Studies related to the head-maturation pathway of bacteriophages T4 and T2: II. Nuclear disruption,protein synthesis and particle formation with the mutant 43−·30−·46−

We describe the aberrant phage multiplication of the triple conditional lethal mutant 43^?(polymerase)· 30^?(ligase)·46^?(exonuclease) of bacteriophage T4D in which phage DNA replication is arrested but some late protein synthesis occurs (33). The nuclear disruption is indistinguishable from wild type. Forty-five empty small and empty large particles are assembled per cell when the multiplicity of infection (m.o.i.) is 100. This number corresponds closely to the 38 phage equivalents of cleaved major head protein determined biochemically. By reducing the m.o.i. the number of observable particles decreases, reaching 1–5 per cell at an m.o.i. of 5(+5). The total synthesis of phage related proteins is not significantly dependant on the m.o.i. The synthesis of late proteins is about 10% of that of wild type at high m.o.i. and decreases with the m.o.i. The different early and late proteins do not show the same relative proportions as in wild type and respond differently to an increased m.o.i. These and other results are discussed with respect to the role of phage DNA in prehead assembly and head maturation.     

Stratigraphic significance of siliceous microfossils collected during dives (off Peru, 5 °–6°S)

The geological evolution of the northern Peru convergent margin can be traced using samples collected during deep-sea dives of the submersible Nautile. In the Paita area (5°–6°S), the sedimentary sequence was intensively sampled along the main scarp of the middle slope area. It consists of Upper Miocene (7–9 Ma) to Pleistocene siltstone, sandstone and rare dolostone. The age distribution of these samples is the basis for a new geologic interpretation of the multichannel seismic line CDP3.Siliceous microfossils (both diatoms and radiolarians) show influence of both cold and temperature waters (local species mixed with upwelling ones). Diatom assemblages studied from the NP1-13 and NP1-15 dives bear a strong resemblance to assemblages from the Pisco Formation of southern Peru.Micropaleontological data from siliceous microfossils, provide evidence for two main unconformities, one is at the base of the Quaternary sequence and the other corresponds to a hiatus of 1 Myr, separating the Upper Miocene (7–8 Ma) sediments from uppermost Miocene (5–6 Ma) sediments.During the past 400 kyr, a wide rollover fold developed in the middle slope area associated with a major seaward dipping detachment fault. A catastrophic debris a valanche occurred as the results of an oversteepening of the landward flank of the rollover fold. The gravity failure of the slope, recognized by SeaBEAM and hydrosweep mapping, displaced enough material to produce a destructive tsunami which occurred 13.8 ± 2.7 kyr ago.