title: The response of type 2 quorum sensing in Klebsiella pneumoniae to a fluctuating culture environment.
abstract: Bacterial cells communicate with one another using chemical signaling molecules. This phenomenon is termed quorum sensing (QS). QS in Klebsiella pneumoniae is mediated by the synthesis of interspecies autoinducer 2 (AI-2), a furanosyl borate diester molecule. The response of Type 2 QS to environmental cues such as carbon sources, the initial pH of the medium, and boracic acid was investigated in the present study using a Vibrio harveyi BB170 reporter assay and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analysis. The results show that glucose can affect AI-2 synthesis to the greatest extent, and 3.0% glucose can stimulate K. pneumoniae to produce more AI-2, with a four times increase in activity compared with that of the control culture. According to our previous research, Type 2 QS in K. pneumoniae is luxS dependent. Therefore, the close relationship between glucose concentration and luxS transcription level was confirmed with qRT-PCR technology. The results show that the response of QS to a fluctuating glucose concentration was observed as a change in the amount of luxS RNA transcripts. A maximum of luxS transcription appeared during the exponential growth phase when the glucose concentration was 30.0 g/L. At the same time, AI-2 production was also slightly impacted by the low initial pH. It is noteworthy that the addition of boracic acid at microdosage (0.1 g/L) can also induce AI-2 synthesis. Presumably, in K. pneumoniae, the 4,5-dihydroxy-2,3-pentanedione cyclizes by the addition of borate and loss of water, is hydrated, and is converted to the final AI-2 signaling molecule.
authors: Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao, People's Republic of China. hzhu@live.cn
authors: Hu
authors: H
authors: Zhu
authors: Hui-Jun
authors: HJ
authors: Liu
authors: Shou-Jiao
authors: SJ
authors: Ning
authors: Yu-Li
authors: YL
authors: Gao
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D001888:Boric Acids / Q000032:analysis; D013437:Carbon-Sulfur Lyases / Q000378:metabolism*; D003470:Culture Media / Q000737:chemistry*; D017931:DNA Primers / Q000235:genetics; D004777:Environment; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D005947:Glucose / Q000378:metabolism; D006714:Homoserine / Q000031:analogs & derivatives* / Q000096:biosynthesis; D006863:Hydrogen-Ion Concentration; D007711:Klebsiella pneumoniae / Q000378:metabolism / Q000502:physiology*; D007783:Lactones; D010420:Pentanes / Q000378:metabolism; D053038:Quorum Sensing / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014733:Vibrio
chemical_list: C493138:4,5-dihydroxy-2,3-pentanedione; D001426:Bacterial Proteins; D001888:Boric Acids; D003470:Culture Media; D017931:DNA Primers; D007783:Lactones; C091088:N-octanoylhomoserine lactone; D010420:Pentanes; D006714:Homoserine; D013437:Carbon-Sulfur Lyases; C117753:LuxS protein, Bacteria; D005947:Glucose; C032688:boric acid