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Infection and Immunity, August 2009, p. 3412-3423, Vol. 77, No. 8
0019-9567/09/$08.00+0     doi:10.1128/IAI.01543-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Screening of Streptococcus pneumoniae ABC Transporter Mutants Demonstrates that LivJHMGF, a Branched-Chain Amino Acid ABC Transporter, Is Necessary for Disease Pathogenesis{triangledown}

Shilpa Basavanna,1 Suneeta Khandavilli,1 Jose Yuste,1 Jonathan M. Cohen,1,2 Arthur H. F. Hosie,3 Alexander J. Webb,3 Gavin H. Thomas,4 and Jeremy S. Brown1*

Centre for Respiratory Research, Department of Medicine, Royal Free and University College Medical School, Rayne Institute, London WC1E 6JJ, United Kingdom,1 Infectious Diseases and Microbiology Unit, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, United Kingdom,2 Department of Microbiology, King's College London Dental Institute, Guy's Campus, London SE1 9RT, United Kingdom,3 Department of Biology (Area 10), University of York, P.O. Box 373, YO10 5YW York, United Kingdom4

Received 19 December 2008/ Returned for modification 28 January 2009/ Accepted 5 May 2009

Bacterial ABC transporters are an important class of transmembrane transporters that have a wide variety of substrates and are important for the virulence of several bacterial pathogens, including Streptococcus pneumoniae. However, many S. pneumoniae ABC transporters have yet to be investigated for their role in virulence. Using insertional duplication mutagenesis mutants, we investigated the effects on virulence and in vitro growth of disruption of 9 S. pneumoniae ABC transporters. Several were partially attenuated in virulence compared to the wild-type parental strain in mouse models of infection. For one ABC transporter, required for full virulence and termed LivJHMGF due to its similarity to branched-chain amino acid (BCAA) transporters, a deletion mutant ({Delta}livHMGF) was constructed to investigate its phenotype in more detail. When tested by competitive infection, the {Delta}livHMGF strain had reduced virulence in models of both pneumonia and septicemia but was fully virulent when tested using noncompetitive experiments. The {Delta}livHMGF strain had no detectable growth defect in defined or complete laboratory media. Recombinant LivJ, the substrate binding component of the LivJHMGF, was shown by both radioactive binding experiments and tryptophan fluorescence spectroscopy to specifically bind to leucine, isoleucine, and valine, confirming that the LivJHMGF substrates are BCAAs. These data demonstrate a previously unsuspected role for BCAA transport during infection for S. pneumoniae and provide more evidence that functioning ABC transporters are required for the full virulence of bacterial pathogens.

* Corresponding author. Mailing address: Centre for Respiratory Research, Department of Medicine, University College Medical School, Rayne Institute, 5 University Street, London WC1E 6JJ, United Kingdom. Phone: 44 20 7679 6008. Fax: 44 20 7679 6973. E-mail: jeremy.brown{at}ucl.ac.uk

{triangledown} Published ahead of print on 26 May 2009.

Editor: J. N. Weiser

Infection and Immunity, August 2009, p. 3412-3423, Vol. 77, No. 8
0019-9567/09/$08.00+0     doi:10.1128/IAI.01543-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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