Laboratory Biofilm Reactor Research Articles

Marine Biofilm Model Comprising a Loop-Type Biofilm Reactor and a Halomonas Strain HIG FST4 1, an Active Biofilm-Forming Bacterium

In ocean and coastal waters, the formation of biofilms on artificial matters often causes intractable phenomena such as the deterioration of surface functions and corrosion, resulting in significant economic damage. Thus, methods for inhibiting biofilm formation are in high demand, and many new anti-biofilm products are being designed on a daily basis. However, practical and safe assays for evaluating anti-biofilm formation have not yet been established. In this study, we developed a more practical and safer biofilm formation test system composed of a loop-type laboratory biofilm reactor (LBR) and HIG FST4 1, a Halomonas strain derived from ballast seawater, in comparison with a slowly rotating test-tube culture (TTC) test. To evaluate biofilm formation in an LBR and TTC, three materials (pure iron, pure aluminum, and soda lime glass) were tested, and Raman spectroscopic analysis was used for the identification and relative quantification of the biofilm contents. Regardless of the test method, biofilm formation progressed in the order of soda lime glass < pure aluminum < pure iron. The Raman peaks showed that the LBR test samples tended to remove polysaccharides compared to the TTC test samples and that the proportion of proteins and lipids in the LBR test samples was much higher than that of the TTC test samples. These results show that the combination of HIG FST4 1 and LBR is suitable for biofilm formation in a practical marine environment.

Proposal for Some Affordable Laboratory Biofilm Reactors and Their Critical Evaluations from Practical Viewpoints.

Biofilms are a result of bacterial activities and are found everywhere. They often form on metal surfaces and on the surfaces of polymeric compounds. Biofilms are sticky and mostly consist of water. They have a strong resistance to antimicrobial agents and can cause serious problems for modern medicine and industry. Biofilms are composed of extracellular polymeric substances (EPS) such as polysaccharides produced from bacterial cells and are dominated by water at the initial stage. In a series of experiments, using Escherichia coli, we developed three types of laboratory biofilm reactors (LBR) to simulate biofilm formation. For the first trial, we used a rotary type of biofilm reactor for stirring. For the next trial, we tried another rotary type of reactor where the circular plate holding specimens was rotated. Finally, a circular laboratory biofilm reactor was used. Biofilms were evaluated by using a crystal violet staining method and by using Raman spectroscopy. Additionally, they were compared to each other from the practical (industrial) viewpoints. The third type was the best to form biofilms in a short period. However, the first and second were better from the viewpoint of “ease of use”. All of these have their own advantages and disadvantages, respectively. Therefore, they should be properly selected and used for specific and appropriate purposes in the future.

Polymer Brush Made from Ionic Liquid and Its Anti-Biofilm Formation Behaviors By Environmental Biota in a Flow-Type Laboratory Biofilm Reactor

Biofilms are formed on materials surfaces by bacterial activities, which leads to the many kinds of contaminations and causes many industrial problems such as scale inside cooling water pipes, corrosion, hygiene issues at kitchens, dining, toilets, bath tubs, chronic diseases in medical fronts etc. To solve the industrial problems, many countermeasures have been proposed so far. The approach from the viewpoint of materials is one of the good ways to solve the biofilm problems. In this research, we investigated how biofilm behaviors formed in a flow type laboratory biofilm reactor (Fig.1) were affected by polymer brush coating of ionic liquids. As polymer brush, N-diethyl-N-(2-methacryloylethyl)-N-methylammonium bis(trifluoromethylsulfonyl) imide (ρDEMM-TFSI) was used with PMMA polymer brush coating as control. The polymer brush coated glass specimens were immersed in the laboratory biofilm reactor where environmental bacteria were mixed into water to form biofilms in the reactor. The specimens with biofilms were evaluated by Raman spectroscopy and optical microscopic observations. And the results were compared with those for PMMA polymer brush specimens. The results were also compared with those obtained by static immersion tests. As well as the results by static methods, ρDEMM-TFSI polymer coating specimens were sensitive to biofilm formation, being compared with the results for PMMA polymer brush coating specimens. The reason could be attributed to the ionic (anionic )polarization of ρDEMM-TFSI coating’s surfaces. However, those biofilms seemed to be concentrated at the vicinity of surfaces. Therefore, the biofilms restricted to the surface area might be removed easily. Figure 1

