Statistical analyses of bacterial species based on physico‐chemical surface properties

Physico‐chemical surface properties of bacterial strains play an important role in their adhesion to surfaces. In the present study data were collected on such properties of 48 widely varying bacterial strains, including for example oral streptococci, staphylococci and Escherichia coli strains. Surface properties were represented by the relative elemental composition, relative molecular group concentration, contact angles and surface free energy, and iso‐electric point. For completeness. Gram staining was included. Principal component analysis revealed four components that could be assigned to recognizable notions, viz. presence or absence of (phospho‐) protein, (negative) charge, hydrophobic properties and iso‐electric point. Together these accounted for 70% of the total variance in the data. Relationships between strains were found with cluster analysis of strains. Staphylococci, Streptococcus mitis and Streptococcus rattus strains all formed separate clusters, while for example the E. coli and Serratia marcescens strains were divided over several clusters. Repeating the cluster analysis with the first four components led to very similar clusters of strains, indicating that these components give an adequate description of the surface properties of these strains.

Key words:

• bacteria
• surface properties
• cluster analysis