A Comparison of the Mechanical Properties of Different Bacterial Species

Abstract

Past attempts at direct measurement of the mechanical characteristics of cells have shown little potential for use with bacteria. However, a technique based on micromanipulation has now been used to compare the mechanical properties of two species of bacteria; Gram-negative Escherichia coli and Gram-positive Staphylococcus epidermis. Gram-negative bacteria have traditionally been considered to be weaker than their Gram-positive counterparts on the basis of them being more susceptible to disintegration by mechanical stress. This observation has been corroborated using micromanipulation, which has directly quantified the differences in cell strength on the basis of bursting force. The bursting force of rapidly growing S. epidermis was found to vary from 3 and 34 $μ$N with an average value of 13.8 $μ$N (standard error 0.8 $μ$N). The corresponding value for continuously growing E. coli (specific growth rate 0.5 h2212;1) was 3.8 $μ$N (standard error 0.4 $μ$N).