Survival in amoeba: a major selection pressure on the presence of bacterial copper and zinc resistance determinants?: identification of a "copper pathogenicity island"

The presence of metal resistance determinants in bacteria usually is attributed to geological or anthropogenic metal contamination in different environments or associated with the use of antimicrobial metals in human healthcare or in agriculture. While this is certainly true, we hypothesize that protozoan predation and macrophage killing are also responsible for selection of copper/zinc resistance genes in bacteria. In this review, we outline evidence supporting this hypothesis, as well as highlight the correlation between metal resistance and pathogenicity in bacteria. In addition, we introduce and characterize the "copper pathogenicity island" identified in Escherichia coli and Salmonella strains isolated from copper- and zinc-fed Danish pigs

The RNA chaperone Hfq promotes fitness of Actinobacillus pleuropneumoniae during porcine pleuropneumonia

Actinobacillus pleuropneumoniae is the etiological agent of porcine pleuropneumonia, an economically important disease of pigs. The hfq gene in A. pleuropneumoniae, encoding the RNA chaperone and posttranscriptional regulator Hfq, is upregulated during infection of porcine lungs. To investigate the role of this in vivo-induced gene in A. pleuropneumoniae, an hfq mutant strain was constructed. The hfq mutant was defective in biofilm formation on abiotic surfaces. The level of pgaC transcript, encoding the biosynthesis of poly-β-1,6-N-acetylglucosamine (PNAG), a major biofilm matrix component, was lower and PNAG content was 10-fold lower in the hfq mutant than in the wild-type strain. When outer membrane proteins were examined, cysteine synthase, implicated in resistance to oxidative stress and tellurite, was not found at detectable levels in the absence of Hfq. The hfq mutant displayed enhanced sensitivity to superoxide generated by methyl viologen and tellurite. These phenotypes were readily reversed by complementation with the hfq gene expressed from its native promoter. The role of Hfq in the fitness of A. pleuropneumoniae was assessed in a natural host infection model. The hfq mutant failed to colonize porcine lungs and was outcompeted by the wild-type strain (median competitive index of 2 × 10−5). Our data demonstrate that the in vivo-induced gene hfq is involved in the regulation of PNAG-dependent biofilm formation, resistance to superoxide stress, and the fitness and virulence of A. pleuropneumoniae in pigs and begin to elucidate the role of an in vivo-induced gene in the pathogenesis of pleuropneumonia.Sargurunathan Subashchandrabose, Rhiannon M. Leveque, Roy N. Kirkwood, Matti Kiupel and Martha H. Mulk

Branched-chain amino acids are required for the survival and virulence of Actinobacillus pleuropneumoniae in swine

In Actinobacillus pleuropneumoniae, which causes porcine pleuropneumonia, ilvI was identified as an in vivo-induced (ivi) gene and encodes the enzyme acetohydroxyacid synthase (AHAS) required for branched-chain amino acid (BCAA) biosynthesis. ilvI and 7 of 32 additional ivi promoters were upregulated in vitro when grown in chemically defined medium (CDM) lacking BCAA. Based on these observations, we hypothesized that BCAA would be found at limiting concentrations in pulmonary secretions and that A. pleuropneumoniae mutants unable to synthesize BCAA would be attenuated in a porcine infection model. Quantitation of free amino acids in porcine pulmonary epithelial lining fluid showed concentrations of BCAA ranging from 8 to 30 micromol/liter, which is 10 to 17% of the concentration in plasma. The expression of both ilvI and lrp, a global regulator that is required for ilvI expression, was strongly upregulated in CDM containing concentrations of BCAA similar to those found in pulmonary secretions. Deletion-disruption mutants of ilvI and lrp were both auxotrophic for BCAA in CDM and attenuated compared to wild-type A. pleuropneumoniae in competitive index experiments in a pig infection model. Wild-type A. pleuropneumoniae grew in CDM+BCAA but not in CDM-BCAA in the presence of sulfonylurea AHAS inhibitors. These results clearly demonstrate that BCAA availability is limited in the lungs and support the hypothesis that A. pleuropneumoniae, and potentially other pulmonary pathogens, uses limitation of BCAA as a cue to regulate the expression of genes required for survival and virulence. These results further suggest a potential role for AHAS inhibitors as antimicrobial agents against pulmonary pathogens.Sargurunathan Subashchandrabose, Rhiannon M. LeVeque, Trevor K. Wagner, Roy N. Kirkwood, Matti Kiupel, and Martha H. Mulk

