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Biphasic Excitation by Leucine in Escherichia coli Chemotaxis. Shahid Khan, 2004.Leucine concentration jumps (applied by photolysis of inert derivatives) triggered swim or tumble responses in Escherichia coli mutants lacking Tsr or Tar, respectively . Wild-type E . coli bacteria were attracted in spatial assays when the initial leucine concentration difference was 5 to 120 µM but were repulsed when it was over 0.5 mM . Their responses to concentration jumps confirmed earlier deductions regarding biphasic excitation . The Lytic Enzyme of Bacteriophage PRD1 Is Associated with the Viral Membrane. Pia S. Rydman, 2002.Bacteriophage PRD1 encodes two proteins (P7 and P15) that are associated with a muralytic activity . Protein P15 is a soluble ß-1,4-N-acetylmuramidase that causes phage-induced host cell lysis . We demonstrate here that P15 is also a structural component of the PRD1 virion and that it is connected to the phage membrane . Small viral membrane proteins P20 and P22 modulate incorporation of P15 into the virion and may connect it to the phage membrane . The principal muralytic protein involved in PRD1 DNA entry seems to be the putative lytic transglycosylase protein P7, as the absence of protein P15 did not delay initiation of phage DNA replication in the virus-host system used . The incorporation of two different lytic enzymes into virions may reflect the broad host range of bacteriophage PRD1 . Partitioning of Chromosomal DNA during Establishment of Cellular Asymmetry in Bacillus subtilis. Joe Pogliano, 2002.The switch from symmetric to asymmetric cell division is a key feature of development in many organisms, including Bacillus subtilis sporulation . Here we demonstrate that, prior to the onset of asymmetric cell division, the B . subtilis chromosome is partitioned into two unequally sized domains, with the origin-proximal one-third of the future forespore chromosome condensed near one pole of the cell . Asymmetric chromosome partitioning is independent of polar division, as it occurs in cells depleted of FtsZ but depends on two transcription factors that govern the initiation of sporulation,  H and Spo0A-P . It is also independent of chromosome partitioning proteins Spo0J and Soj, suggesting the existence of a novel mechanism controlling chromosome structure . Thus, our results demonstrate that, during sporulation, two separable events prepare B . subtilis for asymmetric cell division: the relocation of cell division sites to the cell poles and the asymmetric partitioning of the future forespore chromosome .
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