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J Med Microbiol 57 (2008), 1193-1204; DOI: 10.1099/jmm.0.47798-0
© 2008 Society for General Microbiology
ISSN 1473-5644

Dichotomous metabolism of Enterococcus faecalis induced by haematin starvation modulates colonic gene expression

Toby D. Allen1,2, Danny R. Moore1,2, Xingmin Wang1,2, Viviana Casu1,2, Randal May2, Megan R. Lerner3, Courtney Houchen2, Daniel J. Brackett3,4 and Mark M. Huycke1,2

1 Muchmore Laboratories for Infectious Disease Research, Department of Veterans Affairs Medical Center, Oklahoma City, OK 73104, USA

2 Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA

3 Department of Surgery, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA

4 Research Service, Department of Veterans Affairs Medical Center, Oklahoma City, OK 73104, USA

Correspondence
Mark M. Huycke
mark-huycke{at}ouhsc.edu

Received 4 December 2007
Accepted 10 June 2008

Enterococcus faecalis is an intestinal commensal that cannot synthesize porphyrins and only expresses a functional respiratory chain when provided with exogenous haematin. In the absence of haematin, E. faecalis reverts to fermentative metabolism and produces extracellular superoxide that can damage epithelial-cell DNA. The acute response of the colonic mucosa to haematin-starved E. faecalis was identified by gene array. E. faecalis was inoculated into murine colons using a surgical ligation model that preserved tissue architecture and homeostasis. The mucosa was exposed to haematin-starved E. faecalis and compared with a control consisting of the same strain grown with haematin. At 1 h post-inoculation, 6 mucosal genes were differentially regulated and this increased to 42 genes at 6 h. At 6 h, a highly significant biological interaction network was identified with functions that included nuclear factor-{kappa}B (NF-{kappa}B) signalling, apoptosis and cell-cycle regulation. Colon biopsies showed no histological abnormalities by haematoxylin and eosin staining. Immunohistochemical staining, however, detected NF-{kappa}B activation in tissue macrophages using antibodies to the nuclear localization sequence for p65 and the F4/80 marker for murine macrophages. Similarly, haematin-starved E. faecalis strongly activated NF-{kappa}B in murine macrophages in vitro. Furthermore, primary and transformed colonic epithelial cells activated the G2/M checkpoint in vitro following exposure to haematin-starved E. faecalis. Modulation of this cell-cycle checkpoint was due to extracellular superoxide produced as a result of the respiratory block in haematin-starved E. faecalis. These results demonstrate that the uniquely dichotomous metabolism of E. faecalis can significantly modulate gene expression in the colonic mucosa for pathways associated with inflammation, apoptosis and cell-cycle regulation.

Abbreviations: CRC, colorectal cancer; DAPI, 4',6-diamidino-2-phenylindole; FBS, fetal bovine serum; FITC, fluorescein isothiocyanate; HRP, horseradish peroxidase; IL, interleukin; MnSOD, manganese superoxide dismutase; NF-{kappa}B, nuclear factor-{kappa}B; NLS, nuclear localization sequence; p.i. post-inoculation; qRT-PCR, quantitative real-time RT-PCR.




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[Abstract] [Full Text] [PDF]


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