A. General Introduction to bacteriophage SPO1.
In SPO1 infection, early genes are transcribed by the unmodified host RNA polymerase, from promoters recognized by B. subtilis σA. Early gene 28 specifies a new sigma factor, gp28, which substitutes for σA and directs transcription of the middle genes. Middle genes 33 and 34 specify a new sigma and accessory protein, which direct transcription of the late genes (1,2,3,7). Most of the early genes are found in the "Host-Takeover Module" (6), and specify the host-takeover machinery. The middle genes primarily specify the phage DNA replication machinery, and the late genes specify the structural, morphogenetic, and lytic proteins (5). Promoters for all known early genes have -10 and -35 sequences corresponding to the consensus sequence for host promoters recognized by σA. There are two categories of early genes, immediate-early and delayed-early. The latter are distinguished from middle genes by their independence of gp28 (4).
The sequence of the SPO1 genome has recently been determined and annotated (12). Among the newly identified genes are several that specify putative transcription factors, including: another sigma factor (gp2.21), a protein with substantial homology to previously identified transcription factors gp44 and gp51 (gp25.1), and another chromatin-like DNA binding protein (gp34.25). We are presently testing whether these new transcription factors can account for previously unexplained events in the SPO1 transcription program, such as the distinction between delayed-early and immediate-early genes.
A. General Introduction to bacteriophage SPO1.
D. GP56 (possibly assisted by gp57 and gp58) inhibits host cell division.
E. GP55-53 may inhibit host protein synthesis.