Browsing by Subject "Bacteria"

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Open Access
Alteration of self-assembled patterns by microorganisms in evaporating droplets
(2016-08) Andaç, Tuğba
The science of self-organization comprises a diverse range of processes where a disordered system of components form ordered pattern or structure spontaneously without any external instruction [1]. Plentiful examples of this phenomenon appear in nature at almost all scales [2]. Over the past decades, self-assembly has become the apple of many researchers eye by offering breakthroughs for many applications in not only physics but also chemistry, biology and material sciences [3]. Among several self-assembly methods, using evaporating droplets shines out as it provides ease and simplicity. Along with these advantages, it increases its popularity by providing the opportunity of obtaining a variety of patterns such as uniform depositions, central bumps, polygons and hexagons [4] and more famously (coffee) rings [5]. Nonetheless, most of the studies resulting in these patterns have been carried out by using Brownian particles which uctuate randomly due to the collisions with the molecules of the surrounding uid, while only little is known when it comes to active particles suspended in evaporating droplets. The self-propelling nature of active particles [6] permits them to explore their environment differently from Brownian particles and opens new doors in this research line. Being in the quest of understanding what will happen in the presence of active particles such as the well-studied bacteria Esherichia coli (E.coli ), we investigate and explore the self-assembled patterns in evaporating droplets by using digital video microscopy. We demonstrate that the presence of E.coli bacteria tunes the self-assembled patterns. Moreover, we enrich the patterns by introducing salt. We show that the activity of these microorganisms has an in- uence on salt crystallization based on the characteristic dendritic crystals obtained with active and motile bacteria and unaltered, regular crystals obtained with nonmotile bacteria with inhibited activity. Our results suggest a simpler, faster and cheaper method in which common salt can be used as a biomarker to detect bacterial activity.
Open Access
Alternative screening method for analyzing the water samples through an electrical microfluidics chip with classical microbiological assay comparison of P. aeruginosa
(Elsevier, 2020) Bilican, İsmail; Bahadır, T.; Bilgin, K.; Güler, Mustafa Tahsin
Pseudomonas aeruginosa is a pathogenic bacterium in fresh water supplies that creates a risk for public health. Microbiological analysis of drinking water samples is time consuming and requires qualified personnel. Here we offer a screening system for rapid analysis of spring water that has the potential to be turned into a point-of-need system by means of simple mechanism. The test, which takes 1 h to complete, electrically interrogates the particles through a microfluidic chip suspended in the water sample. We tested the platform using water samples with micro beads and water samples spiked with P. aeruginosa at various concentrations. The mono disperse micro beads were used to evaluate the performance of the system. The results were verified by the gold standard membrane filtration method, which yielded a positive test result only for the P. aeruginosa spiked samples. Detection of 0–11 k bacteria in 30 μL samples was successfully completed in 1 h and compared with a conventional microbiological method. The presented method is a good candidate for a rapid, on-site, screening test that can result in a significant reduction in cost and analysis time compared to microbiological analyses routinely used in practice.
Open Access
Antibacterial electrospun nanofibers from triclosan/cyclodextrin inclusion complexes
(Elsevier, 2014) Celebioglu A.; Umu, O. C. O.; Tekinay, T.; Uyar, Tamer
The electrospinning of nanofibers (NF) from cyclodextrin inclusion complexes (CD-IC) with an antibacterial agent (triclosan) was achieved without using any carrier polymeric matrix. Polymer-free triclosan/CD-IC NF were electrospun from highly concentrated (160% CD, w/w) aqueous triclosan/CD-IC suspension by using two types of chemically modified CD; hydroxypropyl-beta-cyclodextrin (HPβCD) and hydroxypropyl-gamma-cyclodextrin (HPγCD). The morphological characterization of the electrospun triclosan/CD-IC NF by SEM elucidated that the triclosan/HPβCD-IC NF and triclosan/HPγCD-IC NF were bead-free having average fiber diameter of 520±250nm and 1100±660nm, respectively. The presence of triclosan and the formation of triclosan/CD-IC within the fiber structure were confirmed by 1H-NMR, FTIR, XRD, DSC, and TGA studies. The initial 1:1molar ratio of the triclosan:CD was kept for triclosan/HPβCD-IC NF after the electrospinning and whereas 0.7:1molar ratio was observed for triclosan/HPγCD-IC NF and some uncomplexed triclosan was detected suggesting that the complexation efficiency of triclosan with HPγCD was lower than that of HPβCD. The antibacterial properties of triclosan/CD-IC NF were tested against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria. It was observed that triclosan/HPβCD-IC NF and triclosan/HPγCD-IC NF showed better antibacterial activity against both bacteria compared to uncomplexed pure triclosan.
