Recep Avci

University of Florida, Lake Alfred, FL, United States

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Publications (92)255.46 Total impact

  • Langmuir : the ACS journal of surfaces and colloids. 06/2014;
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    Corrosion Science 07/2013; 76:267-274. · 3.62 Impact Factor
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    ABSTRACT: Live attenuated vaccines are adept in stimulating protective immunity. Methods for generating such vaccines have largely adopted strategies used with Salmonella enterica. Yet, when similar strategies were tested in other gram-negative bacteria, the virulence factors or genes responsible to incapacitate Salmonella often failed in providing the desired outcome. Consequently, conventional live vaccines rely on prior knowledge of the pathogen's virulence factors to successfully attenuate them. This can be problematic since such bacterial pathogens normally harbor thousands of genes. To circumvent this problem, we found that overexpression of bacterial appendages, e.g., fimbriae, capsule, and flagella, could successfully attenuate wild-type (wt) Salmonella enterica serovar Typhimurium. Further analysis revealed these attenuated Salmonella strains conferred protection against wt S. Typhimurium challenge as effectively as genetically defined Salmonella vaccines. We refer to this strategy as attenuating gene expression (AGE), a simple efficient approach in attenuating bacterial pathogens, greatly facilitating the construction of live vaccines.
    Virulence 05/2013; 4(5). · 2.79 Impact Factor
  • Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 02/2013; 296:41-49. · 1.19 Impact Factor
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    ABSTRACT: The speciation and spatial distribution of arsenic on rusted steel surfaces affects both measurement and removal approaches. The chemistry of arsenic residing in the rust of ton containers that held the chemical warfare agents bis(2-chloroethyl)sulfide (sulfur mustard) and 2-chlorovinyldichloroarsine (Lewisite) is of particular interest, because while the agents have been decontaminated, residual arsenic could pose a health or environmental risk. The chemistry and distribution of arsenic in rust samples was probed using imaging secondary ion mass spectrometry (SIMS), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy, and scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX). Arsenic in the +3 and or +5 oxidation state is homogeneously distributed at the very top-most layer of the rust samples, and is intimately associated with iron. Sputter depth profiling followed by SIMS and XPS shows As at a depth of several nm, in some cases in a reduced form. The SEM/EDX experiments show that As is present at a depth of several microns, but is inhomogeneously distributed; most locations contained oxidized As at concentrations of a few percent, however several locations showed very high As in a metallic form. These results indicate that the rust material must be removed if the steel containers are to be cleared of arsenic.
    Industrial & Engineering Chemistry Research 01/2013; 52(4):1396–1404. · 2.24 Impact Factor
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    ABSTRACT: Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 - August 2, 2012.
    Microscopy and Microanalysis 07/2012; 18 Suppl 2:4-5. · 2.50 Impact Factor
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    ABSTRACT: Enterotoxigenic Escherichia coli CFA/I is a protective antigen and has been overexpressed in bacterial vectors, such as Salmonella Typhimurium H683, to generate vaccines. Effects that overexpressed CFA/I may engender on the bacterial host remain largely unexplored. To investigate, we constructed a high CFA/I expression strain, H683-pC2, and compared it to a low CFA/I expression strain, H683-pC, and to a non-CFA/I expression strain, H683-pY. The results showed that H683-pC2 was less able to migrate into semisolid agar (0.35%) than either H683-pC or H683-pY. Bacteria that migrated showed motility halo sizes of H683-pC2 < H683-pC < H683-pY. In the liquid culture media, H683-pC2 cells precipitated to the bottom of the tube, while those of H683-pY did not. In situ imaging revealed that H683-pC2 bacilli tended to auto-agglutinate within the semisolid agar, while H683-pY bacilli did not. When the cfaBE fimbrial fiber encoding genes were deleted from pC2, the new plasmid, pC2(-), significantly recovered bacterial swimming capability. Our study highlights the negative impact of overexpressed CFA/I fimbriae on bacterial swimming motility.
    Physical Biology 05/2012; 9(3):036005. · 2.62 Impact Factor
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    ABSTRACT: Nano-silica particles were deposited on acid-etched hydrophilic aluminum (Al) substrates by immersion in well-dispersed nano-silica aqueous suspension and tetramethylamonium hydroxide, followed by a heat treatment. The surface was then further treated by a reaction with fluorosilane. The hydrophobicity, surface morphology, and mechanical properties of the coated Al substrates were investigated, along with their electrochemical properties over time of exposure to two NaCl solutions (0.3% and 3% by weight). All the coated Al surfaces exhibited a water contact angle of 155–158°, i.e., superhydrophobicity. The use of nano-silica suspension significantly enhanced the hydrophobicity of the coated Al. Artificial neural networks were used to provide quantitative understanding in how the microstructure of the treated Al surface contributed to its superhydrophobicity and electrochemical properties. When Ra, total (nano-roughness + micro-roughness) exceeds 450 nm, WCA is greater than 154°, independent of the nano/micro-roughness ratio (RRNM). FESEM and AFM images of these surfaces suggest that a rough two-length-scale hierarchical structure coupled with the low surface energy of fluorosilane topcoat led to the superhydrophobicity of the formed coatings. The coating prepared with the 0.2% nano-silica suspension (vs. other concentrations) featured the highest Young's modulus and the best corrosion protection to the Al substrate in both NaCl solutions.
