RESUMO
Several species of magnetotactic bacteria were discovered in the lakes and ponds of Georgia. Electron microscopic analysis of the bacteria showed a great variety of microbial forms as well as magnetosome arrangements. Pyramidal, cubical or hexagonal magnetic grains could be seen in different species of bacteria. The linear organization of magnetic particles was prevailing, although gathered magnetosomes were also seen. Magnetometric measurement of magnetic particles obtained from coccoid bacteria was performed. Remnent acquisition curves, as well as thermomagenetic curves of investigated material showed that the magnetosomes under study contained pure single-domain magnetite.
Assuntos
Fenômenos Fisiológicos Bacterianos , Magnetismo , Microbiologia da Água , Bactérias/isolamento & purificação , Bactérias/ultraestrutura , Movimento Celular , Grânulos Citoplasmáticos/fisiologia , Grânulos Citoplasmáticos/ultraestrutura , Óxido Ferroso-Férrico , Água Doce , Ferro/fisiologia , Óxidos/metabolismoRESUMO
Morphological and biological properties of Salmonella typhimurium phage IRA were studied. The phage is a member of the Styloviridae family and exhibits a very wide spectrum of lytic activity. Molecular cloning of phage genes whose expression is lethal for the host cell has been performed and consequences of gene expression have been investigated. Expression of recombinant plasmid pKI71 causes structural changes of the cell wall and also degradation of host DNA while plasmid DNA remains intact. Expression of pKI72 blocks normal cell division. The possibility of applying such recombinant clones in marking pathways of microbial contamination in water areas is proposed.