Article

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

Muchmore Laboratories for Infectious Disease Research, Department of Veterans Affairs Medical Center, Oklahoma City, OK 73104, USA.
Journal of Medical Microbiology (Impact Factor: 2.27). 11/2008; 57(Pt 10):1193-204. DOI: 10.1099/jmm.0.47798-0
Source: PubMed

ABSTRACT 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-kappaB (NF-kappaB) signalling, apoptosis and cell-cycle regulation. Colon biopsies showed no histological abnormalities by haematoxylin and eosin staining. Immunohistochemical staining, however, detected NF-kappaB 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-kappaB 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.

Download full-text

Full-text

Available from: Xingmin Wang, Aug 16, 2015
0 Followers
 · 
135 Views
  • Source
    • "Enterococci are intrinsically resistant to several groups of antibiotics and often acquire antibiotic resistance and virulence determinants via horizontal gene transfer (Gilmore et al., 2002; Paulsen et al., 2003; McBride et al., 2007). Virulence factors associated with clinical isolates include gelatinase (GelE), serine protease (SprE) (Hancock and Perego, 2004), cytolysin (Haas et al., 2002; Coburn et al., 2004), enterococcal surface protein (Esp) (Tendolkar et al., 2004), aggregation substance, adhesin to collagen (Nallapareddy et al., 2000; Hirt et al., 2002), enterococcal polysaccharide antigen (Teng et al., 2002), capsular polysaccharide (Hancock and Gilmore, 2002), lipoteichoic acid (Schlievert et al., 1998) and toxic metabolites (Wang and Huycke, 2007; Allen et al., 2008). The combination of antibiotic resistance and virulence determinants makes enterococcal infections increasingly difficult to clinically treat. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The prevalence of gelatinase activity and biofilm formation among environmental enterococci was assessed. In total, 396 enterococcal isolates from swine and cattle faeces and house flies from a cattle farm were screened for gelatinase activity. The most prevalent phenotype on Todd-Hewitt agar with 1.5% skim milk was the weak protease (WP) (72.2% of isolates), followed by the strong protease (SP) 18.7%, and no protease (NP) (9.1%). The majority of WP isolates was represented by Enterococcus hirae (56.9%), followed by Enterococcus faecium (25.9%), Enterococcus casseliflavus (10.4%), Enterococcus gallinarum (5.2%) and Enterococcus saccharolyticus (1.7%). All WP isolates were negative for gelE (gelatinase) and sprE (serine protease) as well as the fsrABDC operon that regulates the two proteases, and only four isolates (7.0%) formed biofilms in vitro. All SP isolates were Enterococcus faecalis positive for the fsrABDC, gelE, sprE genes and the majority (91.2%) formed a biofilm. Diversity of NP isolates was relatively evenly distributed among E. hirae, E. faecium, E. casseliflavus, E. gallinarum, Enterococcus durans, E. saccharolyticus and Enterococcus mundtii. All NP isolates were negative for the fsr operon and only four E. hirae (11.1%) formed a biofilm. Of further interest was the loss of the gelatinase phenotype (18.9% of isolates) from SP isolates after 4 month storage at 4-8 degrees C and several passages of subculture. Results of reverse transcription PCR analysis indicated that mRNA was produced for all the genes in the frs operon and sequencing of the gelE gene did not reveal any significant mutations. However, gelatinase was not detectable by Western blot analysis. Our study shows that E. faecalis with the complete fsr operon and the potential to form a biofilm are relatively common in the agricultural environment and may represent a source/reservoir of clinically relevant strains. In addition, many environmental enterococci, especially E. hirae, produce an unknown WP that can hydrolyse casein but does not contribute to biofilm formation. The stability of the gelatinase phenotype in E. faecalis and its regulation will require additional studies.
    Environmental Microbiology 03/2009; 11(6):1540-7. DOI:10.1111/j.1462-2920.2009.01881.x · 6.24 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Enterococcus faecium and Enterococcus faecalis are commensal bacteria that colonize the gastrointestinal tract. Although these bacteria are in principal non-pathogenic, E. faecium and E. faecalis have emerged as important nosocomial pathogens with high-level resistance to antibiotics causing clinical infections including urinary tract infections, bacteremia and bacterial endocarditis in elderly and immunocompromised patients. Since the prevalence of enterococcal infections in hospitalized patients is still increasing every year, much research is focussed on the pathogenicity of these specific strains. Thus far, no clear evidence is has been found that explains the ecological success of these infectious causing strains. In order to understand what characteristics of E. faecium and E. faecalis really favour its ability to colonize and infect its host, this review focuses on the physiology of these bacteria rather then its pathology. The potential to degrade mucin glycoproteins via the production of specific glycosidases might contribute to an enhanced fitness of the organism because this substrate can be used as an additional nutrient source. Furthermore, E. faecium and E. faecalis have been shown to be resistant to bile acids. Besides bile salt hydrolases (BSH) that can detoxify conjugated bile acids (CBA), also other proteins, like gls24, are associated with CBA resistance. In addition to these characteristics, E. faecalis and to a lesser extend also E. faecium, are the primary source of Reactive Oxygen Species (ROS). In healthy individuals, the mucosa protects the underlying epithelial cell layer against harmful luminal contents like ROS. However, since E. faecium and E. faecalis produce glycosidases that reduce thickness of the mucosa, less protection is provided against ROS. ROS can cause genomic alterations, which is correlated to colorectal cancer. In conclusion, better understanding of the physiology of E. faecium and E. faecalis is essential to gain more insight into the pathogenicity of these bacteria. This review will discuss some essential adaptations of E. faecium and E. faecalis that might contribute to its increased fitness and prevalence.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Intestinal commensals are potential important contributors to the etiology of sporadic colorectal cancer, but mechanisms by which bacteria can initiate tumors remain uncertain. Herein, we describe mechanisms that link Enterococcus faecalis, a bacterium known to produce extracellular superoxide, to the acute induction of chromosomal instability. Immortalized human and nontransformed murine colonic epithelial cells, along with a mouse colonic ligation model, were used to assess the effect of E. faecalis on genomic DNA stability and damage. We found that this human intestinal commensal generated aneuploidy, tetraploidy, and gammaH2AX foci in HCT116, RKO, and YAMC cells. In addition, direct exposure of E. faecalis to these cells induced a G2 cell cycle arrest. Similar observations were noted by exposing cells to E. faecalis-infected macrophages in a dual-chamber coculture system for detecting bystander effects. Manganese superoxide dismutase, catalase, and tocopherols attenuated, and caffeine and inhibitors of glutathione synthase exacerbated, the aneugenic effects and linked the redox-active phenotype of this intestinal commensal to potentially transforming events. These findings provide novel insights into mechanisms by which E. faecalis and intestinal commensals can contribute to cellular transformation and tumorigenesis.
    Cancer Research 01/2009; 68(23):9909-17. DOI:10.1158/0008-5472.CAN-08-1551 · 9.28 Impact Factor
Show more