A proteomic view on staphylococcal virulence, protein secretion and survival of water limitation

PhD ceremony: Ms. X. Yang, 14.45 uur, Doopsgezinde Kerk, Oude Boteringestraat 33, Groningen

Dissertation: A proteomic view on staphylococcal virulence, protein secretion and survival of water limitation

Promotor(s): prof. J.M. van Dijl

Faculty: Medical Sciences

Staphylococcus aureus and Staphylococcus epidermidis are notorious human pathogens that represent major threats to the health and well-being of very young and elderly individuals. Although these bacteria are highly related, they cause diseases in different ways. While S. aureus can breach the natural human defenses by itself, S. epidermidis usually takes advantage of opportunities provided by medical implants (e.g. catheters). The research described in this thesis was aimed at obtaining deeper insights into disease-causing "virulence" factors that these bacteria employ to subvert their host. The results show that S. epidermidis produces a very low number of virulence factors compared to S. aureus, which explains why S. epidermidis requires disruption of the skin to cause invasive disease. Once either species has invaded our body, they can form thick multi-layered biofilms on tissues or medical implants. These biofilms are composed of multiple bacterial layers embedded in an impermeable matrix. This makes the bacteria invulnerable both to our immune system and antibiotics. The results in this thesis show that specific enzymes named sortases, which couple biofilm-promoting proteins to the bacterial surface, play crucial roles in biofilm formation. Furthermore, it was investigated how staphylococci can survive the dry environment of the human skin, which represents an ecological equivalent of the Sahara. They manage this through specific desiccation stress responses that involve drastic changes in cell morphology.