S U M M A R YSpores of five strains of Clostridium botulinum differing widely in their heat resistance contained 7.4 to 13-4 % dipicolinic acid. There appeared to be no correlation between DPA content and heat resistance of the various strains. The rate of loss of DPA during heating at 75 and IOOO was consistently slower than the rate of loss of spore viability, though, in general, heat-resistant strains lost DPA less quickly than did heat-sensitive strains.At the instant of thermal death, spores still retained 28 to 99-6 % of their original DPA, though this DPA could be released on continued heating.

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The high resistance of bacterial spores to heat has been repeatedly postulated to be due to stabilization of spore biopolymers by metal chelate compounds. Binding of calcium dipicolinic acid (Ca(II)-DPA) with spore proteins and amino acids has been discussed in the literature, but equilibrium data are generally lacking. By means of potentiometric pH titrations at 25 degrees C and an ionic strength of 1.0 (KNO(3)), the formation of Ca(II)-DPA (1:1 and 1:2) chelates and the interactions of Ca(II)-DPA chelate with a mole of each of three typical amino acids viz., cysteine, alanine, and glycine has been investigated. Analysis of the potentiometric data indicates that calcium and DPA forms 1:1 and 1:2 chelates with log K(ML1) = 4.39 +/- 0.01 and log K(ML2) = 2.25 +/- 0.01. In the presence of an equimolar amount of each of the amino acids under consideration, the Ca(II)-DPA chelate forms mixed ligand (ternary) chelate yielding the following stepwise stability constants: log K(1) = 4.17 +/- 0.01, log K(2) = 0.78 +/- 0.01 for cysteine, log K(1) = 4.06 +/- 0.01, log K(2) = 0.65 +/- 0.01 for alanine, and log K(1) = 4.30 +/- 0.02, log K(2) = 0.11 +/- 0.01 for glycine. Methods for calculating the stability constants of the mixed ligand system have been developed. On the basis of the potentiometric equilibrium data, possible structures for the various calcium chelate species are discussed. The data suggest that the differences in heat resistance of various strains of bacterial spores may conceivably be related to the differences in composition and stability of coordination complexes in the spore.

A slow manifold is a low-dimensional invariant manifold to which trajectories nearby are rapidly attracted on the way to the equilibrium point. The exact computation of the slow manifold simplifies the model without sacrificing accuracy on the slow time scales of the system. The Maas-Pope intrinsic low-dimensional manifold (ILDM) [Combust. Flame 88, 239 (1992)] is frequently used as an approximation to the slow manifold. This approximation is based on a linearized analysis of the differential equations and thus neglects curvature. We present here an efficient way to calculate an approximation equivalent to the ILDM. Our method, called functional equation truncation (FET), first develops a hierarchy of functional equations involving higher derivatives which can then be truncated at second-derivative terms to explicitly neglect the curvature. We prove that the ILDM and FET-approximated (FETA) manifolds are identical for the one-dimensional slow manifold of any planar system. In higher-dimensional spaces, the ILDM and FETA manifolds agree to numerical accuracy almost everywhere. Solution of the FET equations is, however, expected to generally be faster than the ILDM method.

Spores of Clostridium botulinum 33A in two suspending media, phosphate buffer and pork pea broth, were gamma irradiated at radiation temperatures from +20 °C to −196 °C. The liquid–solid transition around 0 °C introduced a one-step plateaulike change in radiation sensitivity of spores. The spores were considerably more resistant in the solidly frozen medium than in the liquid medium. The solid state reduced indirect effects of radiation by physical blocking of secondary radicals. The one-step transition was much smaller in pork pea broth than in buffer. This indicated that scavenging of secondary radicals by pork pea broth caused a considerable reduction of indirect effects of radiation, but did not completely eliminate them.Freezing alone did not eliminate all indirect effects. This was evident from the gradual reduction in radiation sensitivity of spores in the solidly frozen phosphate buffer betweeen −25 °C and −196 °C. Furthermore, even at −196 °C indirect effects of radiation remained active since (a) spore survival did not level off with respect to temperature and (b) the lethal efficiency of radiation was still appreciably greater in phosphate buffer than in pork pea broth at −196 °C.In frozen pork pea broth at −25 °C to −196 °C temperature had no effect on radiation sensitivity of spores. This indicated that spores were killed by direct hits; apparently physical blocking by the solidly frozen medium, plus radical scavenging by pork pea broth eliminated all indirect effects of radiation.

