Pepsin immobilized on inorganic supports for the continuous coagulation of skim milk

The milk-clotting enzyme pepsin was immobilized onto beads of alumina, titania, glass, stainless steel, iron oxide, and Teflon for treating skim milk in a fluidized-bed reactor. Two covalent attachment procedures using silanized supports and glutaraldehyde and two adsorption procedures were evaluated. The three best catalysts were titania and glass, using the covalent attachment procedure, and alumina, using the adsorption procedure at pH 1.2. The pepsin adsorbed on alumina catalyst has commercial potential compared to the previously used glass catalyst. Attempts to increase the stability of pepsin adsorbed on alumina by cross-linking with glutaraldehyde were unsuccessful owing to the low pH necessary for optimum pepsin adsorption; Desorption of pepsin from alumina during reactor operation was determined. Regeneration of spent catalysts was only partially successful.

Growth and cultivation of the unusual generalized transducing Bacillus bacteriophage SP-15

Additional properties of SP-15, a generalized transducing bacteriophage notable for the ability to transfer an unusually large fragment of deoxyribonucleic acid (DNA) to Bacillus subtilis and B. licheniformis, are presented together with improved methods that enhance its utility. Simple means have been found to provide the rigid control over moisture that is necessary for the assay of plaque-forming units (PFU). Reproducible procedures for propagating transducing phage, which depend upon an appropriate mixing of PFU with uninfected bacteria, have replaced less reliable methods that utilized infected spores. Transduction of B. subtilis W-23 increased linearly when MgSO(4) in recipient cell-SP-15 mixtures was increased from 0.005 to 0.03 m. Methods have been developed that protect SP-15 from the damaging effects of CsCl and of osmotic shock subsequent to dilution. Evidence that the PFU and transducing particles of lysates decay at the same slow rate during extended storage suggests that the decay is a result of damage to protein rather than to DNA. One-step growth experiments, in which SP-15 was propagated on B. subtilis W-23-S(r)/1 mg, indicated a latent period of 100 min, a rise period of 60 min, and a burst size of 25 to 34 PFU per infected cell. These findings suggest explanations for some of the technical difficulties SP-15 has presented.

Correlation between pigment production and amino acid requirements in Bacillus subtilis

Several Bacillus subtilis W-23 auxotrophs were unable to produce wild-type pigment normally on minimal agars supplemented sufficiently for growth. This offers a reliable means for scoring genotypes.

Cotransduction and cotransformation of genetic markers in Bacillus subtilis and Bacillus licheniformis

Bacteriophage SP-15, a large generalized transducing phage of Bacillus, was compared with phages PBS-1 and SP-10 for the ability to cotransduce pairs of genetic markers exhibiting different degrees of linkage. When auxotrophs of B. subtilis W-23 were used as recipients, SP-15 and PBS-1 effected a much higher frequency of cotransduction than did SP-10 with markers that were not closely linked. With more closely linked loci, the differences were not as great. SP-15 cotransduced linked markers at a higher mean frequency than PBS-1, suggesting that SP-15 is able to transfer a larger fragment of the Bacillus genome than any phage heretofore described. The frequency of the joint transfer of genetic markers in B. licheniformis was lower via transforming deoxyribonucleic acid than by transduction with phage SP-10. The availability of three procedures for genetic exchange-transduction by SP-15 and SP-10 as well as transformation-each of which reveals a different degree of linkage, makes B. licheniformis 9945A especially amenable to genetic analysis.

FAR INFRARED AND RAMAN SPECTRA AND STRUCTURE OF DITHIOPHOSGENE

The infrared spectrum in the range 3000–50 cm−1and the Raman spectrum of solutions of dithiophosgene have been obtained. There are no coincidences in the infrared and Raman spectra, and the only structure consistent with this and approximately tetrahedral carbon valencies is[Formula: see text]that is tetrachloro-1,3-dithietane, in which the ring is planar or nearly planar. A tentative assignment of the observed bands is given on the basis of D2hsymmetry.