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PubMed2003

Physiology of biofilms of thermophilic bacilli-potential consequences for cleaning.

Thermophilic Bacillus species readily attached and grew on stainless steel surfaces, forming mature biofilms of >10(6.0) cells/cm2 in 6 h on a surface inoculated with the bacteria. Clean stainless steel exposed only to pasteurized skim milk at 55 degrees C developed a mature biofilm of >10(6.0) cells/cm2 within 18 h. When bacilli were inoculated onto the steel coupons, 18-h biofilms were 30 microm thick. Biofilm growth followed a repeatable pattern, with a reduction in the numbers of bacteria on the surface occurring after 30 h, followed by a recovery. This reduction in numbers was associated with the production of a substance that inhibited the growth of the bacteria. Variations in the environment, including pH and molarity, affected the viability of the cells. Chemicals that attack the polysaccharide matrix of the biofilm were particularly effective in killing and removing cells from the biofilm, demonstrating the importance of polysaccharides in the persistence of these biofilms. Treatment of either the biofilm or a clean stainless steel surface with lysozyme killed biofilm cells and prevented the attachment of any bacteria exposed to the surface. This suggests that lysozyme may have potential as an alternative control method for biofilms of these bacteria.

Animals↗
PubMed2004

Biofilm formation of Candida albicans is variably affected by saliva and dietary sugars.

The pathogenesis of both superficial and systemic candidiasis is closely dictated by properties of the yeast biofilms. Despite extensive investigations on bacterial biofilms, the characteristics of candidal biofilms, and various factors affecting this process remain to be determined. Therefore we examined the effect of human whole saliva and dietary sugars, glucose and galactose on the adhesion and biofilm formation of Candida albicans. Biofilms of C. albicans isolate 192 887 g were developed on polystyrene, flat-bottomed 96-well microtiter plates and monitored using ATP bioluminescence and tetrazolium (XTT) reduction assays as well as the conventional colony forming unit (CFU) evaluation. Our data showed that both the ATP and the XTT assays strongly correlated with the CFU assay (ATP versus CFU: r = 0.994, P = 0.006; XTT versus CFU: r = 0.985, P = 0.015). Compared with a glucose-supplemented (100 mM) medium, galactose containing (500 mM) medium generated consistently lower levels of both candidal adhesion and biofilm formation (all P < 0.05), but a higher pace of biofilm development over time (96 h). Whist the presence of an immobilised saliva coating had little effect on either the candidal adhesion or biofilm formation, the addition of saliva to the incubation medium quantitatively affected biofilm formation especially on day 3 and 4, without any significant effect on yeast adhesion. To conclude, biofilm formation of C. albicans within the oral milieu appears to be modulated to varying extents by dietary and salivary factors and, further investigations are required to elucidate these complex interactions.

Adenosine Triphosphate↗
PubMed2005

Environmental influences on Actinobacillus actinomycetemcomitans biofilm formation.

Fresh clinical isolates of the periodontal pathogen Actinobacillus actinomycetemcomitans have an adherent, rough colony morphology that transforms into a minimally adherent, smooth colony phenotype during successive in vitro passage. The objectives of this study were: (1) to compare biofilm formation of the rough (RVs) and smooth variants (SVs) of several strains of A. actinomycetemcomitans grown under various environmental conditions and (2) to examine the dynamics of biofilm formation. A microtitre plate biofilm assay was used to evaluate biofilm formation of strains grown in broth with modified salt concentration and pH, and to evaluate the effect of pre-conditioning films. Scanning electron microscopy (SEM) was used to monitor microscopic changes in morphology. Dynamics of biofilm formation were measured in a flowcell monitored by confocal microscopy. The RVs generally produced greater biofilm than the SVs. However, medium-dependent differences in biofilm formation were evident for some rough/smooth pairs. The RVs were more tolerant to changes in salt and pH, and more resistant to chlorhexidine than the SVs. Horse serum virtually eliminated, and saliva significantly reduced, biofilm formation by the SVs in contrast to the RVs. SEM revealed no alteration in morphology with change of environment. In a flowcell, the RVs produced towers of microcolonies anchored by a small contact area, whereas the SVs produced an open architecture of reduced height. After 7 days in a flowcell, the rough to smooth phenotype transition could be demonstrated. In conclusion, strain, growth medium and conditioning film all affect biofilm formation. The RVs produce biofilms of unique architecture that may serve to protect the bacterium from environmental perturbations.

