The effect of haematin and catalase on Streptococcus faecalis var. zymogenes growing on glycerol

Adaptation to Adversity: the Intermingling of Stress Tolerance and Pathogenesis in Enterococci

Enterococcus is a diverse and rugged genus colonizing the gastrointestinal tract of humans and numerous hosts across the animal kingdom. Enterococci are also a leading cause of multidrug-resistant hospital-acquired infections. In each of these settings, enterococci must contend with changing biophysical landscapes and innate immune responses in order to successfully colonize and transit between hosts. Therefore, it appears that the intrinsic durability that evolved to make enterococci optimally competitive in the host gastrointestinal tract also ideally positioned them to persist in hospitals, despite disinfection protocols, and acquire new antibiotic resistances from other microbes. Here, we discuss the molecular mechanisms and regulation employed by enterococci to tolerate diverse stressors and highlight the role of stress tolerance in the biology of this medically relevant genus.

Synthesis of catalase by "Streptococcus faecalis subsp. zymogenes"

"Streptococcus faecalis subsp. zymogenes" was grown aerobically and anaerobically with glycerol as the source of carbon, and in the presence and absence of haematin. Catalase activity was found only during aerobic growth in the presence of haematin. The rate of appearance of catalase activity was measured on (a) addition of haematin to haematin-less aerobic cultures, and (b) aeration of haematin-containing anaerobic cultures in the presence or absence of chloramphenicol. These experiments suggested that apocatalase synthesis was induced by aeration and was not dependent on the presence of haematin in the growth medium. The binding of haem to apocatalase was oxygen dependent.

Energy transduction and solute transport in streptococci

Metabolic energy in lactic streptococci can be generated by substrate level phosphorylation and by efflux of end-products in symport with protons. During growth on lactose or glucose Streptococcus cremoris maintains a high proton motive force and phosphate potential. Both energy intermediates dissipate rapidly when the energy supply stops. In the initial phase of starvation the internal phosphoenolpyruvate (PEP) pool increases rapidly and this enables the organism for a prolonged period during starvation to accumulate the energy source via a PEP-dependent uptake system.