Open Access
Antibacterial electrospun poly(lactic acid) (PLA) nanofibrous webs incorporating triclosan/cyclodextrin inclusion complexes
(2013) Kayaci F.; Umu O.C.O.; Tekinay, T.; Uyar, T.
Solid triclosan/cyclodextrin inclusion complexes (TR/CD-IC) were obtained and then incorporated in poly(lactic acid) (PLA) nanofibers via electrospinning. α-CD, β-CD, and γ-CD were tested for the formation of TR/CD-IC by a coprecipitation method; however, the findings indicated that α-CD could not form an inclusion complex with TR, whereas β-CD and γ-CD successfully formed TR/CD-IC crystals, and the molar ratio of TR to CD was found to be 1:1. The structural and thermal characteristics of TR/CD-IC were investigated by 1H NMR, FTIR, XRD, DSC, and TGA studies. Then, the encapsulation of TR/β-CD-IC and TR/γ-CD-IC in PLA nanofibers was achieved. Electrospun PLA and PLA/TR nanofibers obtained for comparison were uniform, whereas the aggregates of TR/CD-IC crystals were present and distributed within the PLA fiber matrix as confirmed by SEM and XRD analyses. The antibacterial activity of these nanofibrous webs was investigated. The results indicated that PLA nanofibers incorporating TR/CD-IC showed better antibacterial activity against Staphylococcus aureus and Escherichia coli bacteria compared to PLA nanofibers containing only TR without CD-IC. Electrospun nanofibrous webs incorporating TR/CD-IC may be applicable in active food packaging due to their very high surface area and nanoporous structure as well as efficient antibacterial property. © 2013 American Chemical Society.
Open Access
Atomic force microscopy for the investigation of molecular and cellular behavior
(Elsevier, 2016-10) Ozkan A.D.; Topal, A. E.; Dana, A.; Güler, Mustafa O.; Tekinay, A. B.
The present review details the methods used for the measurement of cells and their exudates using atomic force microscopy (AFM) and outlines the general conclusions drawn by the mechanical characterization of biological materials through this method. AFM is a material characterization technique that can be operated in liquid conditions, allowing its use for the investigation of the mechanical properties of biological materials in their native environments. AFM has been used for the mechanical investigation of proteins, nucleic acids, biofilms, secretions, membrane bilayers, tissues and bacterial or eukaryotic cells; however, comparison between studies is difficult due to variances between tip sizes and morphologies, sample fixation and immobilization strategies, conditions of measurement and the mechanical parameters used for the quantification of biomaterial response. Although standard protocols for the AFM investigation of biological materials are limited and minor differences in measurement conditions may create large discrepancies, the method is nonetheless highly effective for comparatively evaluating the mechanical integrity of biomaterials and can be used for the real-time acquisition of elasticity data following the introduction of a chemical or mechanical stimulus. While it is currently of limited diagnostic value, the technique is also useful for basic research in cancer biology and the characterization of disease progression and wound healing processes.