Aggregatibacter actinomycetemcomitans↗
PubMed2006

Polysaccharide intercellular adhesin or protein factors in biofilm accumulation of Staphylococcus epidermidis and Staphylococcus aureus isolated from prosthetic hip and knee joint infections.

Nosocomial staphylococcal foreign-body infections related to biofilm formation are a serious threat, demanding new therapeutic and preventive strategies. As the use of biofilm-associated factors as vaccines is critically restricted by their prevalence in natural staphylococcal populations we studied the distribution of genes involved in biofilm formation, the biofilm phenotype and production of polysaccharide intercellular adhesin (PIA) in clonally independent Staphylococcus aureus and Staphylococcus epidermidis strains isolated from prosthetic joint infections after total hip or total knee arthroplasty. Biofilm formation was detected in all S. aureus and 69.2% of S. epidermidis strains. Importantly, 27% of biofilm-positive S. epidermidis produced PIA-independent biofilms, in part mediated by the accumulation associated protein (Aap). Protein-dependent biofilms were exclusively found in S. epidermidis strains from total hip arthroplasty (THA). In S. aureus PIA and proteins act cooperatively in biofilm formation regardless of the infection site. PIA and protein factors like Aap are of differential importance for the pathogenesis of S. epidermidis in prosthetic joint infections (PJI) after THA and total knee arthroplasty (TKA), implicating that icaADBC cannot serve as a general virulence marker in this species. In S. aureus biofilm formation proteins are of overall importance and future work should focus on the identification of functionally active molecules.

Adhesins, Bacterial↗
PubMed2004

The impacts of the AOC concentration on biofilm formation under higher shear force condition.

The logistic growth model was applied in the study to evaluate the impacts of assimilable organic carbon (AOC) concentration on the growth characteristics of biofilm and bulk bacteria under high flow velocity condition. The experimental results showed that there existed a growth and decline relation between biofilm and bulk bacteria at the low (0.05 mg/L) and medium (0.5 mg/L) AOC levels. Increasing the AOC concentration up to 1.0 mg/L, it resulted in high amounts of biofilm and bulk bacteria simultaneously. Although the carrying capacity of biofilm bacteria at the medium condition of AOC level was substantially reduced, the specific growth rate (GR) of biofilm bacteria was largest at this condition. It showed that the reduction of biofilm bacteria quantity did not represent the suppression of bacterial growth. The quantity of bulk water bacteria was obviously dependent with the quantity of biofilm bacteria and the increase of free bacteria with time in networks was mainly due to the growth and detachment of biofilm bacteria, not due to the growth of free bacteria themselves. The maximum growth rate of biofilm bacteria was increased upon increasing the AOC level. It indicated that the AOC level was an important factor affecting the growth of biofilm bacteria.

Bacterial Physiological Phenomena↗
PubMed2005

Virulence of Burkholderia pseudomallei does not correlate with biofilm formation.

Burkholderia pseudomallei is the causative agent of melioidosis but currently the pathogenesis of the disease is still poorly understood. One of the virulent factors of gram-negative bacteria is the ability to produce biofilm to evade host defense. As B. pseudomallei has also been reported to develop the biofilm [1], in the present study, we therefore, quantified the biofilm formation in 50 strains of B. pseudomallei and compared with 50 strains of its avirulent counterpart Burkholderia thailandensis using a modified microtiter-plate test. The results showed that the quantity of biofilm produced by B. pseudomallei was statistically higher (P< 0.01) than that of B. thailandensis (means and SEs of the corrected OD630 were 2.17+/-0.29 and 0.59+/-0.05, respectively). Transmission electron micrographs of the B. pseudomallei strain with high biofilm formation exhibited microcolonies of bacterial cells surrounded by dense extracellular slime matrix comparing with only trace quantity in the low biofilm-producing strain or the biofilm mutants generated by Tn5-OT182 mutagenesis. However, no correlation could be observed between the biofilm formation and virulence, judging from the LD50 values in BALB/c mice. The data obtained with these naturally occurring Burkholderia species and the biofilm mutants are incompatible with the possibility that the biofilm plays a role in the pathogenesis of B. pseudomallei infection.

Animals↗
PubMedDate not supplied

Interleukin-1beta-induced growth enhancement of Staphylococcus aureus occurs in biofilm but not planktonic cultures.

