Properties of a Pseudomonas aeruginosa bacteriophage phi-MC

Base analysis of ϕ-MC deoxyribonucleic acid (DNA) revealed the presence of equimolar amounts of adenine and thymine, and of guanine and cytosine; the latter two comprising 45.5% of the bases. The thermal denaturation profile of the isolated DNA indicates that ϕ-MC DNA is double stranded and has a melting temperature of 87.8°. Neither an unusual base nor glucose was detected in ϕ-MC DNA.The origin of phage ϕ-MC DNA in mitomycin C induced cultures of P. aeruginosa cells has been studied. About 74% of the viral DNA was derived from the medium after induction. This result was compared with that of a virulent phage, ϕ-2 infection in the same host, and it was found that about 55% of the ϕ-2 DNA was derived from the medium.The primary adsorption sites for ϕ-MC were at the terminal ends of host cells. This characteristic appeared to be a unique property of this phage, since other Pseudomonas phages attached uniformly over the entire surface of the cell.

A purification and some properties of an insecticidal exotoxin from Bacillus thuringiensis Berliner

An insecticidal exotoxin from Bacillus thuringiensis var. thuringiensis (Berliner) has been purified. The efficiency of each stage of the purification has been ascertained and the yield of toxic material estimated by means of a quantitative bioassay. It is shown that the exotoxin is an adenine derivative substituted at position 9 and having a molecular weight of approximately 825. It can be dephosphorylated enzymically or chemically under conditions that define the exotoxin as a phosphomonoester. This results in loss of toxicity, both to insects and to mice. Spectroscopic and kinetic data are presented which suggest that a beta-ribofuranosyl moiety may be attached to the adenine. Glucose and allomucic acid have been positively identified as hydrolysis fragments from the exotoxin. These results are discussed and compared with the results of others on similar (or possibly identical) compounds.

The DNA base composition of individual chromosomes and chromosome segments from Chironomus tentans

The base composition of DNA was determined for individual chromosomes from the dipteran Chironomus tentans and for each one of six different segments of one of the chromosomes. The isolations were carried out by micromanipulation and the DNA purines were first extracted from the isolated components and afterwards separated by means of microelectrophoresis on a cellulose fiber. It was found that DNA from this material has an unusual composition corresponding to a guanine + cytosine content of about 30%. This composition was not a function of the polytenic condition but was also found for DNA from testis tissue. Furthermore Drosophila has a more traditional base composition for the bulk of DNA. Statistically significant variations in base data were found between whole chromosomes as well as between the segments from one of the chromosomes.