    Surface and Coatings Technology 04/2012; 206(17):3700–3713. · 1.94 Impact Factor
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    ABSTRACT: The noble shift in corrosion potential to values between +300 and +400 mV SCE and the accompanying increase in cathodic current density and polarization slope at mild cathodic potentials that develop during microbial colonization of passive metals, are collectively known as ennoblement. This phenomenon is of concern as the noble shift in the corrosion potential may lead to pitting corrosion. We have demonstrated, by growing pure cultures of manganese oxidizing bacteria (MOB) Leptothrix discophora SP-6 under well defined conditions, that microbial deposition of manganese oxides causes ennoblement of 316L stainless steel (SS). Exposing 316L corrosion coupons in lakes and streams supported this conclusion; the rate and extent of ennoblement were positively correlated with the rates of deposition and the amounts of biomineralized manganese oxides deposited on the surfaces of the SS corrosion coupons. X-ray photoelectron spectroscopy (XPS) analyses of the deposits from the ennobled coupons revealed a mixture of manganese oxides, as expected. Many natural waters can support growth of MOB. When manganese-oxidizing biofilms accumulate on surfaces of passive metals there is a potential for manganese redox cycling on the metal surface. This process is initiated by depositing minute amounts of manganese oxides on the metal surface. These microbially deposited manganese oxides are then reduced by the electrons derived from anodic dissolution of the metal; the metal is corroding and the manganese oxides are reduced to divalent manganese ions. However, since the manganese ions are liberated within the manganese-oxidizing biofilm, the manganese ions are immediately reoxidized, and the cycle continues.
    Water Science & Technology Water Supply 04/2012; 2(4):65-72.
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    PLoS ONE 04/2012; 7(4):e36283. · 3.53 Impact Factor
  • NACE International Corrosion 2012; 03/2012
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    ABSTRACT: Capturing pathogens on a sensor surface is one of the most important steps in the design of a biosensor. The efficiency of a biosensor at capturing pathogens has direct bearing on its sensitivity. In this work we investigated the capturing of Escherichia coli on substrates modified with antibodies targeting different types of fimbriae: K88ab (F4), K88ac (F4), K99 (F5), 987P (F6), F41, and CFA/I. The results suggest that all these fimbriae can be used for the efficient immobilization of living E. coli cells. The immobilization efficiency was affected by the purity and clone type of the antibody and the fimbriae expression level of the bacteria. For a specific fimbriae type, a higher immobilization efficiency was often observed with the monoclonal antibodies. Immunoimmobilization was utilized in an antibody microarray immersed in a mixed culture of pathogens to demonstrate the rapid and simultaneous label-free detection of multiple pathogens within less than 1 h using a single test. The capture rate of living pathogens exceeds a single bacterium per 100 × 100 μm(2) area per 0.5 h of incubation for a bulk concentration of 10(5) cfu/mL.
    Langmuir 01/2012; 28(2):1351-9. · 4.38 Impact Factor
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    Salmonella - A Diversified Superbug, Edited by Y. Kumar, 01/2012: pages 497-522; Intech Open Access Publisher.
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    ABSTRACT: Generation of a live attenuated vaccine for bacterial pathogens often requires prior knowledge of the pathogen's virulence factors. We hypothesized an alternative approach of heterologous gene expression would make a wild-type (wt) pathogen more susceptible to host cell killing, thus, resulting in immunization. As proof of concept, the heterologous expression of enterotoxigenic E. coli (ETEC) colonization factor antigen I (CFA/I) was tested to attenuate Salmonella. The overexpression of CFA/I resulted in significant attenuation of wt Salmonella. In-depth studies revealed the attenuation depended on the co-expression of chaperone (CfaA) and usher (CfaC) proteins. Remarkably, the CfaAC-attenuated Salmonella conferred protection against wt Salmonella challenge. Mechanistic study indicated CfaAC made Salmonella outer membranes permeable, causing Salmonella to be vulnerable to host destruction. Thus, enhancing bacterial permeability via CfaAC represents an alternative method to attenuate pathogens despite the presence of unknown virulence factors.
    Virulence 01/2012; 3(1):29-42. · 2.79 Impact Factor
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    Salmonella: a diversified superbug, Edited by Yashwant Kumar, 01/2012; InTech., ISBN: 978-953-307-781-9