Staphylococcus aureus causes recalcitrant infections and forms resistant biofilms. Mechanisms of biofilm resistance to host defenses may include changes in gene expression that confer responsiveness to chemical mediators. In earlier studies fresh clinical isolates responded to inflammatory cytokines, but responsiveness was lost after multiple in vitro passages [Meduri et al. Cytokines IL-1beta, IL-6, and TNF-alpha enhance the In vitro growth of bacteria. Am J Respir Crit Care Med 1999;160:961-7]. Since biofilms more closely resemble in vivo growth and are implicated in recalcitrant infections, we hypothesized that biofilms, but not planktonic cells, would respond to cytokines. Biofilms were induced by ethanol in S. aureus ATCC 12600. Biofilms treated with 2 ng/mL interleukin-1beta (IL-1beta) for 6 h contained 2.5-fold more cells than untreated biofilms, but no growth-enhancement occurred in planktonic cultures. As determined by flow cytometry, IL-beta bound to 63.1% of biofilm cells, but only 11.2% of planktonic cells. Our results provide evidence of a differential response of biofilm and planktonic bacteria to chemical mediators, and suggest that biofilm bacteria may evade host defenses by growing more rapidly in response to the inflammatory mediators released by activated host defense cells.

Bacteriological Techniques↗
PubMed2004

Three-dimensional biofilm structure quantification.

Quantitative parameters describing biofilm physical structure have been extracted from three-dimensional confocal laser scanning microscopy images and used to compare biofilm structures, monitor biofilm development, and quantify environmental factors affecting biofilm structure. Researchers have previously used biovolume, volume to surface ratio, roughness coefficient, and mean and maximum thicknesses to compare biofilm structures. The selection of these parameters is dependent on the availability of software to perform calculations. We believe it is necessary to develop more comprehensive parameters to describe heterogeneous biofilm morphology in three dimensions. This research presents parameters describing three-dimensional biofilm heterogeneity, size, and morphology of biomass calculated from confocal laser scanning microscopy images. This study extends previous work which extracted quantitative parameters regarding morphological features from two-dimensional biofilm images to three-dimensional biofilm images. We describe two types of parameters: (1) textural parameters showing microscale heterogeneity of biofilms and (2) volumetric parameters describing size and morphology of biomass. The three-dimensional features presented are average (ADD) and maximum diffusion distances (MDD), fractal dimension, average run lengths (in X, Y and Z directions), aspect ratio, textural entropy, energy and homogeneity. We discuss the meaning of each parameter and present the calculations in detail. The developed algorithms, including automatic thresholding, are implemented in software as MATLAB programs which will be available at site prior to publication of the paper.

Algorithms↗
PubMed2006

Capillary isoelectric focusing--useful tool for detection of the biofilm formation in Staphylococcus epidermidis.

The biofilm formation is an important factor of S. epidermidis virulence. Biofilm-positive strains might be clinically more important than biofilm-negative ones. Unlike biofilm-negative staphylococci, biofilm-positive staphylococci are surrounded with an extracellular polysaccharide substance. The presence of this substance on the surface can affect physico-chemical properties of the bacterial cell, including surface charge. 73 S. epidermidis strains were examined for the presence of ica operon, for the ability to form biofilm by Christensen test tube method and for the production of slime by Congo red agar method. Isoelectric points (pI) of these strains were determined by means of Capillary Isoelectric Focusing. The biofilm negative strains focused near pI value 2.3, while the pI values of the biofilm positive strains were near 2.6. Isoelectric point is a useful criterion for the differentiation between biofilm-positive and biofilm-negative S. epidermidis strains.

Amidohydrolases↗
PubMed2005

The relationship between inhibition of bacterial adhesion to a solid surface by sub-MICs of antibiotics and subsequent development of a biofilm.

