The use of dental implants has been increasing even though failures do occur. The presence of wear debris
and oral microorganisms can contribute to infections and jeopardize implant integration. The aim of this work
was to study the influence of mixed biofilms in the tribological behaviour of commercially pure titanium for
dental implants under different concentrations of fluoride. Samples of titanium with two different surface
topographies were used. Mixed biofilms of Candida albicans and Streptococcus mutans were formed on both
surfaces at 37 °C in a tryptic soy broth containing mucin, peptone, yeast extract and sucrose. After 8 days,
biofilm biomass was analysed by crystal violet staining method. Biofilm biomass was significantly higher for
the samples with higher roughness. Some samples with biofilms were analysed under friction (using a force
of 100 mN) in an artificial saliva solution (Fusayama) without or with different concentrations of fluoride
(30 and 227 ppm). It was verified that the coefficient of friction (COF) decreased in the presence of biofilms.
Moreover, samples with more biomass (0.4 μm of roughness) presented the lowest values of COF. Concerning
the effect of the presence of fluoride, although there were no significant differences on the COF for 30 ppm,
for 227 ppm a transition regimen was observed. These results were confirmed by sample observation under
scanning electron microscopy.
In conclusion, it can be highlighted that biofilm formation on dental implants can significantly affect the
tribological behaviour of titanium, namely, the presence of biofilms reduces the release of wear debris

Celis, J. P.

Cruz, Helena Margarida Vaz

Henriques, Mariana

Rocha, L. A.

Universidade do Minho: RepositoriUM

properties of the resulting layers were evidenced against various micro-organism such as L. ivanovii, P. aeruginosa or E. coli. Additionally, smart coatings switching their surface properties from bactericidal to cell-repellent with temperature were prepared by grafting the peptide onto a thermoresponsive macromolecular layer. Our strategies should be advantageously adapted to coat various materials or items used in medicine or food industries.Tribological behaviour of oral mixed biofilmsHelena Cruz1, Mariana Henriques1, Luís  Rocha1, Jean-Pierre Celis21University of Minho, Portugal, 2KUL, BelgiumThe use of dental implants has been increasing even though failures do occur. The presence of wear debris and oral microorganisms can contribute to infections and jeopardize implant integration. The aim of this work was to study the influence of mixed biofilms in the tribological behaviour of commercially pure titanium for dental implants under different concentrations of fluoride. Samples of titanium with two different surface topographies were used. Mixed biofilms of Candida albicans and Streptococcus mutans were formed on both surfaces at 37 °C in a tryptic soy broth containing mucin, peptone, yeast extract and sucrose. After 8 days, biofilm biomass was analysed by crystal violet staining method. Biofilm biomass was significantly higher for the samples with higher roughness. Some samples with biofilms were analysed under friction (using a force of 100 mN) in an artificial saliva solution (Fusayama) without or with different concentrations of fluoride (30 and 227 ppm). It was verified that the coefficient of friction (COF) decreased in the presence of biofilms. Moreover, samples with more biomass (0.4 μm of roughness) presented the lowest values of COF. Concerning the effect of the presence of fluoride, although there were no significant differences on the COF for 30 ppm, for 227 ppm a transition regimen was observed. These results were confirmed by sample observation under scanning electron microscopy.In conclusion, it can be highlighted that biofilm formation on dental implants can significantly affect the tribological behaviour of titanium, namely, the presence of biofilms reduces the release of wear debris.Session 3: Global scale biofilm systemsUtility of Biofilms in Geologic Carbon SequestrationRobin Gerlach1, Lee H.  Spangler1, Andrew C.  Mitchell2, 1Montana State University, USA, 2Aberystwyth University, UKGeologic carbon sequestration involves the injection of CO2 into underground formations including oil beds, deep un-minable coal seams, and deep saline aquifers with temperature and pressure conditions such that CO2 will likely be in the supercritical state.  Four trapping mechanisms are proposed to play significant roles in the deep geologic sequestration of CO2: formation trapping, capillary trapping, solubility trapping, and mineral trapping.  Our research has shown that microbial biofilms are capable of enhancing formation trapping, solubility trapping, and mineral trapping under conditions found in deep brine aquifers.  i)  We have demonstrated that engineered microbial biofilms are capable of reducing the permeability of rock cores at pressures and temperatures, which would be found in the presence of supercritical CO2. ii)  The biofilms have been demonstrated to be resistant to supercritical CO2. iii) Biofilms precipitate CO2 in the form of calcium carbonate (CaCO3), which resists dissolution by brine and scCO2. iv)  Microbial activity can increase CO2 solubilization in brine thus improving solubility trapping.Pathogen interactions within phylloplane biofilms: importance of the VBNC stateBill Keevil, Arinder Gill, Nicola Gibbins, Jeremy Webb, Jennifer Warner, University of Southampton, UKThe phylloplane is an essential global ecosystem, experiencing hostile fluctuating environmental stresses, yet host to diverse microbial colonists and plant pathogens forming biofilm. Recently, disease outbreaks caused by fresh produce consumption have turned interest to survival of zoonotic pathogens on the phylloplane; despite strong epidemiological evidence suspected pathogens are frequently undetectable. This study aims to understand the size and spatial distribution of bacterial biofilm communities on the salad phylloplane and assess their role in zoonotic pathogen attachment and survival as viable but nonculturable (VBNC) forms. Spinach or watercress leaves were examined for biofilm and exopolymeric substances (EPS) using EDIC/EF microscopy. Microorganisms were confirmed and quantified using culture, DAPI and BacLight staining. Leaves were also spiked with Salmonella Typhimurium, S. Thompson or Escherichia coli O157:H7, some carrying gfp fluorescent markers, and cell-cell or cell-phylloplane interaction monitored continuously using real time fluorescence imaging. Microcolonies and EPS slime were observed in leaf margins, between margins and around stomata. Spiked cultures of motile S. Thompson showed subpopulations with different attachment strategies including directly binding to the leaf surface or to biofilm, and also chemotactic swimming into stomata.  ΔrpoS -19-

