Fig. 2

Aggregation of bacteriophage T4 visualized by scanning electron microscopy, SEM. In high-ionic strength 150 mM NaCl bacteriophage particles distributed uniformly on a silicon surface, as separate objects (a, c, e, g), while in contrast, in low-ionic strength (10 mM) phage particles get organized in clusters (aggregates) (b, d, f, h–j). Images represent the typical forms of phage aggregates. Distribution of phage particles depended on solute, namely physiologic 150 mM NaCl (a, c, e, g) compared with low ionic strength 10 mM NaHCO₃ (b, d, f, h, i). Visible phage particles, deposited on silicon substrate. In-lens SE1 detection (1.2 kV). Note the dispersed phenotype at higher salt concentrations (left panel), while aggregation of phages at low salt concentration (right panel). g Set of representative phage particles at high magnification, with high dispersion, under high (physiologic 150 mM NaCl) solute concentration. SEM scanned at low beam accelerating voltages with SE detection at 1.2 kV acceleration voltage of primary beam. h Set of representative phage particles at high magnification, clustered, under low (10 mM NaHCO₃) solute concentration. In-lens SE1 detection at 1.2 kV acceleration voltage of primary beam. i, j SEM images of T4 bacteriophages on silicon (100) crystal surface deposited in clusters from low ionic strength solution with cation of sodium as 10 mM NaHCO₃, (i) or with cation of potassium as 10 mM KHCO₃, (j). Please notice a similar morphology of aggregates in both cases, when at low Na⁺ or at low K⁺. Scale bars a, b 1 µm; c, d 250 nm; e, f 100 nm; g, h 50 nm; i, j 250 nm