Biofilm Formation on Two Layer CVD Graphene and Its Change of Capacitance

Biofilms formed on materials have brought about many industrial problems so far. Chronic diseases, the deterioration of hygiene conditions etc. could be mentioned for example. We have confirmed that graphene is easy to form biofilms on it in various ways. Therefore, we expect and predict it could be applied to a practical sensor for biofilm detections. In our precious studies, we produced mono layer graphene on glass specimens and confirmed that it was highly sensitive to biofilm formation in a flow type laboratory biofilm reactor. However, monolayer graphene is generally still lacking in uniformity and the non-coating area is often observed. Therefore, we investigated the sensitivity of two layer CVD graphene to biofilm formation and the possibility to biofilm sensor.In this study, we focused on the change of capacitance with biofilm formation on the graphene coating. The graphene coating specimens on copper and PET substrates were set to laboratory biofilm reactors and we formed biofilms on the specimens artificially. After the formation of biofilms, the specimens were checked by Raman spectroscopy and also observed by an optical microscopy. And the specimens' capacitances were measured, using a specially devised jig connecting to a LCR meter. The frequencies were changed from 700 to 2000Hz and the capacitances were measured.As a result, biofilm formed specimens showed small peaks at some characteristics frequencies, while specimens without biofilms showed no peaks at all. Therefore, we presumed that dielectric polarization-relaxation and the loss would occur due to the existence of External Polymeric Substances (EPS) derived from biofilms. We discussed the application possibility of this phenomenon to biofilm sensing.

Effects of phosphate and hydrogen peroxide on the performance of a biological activated carbon filter for enhanced biofiltration

Biofilm formation on biofilters can influence their hydraulic performance, thereby leading to head loss and an increase in energy use and costs for water utilities. The effects of a range of factors, including hydrogen peroxide and phosphate, on the performance of biological activated carbon (BAC) and biofilm formation were investigated using laboratory-scale columns. Head loss, total carbohydrates, and proteins were reduced in the nutrient-enhanced, oxidant-enhanced, and nutrient + oxidant-enhanced BAC filters. However, there were no changes in the removal of dissolved organic matter, trihalomethane formation potential, or selected trace organic contaminants. The biofilm formation on polyvinyl chloride and stainless steel coupons using the laboratory biofilm reactor system was lower when the effluent from a nutrient-enhanced column was used, which indicated that there was less biofilm formation in the distribution systems. This may have been because the effluent from the nutrient-enhanced column was more biologically stable. Therefore, enhanced biofiltration could be used not only to reduce head loss in biofilters, but also to delay biofilm formation in distribution systems.

Comparison of three different HPV genotyping assays for the detection and genotyping of human papilloma viruses in cervical specimens

Laboratory biofilm reactors are tools that researchers use to grow biofilms that exhibit characteristics sufficiently similar to the environment of interest. Numerous biofilm reactors that model various fluid dynamics are described in scientific literature, each with its associated list of advantages and limitations. This chapter focuses on the process used to design and fabricate biofilm reactors with the stated goal of generating a commercial product. The process begins with identifying the environment of interest and key attributes the reactor should include or model. A prototype is then designed, built, and tested in the laboratory. Modifications are made based upon laboratory performance until a design is achieved that is affordable, practical, operationally simple, and relevant and that provides repeatable, convincing results. This process was used to design the industrial surfaces biofilm reactor, developed to model cooling tower biofilms but suitable to study biofilms grown under low shear, high gas transfer, and intermittently wet conditions.

Microbiome Analysis of Biofilms of Silver Nanoparticle-Dispersed Silane-Based Coated Carbon Steel Using a Next-Generation Sequencing Technique.

