Biofilms - Current Issue

Volume 3 Issue 01

Sun, 01 Jan 2006 00:00:00 GMT

Biofilms, Volume 3 Issue 01

Biofilms are increasingly being recognised as the preferred mode of growth of microbes in a wide range of habitats. Biofilms have a large and varied role in human activities from being responsible for a number of diseases in humans and animals to also being invaluable in the treatment of domestic sewage and industrial wastes. Biofilms aims to be the most important forum for the publication of articles on biofilms and the journal of choice for researchers in the biofilm field. Published quarterly, Biofilms contains original research articles and review articles covering the structure, formation and growth of biofilms, gene expression and transfer in biofilms, human and animal diseases involving biofilms, biofilms in the food, oil and pharmaceutical industries, biofilms associated with soil, water, waste treatment, corrosion and marine environments. It also publishes reviews of books and websites and contains announcements of interest to the biofilm community. This journal is included in the Cambridge Journals open access initiative, Cambridge Open Option. Offer readers unrestricted online access to your work, click here for more details.

Effect of oxygen and growth medium on in vitro biofilm formation by Escherichia coli

Research Articles
L. A. Bjergbæk, J. A. J. Haagensen, A. Reisner, S. Molin, P. Roslev,
Biofilms, Volume 3 Issue 01 , pp 1-10

Abstract
The effects of oxygen availability on in vitro biofilm formation by an Escherichia coli K-12 strain and 13 clinical E. coli strains were compared. All E. coli strains were capable of forming monospecies biofilm on polystyrene in aerobic media. The K-12 strain produced biofilm in both aerobic glucose minimal medium (ABTG), and aerobic trypticase soy broth (TSB) whereas the majority of the clinical strains produced significant biofilm only in aerobic TSB (9 of 13). In anaerobic media, E. coli K-12 and 9 of the 13 clinical strains were capable of forming biofilm in vitro. Only three clinical strains formed biofilm in anaerobic TSB whereas six clinical strains produced detectable biofilm in anaerobic ABTG. None of the strains tested were capable of forming biofilm in both anaerobic ABTG and anaerobic TSB. Strains that were good biofilm formers in aerobic ABTG also produced the highest amount of biofilm in anaerobic ABTG (R2 = 0.90). Image analysis revealed notable differences in architecture for biofilms grown in the presence and in the absence of oxygen. In aerobic ABTG, the biofilm was dominated by tall, mushroom-shaped microcolonies with pores and channels whereas biofilm in anaerobic ABTG was thinner and less heterogeneous, resulting in reduced maximum thickness and biovolume. Analysis of phospholipid fatty acid (PLFA) profiles from E. coli K-12 and three clinical strains did not reveal a specific pattern associated with the biofilm phenotypes. Interestingly, the clinical E. coli strains adjusted their PLFA composition much more than did E. coli K-12 in response to changes in growth regimens. Collectively, the results indicate that oxygen availability may affect E. coli biofilm formation in minimal and complex media. The results confirm that E. coli K-12 and some clinical E. coli strains are capable of forming in vitro biofilm under anaerobic conditions. However, the data also suggest that this attribute is highly strain dependent and may vary significantly among clinical isolates.

Action of ciprofloxacin on planktonic bacteria and biofilm of Proteus mirabilis

Research Articles
V. Aiassa, A. I. Barnes, I. Albesa,
Biofilms, Volume 3 Issue 01 , pp 11-17

Abstract
Proteus mirabilis can persist in biofilms, with the bacteria in this state tending to resist antibiotic therapy. Until now, the relationship between the action of ciprofloxacin and the production of reactive oxygen species (ROS) has not been studied in planktonic and biofilmic P. mirabilis. Our results show that ciprofloxacin stimulates the production of ROS in planktonic P. mirabilis, but that the increase in ROS was observed in sensitive strains (n = 4) only in the absence of the extracellular matrix (ECM). This augmentation of ROS was principally intracellular, invoking an increase in intracellular superoxide dismutase (SOD). ROS were assayed by chemiluminescence (CL) and SOD by inhibition of reduction of nitroblue tetrazolium in the presence of methionine, riboflavin and light. The antibiotic-resistant strains (n = 4) did not suffer oxidative stress and exhibited a higher antioxidant capacity than antibiotic-sensitive ones, as indicated by tripyridyltriazine assay. Both types of bacterial strain showed a reduction in antioxidant capacity in the presence of ciprofloxacin, and only the resistant bacteria returned to normal count levels within 5 min of introduction of antibiotic. Ciprofloxacin stimulated ROS more than it did nitric oxide (NO) in planktonic bacteria, as determined by Griess s reaction. Proteus mirabilis biofilms treated with ciprofloxacin did not suffer any increase in ROS but there was an increase in NO and the ratio of intracellular ROS:NO decreased to 25%. Biofilms of P. mirabilis were neither stressed nor inhibited by 40 g ciprofloxacin ml, a dose higher than the minimum inhibitory concentration (i.e. supra MIC). Both resistant and sensitive strains maintained the number of viable bacteria in biofilms incubated with supra MIC ciprofloxacin at concentrations that stressed and reduced substantially the number of colony-forming units of planktonic bacteria per millilitre. These results contribute to understanding of the differences between biofilmic and planktonic bacteria, with respect to susceptibility to oxidative stress caused by ciprofloxacin and also the antioxidant effect of ECM.

