indicated that, for both E. coli and S. aureus, the surface roughness did not affect the microbial adhesion. Only gamma(sAB) had any correlation with the microbial adhesion and gamma(sLW) was almost constant for all the various polysaccharide films tested. In addition, the electron-donor properties of the materials, exhibited via gamma(s+), were positively correlated with the adhesion of S. aureus but not with E. coli. This was in agreement with the results of the MATS (Microbial Adhesion To Solvents) test performed on the two bacteria. This revealed that only S. aureus presented an electron-acceptor characteristic.

Comparison of contact angle measurement and microbial adhesion to solvents for assaying electron donor–electron acceptor (acid–base) properties of bacterial surface

The electron donor–electron acceptor (acid–base properties) of cell surfaces of a series of bacteria were determined by two methods, namely, Microbial Adhesion to Solvents (MATS) and Contact Angle Measurements (CAM) combined with equation of Van Oss. The efficiency of these two methods was then compared. Pseudomonas aeruginosa ATCC 27853, Bacillus subtilis ILP 142B, Staphylococcus aureus ATCC 25923 and four Escherichia coli strains including HB101, AL52, O128B12 and ATCC 25922, acid–base properties were examined under the two different conditions mentioned above. The results showed that the correlation between acid–base properties determined by MATS and CAM was very weak. We have also found that when the microbial cell surface was electron donor by CAM method, similar result was found by MATS, but the reverse was not always true. In contrast, a good correlation between the two methods was obtained when the four E. coli strains were examined.

Adhesion of façade coating colonisers, as mediated by physico-chemical properties

The adhesion of Klebsormidium flaccidum, Stichococcus bacillaris and Chlorella cf. mirabilis, three strains of green microalgae isolated from biofilms on façade coatings were investigated in a parallel plate flow chamber. The model surfaces tested were glass slides, and −CH3 (mediated by octadecyltrichlorosilane [OTS] and hexamethyldisilazane [HMDZ] modification) and -NH2 (aminopropyltriethoxysilane [APS] modification) terminated self-assembled monolayers. Algal physicochemical properties were evaluated by the microbial adhesion to solvents (MATS) assay and by contact angle measurements. The model surfaces were characterised by X-ray photoelectron spectroscopy analysis and by contact angle measurements. Predicted adhesion trends were then compared to in vitro measurements. The adhesion strength of the three algal strains followed the trend: APS > OTS > HMDZ > glass. The adhesion process thus seemed to be mediated by hydrophobic and electrostatic interactions, and was shown to be influenced by the algal culture age and the initial contact time.

Cell surface characterization of Yarrowia lipolytica IMUFRJ 50682

In the present work, the surface characteristics of a wild-type strain of Yarrowia lipolytica (IMUFRJ50682) were investigated. Six different methods to characterize cell surfaces--adhesion to polystyrene; hydrophobic interaction chromatography (HIC); microbial adhesion to solvents (MATS) test; zeta potential; microbial adhesion to hydrocarbons (MATH) test; and contact angle measurement (CAM)--were employed to explain the cell surface behaviour of Y. lipolytica (IMUFRJ50682). This Y. lipolytica strain presents significant differences at the cell surface compared with another Y. lipolytica strain (W29) previously reported in the literature. The main difference is related to the higher cell adhesion to non-polar solvents. The proteins present on the cell wall of Y. lipolytica IMUFRJ50682 seem to play an important role in these particular surface characteristics because of the consistent reduction of this yeast hydrophobic character after the action of pronase on its cell wall.