Previously, we demonstrated that silver nanoparticle-dispersed silane-based coating could inhibit biofilm formation in conditions where seawater was used as a bacterial source and circulated in a closed laboratory biofilm reactor. However, it is still unclear whether the microbiome of a biofilm of silver nanoparticle-dispersed silane-based coating samples (Ag) differs from that of a biofilm of non-dispersed silane-based coating samples (Non-Ag). This study aimed to perform a microbiome analysis of the biofilms grown on the aforementioned coatings using a next-generation sequencing (NGS) technique. For this, a biofilm formation test was conducted by allowing seawater to flow through a closed laboratory biofilm reactor; subsequently, DNAs extracted from the biofilms of Ag and Non-Ag were used to prepare 16S rRNA amplicon libraries to analyze the microbiomes by NGS. Results of the operational taxonomy unit indicated that the biofilms of Non-Ag and Ag comprised one and no phyla of archaea, respectively, whereas Proteobacteria was the dominant phylum for both biofilms. Additionally, in both biofilms, Non-Ag and Ag, Marinomonas was the primary bacterial group involved in early stage biofilm formation, whereas Anaerospora was primarily involved in late-stage biofilm formation. These results indicate that silver nanoparticles will be unrelated to the bacterial composition of biofilms on the surface of silane-based coatings, while they control biofilm formation there.

Electrochemical Responses of Graphene with Biofilm Formation on Various Metallic Substrates by Using Laboratory Biofilm Reactors

Graphene is an advanced material. We confirmed in our previous paper that graphene is very sensitive to biofilm formation. Therefore, it may be utilized as a sensor for biofilm formation in the future. In this experiment, we used graphite and multi-layer graphene, which we obtained by repeating an exfoliation method. The biofilm formation was evaluated by crystal violet staining, Raman spectroscopy, and chronoamperometry in dilute sulfuric acid. The final technique was an adventurous trial. However, the method provided us with reasonable data, as compared with the results of the other two conventional methods.

Electrochemical Responses of Graphene with Biofilm Formation on Various Metallic Substrates By Using Laboratory Biofilm Reactors

We have confirmed that graphene is very sensitive to biofilm formation by environmental biota and by some special bacteria (E.coli and S.epidermidis). Therefore, graphene is not recommended for biomaterials used in the human body. Graphene’s high sensitivity could lead to infections. On the other hand, this high sensitivity might allow grapheme to serve as a sensor for detecting biofilm formation at a very early stage. To obtain more data, we investigated the change of electrochemical responses for graphene on various substrates (while biofilms were forming on these samples). Biofilms were formed on metallic substrates. The procedure is briefly described. A mechanical exfoliation method was repeated by using scotch tape. For each final stage, the graphene on the scotch tape was transferred to the surface of a metallic sheet-type specimen. (Various specimens were used.) The graphene formed on the metallic specimens was confirmed by using Raman spectroscopy and by staining. For the staining, 0.1% crystal violet was used. We expected that the extent of graphene formation would increase with the repeated number of attachments between tapes. Therefore, some transferred specimens, with different repeated numbers than others, were prepared as specimens. Then they were immersed in culture liquids (LB culture liquids and HI ones) including E.coli and Staphylococcus epidermidis. The specimens were also immersed into rotational-type reservoirs filled with culture liquids including bacteria. Each specimen was fixed with a special jig and the culture liquids were stirred continuously. Two laboratory biofilm reactors (a static type and a flow type reactor) were used for this work. Measurements of electrochemical responses (Cyclic voltammetry, immersion potential etc.) were made for all samples, while the changes of Raman shifts with time on those specimens were observed too. Also the final states of the specimens were checked by using crystal violet. Finally, behaviors were analyzed and the applicability to sensing biofilm formation was discussed.

