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Identification and characterization of fhuD1 and fhuD2, two genes involved in iron-hydroxamate uptake in Staphylococcus aureus.

ABSTRACT: Staphylococcus aureus can utilize several hydroxamate siderophores for growth under iron-restricted conditions. Previous findings have shown that S. aureus possesses a cytoplasmic membrane-associated traffic ATPase that is involved in the specific transport of iron(III)-hydroxamate complexes. In this study, we have identified two additional genes, termed fhuD1 and fhuD2, whose products are involved in this transport process in S. aureus. We have shown that fhuD2 codes for a posttranslationally modified lipoprotein that is anchored in the cytoplasmic membrane, while the deduced amino acid sequence predicts the same for fhuD1. The predicted FhuD1 and FhuD2 proteins share 41.0% identity and 56.4% total similarity with each other, 45.9 and 49.1% total similarity with the FhuD homolog in Bacillus subtilis, and 29.3 and 24.6% total similarity with the periplasmic FhuD protein from Escherichia coli. Insertional inactivation and gene replacement of both genes showed that while FhuD2 is involved in the transport of iron(III) in complex with ferrichrome, ferrioxamine B, aerobactin, and coprogen, FhuD1 shows a more limited substrate range, capable of only iron(III)-ferrichrome and iron(III)-ferrioxamine B transport in S. aureus. Nucleotide sequences present upstream of both fhuD1 and fhuD2 predict the presence of consensus Fur binding sequences. In agreement, transcription of both genes was negatively regulated by exogenous iron levels through the activity of the S. aureus Fur protein.

SUBMITTER: Sebulsky MT

PROVIDER: S-EPMC95374 | biostudies-literature | 2001 Sep

REPOSITORIES: biostudies-literature

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Identification and characterization of fhuD1 and fhuD2, two genes involved in iron-hydroxamate uptake in Staphylococcus aureus.

Sebulsky M T MT Heinrichs D E DE

Journal of bacteriology 20010901 17

Staphylococcus aureus can utilize several hydroxamate siderophores for growth under iron-restricted conditions. Previous findings have shown that S. aureus possesses a cytoplasmic membrane-associated traffic ATPase that is involved in the specific transport of iron(III)-hydroxamate complexes. In this study, we have identified two additional genes, termed fhuD1 and fhuD2, whose products are involved in this transport process in S. aureus. We have shown that fhuD2 codes for a posttranslationally m ...[more]

PMID: 11489851

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Project description:BackgroundMastitis in dairy cattle results from infection of mammary tissue by a range of micro-organisms but principally coliform bacteria and Gram positive bacteria such as Staphylococcus aureus. The former species are often acquired by environmental contamination while S. aureus is particularly problematic due to its resistance to antibiotic treatments and ability to reside within mammary tissue in a chronic, subclinical state. The transcriptional responses within bovine mammary epithelial tissue subjected to intramammary challenge with S. aureus are poorly characterised, particularly at the earliest stages of infection. Moreover, the effect of infection on the presence of bioactive innate immune proteins in milk is also unclear. The nature of these responses may determine the susceptibility of the tissue and its ability to resolve the infection.ResultsTranscriptional profiling was employed to measure changes in gene expression occurring in bovine mammary tissues sampled from three dairy cows after brief and graded intramammary challenges with S. aureus. These limited challenges had no significant effect on the expression pattern of the gene encoding beta-casein but caused coordinated up-regulation of a number of cytokines and chemokines involved in pro-inflammatory responses. In addition, the enhanced expression of two genes, S100 calcium-binding protein A12 (S100A12) and Pentraxin-3 (PTX3) corresponded with significantly increased levels of their proteins in milk from infected udders. Both genes were shown to be expressed by mammary epithelial cells grown in culture after stimulation with lipopolysaccharide. There was also a strong correlation between somatic cell count, a widely used measure of mastitis, and the level of S100A12 in milk from a herd of dairy cows. Recombinant S100A12 inhibited growth of Escherichia coli in vitro and recombinant PTX3 bound to E. coli as well as C1q, a subunit of the first component of the complement cascade.ConclusionThe transcriptional responses in infected bovine mammary tissue, even at low doses of bacteria and short periods of infection, probably reflect the combined contributions of gene expression changes resulting from the activation of mammary epithelial cells and infiltrating immune cells. The secretion of a number of proinflammatory cytokines and chemokines from mammary epithelial cells stimulated by the bacteria serves to trigger the recruitment and activation of neutrophils in mammary tissue. The presence of S100A12 and PTX3 in milk from infected udder quarters may increase the anti-bacterial properties of milk thereby helping to resolve the mammary tissue infection as well as potentially contributing to the maturation of the newborn calf epithelium and establishment of the newborn gut microbial population.

Dataset Information

Identification and characterization of fhuD1 and fhuD2, two genes involved in iron-hydroxamate uptake in Staphylococcus aureus.

Publications

Identification and characterization of fhuD1 and fhuD2, two genes involved in iron-hydroxamate uptake in Staphylococcus aureus.

Similar Datasets

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