Many studies have demonstrated that subminimal inhibitory concentrations (sub-MICs) of antibiotics can inhibit initial microbial adherence to medical device surfaces. It has been suggested that, by inhibiting initial adhesion, biofilm formation might be prevented. However, since initial adherence and subsequent biofilm formation may be two distinct phenomena, conclusions regarding the effects of sub-MIC antibiotics on initial adhesion cannot be extrapolated to biofilm formation. In this study, we evaluated the adherence of several clinical isolates of coagulase-negative staphylococci (CoNS) to acrylic and the effect of sub-MICs of vancomycin, cefazolin, dicloxacillin and combinations of these antibiotics on adherence and biofilm formation. Most of the antibiotics used resulted in effective reduction of bacterial adherence to acrylic, in some cases reaching over 70% inhibition of adherence. When strains with a high biofilm-forming capacity were grown in sub-MICs of those antibiotics, there existed combinations of the drugs that significantly inhibited biofilm formation. However, most of the antibiotic combinations that inhibited adherence did not have a profound effect on biofilm formation. When comparing the results of the effect of sub-MIC amounts of antibiotics in inhibiting adherence with their effect on the inhibition of biofilm formation, significant differences were found, mainly when using combinations of antibiotics. In general, the effect on the inhibition of adherence was greater than the effect on inhibiting biofilm formation. These results demonstrate that assays evaluating the inhibition of initial adherence to medical surfaces cannot fully predict the effect on inhibition of biofilm formation.

Anti-Bacterial Agents↗
PubMedDate not supplied

Evaluating trends in biofilm density using the UMCCA model.

We present a series of modeling cases that illustrate the trends described by the unique features of the unified multiple-component cellular automaton (UMCCA) model for a heterogeneous, two-dimensional biofilm. The outputs of the UMCCA model show five general trends. (1) The concentration profiles for the two soluble microbial products are opposite the profile for original substrate. (2) The top of the biofilm is dominated by active biomass and EPS, while the bottom is dominated by residual inert biomass. Within the top layers, active biomass has a much higher concentration than EPS. (3) The top of all biofilm is quite "fluffy," while the bottom is dense. (4) The peak of the composite density does not correspond to the peak of active biomass. (5) All biomass types show considerable local heterogeneity. The series of cases also indicate what conditions lead to particular characteristics observed in some biofilms. Biofilm clusters are promoted by substrate limitation, a high detachment rate, or strong consolidation. A high biofilm density is associated with an old biofilm, which is favored by a low substrate concentration, a high detachment rate, and strong consolidation. Old biofilms also can develop low-density pockets near the substratum, a possible cause of sloughing. Local heterogeneity is generally related to the same factors that cause a high density. We also solved the UMCCA model for conditions similar to the experiments of Bishop et al. (Water Sci. Technol. 31(1) (1995) 143), who measured the total biomass density in layers from the substratum. The model outputs captured all the major trends in the experimental data: the overall thickness and density of biofilms increase with time, and the total biomass density is 5-10 times greater near the substratum than near the top of the biofilm. Furthermore, the model indicates that the residual inert biomass becomes denser toward the substratum, a trend observed experimentally; the UMCCA model suggests that this trend is due to the combined effects of consolidation and inert biomass having a larger maximum density.

Automation↗
PubMedDate not supplied

Action of a cationic surfactant on the activity and removal of bacterial biofilms formed under different flow regimes.

The action of the cationic surfactant cetyltrimethylammonium bromide (CTAB) was investigated to control biofilms (aged 7d) formed by Pseudomonas fluorescens on stainless-steel slides, using flow cells reactors, under turbulent and laminar flow. The effect of CTAB was also investigated using planktonic cells in the presence and absence of BSA, by measuring the cellular respiratory activity and the ATP released. The action of CTAB on biofilms was assessed by means of cellular respiratory activity and variation of biofilm mass, immediately and 3, 7 and 12h after the application of CTAB. The physical stability of the biofilm was also assessed using a rotating device, where the effect of the surfactant on the biofilm stability was evaluated through the variation of the mass remaining on the surface. CTAB significantly reduced the activity of the planktonic cells probably due to the rupture of the cells. This effect was significantly reduced in the presence of BSA. Planktonic cells were more easily inactivated than bacteria in biofilms. Biofilms formed under laminar flow were more susceptible than those formed under turbulent flow, but in both cases total inactivation was not achieved. Biofilm recovery was observed, in terms of respiratory activity, in almost all the cases studied. CTAB application by itself did not promote the detachment of biofilms. The physical stability tests showed that the synergistic action of the surfactant and the application of high shear stress to the biofilm increase its detachment.

Adenosine Triphosphate↗
PubMed2002

The transient-state, multiple-species biofilm model for biofiltration processes.

