Surface proteins of group G Streptococcus in different phases of growth: patterns of production and implications for the host–bacteria relationship

Abstract

Group G Streptococcus (GGS) is a human bacterial pathogen expressing surface proteins FOG and protein G (PG) which interact with several host defence systems, including the complement and contact systems. Selected reaction monitoring mass spectrometry, electron microscopy and protein binding assays were used to track the amounts of FOG and PG intracellularly and on the bacterial surface during different phases of growth. Large and increasing amounts of PG were present on the surface in the stationary growth phase, and this was due to de novo production. In contrast, the amount of FOG did not change substantially during this phase. Apart from PG, a number of housekeeping proteins also increased in abundance in the stationary phase. These results show that GGS protein production is active during the stationary phase and that the bacteria actively remodel their surface and enter a less pro-inflammatory state in this phase.

Saliva-Induced Clotting Captures Streptococci: Novel Roles for Coagulation and Fibrinolysis in Host Defense and Immune Evasion

“…The Streptococcus parasanguinis strain is FK1, and the Streptococcus oralis strain is FK4 isolated from a healthy carrier. Bacteria were cultured in THY broth (Todd-Hewitt broth [Difco] supplemented with 0.5% [wt/vol] yeast extract [Oxoid]) and harvested in the mid-exponential phase (0.4 < optical density at 620 nm [OD 620 ] < 0.5; path length, 13 mm [Thermo Spectronic Genesys 20]) to limit variation across experiments ( 20 ).…”

“…Selected reaction monitoring (SRM) assays were either obtained from DDB ( 20 , 27 , 35 ) or developed (for fibrinopeptides A and B and streptokinase) as previously described ( 36 ). SRM data were collected using widths of 0.7 full width at half-maximum (FWHM) in both quadrupoles and 5 ms of dwell time.…”