MacSyDB/CapsuleDB
Extracellular capsules constitute the outermost layer of some prokaryotic cells where they establish the first contact between the microorganism and its environment. They fulfill a myriad of roles, often linked to colonization and persistence. Their physical properties prevent dessication by retaining moisture near the cell surface, enhance survival in harsh environments, and protect cells from phagocytosis by grazing protozoa. Capsules also play an essential role during infection; they downregulate pro-inflammatory cytokines, protect cells against reactive oxygen species generated by the host, and help bacteria to evade phagocytosis by macrophages and complement activation. Capsules also reduce the efficiency of antibiotics and cationic antimicrobial peptides.
Capsules are very diverse genetically and can be synthesized through different pathways. Accordingly, we have designed eight different capsule models:
- Group I or Wxz/Wzy-dependent
- Group II and III or ABC-dependent
- PGA capsule (Poly-γ-d-glutamate proteic capsule)
Synthase-dependent capsules, divided in two subtypes:
- Syn_HAS or Hyaluronic acid capsules
- Syn_CPS3 or capsules of type cps3
Group IV capsules are subdivided in three subtypes:
- GroupIV_f, based on Francisella tularensis GroupIV capsule
- GroupIV_e, based on Escherichia coli GroupIV capsule
- GroupIV_s, based on Salmonella sp. GroupIV capsule