RESUMO
Microbial flow tracers are presently limited to a strain of Bacillus globigii and a few highly specific bacteriophages. Bacillus subtilis 65-8 produces a black pigment as part of the primary metabolism under minimal nutritional conditions, with glucose as the sole carbon and energy source. This work shows that Bacillus subtilis 65-8 spores are thermostable (55 degrees C during 150 días), halotolerant (they germinate and grow in an enriched medium with up to 12% NaCl), persistent in a system of sand-soil and sewage, even in the presence of added commercial oil derivatives (kerosene, leaded gasoline and unleaded diesel), they are capable to move through porous systems even as the liquids, viscous as they may be, move through. Moreover, spores were resistant to the presence of autochtonous microorganisms in sewage, where we did not detect any other organism with differential characteristics like our strain (black pigment production in minimal medium) which could interfere with the identification of our biological flow tracer. The characteristics of Bacillus subtilis 65-8 make it a suitable biological flow tracer.
Assuntos
Bacillus subtilis/crescimento & desenvolvimento , Microbiologia Industrial/métodos , Movimento Celular , Meios de Cultura , Concentração de Íons de Hidrogênio , Esporos Bacterianos/crescimento & desenvolvimento , Temperatura , Fatores de TempoRESUMO
This paper shows that Serratia marcescens WF yields free proteolytic activity partially associated to growth, i.e. when the maximal rate of growth is reached, when it was growing in a saline medium supplemented with casein peptone. When the culture medium was utilized for a second time after it was used up (exhausted medium), growth and yield of free proteolytic activity showed the same partial association. With a protein medium containing peptides from 1000 to 5000 of molecular weight, from casein peptone, growth and yield of free proteolytic activity were partially associated too. In this paper, we demonstrated that Serratia marcescens WF yields free proteolytic activity only when growth rate is decelerating and under no growth conditions. We also demonstrated than the inducer structure acts gratuitously, because it cannot be used like a carbon and/or energy source. The structural form of the true inducer remains to be established. Finally, we propose that when growth rate is decelerating, or under no growth conditions, Serratia marcescens WF yields free proteolytic activity to obtain nitrogen from protein sources, apparently as the only function.