Figure 4.

Comparison of force curves obtained by approaching bare silicon nitride tips to bacterial lawns immobilized on glass with force curves obtained by approaching bacterial-coated tips to clean glass surfaces. All measurements were performed in 1 mM Tris (pH 7.5). +, bare silicon nitride tip probing D21 bacterial lawn; ○, silicon nitride tip coated with D21 probing glass substrate; ≍⃒, bare silicon nitride tip probing D21f2 bacterial lawn; □, silicon nitride tip coated with D21f2 probing glass substrate.