Papers by Keyword: Biofilm

Abstract: Bioleaching is the extraction of metals from ore by microorganisms. Initial attachment and formation of biofilm by microorganisms are very important for the bioleaching due to the mineral oxidation processes. However, very few techniques were proposed to monitor initial stage of biofilms in real time. Therefore, the aim of this work was to probe an electrochemical method on the bacterial biofilm model under the laboratory conditions. It was found that electrochemical method can be suggested for the real time detection of initial phase of P. polymyxa biofilm formation by observation of the potential increase. However, detection of biofilm development at late stages was not successful due to the decrease of the electrochemical potential by full coverage of the test surface. Nevertheless, this technique is supposed as a promising method for early stage detection of desirable biofilms of acidophilic iron oxidizing microorganisms in bioleaching.

Abstract: The Acidithiobacillus genus plays a relevant role in bioleaching. The molecular understanding of biofilm formation has been pointed out to design biological strategies to improve the efficiency of this industrial process and to prevent environmental damages caused by acid mine/rock drainages. In Acidithiobacillus spp., the molecular mechanisms involved in biofilm formation are currently emerging. The second messenger cyclic diguanylate (c-di-GMP) appears as a key player for biofilm formation by Acidithiobacillus sp. Here, results obtained from genomic analysis to characterize c-di-GMP pathway in At. thiooxidans are reported. Intracellular levels of c-di-GMP have been previously measured and data indicated that they are higher in adhered cells than planktonic ones. During the course of characterization of c-di-GMP effectors, a complete pel-like gene cluster has been identified in At. thiooxidans. By using total RNA obtained from planktonic and adhered sulfur-grown cells, transcriptomic analysis revealed that pelA belonging to the pel-like gene cluster is overexpressed in adhered cells. Moreover, genetic experiments were performed to compare wild type and null-mutant strains of At. thiooxidans for assessing the role of Pel exopolysaccharide. All together, the results obtained suggest a specific role for Pel machinery in the attachment to solid energy substrates by At. thiooxidans.

Abstract: In the present work, the efficacy of the Ti–7.5Mo alloy nanotube and Ti–7.5Mo alloy nanotube with chlorhexidine against bacterial biofilm formation was evaluated. Nanotubes were processed using anodization in 0.25% NH₄F electrolyte solution. Biofilms were cultured in discs immersed in sterile brain heart infusion broth (BHI) containing 5% sucrose, inoculated with microbial suspension (106 cells/ml) and incubated for 5 days. Next, the discs were placed in tubes with sterile physiological solution 0.9% sodium chloride (NaCl) and sonicated to disperse the biofilms. Tenfold serial dilutions were carried and aliquots seeded in selective agar, which were then incubated for 48 h. Then, the numbers CFU/ml (log 10) were counted and analyzed statistically. Scanning electron microscopy (SEM) on discs with biofilms groups and contact angle was carried out. The results show that there is no difference in bacterial adhesion between of the Ti–7.5Mo alloy nanotube and Ti–7.5Mo alloy nanotube with chlorhexidine.

Abstract: Bacterial quorum sensing (QS) is one of the cell-to-cell communication systems. N-Acyl-homoserine lactones (AHLs) are the most common QS signals and responsible for biofilm formation in gram-negative bacteria. Inactivation of QS, also referred to as quorum quenching, has been regarded as a popular strategy to control membrane bioreactor (MBR) operations because biofouling in MBR wastewater treatment systems is often caused by biofilm formation. In the present study, 24 bacterial strains were isolated from the secondary effluent of a wastewater treatment plant and AHL productivity and biofilm formation were evaluated on 8 out of 24 isolates. The isolated 8 strains can produce AHLs that only possess a long (C8-C14) acyl side chain. The representative 3 strains were selected from these isolates based on the higher activity of biofilm formation. The AHL separation analysis with a thin layer chromatography clearly showed that N-octanoyl-L-homoserine lactone (C8-HSL) and N-hexanoyl-L-homoserine lactone (C6-HSL) existed in the secondary effluent sample, while no C6-HSL producing strain was isolated. C8-HSL was identified as the product of isolate No. 6. These results suggest that the secondary effluent probably contains various cell-to-cell signaling molecules derived not only from the inhabitants but also from the other microorganisms involved in the activated sludge for the biological pre-treatment. In this secondary effluent, AHL trapping techniques can be proposed as one of the acceptable strategies for the control of the QS systems because the remaining AHLs have relatively long acyl side chain and low concentrations.

Abstract: In Indonesia, breast cancer is noted as the most common cancer in women. Accordingly, this research was conducted to synthesize biofilm from bacterial cellulose by adding ethanol extract of mangosteen peel. The pellicle of bacterial cellulose was soaked in a 100 mL ethanol solution of mangosteen peel extract varied by 0.5%, 1%, 1.5%, and 2% v/v. The samples were characterized using the SEM, FTIR, and MTT Assay using the T47D breast cancer cells. The results using the SEM showed the thickness of the bacterial cellulose biofilm samples was 5.63 μm, while the 2% v/v thickness of the bacterial cellulose of the extract of mangosteen peel biofilm samples was 12.2 μm. The FTIR results showed a weak interaction between the O-H groups of the microbial cellulose and the C=C functional group in the phenolic compounds of the mangosteen peel extract. Based on the MTT Assay test results using the T47D breast cancer cells, the highest percentage of cell death result was 25.47% on the 2% v/v bacterial cellulose of the mangosteen peel extract samples. The Garcinia mangostana extracts added in the bacterial cellulose biofilms still required optimal concentrations in order to become potential killing mechanism for the T47D breast cancer cells.

