ABSTRACT
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.
ABSTRACT
Polyribosomes were obtained in high yield from Rhynchosciara salivary glands by a method which uses the non-ionic detergent Nonidet P 40, in moderate salt buffer and DTT as RNase inhibitor. The polysomal profiles from glands of animals which have just started to spin the communal cocoon are slightly but consistently different from those obtained from about 5 day older animals, in which DNA puffs were open in the salivary gland chromosomes. The heaviest polyribosomes which could be detected by either radioactive uridine or amino acid incorporation have 8 to 9 ribosomes. The data indicate the existence of stable messengers in the salivary glands.
Subject(s)
Diptera/ultrastructure , Polyribosomes/analysis , Salivary Glands/ultrastructure , Animals , Cell Fractionation , Dactinomycin/pharmacology , Edetic Acid/pharmacology , Larva , Metamorphosis, Biological , Polyribosomes/drug effects , Puromycin/pharmacology , Ribonucleases/pharmacology , Ribonucleoproteins/analysisABSTRACT
The site of histone synthesis was studied in polytene cells of the salivary glands of the Rhynchosciara americana (Diptera). It was found that, as is the case in non-polytene systems, these proteins are synthesized in the cytoplasm in a class of light polysomes which contain 3-4 ribosomes. This class of polyribosomes is most active at about 5 days before pupation when the nuclei are most active in DNA synthesis and the chromosomes of the gland show many open 'DNA puffs'.