FIG. 4.

Evidence for homologous recombination and mosaicism of gene cassettes among ssDNA filamentous bacteriophages. Genes in cassettes bearing homologous genes are coordinately colored; orthologous gene cassettes with various degrees of similarity are represented by various shades of the same color, whereas nonorthologous replacements are denoted by differently colored cassettes. The darker regions in genes I and IV of phages IKe and I2-2 indicate homologous recombination events with M13/fd-like sequences first noted by Peeters et al. (106). The sequences of bacteriophages fd (8), M13 (140), Ike (106), and I2-2 (123) were obtained from the public database; the φYP01 sequence represents an inferred prophage in the Yersinia pestis genome (104) beginning at gene YP02274 and continuing through downstream genes.