Molecular identification of species comprising an unusual biofilm from a groundwater treatment plant

Research Articles
M. R. Gillings, M. P. Holley, M. Selleck,
Biofilms, Volume 3 Issue 01 , pp 19-24

Abstract
Orica s groundwater treatment plant in Botany, NSW, Australia, was designed to remove and destroy volatile organic compounds from polluted groundwater and to treat the water for reuse on the Botany Industrial Park. The initial steps in this process involved acidification of the groundwater and air stripping. During this operation, very large quantities of a biofilm formed within the air stripper, necessitating weekly clean-outs. We investigated the composition of this biofilm using molecular methods. Total DNA extracted from biofilm material was used as a template for amplification of both bacterial 16 S ribo-somal DNA (rDNA) and the eukaryotic rDNA internal transcribed spacer region. Cloning and sequencing of these products showed that the biofilm was composed primarily of a bacterium belonging to the genus Acidocella, a filamentous fungus (Trichoderma asperellum), and the ascomycetous yeasts Pichia, Candida and Geotrichum. This unusual biofilm was composed of acidophiles that were capable of rapidly generating large amounts of biomass under these conditions. When acidification of the groundwater ceased, the biofilm no longer formed.

Bacterial adhesion to stainless steel is reduced by aqueous fish extract coatings

Research Articles
N. Bernbom, R. L. Jørgensen, Y. Y. Ng, R. L. Meyer, P. Kingshott, R. M. Vejborg, P. Klemm, F. Besenbacher, L. Gram,
Biofilms, Volume 3 Issue 01 , pp 25-36

Abstract
Microbial adhesion and biofilm formation on surfaces pose major problems and risks to human health. One way to circumvent this problem is to coat surfaces (in this report stainless steel) with a non-toxic fish extract that generates an abiotic surface with less bacterial attachment than uncoated surfaces or surfaces coated with, for example, tryptone soy broth. The bacteria grow well in the fish extract; hence a general bacteriocidal effect is not the reason for the antifouling effect. Bacterial attachment was quantified by different methods including (a) direct fluorescence microscopy, (b) removal by ultrasound and subsequent quantification of the adhered bacteria, and (c) regrowth of the adhered bacteria measured by indirect conductometry. Surprisingly, the bacterial counts on surfaces coated with aqueous fish extract were 10 100 times lower than on surfaces coated with laboratory broths when surfaces were submerged in bacterial suspensions. The effect was seen for Pseudomonas fluorescens AH2, Pseudomonas aeruginosa PAO1, Escherichia coli MG1655, Vibrio anguillarum 90-11-287 and Aeromonas salmonicida Jno 3175 88. It lasted for at least 7 days. Atomic force microscopy showed that steel surfaces conditioned with fish extract were covered by a thin layer of spherical, nanosized particles. Chemical analysis of the surfaces coated with adsorbed fish extract using X-ray photoelectron spectroscopy revealed that the layer was proteinaceous and had a thickness less than 2 nm. Numerous protein bands peaks were also detected by sodium dodecyl sulphate polyacrylamide gel electrophoresis and matrix-assisted laser desorption ionization time-of-flight mass spectrometry techniques. We conclude that coating the stainless steel surface with fish extract results in a thin protein layer that reduces bacterial adhesion significantly.

Adaptation of microbial communities in soil contaminated with polychlorinated biphenyls, leading to the transformation of more highly chlorinated congeners in biofilm communities

Research Articles
A. J. Macedo, T. R. Neu, U. Kuhlicke, W.-R. Abraham,
Biofilms, Volume 3 Issue 01 , pp 37-46

Abstract
A site polluted for many years with polychlorinated biphenyls (PCB) was used to elucidate the metabolic adaptation of microbial communities to these xenobiotics. Soil samples taken along a gradient of PCB-pollution at this site were used to grow biofilm communities on PCB oil. The biofilm communities originating from the non-polluted soil formed rather uniform and thin bacterial layers on PCB oil, while the biofilms originating from contaminated soil samples formed agglomerated structures on the PCB droplets. Biofilm communities were very diverse but those from highly polluted soil were dominated by Burkholderia species, a genus known for degrading several PCBs. All biofilm communities could transform low to medium chlorinated PCB congeners but a strong increase in the rate and degree of PCB transformation in communities from heavily polluted soil was observed. Notably, pentachlorinated congeners were transformed only by biofilms derived from the highly polluted soil but at the same time the content of trichlorinated congeners did not decrease. It is assumed that biofilms from the highly contaminated soil reductively dechlorinated PCB, converting pentachlorinated congeners to trichlorinated congeners in the spherical biofilm aggregates by diffusing to the surface of the aggregates, where aerobic transformation took place.

Effects of smectite clay on biofilm formation by microorganisms

Research Articles
A. Alimova, M. Roberts, A. Katz, E. Rudolph, J. C. Steiner, R. R. Alfano, P. Gottlieb,
Biofilms, Volume 3 Issue 01 , pp 47-54

Abstract
We have investigated the role of smectite clay particles in biofilm formation by several different species of bacteria (Pseudomonas syringae, Escherichia coli, Staphylococcus aureus and Bacillus subtilis). We observed that the presence of clay particles enhances the formation of biofilms and, after 24 h, the bacterial populations in the clay mixtures were greater than the respective populations in media without clay. Smectite-bearing clay slurries uniformly develop bacteria clay aggregates with a substantial biofilm component within 24 h, while the exclusively bacterial suspensions do not develop any observable biofilm component. The biofilm clay aggregates vary in size from tens of micrometers to several millimeters. Biofilm formation was evaluated by phase contrast microscopy and fluorescence staining. Biofilm promotion by smectite clays may indicate the importance of transport of bacteria by aerosol dust particles.