Contribution of NADH Oxidase to Aerobic Metabolism of Streptococcus pyogenes

Abstract

The gram-positive microorganism Streptococcus pyogenes (group A streptococcus) is the causative agent of numerous infections of the skin and pharynx ranging from superficial diseases including erysipelas, impetigo, and pharyngitis to those characterized by extensive tissue destruction, such as necrotizing fasciitis. The initial stage of all streptococcal infections involves the attachment of the organism to epithelial cells of the nasopharynx or epidermis (49), and considerable evidence suggests that the ability to sense an aerobic environment and survive plays an important role in this process (17,47,48). A good example of this is streptococcal fibronectin-binding protein F, which is regulated in response to oxidative stress (16,48).The mechanisms and gene products that allow S. pyogenes to survive in aerobic environments remain largely unknown. While S. pyogenes produces a single Mn-containing superoxide dismutase (SOD) that is essential for aerobic streptococcal growth (16), it lacks many of the proteins known to be important for aerobic growth. Since the lactic acid bacteria (including those in the genera Streptococcus, Enterococcus, and Lactococcus) cannot synthesize heme (11), S. pyogenes lacks the catalases and cytochrome oxidases required for oxidative energy-linked metabolism and instead depends on substrate level phosphorylation for growth. In addition, streptococci lack the moderate-to-high levels of intracellular glutathione found in gram-negative bacteria (12). Without such mechanisms for handling oxidative stress, it seems that aerobic conditions should severely restrict streptococcal growth, yet O 2 seems to have a positive effect on the growth yields of some other lactic acid bacteria (25,30). This suggests the existence of other enzymes that are important for aerobic streptococcal growth.Recently, other lactic acid bacteria have been found to contain unique flavoproteins involved in oxidative metabolism that are very different from the respiratory redox enzymes of cytochrome-containing bacteria like Escherichia coli (8,20,41,42). One such flavoprotein, NADH peroxidase (NPXase), has been characterized extensively in Enterococcus faecalis, where it uses H 2 O 2 as an electron acceptor, thereby providing an enzymatic defense against peroxide stress (41). Another E. faecalis flavoprotein, NADH oxidase (NOXase), catalyzes the direct four-electron reduction of O 2 to water and serves as an electron acceptor during active aerobic metabolism in this organism (42). These two flavoproteins have 44% amino acid identity to one another, with the most highly conserved segments containing the nonflavin redox center and the flavin adenine dinucleotide (FAD)-and NADH-binding regions. The nonflavin redox center in each of these enzymes is an unusual stabilized cysteine-sulfenic acid that cycles between oxidized and reduced states (33).A role for these two flavoproteins in facilitating the aerobic metabolism of lactic acid bacteria may require the regeneration of one NAD ϩ molecule by NPXase, and the regeneration ...

Characterization of the Streptococcus pneumoniae NADH oxidase that is required for infection

“…Growth was significantly inhibited under conditions of vigorous aeration, probably because the low-level, non-inducible NADH oxidase (0n26 U mg −" under anaerobic conditions and 0n28 U mg −" under aerobic conditions) was not sufficient fully to protect bacteria against oxygen toxicity. The results from another laboratory also support our findings that NADH oxidase is required for S. pyogenes growth in oxygen-rich conditions (Gibson et al, 2000). The in vitro growth inhibition was almost complete when the gene for NADH oxidase was deleted in the nox allelicreplacement mutant.…”

“…pneumoniae is classified as a facultative anaerobe. Although it can grow in the presence or absence of oxygen, its energy metabolism is of an anaerobic type regardless of growth conditions (Konings & Otto, 1983 ;Poolman, 1993 (Badway & Karnovsky, 1980), Mycoplasma pneumoniae (Himmerlreich et al, 1996), Brachyspira hyodysenteriae (Stanton et al, 1999), Streptococcus pyogenes (Gibson et al, 2000) and Streptococcus mutans (Higuchi et al, 1993) and in S. pneumoniae it has been shown to be important for virulence in a murine model using an intraperitoneal challenge (Auzat et al, 1999). The enzyme was proposed to have a protective role in defence against O # toxicity (Higuchi, 1992), or to function as an oxygen sensor (Auzat et al, 1999).…”

Stress Physiology of Lactic Acid Bacteria

“…They catalyze either the two-electron reduction of oxygen to H 2 O 2 (performed by Nox1) or the four-electron reduction of oxygen to water (AhpCF) and thereby provide a very efficient enzymatic defense against oxidative stress (249). S. thermophilus, on the other hand, does not appear to encode a Nox1 enzyme but uses a single NADH oxidase to reduce oxygen directly to water (250).…”

Enterococcus haemoperoxidus sp. nov. and Enterococcus moraviensis sp. nov., isolated from water.

“…nov.) were clearly and strongly positive in the catalase test when cultivated on blood medium but negative when grown on blood-free medium. Lactic acid bacteria (including enterococci) are generally unable to synthesize haem groups (Gibson et al, 2000 ;Whittenbury, 1978 ;Deibel & Evans, 1960 ;Smith, 1954). The destruction of peroxide by some enterococcal strains was detected when cultivated on bloodcontaining medium under aerobic conditions.…”