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    ABSTRACT: Flagella are cell surface appendages involved in a number of bacterial behaviors, such as motility, biofilm formation, and chemotaxis. Despite these important functions, flagella can pose a liability to a bacterium when serving as potent immunogens resulting in the stimulation of the innate and adaptive immune systems. Previous work showing appendage overexpression, referred to as attenuating gene expression (AGE), was found to enfeeble wild-type Salmonella. Thus, this approach was adapted to discern whether flagella overexpression could induce similar attenuation. To test its feasibility, flagellar filament subunit FliC and flagellar regulon master regulator FlhDC were overexpressed in Salmonella enterica serovar Typhimurium wild-type strain H71. The results show that the expression of either FliC or FlhDC alone, and co-expression of the two, significantly attenuates Salmonella. The flagellated bacilli were unable to replicate within macrophages and thus were not lethal to mice. In-depth investigation suggests that flagellum-mediated AGE was due to the disruptive effects of flagella on the bacterial membrane, resulting in heightened susceptibilities to hydrogen peroxide and bile. Furthermore, flagellum-attenuated Salmonella elicited elevated immune responses to Salmonella presumably via FliC's adjuvant effect and conferred robust protection against wild-type Salmonella challenge.
    PLoS ONE 01/2012; 7(10):e46828. · 3.53 Impact Factor
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    ABSTRACT: Thermal-expansion measurements of the Group 5 elements V, Nb, and Ta reveal a structural distortion below 300 K. Data for single-crystalline Nb and Ta display anisotropic thermal expansion, martensitic in character, that is inconsistent with cubic crystal structures at low temperature. Published results on V show similar behavior. Interstitial impurities suppress the transition.
    Physical Review Letters 08/2011; 107(7):075503. · 7.73 Impact Factor
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    ABSTRACT: A custom-made stainless steel column was designed to contain various materials that would trap the hydrocarbons and hydrocarbon derivatives during the processes of fungal fermentation ultimately yielding preparative amounts of volatile organic substances (VOCs). Trapping materials tested in the column were Carbotrap materials A and B (Supelco) as well as bentonite-shale from the oil bearing areas of Eastern Montana, the former allowed for the effective and efficient trapping of VOCs from purged cultures of Hypoxylon sp. Trapping efficiencies of various materials were measured by both gravimetric as well as proton transfer reaction mass spectroscopy with the Carbotraps A and B being 99% efficient when tested with known amounts of 1,8-cineole. Trapped fungal VOCs could effectively be removed and recovered via controlled heating of the stainless steel column followed by passage of the gases through a liquid nitrogen trap at a recovery rate of ca 65-70%. This method provides for the recovery of mg quantities of compounds normally present in the gas phase that may be needed for spectroscopy, bioassays and further separation and analysis and may have wide applicability for many other biological systems involving VOCs. Other available Carbotraps could be used for other applications.
    Biotechnology Letters 06/2011; 33(10):1963-72. · 1.85 Impact Factor
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    ABSTRACT: To assess whether anticolonization factor antigen I (CFA/I) fimbriae antibodies (Abs) from enterotoxigenic Escherichia coli (ETEC) can protect against various routes of challenge, BALB/c mice were immunized with a live attenuated Salmonella vaccine vector expressing CFA/I fimbriae. Vaccinated mice elicited elevated systemic IgG and mucosal IgA Abs, unlike mice immunized with the empty Salmonella vector. Mice were challenged with wild-type ETEC by the oral, intranasal (i.n.), and intraperitoneal (i.p.) routes. Naïve mice did not succumb to oral challenge, but did to i.n. challenge, as did immunized mice; however, vaccinated mice were protected against i.p. ETEC challenge. Two intramuscular (i.m.) immunizations with CFA/I fimbriae without adjuvant conferred 100% protection against i.p. ETEC challenge, while a single 30 μg dose conferred 88% protection. Bactericidal assays showed that ETEC is highly sensitive to anti-CFA/I sera. These results suggest that parenteral immunization with purified CFA/I fimbriae can induce protective Abs and may represent an alternative method to elicit protective Abs for passive immunity to ETEC.
    BioMed Research International 01/2011; 2011:632396. · 2.71 Impact Factor
  • Abstracts of Papers of the American Chemical Society. 08/2010; 240.

Publication Stats

816 Citations
255.46 Total Impact Points

Institutions

  • 2013
    • University of Florida
      • Department of Infectious Diseases and Pathology
      Lake Alfred, FL, United States
  • 1993–2013
    • Montana State University
      • • Department of Physics
      • • Department of Chemistry & Biochemistry
      • • Department of Immunology and Infectious Diseases
      Bozeman, Montana, United States
  • 2009
    • University of Chicago
      • Section of Pulmonary and Critical Care Medicine
      Chicago, IL, United States
  • 1999–2000
    • University of Portsmouth
      • School of Pharmacy and Biomedical Sciences
      Portsmouth, ENG, United Kingdom