Tribological behaviour of oral mixed biofilms

properties of the resulting layers were evidenced against various micro-organism such as L. ivanovii, P. 
aeruginosa or E. coli. Additionally, smart coatings switching their surface properties from bactericidal to cell-
repellent with temperature were prepared by grafting the peptide onto a thermoresponsive macromolecular 
layer. Our strategies should be advantageously adapted to coat various materials or items used in medicine or 
food industries.
Tribological behaviour of oral mixed biofilms
Helena Cruz1, Mariana Henriques1, Luís  Rocha1, Jean-Pierre Celis2
1University of Minho, Portugal, 2KUL, Belgium
The use of dental implants has been increasing even though failures do occur. The presence of wear debris 
and oral microorganisms can contribute to infections and jeopardize implant integration. The aim of this work 
was to study the influence of mixed biofilms in the tribological behaviour of commercially pure titanium for 
dental implants under different concentrations of fluoride. Samples of titanium with two different surface 
topographies were used. Mixed biofilms of Candida albicans and Streptococcus mutans were formed on both 
surfaces at 37 °C in a tryptic soy broth containing mucin, peptone, yeast extract and sucrose. After 8 days, 
biofilm biomass was analysed by crystal violet staining method. Biofilm biomass was significantly higher for 
the samples with higher roughness. Some samples with biofilms were analysed under friction (using a force 
of 100 mN) in an artificial saliva solution (Fusayama) without or with different concentrations of fluoride 
(30 and 227 ppm). It was verified that the coefficient of friction (COF) decreased in the presence of biofilms. 
Moreover, samples with more biomass (0.4 μm of roughness) presented the lowest values of COF. Concerning 
the effect of the presence of fluoride, although there were no significant differences on the COF for 30 ppm, 
for 227 ppm a transition regimen was observed. These results were confirmed by sample observation under 
scanning electron microscopy.
In conclusion, it can be highlighted that biofilm formation on dental implants can significantly affect the 
tribological behaviour of titanium, namely, the presence of biofilms reduces the release of wear debris.
Session 3: Global scale biofilm systems
Utility of Biofilms in Geologic Carbon Sequestration
Robin Gerlach1, Lee H.  Spangler1, Andrew C.  Mitchell2, 
1Montana State University, USA, 2Aberystwyth University, UK
Geologic carbon sequestration involves the injection of CO2 into underground formations including oil beds, 
deep un-minable coal seams, and deep saline aquifers with temperature and pressure conditions such that CO2 
will likely be in the supercritical state.  
Four trapping mechanisms are proposed to play significant roles in the deep geologic sequestration of CO2: 
formation trapping, capillary trapping, solubility trapping, and mineral trapping.  
Our research has shown that microbial biofilms are capable of enhancing formation trapping, solubility 
trapping, and mineral trapping under conditions found in deep brine aquifers.  
i)  We have demonstrated that engineered microbial biofilms are capable of reducing the permeability of 
rock cores at pressures and temperatures, which would be found in the presence of supercritical CO2. 
ii)  The biofilms have been demonstrated to be resistant to supercritical CO2. 
iii) Biofilms precipitate CO2 in the form of calcium carbonate (CaCO3), which resists dissolution by brine and 
scCO2. 
iv)  Microbial activity can increase CO2 solubilization in brine thus improving solubility trapping.
Pathogen interactions within phylloplane biofilms: importance of the VBNC state
Bill Keevil, Arinder Gill, Nicola Gibbins, Jeremy Webb, Jennifer Warner, University of Southampton, UK
The phylloplane is an essential global ecosystem, experiencing hostile fluctuating environmental stresses, yet 
host to diverse microbial colonists and plant pathogens forming biofilm. Recently, disease outbreaks caused 
by fresh produce consumption have turned interest to survival of zoonotic pathogens on the phylloplane; 
despite strong epidemiological evidence suspected pathogens are frequently undetectable. This study aims 
to understand the size and spatial distribution of bacterial biofilm communities on the salad phylloplane and 
assess their role in zoonotic pathogen attachment and survival as viable but nonculturable (VBNC) forms. 
Spinach or watercress leaves were examined for biofilm and exopolymeric substances (EPS) using EDIC/EF 
microscopy. Microorganisms were confirmed and quantified using culture, DAPI and BacLight staining. Leaves 
were also spiked with Salmonella Typhimurium, S. Thompson or Escherichia coli O157:H7, some carrying 
gfp fluorescent markers, and cell-cell or cell-phylloplane interaction monitored continuously using real time 
fluorescence imaging. Microcolonies and EPS slime were observed in leaf margins, between margins and around 
stomata. Spiked cultures of motile S. Thompson showed subpopulations with different attachment strategies 
including directly binding to the leaf surface or to biofilm, and also chemotactic swimming into stomata.  ΔrpoS 
-19-


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http://repositorium.sdum.uminho.pt/bitstream/1822/26129/1/Pages%20from%20biofilms-handbook-final-1-pq.pdf

Tribological behaviour of oral mixed biofilms

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