Polymer Brush Made By Ionic Liquids and the Inhibition Effects for Biofilm Formation

The polymer brush generally has high water repellency, adhesion, durability and antifouling properties. As for the last characteristics, it often works well to clean materials’ surfaces. Since it displays the lotus effect, it repels water. This water (which rolls off of the surface) picks up and carries away contaminants. What about its effect for biofilm? In this study, we seek the answer by using a polymer brush formed on glass. Biofilms are produced by bacterial activities. Usually, bacteria attach to tissues in human bodies, and also to solid materials, since organic compounds (which serve as their nutrition) exist there. When the number of bacteria attached to these interfaces increases and reaches the threshold value, then exopolymeric substances are excreted from their cells. Therefore bacteria on materials’ surfaces are surrounded by sticky water including various kinds of organic polymers (exopolymeric substances: EPS). At this point, biofilms form on materials. Generally speaking, bacteria in biofilms have a high tolerance against biocides and antibiotics. This means that biomaterials should have high anti-biofilm formation capabilities. The application of a polymer brush to the surface finishing of biomaterials may serve as a countermeasure to protect biomaterials against biofilm formation. In this study, a polymer brush was formed on glass specimens by living radical polymerization of ionic liquids (N,N-diethyl-N-(2-methacryloylethyl)-N-methylammonium bis imide(DEMM-TFSI). Also their inhibition effects against biofilm formation were investigated. The biofilm evaluation system was mainly composed of artificial biofilm production and various evaluation processes. In this study, the artificial biofilm formation was carried out by two different processes. One was a static process where specimens were placed in plastic wells filled with liquid cultures (LB and HI cultures) with and without bacteria (E.coli and S. epidermidis, respectively). The other was the process using a flow type Laboratory Biofilm Reactor (LBR). The specimen was suspended in a reservoir and fixed by a jig. And the same culture liquids, including bacteria in the reservoir, flowed by using a rotating stirrer. After a certain amount of time (a couple of days), each sample was taken out of the system and the specimen’s surface was observed by Raman spectroscopy and stained by crystal violet (0.1%) to check the extent of biofilm formation. The results were analyzed, compared, and discussed qualitatively and quantitatively. We confirmed that the polymer brush tended to control biofilm formation. The mechanism was considered in the following two ways. One of them would be the Lotus effect where the surface profile of a polymer brush might work well (Lotus effect). The other one was the antibacterial and anti-biofilm effects by ionic liquids. In this case, ionic liquid as a raw material was almost completely fixed and insoluble. However, a very small amount might dissolve at the tip of polymer brush.

Effects of Ionic Liquids on Biofilm Formation in a Loop-Type Laboratory Biofilm Reactor

Biofilm formation was carried out using low concentrations of ionic liquid (IL) to investigate the potential control of biofilm formation with IL. A 2000ml reservoir was filled with tap water with/without a low concentration of ionic liquid in aqueous solution. The apparatus (Laboratory Biofilm Reactor: LBR) was a loop type Laboratory Biofilm Reactor (LBR) composed of an acrylic pump and a bottom tank. A pump circulated the water in the loop system of the laboratory biofilm reactor (LBR). The glass specimens were immersed in the LBR with/without a low concentration of ionic liquid in aqueous solution for 2 or 7days. They were observed and evaluated by using Crystal Violet, a 3D optical microscope and a Raman spectrometer to determine their biofilm behavior. The results were discussed from the viewpoint of a cooling pipe system simulation. We found out and confirmed that the formation of biofilm was controlled when a low concentration of aqueous solution of ionic liquids was circulated.

Biofilm Formation Behaviors on Graphene by E. coli and S. epidermidis

The formation of biofilm on graphene materials was investigated in this study. Two kinds of laboratory biofilm reactors were used to produce biofilms artificially on glass specimens (on the laboratory scale). One of them was a loop-type and the biofilms were measured by Raman spectroscopy. The other one was the static immersion test in a culture containing bacteria. The biofilm formation was evaluated by using crystal violet. We expected that the graphene would have a strong resistance against biofilm formation. However, on the contrary, graphene tended to become more sensitive to biofilm formation when the portion of graphene increased. When we come to think about the future application for graphene, it should not be used for biomaterials, but as sensor for infectious diseases.

