A laboratory class was designed for the study of the ecology of amylolytic bacteria in soil, although other sources may be equally suitable for this purpose. Groups of three students carried out the following: (a) preparation and sterilization of medium and plates, (b) collection and preparation of soil samples, spreading the samples on the plates, (c) incubation of the plates at 373C overnight, a further 1 h incubation at 603C to observe amylolytic activity due to thermophilic bacteria, and (d) interpretation and discussion of the results. These tasks are accomplished in two periods of 4 h on consecutive days. No sophisticated instruments are required for these experiments, which can be carried out in three classes of 4 h each. On the "rst day the students prepare culture media, bu!ers and reagents, as well as collect and grow soil samples. The second day is spent for both taxonomic identi"cation of colonies and the HAI determination.

A laboratory class was designed for the study of the ecology of amylolytic bacteria in soil, although other sources may be equally suitable for this purpose. Groups of three students carried out the following: (a) preparation and sterilization of medium and plates, (b) collection and preparation of soil samples, spreading the samples on the plates, (c) incubation of the plates at 37 degrees C overnight, a further 1 h incubation at 60 degrees C to observe amylolytic activity due to thermophilic bacteria, and (d) interpretation and discussion of the results. These tasks are accomplished in two periods of 4h on consecutive days. No sophisticated instruments are required for these experiments, which can be carried out in three classes of 4h each. On the first day the students prepare culture media, buffers and reagents, as well as collect and grow soil samples. The second day is spent for both taxonomic identification of colonies and the HAI determination.