Fig. 1.

The stringent response was critical for S. aureus abscess lesion and biofilm formation. (a) Mice were infected subcutaneously with S. aureus HG001 wildtype, rsh_syn and rsh_syn complement strains. Lesions were measured 24 h post-infection using a caliper, n = 8–10/group. Statistical significance was determined using one-way ANOVA (****, p < 0.0001) (b) Bacteria were recovered 48 h post-infection from mouse abscesses infected with S. aureus HG001, ∆ rsh_syn and complemented-rsh_syn and then plated for enumeration, n = 9–10/group. (c) Weight loss/gain of infected mice was assessed by measuring the mouse weights pre-infection and 48 h post-infection, n = 9–10/group (*, p < 0.05). (d) Mice were infected subcutaneously with S. aureus Newman parent strain and its Δusp2 mutant. Lesion formation was measured 24 h post-infection using a caliper, n = 7–9/group. Statistical significance was determined using unpaired t-tests (**, p < 0.01). (e) Bacteria were recovered from Newman- and Δusp2- infected mice abscesses after 48 h and plated for enumeration, n = 7–9/group. (f) Newman and Δusp2 biofilms were grown in flow cells. After 72 h, bacteria were stained with Syto-9 (live bacteria stain) and propidium iodide (dead bacteria stain) prior to confocal imaging. The scale bar represents 30 μm in length and each image shows the xy, yz and xz dimensions. Two independent experiments were conducted for both animal studies and flow cell experiment.