Biofilm Formation Behaviors on Graphene By E. coli and S. epidermidis

Biomaterials should have some required performances such as mechanical properties and biocompatibility. From the viewpoint, they have been investigated so far. However, an important factor has been missing in some cases. That is the infection resistance. And the final one is related closely to the biofilm and its control. In this experiment, we focus on graphene, an advanced material. The graphene has many high performances and biocompatibility. From the viewpoint, it may get a chance to be applied to biomaterials. However, our prelimnary experiments showed that graphene has its high sensitivity to resident microbiota and tended to form biofilms easily. Since resident microbiota form complicated flora composed of plural bacteria, it is very hard to tell which bacterium formed biofilm mainly. However, it would be very important to investigate the biofilm formation capability by a certain bacterium, when we come to think about the applicability to biomaterials. In this experiment, we chose E.coli as gram negative bacterium and S.epdermidis as gram positive one, since both cause infections and chronic diseases in our human bodies very often. Graphene was prepared by CVD (Cemical Vapor Deposition) and mechanical methods (tape-detachment process). The specimens were measured and the formation of graphene was confirmed by a Laser Raman Spectroscopy. The specimen was set in spme kinds of laboratory biofilm reactors (LBRs) which we have developed in our loboratory. LBRs were filled with liquid cultures including target bacteira. The test continued in a couple of days at a certain temperature (25 degrees Celsius for E.coli and 37 degrees Celsius for S.epidermidis.) After the immersion test in those LBRs, biofilms on graphene samples were observed and measured by Raman Spectroscopy, staing by crystal violets and optical microscopic observations. The results were compared, analyzed in various cases and the applicability of the advanced material to biomaterials and human bodies was discussed.

Effects of Ionic Liquids on Biofilm Formation in a Loop-Type Laboratory Biofilm Reactor

Biofouling and biofilm formation on inside walls of pipes where various liquids flow have caused varoius netagive industrial problems so far, since it would lead to corrosion, slimes and scales to deteriorate the functions such as heat exhcnage capability and materials qualities/characteristics themselves. As the countermeasure, various biocides and chemical cleaners have been used to control liquid qualities and to prevent those negative industrial problems. Various acids, alkaline agents, surfactants etc. have been used conventionally so far. At this point, hypoochlorous acid and some organic agents seem to be excellent chemical cleaners. However, the former might induce corrosoin on the substrate walls. On the other hand, the latter might evaoprate during the use, evne though any of them might show higher performances. In this experiment, we focused on some ionic liquids. They might be able to overdome those defencts mentioned above. When we come to think about the applicability of ionic liquids to practical industrial purposes, the price and the environmental friendliness may be serious problems in the futuure. In those cases, it will be key points how we could minimize the amount of use for the purpose. Therefore, we tried in this experiment to confirm how very small amounts of some ionic liquids could control biofilm formation. To produce biofilms articially with good reproducibility, we used a loop-type laboratory biofilm reactor which we designed and produced in our laboratory. Two kinds of ionic liquids were used for the experiments. 1-Butyl-3-methylimidazolium Tetrafluoroborate(BMImBF4) and Tributhylocthylphosphonium chloride(P4448Cl). Small amount of them were added into LBR filled with tap water. The liquids including ionic liquids were circulated by a pump and biofilms formed on specimens placed with a stick-type jig, being parallel to the flow direction. After a couple of days passed, the specimens were talken out from the system and the material surfaces were observed. Some types of liquids without ionic liquids were used as control and all of these specimens after exposures in the LBR were analyzed by optical micrscopes, staining by crystal violets and Raman spectroscopy and discussed. The effect of ionic liquds were obviously recognized during the initial stage of biofilm formations. However, ionic liquids also had the difficulty to disolve the solidified biofilms contained lots of calcium carbonate produced at the second half of biofilm formation process.

