Initial Attachment Of Bacteria Research Articles

Nanoscale adhesion forces of glucosyltransferase B and C genes regulated Streptococcal mutans probed by AFM.

Glucosyltransferases (Gtfs), represented by GtfB and GtfC, are important virulence factors of Streptococcus mutans and the major etiologic pathogens of tooth decay. However, the individual roles of gtfB and gtfC in the initial attachment of S. mutans are not known. We used atomic force microscopy to explore the contribution of gtfB and gtfC, as well as enamel-surface roughness, on the initial attachment of S. mutans. Adhesion forces of four S. mutans strains (wild-type, ΔgtfB, ΔgtfC, and ΔgtfBC), onto etched enamel surfaces, were determined. Force curves showed that, with increasing etching time from 0 to 10s, the forces of all strains increased accordingly with acid-exposure time, the adhesion forces of wild-type strains were significantly greater than those of mutant strains (p<.05), and the forces of the three mutants were similar (p<.05). When the etching time was increased from 10 to 30s, difference in force between 20 and 30s was not observed, and adhesion forces among ΔgtfB, ΔgtfC, and wild-type strains were not significantly different when the etching time was >20s (p>.05). These data suggest that the roughness and morphology of enamel surfaces may have a significant influence upon the initial attachment of bacteria, and that gtfB and gtfC are essential for the adhesion activity of bacteria. Furthermore, gtfB seems to be more important than gtfC for bacterial-biofilm formation, and gtfB inactivation is an effective strategy to inhibit the virulence of cariogenic biofilms.

Quantification of Adhesion Force of Bacteria on the Surface of Biomaterials: Techniques and Assays.

Biomaterials associated infection (BAI) has been identified as one of the leading causes of failure of bioimplants. A failed implant requires revision surgery, which is about 20 times costlier and more painful than primary surgery. Infection starts from initial attachment of bacteria onto the surface of biomaterials followed by colonization and biofilm formation. Once a biofilm is developed the bacteria become resistant toward antibiotics. On account of microbial cell development, their metabolic activity and viability are strongly affected by the adhesion. Hence a thorough investigation warrants an in-depth understanding of the interfacial adhesion. Several methods such as plate-and-wash assay, spinning-disc assay, centrifugation assay, step-pressure technique, optical tweezers, atomic force microscopy (AFM) and nanoindentation are used for the measurement of the bacterial adhesion. Most of the aforementioned techniques are nonquantitative and provide only approximate values of adhesion forces. Techniques such as AFM and nanoindentation can quantify a wide range of force 10 pN to 1 μN and 1 nN to 10 μN respectively, and hence they are particularly useful for exact quantification of the adhesion force as well as adhesion strength of bacterial cells on various surfaces of biomaterials. In this review, we present a comparative study of the techniques available to measure the bacterial adhesion force and strength, discuss the use of AFM in adhesion force quantification in detail and conclude by hypothesizing that the AFM technique has an edge over other techniques for quantification of bacterial adhesion force.

Modified membrane with antibacterial properties

Bacteria have been considered as a major foulant that initiates the formation of biofilm on the polymeric membrane surface. Some polymeric membranes are naturally antibacterial and have low fouling properties, however, numerous efforts have been devoted to improve their antibacterial performance. These modifications are mostly carried out through blending the membrane with an antibacterial agent or introducing the antibacterial agent on the membrane surface by chemical grafting. Currently, a significant number of researches have reported nanocomposite membrane as a new approach to fabricate an excellent antibacterial membrane. The antibacterial nanoparticles are dispersed homogenously in membrane structure by blending method or coating onto the membrane surface. Aim of the modifications is to prevent the initial attachment of bacteria to membrane surface and kill bacteria when attached on the membrane surface. In this paper, several studies on antibacterial modified membranes, particularly for water treatment, will be reviewed comprehensively. Special attention will be given on polymeric membrane modifications by introducing antibacterial agents through different methods, such as blending, grafting, and coating.

Influence of carbon steel grade on the initial attachment of bacteria and microbiologically influenced corrosion

The influence of the composition and microstructure of different carbon steel grades on the initial attachment (≤ 60 min) of Escherichia coli and subsequent longer term (28 days) corrosion was investigated. The initial bacterial attachment increased with time on all grades of carbon steel. However, the rate and magnitude of bacterial attachment varied on the different steel grades and was significantly less on the steels with a higher pearlite phase content. The observed variations in the number of bacterial cells attached across different steel grades were significantly reduced by applying a fixed potential to the steel samples. Longer term immersion studies showed similar levels of biofilm formation on the surface of the different grades of carbon steel. The measured corrosion rates were significantly higher in biotic conditions compared to abiotic conditions and were found to be positively correlated with the pearlite phase content of the different grades of carbon steel coupons.