We describe the transient-state, multiple-species biofilm model (TSMSBM), which is a novel synthesis of key modeling features needed to describe multiple-species biofilms that experience time-varying conditions, particularly including periodic detachment by backwashing. The TSMSBM includes six features that are essential for describing multiple-species biofilms that undergo changes over time: (1) four biomass types: heterotrophs, ammonia oxidizers, nitrite oxidizers, and inert biomass; (2) seven chemical species: input biodegradable organic material (BOM), NH4(+)-N, NO2(-)-N, NO3(-)-N, utilization-associated products, biomass-associated products, and dissolved oxygen; (3) eight reactions that describe the rates of consumption or production of the different species, as well as the stoichiometric linkages among the rates; (4) reaction with diffusion of all the soluble species in the biofilm; (5) growth, decay, detachment, and flux of each biomass type by location in the biofilm; and (6) constant or periodic detachment of biofilm, both of which allow for protection of biomass deep inside the biofilm. The last two features of the TSMSBM provide novel additions to biofilm modeling, and the synthesis of all features is a unique advancement. A series of examples illustrates insights that the TSMSBM can provide about the transient development of multiple-species biofilms; the roles of soluble microbial products and detachment in controlling the distribution of biomass types and process performance; and how backwashing affects the biofilm in drinking-water biofiltration.

Biofilms↗
PubMed2003

Degradation of polymers in a biofilm airlift suspension reactor.

The effect of degradation of polymeric substrates (starch and soy proteins mixture) on the structure of biofilms has been studied. The characteristics of the obtained biofilms were compared to those obtained on corresponding monomeric substrates (glucose and aspartic acid). Based on literature suggestions it was hypothesized that the polymeric substrates, which have a low diffusion rate in the biofilm matrix, would affect the biofilm structure if hydrolytic activity occurs in the biofilm. The obtained biofilm could be expected to present properties like low density and rough surface, facilitating transport and conversion of large polymeric molecules. From the present study it was concluded that the structure of the formed biofilms was influenced by the substrate degraded, however no unequivocal effect of degradation of a polymer on the biofilm structure could be observed. The hydrolytic activity with soy protein and starch as substrate was under stable conditions found to be mainly associated to the biofilm (more than 95% of the total activity). During unstable conditions or start-up significant hydrolytic activity occurred outside the biofilm.

Biodegradation, Environmental↗
PubMed1997

Acetate removal in sewer biofilms under aerobic conditions.

Removal of acetate has been investigated in sewer biofilms by continuous-flow biofilm reactor studies simulating the conditions in a gravity sewer. Non-steady-state conditions are prevailing in sewers, due to periodic variations in substrate concentrations. In order to simulate two extreme situations in a gravity sewer, biofilms defined as high-loaded and low-loaded, respectively, were grown by continuously feeding wastewater to the reactors with and without supplementary addition of acetate. During short-term experiments with high acetate concentrations (1-2 h), surface removal rates of acetate and dissolved oxygen (DO) and observed yield coefficients were determined, as well as the influence of DO concentration on acetate removal rates. The low-loaded biofilms showed very high acetate removal rates in short-term experiments at high acetate concentrations. The DO uptake rates were low, resulting in an average observed yield coefficient of 0.79 g biomass produced per gram acetate (as chemical oxygen demand, COD) consumed. This indicated a luxury uptake by the cells probably for storage inside the cells or for production of extracellular polymeric substances. The high-loaded biofilms showed lower acetate removal rates during the short-term experiments, with an average yield coefficient of 0.49 g biomass produced per gram acetate (as COD) consumed. The level of the acetate removal rates seemed to be related to the structure of the biofilm. The highest acetate removal rates were found for the low-loaded biofilm, where the biofilm was very hairy with 'streamers" with a length of 8-9 mm. At low acetate removal rates (high-loaded biofilm), the "streamer" lengths were only 3-5 mm. The surface removal rates for acetate and DO seemed to follow 1/2 order approximations to biofilm kinetics. For a DO of 0.8 and 6.0 g/m3, the limiting acetate concentrations were about 34 and 20 g-COD/m3, respectively. Under real gravity sewer conditions, the typical concentration ranges for acetate and DO are at levels where any of them may be rate-limiting for microbial acetate removal.

Acetates↗
PubMed2003

Formation of Propionibacterium acnes biofilms on orthopaedic biomaterials and their susceptibility to antimicrobials.

