Identification and analysis of Staphylococcus aureus components expressed by a model system of growth in serum - PubMed (original) (raw)

Identification and analysis of Staphylococcus aureus components expressed by a model system of growth in serum

M D Wiltshire et al. Infect Immun. 2001 Aug.

Abstract

A model system mimicking Staphylococcus aureus bacteremia was developed by growth in serum under microaerobic conditions. Eight genes induced by growth in serum were identified, including an antimicrobial peptide biosynthesis locus, amino acid biosynthetic loci, and genes encoding putative surface proteins. Nine independent insertions were found in the major lysine biosynthesis operon, which encodes eight genes, is repressed by lysine in vitro, and is expressed in vivo.

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Figures

FIG. 1

FIG. 1

Diagrammatic representation of the dap_operon of S. aureus, showing the sequenced regions cloned in pSEG10 and pMTOPO9 and those cloned to generate the_lacZ transcriptional fusion strains. Shaded genes are putatively involved in lysine biosynthesis. Tn_917_insertions from left to right: aspartokinase II (lysC) control-leader region (putative)—_seg_22 (siblings_seg_30 and _seg_33); aspartokinase II (lysC)—_seg_14, _seg_25 (bottom, sibling _seg_50), _seg_45 (top, sibling _seg_48), _seg_13, and_seg_1 (sibling _seg_21); aspartate semialdehyde dehydrogenase (asd)—_seg_24 and _seg_26; and dihydrodipicolinate synthase (dapA)—_seg_10. ABC, ATP-binding cassette.

FIG. 2

FIG. 2

Expression of lysC, asd, and_dapA_ in different chemically defined media (CDM). Shown is analysis of transcription (closed symbols) of_lysC_::lacZ (MDW41) (diamonds),asd::lacZ (MDW42) (circles), and dapA::lacZ (MDW43) (triangles). Basal CDM was prepared without the aspartate family amino acids (lysine [Lys], methionine [Met], threonine [Thr], and isoleucine [Ile]). Supplements to 100 mg of Lys and Met per liter and to 150 mg of Thr and Ile per liter were added as follows: a, none; b, Lys, Met, Thr, and Ile; c, Lys; and d, Met, Thr, and Ile. A representative growth curve (MDW41) is shown on each graph (OD600 [open squares]). MUG, methylumbelliferyl-β-

d

-galactoside.

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