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- MakaleAçık Erişim2015Scopus SJRQ1Impact of the exopolysaccharide layer on biofilms, adhesion and resistance to stress in Lactobacillus johnsonii FI9785
Dertli, Enes; Mayer, Melinda J.; Narbad, Arjan
Background: The bacterial cell surface is a crucial factor in cell-cell and cell-host interactions. Lactobacillus johnsonii FI9785 produces an exopolysaccharide (EPS) layer whose quantity and composition is altered in mutants that harbour genetic changes in their eps gene clusters. We have assessed the effect of changes in EPS production on cell surface characteristics that may affect the ability of L. johnsonii to colonise the poultry host and exclude pathogens. Results: Analysis of physicochemical cell surface characteristics reflected by Zeta potential and adhesion to hexadecane showed that an increase in EPS gave a less negative, more hydrophilic surface and reduced autoaggregation. Autoaggregation was significantly higher in mutants that have reduced EPS, indicating that EPS can mask surface structures responsible for cell-cell interactions. EPS also affected biofilm formation, but here the quantity of EPS produced was not the only determinant. A reduction in EPS production increased bacterial adhesion to chicken gut explants, but made the bacteria less able to survive some stresses. Conclusions: This study showed that manipulation of EPS production in L. johnsonii FI9785 can affect properties which may improve its performance as a competitive exclusion agent, but that positive changes in adhesion may be compromised by a reduction in the ability to survive stress.
AtıfScopus201WoS179OpenAlex211
İncele - MakaleAçık Erişim2014Scopus SJRQ1Steady, dynamic and creep rheological analysis as a novel approach to detect honey adulteration by fructose and saccharose syrups: Correlations with HPLC-RID results
Yilmaz, Mustafa Tahsin; Tatlisu, Nevruz Berna; Toker, Omer Said; Karaman, Safa; Dertli, Enes; Sagdic, Osman; Arici, Muhammet
In this study, natural honey was adulterated with the addition of adulterants, namely saccharose and fructose syrups at a ratio of 0%, 10%, 20%, 30%, 40% and 50% by weight. Steady, dynamic and creep tests were conducted, revealing that the changes in the flow, viscoelastic and creep behavior of natural honey were clear and remarkable. Syrup addition decreased viscosity (η), storage (G') and loss modulus (G″) values of the control honey samples. Deformation represented by the compliance (J(t)) values was more prominent in the adulterated honey samples. In addition, HPLC-RID analysis was conducted to determine major sugar composition of the adulterated samples. Pearson's correlation test indicated that there were significant (P<0.05; 0.01) correlations between sugar composition and rheology parameters, η (viscosity), K″, K* (intercepts for G″ and complex modulus (G*), respectively) and η0 (viscosity of Maxwell dashpot), suggesting that K', K″, K* and η0 could be prominent indicators for presence of saccharose or fructose syrups added in natural honey within the studied concentration levels. These results suggested that use of steady, dynamic and creep analysis would be a novel and potential approach to detect honey adulteration by fructose and saccharose syrups.
AtıfScopus81WoS72OpenAlex80İncele - MakaleAçık Erişim2013Scopus SJRQ1Spontaneous Mutation Reveals Influence of Exopolysaccharide on Lactobacillus johnsonii Surface Characteristics
Horn, Nikki; Wegmann, Udo; Dertli, Enes; Mulholland, Francis; Collins, Samuel R. A.; Waldron, Keith W.; Bongaerts, Roy J.; Mayer, Melinda J.; Narbad, Arjan
As a competitive exclusion agent, Lactobacillus johnsonii FI9785 has been shown to prevent the colonization of selected pathogenic bacteria from the chicken gastrointestinal tract. During growth of the bacterium a rare but consistent emergence of an altered phenotype was noted, generating smooth colonies in contrast to the wild type rough form. A smooth colony variant was isolated and two-dimensional gel analysis of both strains revealed a protein spot with different migration properties in the two phenotypes. The spot in both gels was identified as a putative tyrosine kinase (EpsC), associated with a predicted exopolysaccharide gene cluster. Sequencing of the epsC gene from the smooth mutant revealed a single substitution (G to A) in the coding strand, resulting in the amino acid change D88N in the corresponding gene product. A native plasmid of L. johnsonii was engineered to produce a novel vector for constitutive expression and this was used to demonstrate that expression of the wild type epsC gene in the smooth mutant produced a reversion to the rough colony phenotype. Both the mutant and epsC complemented strains had increased levels of exopolysaccharides compared to the wild type strain, indicating that the rough phenotype is not solely associated with the quantity of exopolysaccharide. Another gene in the cluster, epsE, that encoded a putative undecaprenyl-phosphate galactosephosphotransferase, was deleted in order to investigate its role in exopolysaccharide biosynthesis. The ΔepsE strain exhibited a large increase in cell aggregation and a reduction in exopolysaccharide content, while plasmid complementation of epsE restored the wild type phenotype. Flow cytometry showed that the wild type and derivative strains exhibited clear differences in their adhesive ability to HT29 monolayers in tissue culture, demonstrating an impact of EPS on surface properties and bacteria-host interactions.
AtıfScopus71WoS66OpenAlex72İncele - MakaleAçık Erişim2013Scopus SJRQ1Structure and biosynthesis of two exopolysaccharides produced by lactobacillus johnsonii FI9785
Dertli, Enes; Colquhoun, Ian J.; Gunning, A. Patrick; Bongaerts, Roy J.; Le Gall, Gwénaëlle; Bonev, Boyan B.; Mayer, Melinda J.; Narbad, Arjan
Exopolysaccharides were isolated and purified from Lactobacillus johnsonii FI9785, which has previously been shown to act as a competitive exclusion agent to control Clostridium perfringens in poultry. Structural analysis by NMR spectroscopy revealed that L. johnsonii FI9785 can produce two types of exopolysaccharide: EPS-1 is a branched dextran with the unusual feature that every backbone residue is substituted with a 2-linked glucose unit, and EPS-2 was shown to have a repeating unit with the following structure: -6)-α-Glcp-(1-3)-β-Glcp-(1-5)-β-Galf-(1-6)-α-Glcp-(1-4) -β-Gal p-(1-4)-β-Glcp-(1-. Sites on both polysaccharides were partially occupied by substituent groups: 1-phosphoglycerol and O-acetyl groups in EPS-1 and a single O-acetyl group in EPS-2. Analysis of a deletion mutant (δepsE) lacking the putative priming glycosyltransferase gene located within a predicted eps gene cluster revealed that the mutant could produce EPS-1 but not EPS-2, indicating that epsE is essential for the biosynthesis of EPS-2. Atomic force microscopy confirmed the localization of galactose residues on the exterior of wild type cells and their absence in the δepsE mutant. EPS2 was found to adopt a random coil structural conformation. Deletion of the entire 14-kb eps cluster resulted in an acapsular mutant phenotype that was not able to produce either EPS-2 or EPS-1. Alterations in the cell surface properties of the EPS-specific mutants were demonstrated by differences in binding of an anti-wild type L. johnsonii antibody. These findings provide insights into the biosynthesis and structures of novel exopolysaccharides produced by L. johnsonii FI9785, which are likely to play an important role in biofilm formation, protection against harsh environment of the gut, and colonization of the host.
AtıfScopus131WoS120OpenAlex134İncele