Failure to treat and eradicate prosthetic hip infection with systemic antibiotic regimens is usually due to the fact that the infection is associated with biofilm formation and that bacterial cells growing within a biofilm exhibit increased resistance to antimicrobial agents. In this in vitro study, we investigated the susceptibility of prosthetic hip Propionibacterium acnes and Staphylococcus spp. isolates growing within biofilms on polymethylmethacrylate (PMMA) bone cement to a range of antibiotics. All P. acnes isolates in the biofilm mode of growth demonstrated considerably greater resistance to cefamandole, ciprofloxacin and vancomycin. In contrast, only four of the eight P. acnes isolates demonstrated an increase in resistance to gentamicin. All ten Staphylococcus spp. isolates in the biofilm mode of growth exhibited large increases in resistance to gentamicin and cefamandole with eight of the ten isolates also exhibiting an increase in resistance to vancomycin. However, only three of the ten Staphylococcus spp. isolates exhibited an increase in resistance to ciprofloxacin. Biofilms were also formed on three different titanium alloys and on PMMA bone cement using P. acnes, Staphylococcus epidermidis and Staphylococcus aureus strains to determine if the underlying biomaterial surface had an effect on biofilm formation and the antimicrobial susceptibility of the bacteria growing within biofilms. Although differences in the rate at which the three strains adhered to the different biomaterials were apparent, no differences in biofilm antibiotic resistance between the biomaterials were observed. In the light of these results, it is important that the efficacy of other antibiotics against P. acnes and Staphylococcus spp. prosthetic hip isolates growing within biofilms on orthopaedic biomaterials be determined to ensure optimal treatment of orthopaedic implant infection.

Alloys↗
PubMed2001

Influence of the hydrodynamics on the biofilm formation by mass transport analysis.

Biofilm are formed wherever there is some water in our environment: pipes, pipelines, tap water systems, air conditioning systems... Furthermore, the ecological and economical consequences are very important: energy losses, bacterial contamination, material deterioration. The aim of this work is to develop a new method to detect and monitor the biofilm formation. This method can also determine some mechanical properties of the biofilm. An application of this method is a realization of a biofilm sensor. Biofilm is considered as an inert porous layer with respect to mass transport. In our experiment, the biofilm is grown on a gold electrode in natural seawater. Its thickness is determined by considering the oxygen diffusion limiting current measured for different rotation speeds on this electrode. Two different incubators are used during the biofilm development: one, with a laminar flow, permits the rotation of the electrode during the biofilm formation, and for the second, a tube is used under turbulent conditions during the biofilm formation. This experiment allows us to characterize the mechanical behavior (thickness, elasticity, rigidity) of the biofilm in function of different conditions of development.

Biofilms↗
PubMed2003

Effect of acid shock on protein expression by biofilm cells of Streptococcus mutans.

Streptococcus mutans is a component of the dental plaque biofilm and a major causal agent of dental caries. Log-phase cells of the organism are known to induce an acid tolerance response (ATR) at sub-lethal pH values ( approximately 5.5) that enhances survival at lower pH values such as those encountered in caries lesions. In this study, we have employed a rod biofilm chemostat system to demonstrate that, while planktonic cells induced a strong ATR at pH 5.5, biofilm cells were inherently more acid resistant than such cells in spite of a negligible induction of an ATR. Since these results suggested that surface growth itself triggered an ATR in biofilm cells, we were interested in comparing the effects of a pH change from 7.5 to 5.5 on protein synthesis by the two cell types. For this, cells were pulse labeled with [(14)C]-amino acids following the pH change to pH 5.5, the proteins extracted and separated by two-dimensional (2D) electrophoresis followed by autoradiography and computer-assisted image analysis. A comparison between the cells incubated at pH 5.5 and the control biofilm cells revealed 23 novel proteins that were absent in the control cells, and 126 proteins with an altered relative rate of synthesis. While the number of changes in protein expression in the biofilm cells was within the same range as for planktonic cells, the magnitude of their change was significantly less in biofilm cells, supporting the observation that acidification of biofilm cells induced a negligible ATR. Mass spectrometry and computer-assisted protein sequence analysis revealed that ATR induction of the planktonic cells resulted in the downregulation of glycolytic enzymes presumably to limit cellular damage by the acidification of the external environment. On the other hand, the glycolytic enzymes in control biofilm cells were significantly less downregulated and key enzymes, such as lactate dehydrogenase were upregulated during pH 5.5 incubation, suggesting that the enhanced acid resistance of biofilm cells is associated with the maintenance of pH homeostasis by H+ extrusion via membrane ATPase and increased lactate efflux.

Acids↗