Open Access
Bacteria encapsulated electrospun nanofibrous webs for remediation of methylene blue dye in water
(Elsevier, 2017-04) Sarioglu O.F.; Keskin, N. O. S.; Celebioglu A.; Tekinay, T.; Uyar, Tamer
In this study, preparation and application of novel biocomposite materials that were produced by encapsulation of bacterial cells within electrospun nanofibrous webs are described. A commercial strain of Pseudomonas aeruginosa which has methylene blue (MB) dye remediation capability was selected for encapsulation, and polyvinyl alcohol (PVA) and polyethylene oxide (PEO) were selected as the polymer matrices for the electrospinning of bacteria encapsulated nanofibrous webs. Encapsulation of bacterial cells was monitored by scanning electron microscopy (SEM) and fluorescence microscopy, and the viability of encapsulated bacteria was checked by live/dead staining and viable cell counting assay. Both bacteria/PVA and bacteria/PEO webs have shown a great potential for remediation of MB, yet bacteria/PEO web has shown higher removal performances than bacteria/PVA web, which was probably due to the differences in the initial viable bacterial cells for those two samples. The bacteria encapsulated electrospun nanofibrous webs were stored at 4 °C for three months and they were found as potentially storable for keeping encapsulated bacterial cells alive. Overall, the results suggest that electrospun nanofibrous webs are suitable platforms for preservation of living bacterial cells and they can be used directly as a starting inoculum for bioremediation of water systems.
Open Access
Bacteria immobilized electrospun polycaprolactone and polylactic acid fibrous webs for remediation of textile dyes in water
(Elsevier, 2017-10) Sarioglu O.F.; S. Keskin, N. O.; Celebioglu A.; Tekinay, T.; Uyar, Tamer
In this study, preparation and application of novel biocomposite materials for textile dye removal which are produced by immobilization of specific bacteria onto electrospun nanofibrous webs are presented. A textile dye remediating bacterial isolate, Clavibacter michiganensis, was selected for bacterial immobilization, a commercial reactive textile dye, Setazol Blue BRF-X, was selected as the target contaminant, and electrospun polycaprolactone (PCL) and polylactic acid (PLA) nanofibrous polymeric webs were selected for bacterial integration. Bacterial adhesion onto nanofibrous webs was monitored by scanning electron microscopy (SEM) imaging and optical density (OD) measurements were performed for the detached bacteria. After achieving sufficient amounts of immobilized bacteria on electrospun nanofibrous webs, equivalent web samples were utilized for testing the dye removal capabilities. Both bacteria/PCL and bacteria/PLA webs have shown efficient remediation of Setazol Blue BRF-X dye within 48 h at each tested concentration (50, 100 and 200 mg/L), and their removal performances were very similar to the free-bacteria cells. The bacteria immobilized webs were then tested for five times of reuse at an initial dye concentration of 100 mg/L, and found as potentially reusable with higher bacterial immobilization and faster dye removal capacities at the end of the test. Overall, these findings suggest that electrospun nanofibrous webs are available platforms for bacterial integration and the bacteria immobilized webs can be used as starting inocula for use in remediation of textile dyes in wastewater systems.
Open Access
Bacteria-immobilized electrospun fibrous polymeric webs for hexavalent chromium remediation in water
(Springer Berlin Heidelberg, 2016) Sarioglu, O.F.; Celebioglu A.; Tekinay, T.; Uyar, Tamer
The development of hexavalent chromium remediating fibrous biocomposite mats through the immobilization of a hexavalent chromium reducing bacterial strain, Morganella morganiiSTB5, on the surfaces of electrospun polystyrene and polysulfone webs is described. The bacteria-immobilized biocomposite webs have shown removal yields of 93.60 and 93.79 % for 10 mg/L, 99.47 and 90.78 % for 15 mg/L and 70.41 and 68.27 % for 25 mg/L of initial hexavalent chromium within 72 h, respectively, and could be reused for at least five cycles. Storage test results indicate that the biocomposite mats can be stored without losing their bioremoval capacities. Scanning electron microscopy images of the biocomposite webs demonstrate that biofilms of M. morganii STB5 adhere strongly to the fibrous polymeric surfaces and are retained after repeated cycles of use. Overall, the results suggest that reusable bacteria-immobilized fibrous biocomposite webs might be applicable for continuous hexavalent chromium remediation in water systems.
Open Access
Biosystems engineering of prokaryotes with tumor-killing capacities
(Bentham Science Publishers Ltd., 2016) Kalyoncu, E.; Olmez, T. T.; Ozkan, A. D.; Sarioglu, O. F.