Colloidal crystal based plasma polymer patterning to control Pseudomonas aeruginosa attachment to surfaces

Event Abstract Back to Event Colloidal crystal based plasma polymer patterning to control Pseudomonas aeruginosa attachment to surfaces Hitesh Pingle1, Peng-Yuan Wang1, 2, Helmut Thissen2, Sally Mcarthur1 and Peter Kingshott1 1 Swinburne University Of Technology,Hawthorn, Department of Chemistry and Biotechnology, Australia 2 CSIRO Manufacturing Flagship, Bay view Avenue, Clayton,, Australia Introduction: Infections from biofilm formation on medical devices is a global problem with risks to human health and huge costs to health care worldwide[1],[2]. Bacteria have unique capabilities to generate resistance against antimicrobial agents. Recent studies have shown that extra-cellular DNA is a key molecule that helps biofilms form[3],[4], but the precise mechanisms of how bacteria and DNA interact at surfaces remains unknown. It has been shown that micro- and nanotopography and chemistry on surfaces can influence initial biomolecule adsorption, and subsequent bacterial adhesion[5]-[7]. However, there are fewer reports using such approaches for selectively grafting of DNA to understand the mechanisms of initial bacterial attachment responsible for biofilm formation. Material and Methods: Colloidal self-assembly was used to pattern surfaces with colloidal crystals to use as masks against allylamine plasma polymer (AAMpp) and acrylic acid plasma (AACpp) deposition to generate highly ordered patterns from the micro- to the nanoscale. PEG-aldehyde was grafted to the plasma regions via ‘cloud point’ grafting to prevent the attachment of bacteria on the plasma patterned surface regions, thereby controlling the adhesive sites by choice of the colloidal crystal morphology. Salmon sperm DNA was physically or covalently attached on both patterned and flat surfaces. P. aeruginosa was chosen to study the bacterial interactions with these chemically patterned surfaces. Scanning electron microscope (SEM), x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and Epi-fluorescence microscopy were used for pattern characterization, surface chemical analysis, and imaging of attached bacteria. Results: The AAMpp, AACpp, PEG and eDNA patterns were developed using the colloidal lithography approach. XPS results confirm the successful grafting of PEG and eDNA on the plasma coated surfaces. The AAMpp surface showed increased bacterial attachment compared to control while PEG and eDNA coated surface showed reductions in bacterial attachment as highlighted in Figures 1 and 2. FIG. 1. Epifluorescence images of DAPI stained P. aeruginosa attachment to (a) a 5 µm AAMpp pattern (b) a 5 µm AAMpp-DNA pattern (c) a 5 µm AAMpp_PEG pattern (d) a 5 µm AAMpp-PEG_DNA pattern. All scale bars: 50µm. FIG. 2. SEM images of P. aeruginosa attachment onto (a) a 5 µm AAMpp pattern (b) a 5 µm AAMpp-DNA pattern (c) a 5 µm AAMpp-PEG pattern (d) a 5 µm AAMpp-PEG-DNA pattern All scale bars: 10µm. Discussion: The bacterial attachment increase on the AAMpp surface is most likely due to the amine groups displaying a positive charge that attract the negatively charged extra-cellular polysaccharides on the bacterial cell surfaces. AACpp and DNA both contain negatively charged groups thus repulsion of bacteria is the most likely cause for the reduced bacterial attachment. Micron sized plasma patterns were able to trap bacteria due to the different chemistries presented. Different sized plasma patterns were generated through the use of different sized colloidal particles used as masks for plasma deposition. Conclusion: Surface charge plays an essential role in initial attachment of bacteria. Different chemical patterns made from colloidal crystal masking are easy to fabricate and could be useful in further applications in biomaterials research. The results showed that PEG and DNA patterns can be easily fabricated with exquisite control of pattern size and spacing and this is a useful tool to help understand how bacterial attach to surfaces. The Australian Research Council is acknowledged for funding a PhD scholarship for Hitesh Pingle through the Discovery.; The Scientific Industrial Endowment Fund (SIEF) is acknowledged for providing a John Stocker Postdoctoral Research Fellowship for Peng Yuan Wang.; This work was supported in part at both the Bio-interface Engineering Hub at Swinburne and the Melbourne Centre for Nanofabrication as part of the Victorian Node of the Australian National Fabrication Facility, a company established under the National Collaborative Research Infrastructure Strategy to provide nano and micro-fabrication facilities for Australia’s researchers.

