TABLE 1

Pairwise comparison of R0 of planktonic staphylococci, FLR, and the dimensions of ellipsoidally deformed bacterial cells from matching experimental and theoretically calculated Lifshitz-Van der Waals forces for wild-type S. aureus NCTC 8325-4 and ATCC 12600 and their isogenic Δpbp4 mutantse

S. aureus strainR0 (nm)aFLR (nN)bkbrLW (nm)bRLW (nm)bR0rLW (nm)brheight image (nm)cR0rheight image (nm)b
NCTC 8325-4
    Parent strain618 ± 35−0.8 ± 0.23 ± 1638 ± 44
    Δpbp4 mutant570 ± 38−2.7 ± 0.3304 ± 97780 ± 202266 ± 135508 ± 40d82 ± 78
ATCC 12600
    Parent strain678 ± 38−0.5 ± 0.13 ± 1690 ± 31
    Δpbp4 mutant620 ± 33−1.6 ± 0.4327 ± 99854 ± 197293 ± 132583 ± 27d49 ± 60
  • a Data after the plus-or-minus signs indicate standard deviations in hydrodynamic radii over nine aliquots taken from three separate bacterial cultures of each strain.

  • b Data after the plus-or-minus signs indicate standard deviations calculated by error propagation.

  • c Data after the plus-or-minus signs indicate standard deviations in the height of bacterial cells over at least 60 staphylococci taken from three different cultures of each strain.

  • d The polar radius (rheight image) determined in the AFM peak force-QNM mode is significantly smaller than the hydrodynamic radius (R0) measured by DLS, according to a one-sided Student's t test (P < 0.05).

  • e For an explanation of the dimensional parameters, see Fig. 1. The deformation of the bacterial cell is expressed in terms of the difference between the hydrodynamic radius and the polar radius, i.e., (R0rLW) and (R0rheight image), in which rheight image is obtained from AFM imaging. For the shaded cells, results could not be calculated due to the assumption of undeformable wild-type strains.