The pH of skin is critical for skin health and resilience and plays a key role in controlling the skin microbiome. It has been well reported that under dysbiotic conditions such as atopic dermatitis (AD), eczema, etc. there are significant aberrations of skin pH, along with a higher level of
Staphylococcus aureus
compared to the commensal
Staphylococcus epidermidis
on skin. To understand the effect of pH on the relative growth of
S. epidermidis
and
S. aureus
, we carried out simple in vitro growth kinetic studies of the individual microbes under varying pH conditions. We demonstrated that the growth kinetics of
S. epidermidis
is relatively insensitive to pH within the range of 5–7, while
S. aureus
shows a stronger pH dependence in that range. Gompertz’s model was used to fit the pH dependence of the growth kinetics of the two bacteria and showed that the equilibrium bacterial count of
S. aureus
was the more sensitive parameter. The switch in growth rate happens at a pH of 6.5–7. Our studies are in line with the general hypothesis that keeping the skin pH within an acidic range is advantageous in terms of keeping the skin microbiome in balance and maintaining healthy skin.
In vitro growth kinetics of mouse trisomies 12 and 19