The effect of metal microstructure on the initial attachment of Escherichia coli to 1010 carbon steel

Metallurgical features have been shown to play an important role in the attachment of microorganisms to metal surfaces. In the present study, the influence of the microstructure of as-received (AR) and heat-treated (HT) 1010 carbon steel on the initial attachment of bacteria was investigated. Heat treatment was carried out with the aim of increasing the grain size of the carbon steel coupons. Mirror-polished carbon steel coupons were immersed in a minimal medium inoculated with Escherichia coli (ATCC 25922) to investigate the early (15, 30 and 60 min) and relatively longer-term (4 h) stages of bacterial attachment. The results showed preferential colonisation of bacteria on the grain boundaries of the steel coupons. The bacterial attachment to AR steel coupons was relatively uniform compared to the HT steel coupons where an increased number of localised aggregates of bacteria were found. Quantitative analysis showed that the ratio of the total number of isolated (ie single) bacteria to the number of bacteria in aggregates was significantly higher on the AR coupons than the HT coupons. Longer-term immersion studies showed production of extracellular polymeric substances by the bacteria and corrosion at the grain boundaries on both types of steel coupon tested.

Influence of Growth Temperature on Cyclolipopeptides Production and on Adhesion Behaviour in Environmental Strains of Pseudomonas fluorescens

Summary The present study deals with the influence of growth temperature on biosurfactant production and the adhesion process in the psychrotrophic species Pseudomonas fluorescens . We studied a strain panel composed of nine wild cyclolipopeptide (CLPs) producers and by two biosurfactant mutants. Where cyclolipopeptide production was characterized at either 8°C or 17°C, cyclolipopeptide production was highlighted by hemolytic and tensiometric methods. Their ionic charge was evaluated by a double diffusion test and their identification was made as amphisin- or viscosin- or viscosinamide-like biosurfactants by Reverse Phase- High Performance Liquid Chromatography- Mass Spectroscopy. This categorization was corroborated by the 16S rRNA phylogenetic study. In Pseudomonas fluorescens , the number and relative quantity of cyclolipopeptide produced and bacterial adhesion differed with the growth temperature. Seven new cyclolipopeptides were characterized, of which three belong to the viscosinamide family. Biosurfactant secretion is intensive at 17°C and the highest adhesion is obtained at a lower temperature (8°C). Cyclolipopeptides appeared to antagonize the adhesion process. Strain hydrophobicity was wholly independent of growth temperature and could not be correlated with the initial attachment of bacteria, which was thermoregulated. Our study demonstrates that bacterial adhesion is controlled by the growth temperature but not by cyclolipopeptides or cell hydrophobicity.

Effect of rhamnolipids on initial attachment of bacteria on glass and octadecyltrichlorosilane-modified glass

Bacterial attachment on solid surfaces has various implications in environmental, industrial and medical applications. In this study, the effects of rhamnolipid biosurfactants on initial attachment of bacteria on hydrophilic glass and hydrophobic octadecyltrichlorosilane (OTS) modified glass were evaluated under continuous-flow conditions. The bacteria investigated were three Gram-negative species Pseudomonas aeruginosa, Pseudomonas putida, and Escherichia coli, and two Gram-positive species Staphylcoccus epidermidis and Bacillus subtilis. Rhamnolipids, at 10 and 200mg/l, significantly reduced the attachment of all but S. epidermidis on both glass and OTS-modified glass. For S. epidermidis rhamnolipids reduced the attachment on OTS-modified glass but not on glass. Studies were further done to identify the mechanism(s) by which rhamnolipids reduced the cell attachment. The following potential properties of rhamnolipids were investigated: inhibition of microbial growth, change of cell surface hydrophobicity, easier detachment of cells already attached to substratum, and modification of substratum surface properties. Results showed that rhamnolipids were ineffective for the latter two effects. Rhamnolipids, up to 200mg/l, inhibited the growth of B. subtilis, S. epidermidis and P. aeruginosa PAO1 but not the growth of E. coli, P. putida and P. aeruginosa E0340. Also, rhamnolipids tended to increase the hydrophobicity of P. aeruginosa PAO1 and E. coli, decrease the hydrophobicity of P. putida and S. epidermidis, and have no clear effect on the hydrophobicity of B. subtillis. These trends however did not correlate with the observed trend of cell attachment reduction. The responsible mechanism(s) remained unknown.