Certain bacteria selectively attack tumor tissues and trigger tumor shrinkage by producing toxins and modulating the local immune system, but their clinical utility is limited because of the dangers posed by systemic infection. Genetic engineering can be used to minimize the risks associated with tumor-targeting pathogens, as well as to increase their efficiency in killing tumor cells. Advances in genetic circuit design have led to the development of bacterial strains with enhanced tumor-targeting capacities and the ability to secrete therapeutics, cytotoxic proteins and prodrug-cleaving enzymes, which allows their safe and effective use for cancer treatment. The present review details the recent advances in the design and application of these modified bacterial strains.
Open Access
Cascaded contraction-expansion channels for bacteria separation from RBCs using viscoelastic microfluidics
(Elsevier, 2021-06-29) Bilican, İsmail
Implementation of viscoelasticity-based particle migration techniques has attracted significant interest thanks to its simplicity to achieve particle separation and enrichment at high sensitivity and accuracy for the last decade. Many methods have previously been developed for particle focusing and separation, but they all require long fluidic channels to enable the desired elastic force on particles. Here, a cascade contraction-expansion microfluidic system with a much shorter channel length is presented. Experimental results show that this system achieved continuous, sheathless particle separation in a viscoelastic fluid, and Enterococcus faecalis was successfully separated from red blood cells (RBCs). Thanks to its small size, the system provides extra advantage for its integration into small chips.
Open Access
Complete dissipation of 2, 4, 6-trinitrotoluene by in-vessel composting
(Royal Society of Chemistry, 2015) Gumuscu, B.; Cekmecelioglu, D.; Tekinay, T.
We demonstrate complete removal of 2,4,6-trinitrotoluene (TNT) in 15 days using an in-vessel composting system, which is amended with TNT-degrading bacteria strains. A mixture of TNT, food waste, manure, wood chips, soil and TNT-degrading bacteria consortium are co-composted for 15 days in an aerobic environment. Variations in the TNT degradation rates are assessed when composting reactors are operated at different carbon/nitrogen ratios (C/N), aeration rates, TNT concentrations and TNT-degrading bacteria inoculum loads. Changes in TNT concentrations are measured using high performance liquid chromatography, and C/N are determined using elemental analysis every 5 days. Temperature and moisture of the system are measured every 6 hours. Optimum TNT degradation performance is achieved by combining C/N of 20/1 and a 5 L min-1 aeration rate. Complete removal is achieved for TNT concentrations of 2, 10, and 100 g kg-1 in 15 days by the help of Citrobacter murliniae STE10, Achromobacter spanius STE11, Kluyvera cryocrescens STE12, and Enterobacter amnigenus STE13 bacteria strains. The final products of composting are used to cultivate four different plant seedlings for 10 weeks and showed no toxic effect, which is promising for the potential agricultural use of TNT-contaminated lands after remediation. © The Royal Society of Chemistry.
Open Access
Development of biointegrated electrospun nanofibers for environmental applications
(2016-08) Sarıoğlu, Ömer Faruk
Electrospinning is an easy and economical production technique to produce nanofiber/nanofibrous webs from different polymers, polymer mixtures, inorganic materials, supramolecular structures and composite materials. These nanofibers have unique physical/chemical properties due to their large surface areas and highly nanoporous structures. Since these nanofibers have superior properties, various functions and can be modified by physical/chemical methods, they have a great potential to be applied in membrane/filter applications. Bioremediation is a commonly used technique for removal of water contaminants, and different kinds of bacteria have been used for bioremediation of water systems. Use of biointegrated hybrid materials is an alternative approach for bioremediation, and this may provide higher efficiency, ease of application and reusability. As a carrier system, electrospun nanofibers are suitable materials for integration of bacteria, since electrospinning can allow production of nano/micro scale composites with tunable physical/chemical properties. In this thesis, it was aimed to integrate bacteria that have bioremediation capability with electrospun nanofibers by using immobilization/encapsulation techniques and test the potential of these biocomposites for treatment of contaminated water systems. The integration of bacteria that can remediate ammonium, heavy metal, textile dye and surfactant with electrospun nanofibers was achieved by two different approaches. In the first approach, bacterial cells were physically immobilized on cellulose acetate (CA), polysulfone (PSU), polystyrene (PS), polycaprolactone (PCL) and polylactic acid (PLA) electrospun nanofibers. In order to observe effects of nanofiber/nanofibrous web morphology and arrangements on the immobilization of bacteria, some of these nanofibers were produced as porous, parallelly arranged, and with different diameters. In the second approach, by using polyvinyl alcohol (PVA) and polyethylene oxide (PEO) polymers, simultaneous encapsulation of bacteria in nanofiber structures was provided. Afterwards, all these different kinds of biocomposites were tested for their remediation potential in accordance with the intended use of the integrated bacteria.
