Survival of Clostridium botulinum Spores

Radiation survival curves of spores of Clostridium botulinum strain 33A exhibited an exponential reduction which accounted for most of the population, followed by a “tail” comprising a very small residual number [7 to 0.7 spore(s) per ml] which resisted death in the range between 3.0 and 9.0 Mrad dose levels. The “tail” was not caused by protective spore substances released into the suspensions during irradiation, by the presence of accumulated radiation “inactivated” spores, or by heat shock of pre-irradiated spores. The theoretical number of spore targets which must be inactivated by irradiation was estimated both by a graphical and by a computation method to be about 80, and the D value was calculated to be 0.295 and 0.396 Mrad, respectively, in buffer and in pork pea broth.     

Effect of Temperature of Liquid Nitrogen on Radiation Resistance of Spores of Clostridium botulinum

An apparatus consisting of a Dewar flask and a relay system controlling the flow of liquid nitrogen permitted the irradiation of samples in tin cans or Pyrex tubes at temperatures ranging from 0 ± 1.5 C to -194 ± 2 C. An inoculated pack comprising 320 cans of ground beef containing 5 × 10⁴ spores of Clostridium botulinum 33A per can (10 cans per radiation dose) was irradiated with Co⁶⁰ at 0 and -196 C. Incubation was carried out at 30 C for 6 months. Approximately 0.9 Mrad more radiation was required to inactivate the spores at -196 C than at 0 C. Cans irradiated at -196 C showed partial spoilage at 3.6 Mrad and no spoilage at 3.9 Mrad; the corresponding spoilage-no spoilage doses at 0 C were 2.7 and 3.0, respectively. The majority of positive cans swelled in 2 to 14 days; occasional swelling occurred as late as 20 days. At progressively higher doses, swelling was delayed proportionally to the radiation dose received. The remaining nonswollen cans had no toxin after 6 months of storage, although occasional cans contained very low numbers of viable spores comprising on the average 0.1% of the original spore inoculum. The D₁₀ values in phosphate buffer were 0.290 Mrad for 0 C and 0.396 Mrad for -196 C; in ground beef, the corresponding D₁₀ values were 0.463 Mrad and 0.680 Mrad, respectively. These D₁₀ values indicate that the lethal effect of γ rays decreased at -196 C as compared with 0 C by 13.5% in phosphate buffer, and by 47% in ground beef.     

GENETIC RELATEDNESS OF TWO POPULATIONS OF THE SOUTHERN ELEPHANT SEAL, MIROUNGA LEONINA

Blood samples from southern elephant seals ( Mirounga leonina ) from Heard and Macquarie Islands were surveyed electrophoretically for protein variation. Thirty proteins encoded by a minimum of 35 loci were screened, four of which were found to be polymorphic. Statistically significant differences in allele frequencies were found between the two populations at three loci. Heterozygosity estimates for the Heard and Macquarie island populations were 0.034 ± 0.020 (mean ± standard error) and O.029 ± 0.017 respectively, with a Nei distance of 0.007. The findings suggest that the two populations may have diverged genetically and very limited gene flow exists between the islands, a finding consistent with limited information from mark-recapture studies.     

Comparison of two scores for allocating resources to doctors in deprived areas.

Current proposals in the general practitioner contract include additional payments to doctors working among deprived populations. The underprivileged area score will be used to identify local authority wards with the greatest levels of deprivation, thus acting as the basis for distributing considerable resources. Two methods of identifying deprived populations--the underprivileged area score and the material deprivation score--were compared to determine whether they result in similar allocation of resources to regions. Financial allocations to regions based on figures derived from the contract differed considerably if the material deprivation score was used instead of the underprivileged area score: Northern and Mersey regions gained over 50% of their allocation whereas East Anglia, Oxford, and South West Thames regions lost more than 30% of theirs. Such differences have considerable implications for doctors working among deprived populations as up to 60m pounds each year might be distributed by these payments.     

Cloning of genes governing the deoxysugar portion of the erythromycin biosynthesis pathway in Saccharopolyspora erythraea (Streptomyces erythreus).

Genes that govern the formation of deoxysugars or their attachment to erythronolide B and 3 alpha-mycarosyl erythronolide B, intermediates of the biosynthesis of the 14-membered macrolide antibiotic erythromycin, were cloned from Saccharopolyspora erythraea (formerly Streptomyces erythreus). Segments of DNA that complement the eryB25, eryB26, eryB46, eryC1-60, and eryD24 mutations blocking the formation of erythronolide B or 3 alpha-mycarosyl erythronolide B, when cloned in Escherichia coli-Streptomyces shuttle cosmids or plasmid vectors that can transform S. erythraea, were located in a ca. 18-kilobase-pair region upstream of the erythromycin resistance (ermE) gene. The eryC1 gene lies just to the 5' side of ermE, and one (or possibly two) eryB gene is approximately 12 kilobase pairs farther upstream. Another eryB gene may be in the same region, while an additional eryB mutation appears to be located elsewhere. The eryD gene lies between the eryB and eryC1 genes and may regulate their function on the basis of the phenotype of an EryD- mutant.