The development of the anti-biofouling coating agent using metal nanoparticles and analysis by Raman spectroscopy and FIB system

Thus far, biofouling on material surfaces has been investigated from various viewpoints, and concrete methods for its evaluation have been proposed. Biofilms, which are formed by bacterial activities, are essential components of biofouling. They play an important role in the occurrence of biofouling on the materials of structures, which leads to serious economic loss. Therefore, the establishment of countermeasures for biofilm formation and its control are needed urgently. In addition, appropriate evaluation techniques to measure biofilm formation are required. Thus far, we have used scientific evaluation devices and techniques such as an optical microscope and Raman spectroscopy to evaluate biofouling/biofilms. In this study, we used the silane coating of dispersed silver and copper nanopowder rather than that of dispersed organometals. Specimens were immersed into a laboratory biofilm reactor. Then, the biofouling behavior on the sheets was investigated using an optical microscope, Raman spectroscopy, a focused ion beam system (FIB), and scanning electron microscopy (SEM). The optical-microscope observations showed many deposits on the specimens without any metallic dispersions. Although the amount of deposits on the specimens decreased with copper dispersions, many deposits were still observed on them with silver dispersion. These deposits were not confirmed by Raman spectroscopy because of the surface plasmon resonance of silver. Next, we observed and analyzed the specimens using the FIB system (combination of FIB–SEM and EDX) instead of Raman spectroscopy. The SEM image showed that the deposition had formed pores and irregularities on the specimens. FIB–SEM confirmed the existence of deposition on coating layers and revealed that it originated from biooraganisms. Based on these experiments, we could conclude that the structure of antifouling coating could be observed and analyzed using a combination of FIB–SEM and EDX even when other analysis methods are not useful because of various reasons.

Mineral Ecology: Surface Specific Colonization and Geochemical Drivers of Biofilm Accumulation, Composition, and Phylogeny.

This study tests the hypothesis that surface composition influences microbial community structure and growth of biofilms. We used laboratory biofilm reactors (inoculated with a diverse subsurface community) to explore the phylogenetic and taxonomic variability in microbial communities as a function of surface type (carbonate, silicate, aluminosilicate), media pH, and carbon and phosphate availability. Using high-throughput pyrosequencing, we found that surface type significantly controlled ~70–90% of the variance in phylogenetic diversity regardless of environmental pressures. Consistent patterns also emerged in the taxonomy of specific guilds (sulfur-oxidizers/reducers, Gram-positives, acidophiles) due to variations in media chemistry. Media phosphate availability was a key property associated with variation in phylogeny and taxonomy of whole reactors and was negatively correlated with biofilm accumulation and α-diversity (species richness and evenness). However, mineral-bound phosphate limitations were correlated with less biofilm. Carbon added to the media was correlated with a significant increase in biofilm accumulation and overall α-diversity. Additionally, planktonic communities were phylogenetically distant from those in biofilms. All treatments harbored structurally (taxonomically and phylogenetically) distinct microbial communities. Selective advantages within each treatment encouraged growth and revealed the presence of hundreds of additional operational taxonomix units (OTU), representing distinct consortiums of microorganisms. Ultimately, these results provide evidence that mineral/rock composition significantly influences microbial community structure, diversity, membership, phylogenetic variability, and biofilm growth in subsurface communities.

Application of a Loop-Type Laboratory Biofilm Reactor to the Evaluation of Biofilm for Some Metallic Materials and Polymers such as Urinary Stents and Catheters.

A laboratory biofilm reactor (LBR) was modified to a new loop-type closed system in order to evaluate novel stents and catheter materials using 3D optical microscopy and Raman spectroscopy. Two metallic specimens, pure nickel and cupronickel (80% Cu-20% Ni), along with two polymers, silicone and polyurethane, were chosen as examples to ratify the system. Each set of specimens was assigned to the LBR using either tap water or an NB (Nutrient broth based on peptone from animal foods and beef extract mainly)—cultured solution with E-coli formed over 48–72 h. The specimens were then analyzed using Raman Spectroscopy. 3D optical microscopy was employed to corroborate the Raman Spectroscopy results for only the metallic specimens since the inherent roughness of the polymer specimens made such measurements difficult. The findings suggest that the closed loop-type LBR together with Raman spectroscopy analysis is a useful method for evaluating biomaterials as a potential urinary system.

