Figure 1.
The change in the percentage compositions of SCV colonies of populations of S. aureus S. epidermidis and S. lugdunensis cultures exposed to temperature stress at 4°C for a period of 8 wks (n = 9).
Figure 2.
Morphological variations in size, pigmentation, haemolysis and Gram stain between WT and their corresponding SCVs in S. aureus, S. epidermidis and S. lugdunensis.
Column (A) shows differences in size and pigmentation between WT colonies (left) being larger and more pigmented than their SCVs (right) which are minute with diminished pigmentation (scale bar represents 1 mm). Column (B) shows the differences in response to Gram staining with WT cells (left) staining significantly darker than their corresponding SCVs (right).
Figure 3.
TEM images of (a) S. aureus, (b) S. epidermidis and (c) S. lugdunensis WT and SCV cells showing their respective ultra-structural characteristics.
WT cells had clearly defined cell-walls in comparison to SCVs which had thicker, more diffuse cell-walls following exposure to stress (4°C).
Table 1.
Analysis of the incidence of apparent “symmetrical” vs. “asymmetrical” cell divisions in WT vs. SCV cells from TEM cell preparations of S. aureus, S. epidermidis and S. lugdunensis.
Figure 4.
Principal Component Analysis (PCA) scores (t1 versus t2) scatter plotted from staphylococcal cell-wall amino acid profile data.
The staphylococci cultures were grown under ideal conditions at 37°C representing the reference control samples (Cont) or subjected to prolonged exposure to 4°C for 8 weeks (TE) before sampling and amino acid analyses. Three different strains, S. aureus (SA), S. epidermidis (SE) and S. lugdunensis (SL) were investigated in replicates (n = 9) for each strain for responses to the temperature conditions.
Figure 5.
The p1 scores for amino acids from the cell wall extracts of S. aureus following prolonged exposure at 4°C for 8 weeks compared with corresponding cultures grown under ideal conditions at 37°C representing the reference control samples.
S. aureus responded to the cold stress by generally increasing amino acid composition in this fraction relative to the control, i.e. reference samples from all three strains.
Figure 6.
The p2 scores for amino acids from the cell wall extracts of S. epidermidis and S. lugdunensis following prolonged exposure at 4°C for 8 weeks compared with corresponding cultures grown under ideal conditions at 37°C representing the reference control samples.
S. epidermidis and S. lugdunensis responded to the cold stress by substantially altering amino acid profiles relative to the respective controls. It should be emphasized that the PC2 were inversely correlated to cold treatment such that negative loadings, e.g. - 0,20 for GLN, indicated increased amino acid levels in the cold treated S. epidermidis and S. lugdunensis samples, and vice versa.