Open Access
Electron beam lithography designed silver nano-disks used as label free nano-biosensors based on localized surface plasmon resonance
(Optical Society of America, 2012-01-20) Cinel, N. A.; Butun, S.; Özbay, Ekmel
We present a label-free, optical nano-biosensor based on the Localized Surface Plasmon Resonance (LSPR) that is observed at the metaldielectric interface of silver nano-disk arrays located periodically on a sapphire substrate by Electron-Beam Lithography (EBL). The nano-disk array was designed by finite-difference and time-domain (FDTD) algorithm-based simulations. Refractive index sensitivity was calculated experimentally as 221-354 nm/RIU for different sized arrays. The sensing mechanism was first tested with a biotin-avidin pair, and then a preliminary trial for sensing heat-killed Escherichia coli (E. coli) O157:H7 bacteria was done. Although the study is at an early stage, the results indicate that such a plasmonic structure can be applied to bio-sensing applications and then extended to the detection of specific bacteria species as a fast and low cost alternative. © 2012 Optical Society of America.
Open Access
Electrospinning of polymer-free cyclodextrin/geraniol-inclusion complex nanofibers: enhanced shelf-life of geraniol with antibacterial and antioxidant properties
(Royal Society of Chemistry, 2016) Aytac Z.; Yildiz, Z. I.; Kayaci-Senirmak, F.; Keskin, S. N. O.; Tekinay, T.; Uyar, Tamer
Free-standing nanofibrous webs of cyclodextrin/geraniol-inclusion complex (CD/geraniol-IC-NF) showing antibacterial, antioxidant activity and slow release of geraniol were developed as flavour/fragrance releasing materials via electrospinning. The electrospinning of CD/geraniol-IC-NFs with uniform and bead-free morphology was achieved without using a polymer matrix. Three types of CDs modified with hydroxypropyl and methyl groups (HPβCD, MβCD, and HPγCD) were used to obtain CD/geraniol-IC-NFs. The polymer-free CD/geraniol-IC-NFs allow us to attain much higher geraniol loading (∼11%, w/w) when compared to electrospun polymeric nanofibers containing CD/geraniol-IC (∼5%, w/w). Geraniol has a volatile nature, yet, a significant amount of geraniol (∼60-90%) was preserved in CD/geraniol-IC-NFs due to the complexation, whereas evaporation of geraniol was unavoidable for polymeric nanofibers incorporating geraniol without cyclodextrin. Short-term (3 h) temperature dependent release (37 °C, 50 °C, and 75 °C) and long-term open air (50 days, at RT) release tests revealed that MβCD/geraniol-IC-NF released less geraniol compared to HPβCD/geraniol-IC-NF and HPγCD/geraniol-IC-NF, indicating that much stronger inclusion complexation was formed between MβCD and geraniol. The release of geraniol from CD/geraniol-IC-NFs prevented the colonization of Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria to a great extent, as observed in the antibacterial activity results. It was observed that CD/geraniol-IC-NFs had higher antioxidant activity compared to pure geraniol due to the solubility increase. In brief, the results reported here may open a new door to enhance the performance of essential oils and flavour/fragrances, to preserve volatile compounds from evaporation and to better understand the potential of CD/IC-NFs as carrier systems for guest compounds in the food, cosmetic and household cleaning industries.
Open Access
Encapsulation of living bacteria in electrospun cyclodextrin ultrathin fibers for bioremediation of heavy metals and reactive dye from wastewater
(Elsevier B.V., 2018) San-Keskin, Nalan Oya; Çelebioğlu, Aslı; Sarıoğlu, Ömer Faruk; Uyar, Tamer; Tekinay, T.