Effect of Silver or Copper Nanoparticles-Dispersed Silane Coatings on Biofilm Formation in Cooling Water Systems.

Biofouling often occurs in cooling water systems, resulting in the reduction of heat exchange efficiency and corrosion of the cooling pipes, which raises the running costs. Therefore, controlling biofouling is very important. To regulate biofouling, we focus on the formation of biofilm, which is the early step of biofouling. In this study, we investigated whether silver or copper nanoparticles-dispersed silane coatings inhibited biofilm formation in cooling systems. We developed a closed laboratory biofilm reactor as a model of a cooling pipe and used seawater as a model for cooling water. Silver or copper nanoparticles-dispersed silane coating (Ag coating and Cu coating) coupons were soaked in seawater, and the seawater was circulated in the laboratory biofilm reactor for several days to create biofilms. Three-dimensional images of the surface showed that sea-island-like structures were formed on silane coatings and low concentration Cu coating, whereas nothing was formed on high concentration Cu coatings and low concentration Ag coating. The sea-island-like structures were analyzed by Raman spectroscopy to estimate the components of the biofilm. We found that both the Cu coating and Ag coating were effective methods to inhibit biofilm formation in cooling pipes.

アンチバイオファウリング性を持つ有機金属分散シラン系樹脂コンポジットコーティング剤の作製とその効果

The authors experimentally investigated an anti-biofouling coating based on silane compounds. Silver and copper were dispersed into the compound as metal organic compounds. Then the composite coating was applied to glass surfaces. The coated glass was set in a specially designed loop-type laboratory biofilm reactor (LBR). After the specimen was immersed in the LBR for two weeks, its surfaces were observed and analyzed using an optical microscope and a Raman spectrometer. The amount of deposit on the silane compound dispersed with metal organic compounds was much less than that deposited on the silane compound without dispersion. Raman spectroscopy revealed that the deposit included bacteria, lipids, protein, and DNA. The availability of the composite coating as an anti-biofouling surface finishing was discussed. Results were compared to those from a similar study performed earlier on pure iron. Results show that glass is effective for the evaluation of anti-biofouling.

Mineral Microniches Control the Diversity of Subsurface Microbial Populations

Rocks and minerals surround the subsurface microbial habitat, yet mineralogy and rock chemistry are rarely considered when characterizing microbial diversity and the microbial ecosystem. Using laboratory biofilm reactors with both a pure culture of Thiothrix unzii and a mixed environmental sulfur-metabolizing community we found that the combination of buffering-capacity, cell wall electronegativity, nutrient content of the rock, and competitive exclusion of some populations control biomass density, α-diversity (local diversity), and β-diversity (global diversity) of the attached communities on mineral and rock surfaces. This suggests that different populations are better adapted to, and more competitive on, specific rock types. The primary influence on rock/mineral colonization by sulfur-oxidizing organisms is the acid-buffering capacity of the mineral substratum, with neutrophiles preferentially colonizing highly buffering carbonate rocks, while acidophiles select nonbuffering quartz. Beyond chemical controls, Thiothrix (often found in mid-ocean ridge environments) demonstrates an affinity for basalt, where it excludes other sulfur-oxidizers. A pure culture of T. unzii preferentially colonizes carbonates while all very closely related Thiothrix spp. are excluded from these same rock samples in a mixed culture. We report here experimental evidence that microorganisms colonize rock surfaces according to the rock's chemistry and the organism's metabolic requirements and tolerances. These results suggest that adaptations to specific rocks are retained even when the organism is displaced in time and space from an ancestral rock habitat.