IntroductionChronic infection with hepatitis C virus (HCV) is an established risk factor for liver cancer. Although several epidemiologic studies have evaluated the risk of extrahepatic malignancies among people living with HCV, due to various study limitations, results have been heterogeneous.MethodsWe used data from the British Columbia Hepatitis Testers Cohort (BC-HTC), which includes all individuals tested for HCV in the Province since 1990. We assessed hepatic and extrahepatic cancer incidence using data from BC Cancer Registry. Standardized incidence ratios (SIR) comparing to the general population of BC were calculated for each cancer site from 1990 to 2016.ResultsIn total, 56,823 and 1,207,357 individuals tested positive and negative for HCV, respectively. Median age at cancer diagnosis among people with and without HCV infection was 59 (interquartile range (IQR): 53-65) and 63 years (IQR: 54-74), respectively. As compared to people living without HCV, a greater proportion of people living with HCV-infection were men (66.7% vs. 44.7%, P-value <0.0001), had comorbidities (25.0% vs. 16.3%, P-value <0.0001) and were socially deprived (35.9% vs. 25.0%, P-value <0.0001). The SIRs for liver (SIR 33.09; 95% CI 29.80-36.39), anal (SIR: 2.57; 95% CI 1.52-3.63), oesophagus (SIR: 2.00; 95% CI 1.17-2.82), larynx (SIR: 3.24; 95% CI 1.21-5.27), lung (SIR: 2.20; 95% CI 1.82-2.58), and oral (SIR: 1.78; 95% CI 1.33-2.23) cancers were significantly higher among individuals living with HCV. The SIRs for bile duct and pancreatic cancers were significantly elevated among both individuals living with (SIR; 95% CI: 2.20; 1.27-3.14; 2.18; 1.57-2.79, respectively) and without HCV (SIR; 95% CI: 2.12; 1.88-2.36; 1.20; 1.11-1.28, respectively).Discussion/ConclusionIn this study, HCV infection was associated with increased incidence of several extrahepatic cancers. The elevated incidence of multiple cancers among negative HCV testers highlights the potential contributions of screening bias and increased cancer risks associated with factors driving acquisition of infection among this population compared to the general population. Early HCV diagnosis and treatment as well as public health prevention strategies are needed to reduce the risk of extrahepatic cancers among people living with HCV and potentially populations who are at higher risk of HCV infection.

Streptomyces venezuelae S13 produced a pH-indicating sporulation pigment on a glucose-salts-agar medium consisting of glucose, KNO,, MgSO4, and NaIHPO4, pH 7. Pigmentation on this medium appeared to be closely associated with sporulation, which normally required 5 to 7 days at 30 C. The pigment was soluble in water as well as in a number of organic solvents. Butanol-extracted pigment exhibited absorption maxima at 430 and 520 nm at pH 3 and 12, respectively. Although many salts of organic acids and amino acids could replace glucose as the sole carbon source in basal salts-agar medium for growth and pigmentation, most sugars that were tested supported. good growth but negligible pigmentation. Among the nitrogenous substances tested, KNO3 was most desirable for pigmentation. The organism did not exhibit any specific requirements for divalent cations with respect to growth and pigmentation. In the absence of MgSO4, however, glucose-salts-agar prepared by autoclaving all components together failed to support growth. The production of the sporulation pigment on glucose-salts-agar was comparable to that obtained on tomato paste-oatmealagar medium. Incorporation of partially purified pigment material into broth medium that did not normally support sporulation induced sporulation, and amino acid-salts-agar medium could induce vegetative mycelia to pigment when transferred from medium that did not support either pigmentation or sporulation.

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