Journal of Bacteriology, May 2001, p. 2715-2723, Vol. 183, No. 9
Department of Science and Mathematics,
University of Texas of the Permian Basin, Odessa, Texas
79762,1 and Section of Molecular
Genetics and Microbiology, The University of Texas at Austin, Austin,
Texas 787122
Received 22 November 2000/Accepted 20 February 2001
Plesiomonas shigelloides is a gram-negative pathogen
which can utilize heme as an iron source. In previous work, P. shigelloides genes which permitted heme iron utilization in a
laboratory strain of Escherichia coli were isolated. In the
present study, the cloned P. shigelloides sequences were
found to encode ten potential heme utilization proteins: HugA, the
putative heme receptor; TonB and ExbBD; HugB, the putative periplasmic
binding protein; HugCD, the putative inner membrane permease; and the
proteins HugW, HugX, and HugZ. Three of the genes, hugA,
hugZ, and tonB, contain a Fur box in their putative
promoters, indicating that the genes may be iron regulated. When the
P. shigelloides genes were tested in E. coli
K-12 or in a heme iron utilization mutant of P. shigelloides, hugA, the TonB system genes, and hugW, hugX, or
hugZ were required for heme iron utilization. When the
genes were tested in a hemA entB mutant of E. coli,
hugWXZ were not required for utilization of heme as a porphyrin
source, but their absence resulted in heme toxicity when the strains
were grown in media containing heme as an iron source. hugA
could replace the Vibrio cholerae hutA in a heme iron
utilization assay, and V. cholerae hutA could complement a
P. shigelloides heme utilization mutant, suggesting that
HugA is the heme receptor. Our analyses of the TonB system of P. shigelloides indicated that it could function in tonB
mutants of both E. coli and V. cholerae and
that it was similar to the V. cholerae TonB1 system in the
amino acid sequence of the proteins and in the ability of the system to
function in high-salt medium.
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.9.2715-2723.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Characterization of the Plesiomonas
shigelloides Genes Encoding the Heme Iron Utilization
System
*
Corresponding author. Mailing address: Department of
Science and Mathematics, University of Texas of the Permian Basin, 4901 E. University Blvd., Odessa, TX 79762-0001. Phone: (915) 552-2270. Fax:
(915) 552-2374. E-mail: henderson_d{at}utpb.edu.
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