Cyclodextrins (CD) are cyclic oligosaccharides produced from the enzymatic degradation of starch as a white powder form; on the other hand, they can be transformed into ultrathin electrospun fiber form by electrospinning technique. The electrospun cyclodextrin fibers (CD-F) can be quite attractive materials to encapsulate bacteria for bioremediation purposes. For instance, CD-F not only serve as a carrier matrix but also it serves as a feeding source for the encapsulated bacteria. In the present study, we demonstrate a facile approach by encapsulation of bacteria into CD-F matrix for wastewater treatment application. The natural and non-toxic properties of CD-F render a better bacterial viability for fibrous biocomposite. The encapsulated bacteria in CD-F exhibit cell viability for more than 7 days at 4 °C storage condition. Furthermore, we have tested the bioremediation capability of bacteria/CD-F biocomposite for the treatment of heavy metals (Nickel(II) and Chromium(VI)) and textile dye (Reactive Black 5, RB5). The bacteria/CD-F biocomposite has shown removal efficiency of Ni(II), Cr(VI) and RB5 as 70 ± 0.2%, 58 ± 1.4% and 82 ± 0.8, respectively. As anticipated, the pollutants removal capabilities of the bacteria/CD-F was higher compare to free bacteria since bacteria can use CD as an extra carbon source which promotes their growth rate. This study demonstrates that CD-F are suitable platforms for the encapsulation of bacterial cells to develop novel biocomposites that have bioremediation capabilities for wastewater treatment.
Open Access
Evaluation of contact time and fiber morphology on bacterial immobilization for development of novel surfactant degrading nanofibrous webs
(Royal Society of Chemistry, 2015) Sarioglu O.F.; Celebioglu A.; Tekinay, T.; Uyar, Tamer
Novel electrospun fibrous biocomposites were developed by immobilizing two different sodium dodecyl sulfate (SDS) biodegrading bacterial strains, Serratia proteamaculans STB3 and Achromobacter xylosoxidans STB4 on electrospun non-porous cellulose acetate (nCA) and porous cellulose acetate (pCA) webs. The required contact time for bacterial immobilization was determined by SEM imaging and viable cell counting of the immobilized bacteria, and bacterial attachment was ended at day 25 based on these results. SDS biodegradation capabilities of bacteria immobilized webs were evaluated at different concentrations of SDS, and found to be highly efficient at concentrations up to 100 mg L-1. It was observed that SDS remediation capabilities of bacteria immobilized webs were primarily based on the bacterial existence and very similar to the free-bacterial cells. A reusability test was applied on the two most efficient webs (STB3/pCA and STB4/pCA) at 100 mg L-1 SDS, and the results suggest that the webs are potentially reusable and improvable for SDS remediation in water. SEM images of bacteria immobilized webs after the reusability test demonstrate strong bacterial adhesion onto the fibrous surfaces, which was also supported by the viable cell counting results. Our results are highly promising and suggest that bacteria immobilized electrospun fibrous webs have the potential to be used effectively and continually for remediation of SDS from aqueous environments.
Open Access
Mathematical modelling of bacterial quorum sensing: a review
(Springer, 2016) Pérez-Velázquez, J.; Gölgeli, M.; García-Contreras, R.
Bacterial quorum sensing (QS) refers to the process of cell-to-cell bacterial communication enabled through the production and sensing of the local concentration of small molecules called autoinducers to regulate the production of gene products (e.g. enzymes or virulence factors). Through autoinducers, bacteria interact with individuals of the same species, other bacterial species, and with their host. Among QS-regulated processes mediated through autoinducers are aggregation, biofilm formation, bioluminescence, and sporulation. Autoinducers are therefore “master” regulators of bacterial lifestyles. For over 10ï¿½years, mathematical modelling of QS has sought, in parallel to experimental discoveries, to elucidate the mechanisms regulating this process. In this review, we present the progress in mathematical modelling of QS, highlighting the various theoretical approaches that have been used and discussing some of the insights that have emerged. Modelling of QS has benefited almost from the onset of the involvement of experimentalists, with many of the papers which we review, published in non-mathematical journals. This review therefore attempts to give a broad overview of the topic to the mathematical biology community, as well as the current modelling efforts and future challenges. ï¿½ 2016, Society for Mathematical Biology.