FT-IR, FT-Raman spectra and scaled quantum mechanical study of 4-amino-1-benzylpiperidine

WOS: 000292800500010In this work, we report a combined experimental and theoretical study on molecular structure, vibrational spectra of 4-amino-1-benzyl piperidine (4A1BP). The FT-IR and FT-Raman spectrum have been recorded in the region 4000-400 cm(-1) and 3500-50 cm(-1) respectively. The molecular geometry, harmonic vibrational frequencies and bonding features of 4A1BP have been calculated by using density functional theory methods with B3LYP and 6-31G(d,p) basis set. Using the same basis set NBO analysis was performed. The calculated HOMO and LUMO energies show that the charge transfers occur with in the molecule. The theoretical FT-IR and FT-Raman spectra for the title molecule have been constructed. Mulliken charges were also calculated using B3LYP/6-31, 6-311, 6-311++G(d,p) level method. (C) 2011 Elsevier B.V. All rights reserved

FT-IR, FT-Raman, NMR spectral analysis and theoretical NBO, HOMO-LUMO analysis of bis(4-amino-5-mercapto-1,2,4-triazol-3-yl)ethane by ab initio HF and DFT methods

WOS: 000282708800008A combined experimental and theoretical studies were conducted on the molecular structure and vibrational spectra of bis(4-amino-5-mercapto-1,2,4-mazol-3-yl) ethane (BAMTE) The FT-IR and FT-Raman spectra of BAMTE were recorded in the solid phase The molecular geometry and vibrational frequencies of BAMTE in the ground state have been calculated by using the ab initio HF (Hartree-Fock) and density functional methods (B3LYP) invoking 6-311++C(d,p) basis set. The optimized geometric bond lengths and bond angles obtained by HF method shows best agreement with the experimental values. Comparison of the observed fundamental vibrational frequencies of BAMTE with calculated results by HF and density functional methods indicates that B3LYP is superior to the scaled Hartree-Fock approach for molecular vibrational problems. The difference between the observed and scaled wave number values of most of the fundamentals is very small The thermodynamic functions and atomic charges of the title compound was also performed at HF/B3LYP/6-311++G(d,p) level of theories A detailed interpretation of the FT-IR, FT-Raman, NMR spectra of BAMTE was also reported The theoretical spectrograms for Infrared and Raman spectra of the title molecule have been constructed Natural bond orbital analysis has been carried out to explain the charge transfer or delocalization of charge due to the intra-molecular interactions. Energy of the highest occupied molecular (HOMO) orbital and lowest unoccupied (LUMO) molecular orbital have been predicted (C) 2010 Elsevier B V All rights reserve

Density functional theory studies on 2,5-bis(4-hydroxy-3-methoxybenzylidene)cyclopentanone

WOS: 000293484000001The optimized molecular structure, vibrational frequencies, corresponding vibrational assignments of 2,5-bis(4-hydroxy-3-methoxybenzylidene)cyclopentanone (BHMBC) have been investigated by using density functional theory (B3LYP) methods at 6-311 G(d,p) basis set. The energy and oscillator strength calculated by Time Dependent Density Functional Theory (TD-DFT) results almost compliments with experimental findings. Then, gauge-including atomic orbital (GIAO) (13)C NMR and (1)H NMR chemical shifts calculations of the BHMBC molecule were carried out by using B3LYP functional with 6-311G(d,p) basis sets. The mass spectrum is also recorded. Moreover, we have not only simulated highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) but also determined the transition state and energy band gap. The stability of the molecule arising from hyperconjugative interaction and charge delocalization has been analyzed using natural bond orbital (NBO) analysis. Besides, molecular electrostatic potential (MEP) were performed by the DFT method and the infrared and Raman intensities have also been reported. (C) 2011 Elsevier B.V. All rights reserved