Abstract: Most microorganisms grow on surfaces as biofilms rather than as individual planktonic cells, and cells within biofilms show high levels of resistance against antimicrobial drugs. Thereby biofilm formation complicates treatment and contributes to high morbidity and mortality rates associated with infections. This study explores the physical, optical, and nano-structural properties of silver and copper nanoparticles dispersed in aqueous suspensions (nanoparticulate colloidal water) and examines their in vitro activity against microbial biofilms. Silver and copper nanoparticulate colloidal water of various concentrations were prepared and studied. Their surface energies, surface charge and surface plasmonic resonance properties were determined using contact angle measurement, zeta potential measurement and optical spectrometry, respectively. A model of biofilm formation on the wells of microtiter plates was used to determine the activity of the nanoparticulate suspensions against fungal and bacterial biofilms. Scanning electron microscopy (SEM) was used to observe the nanoparticle interactions with microbial cells within the biofilms. Results show that silver nanoparticle-containing liquids have higher surface energy than their copper counterparts; and that the surface energy increases as the concentration of silver nanoparticles increases. Altogether, the effectiveness of silver nanoparticle colloidal suspensions in controlling biofilm formation is observed and reported. For a given size of silver nanoparticles studied, it is found that the effective concentrations against microbial biofilms are far lower than their cytotoxic concentrations, indicating an overall safety and a good therapeutic index thus substantial application potential.

Abstract: This European Union ERASysApp funded study will investigate one of the major drawbacks of bioleaching of the copper containing mineral chalcopyrite, namely the long lag phase between construction and inoculation of bioleaching heaps and the release of dissolved metals. In practice, this lag phase can be up to three years and the long time period adds to the operating expenses of bioheaps for chalcopyrite dissolution. One of the major time determining factors in bioleaching heaps is suggested to be the speed of mineral colonization by the acidophilic microorganisms present. By applying confocal microscopy, metatranscriptomics, metaproteomics, bioinformatics, and computer modeling the authors aim to investigate the processes leading up to, and influencing the attachment of three moderately thermophilic sulfur-and/or iron-oxidizing model species: Acidithiobacillus caldus, Leptospirillum ferriphilum, and Sulfobacillus thermosulfidooxidans. Stirred tank reactors containing chalcopyrite concentrate will be inoculated with these species in various orders and proportions and the effects on the lag phase and rates of metal release will be compared. Meanwhile, confocal microscopy studies of cell attachment to chalcopyrite mineral particles, as well as metatranscriptomics and metaproteomics of the formed biofilms will further increase understanding of the attachment process and help develop a model thereof. By fulfilling our goal to decrease the length of the lag phase of chalcopyrite bioleaching heaps we hope to increase their economic feasibility and therefore, industrial interest in bioleaching as a sustainable technology.

Abstract: Gold extraction by cyanidation from refractory gold ores results in the formation of thiocyanate-and cyanide-contaminated wastewater effluents that must be treated before recycle or discard. Activated sludge processes, such as ASTERTM, can be used for biodegradation of these effluent streams. The destruction of these compounds is catalyzed by a mixed microbial culture, however, very little is known about the community composition and metabolic potential of the thiocyanate-and cyanide-degrading microorganisms within the community. Here we describe our on-going attempts to better understand the key microorganisms, within the ASTERTM bioprocess, that contribute to the destruction of thiocyanate and cyanide, and how this knowledge relates to further process optimisation.

Abstract: Rare earth elements (REEs) are highly valuable due to the complex nature of their extraction from primary and secondary sources. A key feature is that REEs often co-occur with uranium and thorium which, being radioactive, increase the hazard and complexity of REE recovery. A bioprocess which utilizes enzymatically-generated inorganic phosphate to precipitate REEs from solution as their phosphate biominerals is highly effective in the recovery of REEs, effecting rapid recovery onto immobilized bacterial biofilm at high flow-through rates. This also bioprecipitates U and Th. The metal recovery process requires addition of an organic phosphate substrate, e.g. glycerol 2-phosphate (G2P), the cleavage of which provides the inorganic phosphate source for REE biomineralization. G2P is expensive, precluding its large scale use, but early work using uranium showed that tributyl phosphate (TBP) can be used as an alternative phosphate donor molecule. The potential for substitution of G2P by TBP for biorecovery of neodymium is described and a new approach is proposed for enhancing the metal selectivity for REEs against uranium.

Abstract: Biofilm formation of microorganisms on relevant surfaces is of great importance for biomining and acid mine drainage (AMD). Thermo-acidophilic archaea like Acidianus, Sulfolobus and Metallosphaera are of special interest due to their ability to enhance leaching rates. Visualization and investigation of microbial attachment and biofilm formation of metal-oxidizing organisms up to now has been done mostly with mesophilic or moderately thermophilic bacteria. In this study, attachment and biofilms by the crenarchaeota Sulfolobus metallicus DSM 6482^T and a new isolate Acidianus sp. DSM 29099 on sulfur or pyrite were analyzed. Confocal laser scanning microscopy (CLSM) combined with fluorescent dyes specific for nucleic acids or glycoconjugates were used to monitor biofilm formation on surfaces. The data indicate that cell attachment and the subsequently formed biofilm structures were species and substrate dependent. The investigation of binary biofilms on pyrite showed that both species were heterogeneously distributed on pyrite surfaces in the form of individual cells or microcolonies. In addition, physical contact between the two species was visible, as revealed by specific lectins able to distinguish single species.