Open Access
Multicellular individuality: the case of bacteria
(Springer, 2019) Ventura, Rafael
Recent attention to complex group-level behavior amongst bacteria has led some to conceive of multicellular clusters of bacteria as individuals. In this article, I assess these recent claims by first drawing a distinction between two concepts of individuality: physiological and evolutionary. I then survey cases that are representative of three different modes of growth: myxobacteria (surface-attached agglomerative growth), Bacillus subtilis (agglomerative growth not attached to a surface), and cyanobacteria (filamentous growth). A closer look at these cases indicates that multicellular individuality among bacteria is remarkably complex. Physiologically, the three cases of multicellular clusters do not form physiological individuals. But matters are different when it comes to evolutionary individuality; although multicellular clusters that grow by agglomeration are not highly individuated, filament-forming groups achieve a relatively high degree of individuality. I also suggest that debates about bacterial multicellular individuality may have been obscured by a failure to see that selection on highly individuated groups is by no means the only mechanism to bring about the complex group-level behaviors that have led some to view bacteria as multicellular individuals.
Open Access
One-step synthesis of size-tunable Ag nanoparticles incorporated in electrospun PVA/cyclodextrin nanofibers
(Pergamon Press, 2014) Celebioglu A.; Aytac Z.; Umu, O. C. O.; Dana, A.; Tekinay, T.; Uyar, Tamer
One-step synthesis of size-tunable silver nanoparticles (Ag-NP) incorporated into electrospun nanofibers was achieved. Initially, in situ reduction of silver salt (AgNO3) to Ag-NP was carried out in aqueous solution of polyvinyl alcohol (PVA). Here, PVA was used as reducing agent and stabilizing polymer as well as electrospinning polymeric matrix for the fabrication of PVA/Ag-NP nanofibers. Afterwards, hydroxypropyl-beta-cyclodextrin (HPβCD) was used as an additional reducing and stabilizing agent in order to control size and uniform dispersion of Ag-NP. The size of Ag-NP was ∼8 nm and some Ag-NP aggregates were observed for PVA/Ag-NP nanofibers, conversely, the size of Ag-NP decreased from ∼8 nm down to ∼2 nm within the fiber matrix without aggregation were attained for PVA/HPβCD nanofibers. The PVA/Ag-NP and PVA/HPβCD/Ag-NP nanofibers exhibited surface enhanced Raman scattering (SERS) effect. Moreover, antibacterial properties of PVA/Ag-NP and PVA/HPβCD/Ag-NP nanofibrous mats were tested against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria.
Open Access
Production and structural characterization of biosurfactant produced by newly isolated staphylococcus xylosus STF1 from petroleum contaminated soil
(Elsevier BV, 2015) Keskin, N. O. S.; Han, D.; Ozkan A.D.; Angun, P.; Umu, O. C. O.; Tekinay, T.
Petroleum-contaminated soil was used to isolate and characterize biosurfactant producing bacteria. The strain could produce higher amount of biosurfactant in medium supplemented with motor oil as sole source of carbon and energy. A new biosurfactant producing bacterium, designated as Staphylococcus xylosus STF1 based on morphological, physiological, biochemical tests and 16S rRNA gene sequencing. The isolated bacterium was first screened for the ability to produce biosurfactant. Partial sequence of STF1 strain of 16S rDNA gene was highly similar to those of various members of the family Staphylococcaceae. Biochemical characterizations including FT-IR, Raman spectroscopy and Mass spectroscopy studies suggested the biosurfactant to be lipopeptide. Study also confirmed that the cell free supernatant exhibited high emulsifying activity against the different hydrocarbons. Moreover, the partially purified biosurfactant exhibited antimicrobial activity by inhibiting the growth of several bacterial species. The strain could be a potential candidate for the production of polypeptide biosurfactant which could be useful in a variety of biotechnological and industrial processes, particularly in the food and oil industry. © 2015 Elsevier B.V.