On the origin ofd-aminoacid residues in microbial peptides

Zusammenfassung Ein Gemisch von Angolid und seinen drei valinhaltigen Homologen ausl-valinhaltiger Kultur vonPithomyces sacchari enthielt gleiche Mengen zweier Isomere mit nur einem Valinrest, was wahrscheinlich macht, dass Angolid durch Umkehrung einesl-Rests aus einem zyklisch-symmetrischen Vorläufer entsteht.

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This investigation was supported by a grant No. MA 2480 from the Medical Research Council of Canada. We are most grateful to Dr.J. A. Verpoorte for the aminoacid analyses.     

The leakage of intracellular constituents from heated suspensions ofStaphylococcus aureus

Résumé Une analyse a été fait des substances que perdent les cellules deStaphylococcus aureus chauffées à 50 °C et 60 °C. Ces substances comprennent des acides aminés, de la proteine et des substances absorbantes à une longeur d'onde de 260 nm.     

Post-pleistocene dispersal in the Mexican vole ( Microtus mexicanus ): an example of an apparent trend in the distribution of southwestern mammals

The present distribution of the Mexican vole ( Microtus mexicanus ) is not entirely the product of post-Pleistocene forest fragmentation and extinction; recent dispersal also is indicated. Literature records further suggest that this phenomenon may reflect a general pattern of northward range expansion in many southwestern mammal species.     

Role of post-Pleistocene dispersal in determining the modern distribution of Abert's squirrel

Abert's squirrel is a forest-dwelling mammal, dependent upon ponderosa pine, that now ranges from southern Wyoming to northern Mexico. During the late Pleistocene, ponderosa pine and this squirrel occurred no further north than central Arizona and New Mexico. In consequence, the present range of the squirrel north of the 36thparallel must have been the result of post-Pleistocene (Holocene) dispersal. If such dispersal took place after the fragmentation of the northern montane conifer forest, at least some leakage across barriers of unsuitable (non-ponderosa pine) habitat must have occurred. Dispersal following transplanting "experiments" has shown that such barriers can be crossed; other evidence is provided that suggests this may occur sufficiently often to produce significant changes in distribution within short periods of time. Thus, explanations for the distribution of Abert's squirrel, based only on historical legacy and local extinctions, are found to be insufficient. An alternative explanation is proposed in which post-Pleistocene dispersal also plays an important role.