En el presente trabajo ponemos a prueba interpretaciones en boga que le otorgan a la actividad minera un rol central dentro del expansionismo incaico al norte de Chile, y en particular a la región atacameña y el altiplano sur de Tarapacá. Luego de sintetizar la información acerca de la minería en la región durante el Período Intermedio Tardío (ca. 950-1.400 d.C.), revisamos las evidencias arqueológicas de minería del cobre incaica en la región atacameña y el altiplano sur de Tarapacá (ca. 1.400-1.540 d.C.), reconstruyendo a partir de dicha revisión las modalidades de organización de la producción y su administración, así como el consecuente paisaje minero-metalúrgico instaurado por los Incas en la región. Concluimos señalando que no sólo la minería jugó un rol esencial dentro de la reorganización económica incaica en el área de estudio, sino que esta actividad y su simbolismo asociado fueron los ejes alrededor de los cuales el Tawantinsuyu reorganizó los espacios sociales y sagrados a nivel regional.Palabras claves: producción minera, Tawantinsuyu, centros provinciales, paisaje minero-metalúrgico, norte de Chile. The present paper examines current interpretations of the importance of mining activity in Inka expansion into northern

800 d.C. Relaciones: Tiwanaku Expansivo. VI. Grupo d e tumbas sin cerámica o alisado. Último momento del influjo de la tradición Tiwanaku. Desaparición de todos los tipos anteriores. 1000 d.C. Relaciones: Tiwanaku Decadente. Tal vez con este momento se relacione la aparición d e un vaso d e tipologia Isla Uujuy). VII. Grupo de tumbas sin cerámica o con escudillas alisadas y10 "concho de vino" (tipos 12 y 13). 1300 d.C. Relaciones: Huruquilia-Yura, Tilcara-Yavi. VlII. Grupo d e tumbas con materiales inkaicos. 1500 d.C. Relaciones: 1nk.a.

Penicillin-binding proteins (PBPs) of Listeria monocytogenes were detected by their ability to bind to [2,3-3H]benzylpenicillin. Five proteins with M,s of 95,000, 84,000, 80,000, 76,000, and 49,000 were detected. PBPs 1 to 4 had a high affinity for [2,3-3H]benzylpenicillin and were relatively scarce (80 to 150 molecules per cell). In contrast, PBP 5 was more abundant (600 molecules per cell) but had a low affinity for [2,3-3Hlbenzylpenicillin. L. monocytogenes has a relatively high natural resistance to cephalosporins. Competition experiments showed that cephalosporins bound very poorly to PBP 3 but were good inhibitors of PBPs 1, 2, and 4, which were completely blocked at concentrations well below the MIC. Analysis of a spontaneous imipenem-resistant mutant revealed that resistance was likely due to an altered PBP 3 with a reduced affinity for [2,3-3H]benzylpenicillin. These results suggest that PBP 3 is a primary lethal target for ,-lactams in L.monocytogenes.

Despite the fact that the extreme thermophilic bacteria belonging to the genus Thermus are classified as strict aerobes, we have shown that Thermus thermophilus HB8 (ATCC 27634) can grow anaerobically when nitrate is present in the growth medium. This strain-specific property is encoded by a respiratory nitrate reductase gene cluster (nar) whose expression is induced by anoxia and nitrate (S. Ramı́rez-Arcos, L. A. Fernández-Herrero, and J. Berenguer, Biochim. Biophys. Acta, 1396:215–1997). We show here that this nar operon can be transferred by conjugation to an aerobic Thermus strain, enabling it to grow under anaerobic conditions. We show that this transfer takes place through a DNase-insensitive mechanism which, as for the Hfr (high frequency of recombination) derivatives ofEscherichia coli, can also mobilize other chromosomal markers in a time-dependent way. Three lines of evidence are presented to support a genetic linkage between nar and a conjugative plasmid integrated into the chromosome. First, the naroperon is absent from a plasmid-free derivative and from a closely related strain. Second, we have identified an origin for autonomous replication (oriV) overlapping the last gene of thenar cluster. Finally, the mating time required for the transfer of the nar operon is in good agreement with the time expected if the transfer origin (oriT) were located nearby and downstream of nar.