Journal of Microbiology

Research Support, Non-U.S. Gov'ts

Role of Hydrogen Generation by Klebsiella pneumoniae in the Oral Cavity: Tomoko Kanazuru , Eisuke F. Sato , Kumiko Nagata , Hiroshi Matsui , Kunihiko Watanabe , Emiko Kasahara , Mika Jikumaru , June Inoue , Masayasu Inoue; J. Microbiol. 2010;48(6):778-783. Published online January 9, 2011; DOI: https://doi.org/10.1007/s12275-010-0149-z

Abstract: Some gastrointestinal bacteria synthesize hydrogen (H2) by fermentation. Despite the presence of bactericidal factors in human saliva, a large number of bacteria also live in the oral cavity. It has never been shown that oral bacteria also produce H2 or what role H2 might play in the oral cavity. It was found that a significant amount of H2 is synthesized in the oral cavity of healthy human subjects, and that its generation is enhanced by the presence of glucose but inhibited by either teeth brushing or sterilization with povidone iodine. These observations suggest the presence of H2-generating bacteria in the oral cavity. The screening of commensal bacteria in the oral cavity revealed that a variety of anaerobic bacteria generate H2. Among them, Klebsiella pneumoniae (K. pneumoniae) generated significantly large amounts of H2 in the presence of glucose. Biochemical analysis revealed that various proteins in K. pneumoniae are carbonylated under standard culture conditions, and that oxidative stress induced by the presence of Fe++ and H2O2 increases the number of carbonylated proteins, particularly when their hydrogenase activity is inhibited by KCN. Inhibition of H2 generation markedly suppresses the growth of K. pneumoniae. These observations suggest that H2 generation and/or the reduction of oxidative stress is important for the survival and growth of K. pneumoniae in the oral cavity.

Prediction of Bacterial Proteins Carrying A Nuclear Localization Signal and Nuclear Targeting of HsdM from Klebsiella pneumoniae: Je Chul Lee , Dong Sun Kim , Dong Chan Moon , Jung-Hwa Lee , Mi Jin Kim , Su Man Lee , Yong Seok Lee , Se-Won Kang , Eun Jung Lee , Sang Sun Kang , Eunpyo Lee , Sung Hee Hyun; J. Microbiol. 2009;47(5):641-645. Published online October 24, 2009; DOI: https://doi.org/10.1007/s12275-009-0217-4

Abstract: Nuclear targeting of bacterial proteins is an emerging pathogenic mechanism whereby bacterial proteins can interact with nuclear molecules and alter the physiology of host cells. The fully sequenced bacterial genome can predict proteins that target the nuclei of host cells based on the presence of nuclear localization signal (NLS). In the present study, we predicted bacterial proteins with the NLS sequences from Klebsiella pneumoniae by bioinformatic analysis, and 13 proteins were identified as carrying putative NLS sequences. Among them, HsdM, a subunit of KpnAI that is a type I restriction-modification system found in K. pneumoniae, was selected for the experimental proof of nuclear targeting in host cells. HsdM carried the NLS sequences, 7KKAKAKK13, in the N-terminus. A transient expression of HsdM-EGFP in COS-1 cells exhibited exclusively a nuclear localization of the fusion proteins, whereas the fusion proteins of HsdM with substitutions in residues lysine to alanine in the NLS sequences, 7AAAKAAA13, were localized in the cytoplasm. HsdM was co-localized with importin α in the nuclei of host cells. Recombinant HsdM alone methylated the eukaryotic DNA in vitro assay. Although HsdM tested in this study has not been considered to be a virulence factor, the prediction of NLS motifs from the full sequenced genome of bacteria extends our knowledge of functional genomics to understand subcellular targeting of bacterial proteins.

Journal Article

Development of a Method Based on Surface Enhanced Laser Desorption and Ionization Time of Flight Mass Spectrometry for Rapid Identification of Klebsiella pneumoniae: Daiwen Xiao , Yongchang Yang , Hua Liu , Hua Yu , Yingjun Yan , Wenfang Huang , Wei Jiang , Weijin Liao , Qi Hu , Bo Huang; J. Microbiol. 2009;47(5):646-650. Published online October 24, 2009; DOI: https://doi.org/10.1007/s12275-009-0092-z

Abstract: A method based on surface enhanced laser desorption and ionization time of flight mass spectrometry (SELDI-TOF MS) was developed for the rapid identification of Klebsiella pneumoniae by directly applying bacterial colonies without further protein extraction. A total of 40 K. pneumoniae and 114 other related microorganisms isolated clinically were analyzed by SELDI-TOF MS. An identification model for K. pneumoniae was established by artificial neural networks (ANNs) with classification accuracy of 100%. The model was blindly tested with 43 K. pneumoniae and 53 control bacteria again. The results showed that the model was successful with accuracy of 96.9%, sensitivity of 100% and specificity of 94.3%. This strategy is potential for rapid identification of K. pneumoniae.

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