Near-ultraviolet (NUV) radiation killing of Escherichia coli K-12 can be enhanced by a sub-lethal concentration of hydrogen peroxide. This can be divided into a "RecA-dependent" and "RecA-independent" synergistic killing action. Stationary phase wild-type and 8 closely related repair-deficient mutants were examined for their NUV sensitivities in the presence and absence of H2O2.
View Article and Find Full Text PDFMajor events that led to acceptance of 30 to 300 as the most suitable number of colonies on plates for counting were reviewed. Three new sets of data were collected, involving triplicate plates of fifteen 1: 1.4 serial dilutions of 65 samples of raw milk.
View Article and Find Full Text PDFThe rate of nitrous acid deamination of labeled cytosine residues in native Escherichia coli deoxyribonucleic acid was monitored in vitro by release of acid-soluble counts after treatment with uracil deoxyribonucleic acid glycosylase. The reaction exhibited a lag and was not stimulate by several agents previously shown to enhance base substitution mutagenesis during nitrous acid treatment of duplex deoxyribonucleic acid. We conclude that a significant proportion of nitrous acid induced mutagenic lesions are novel lesions and not cytosine deaminations.
View Article and Find Full Text PDFThe interaction of the non-histone chromosomal protein HMG (high-mobility group) 1 with histone H1 subfractions was investigated by equilibrium sedimentation and n.m.r.
View Article and Find Full Text PDFJ Assoc Off Anal Chem
September 1979
A reverse phase paired ion liquid chromatographic procedure is described for determining methscopolamine bromide (Pamine) in the presence of neomycin sulfate in 5 veterinary formulations (Biosol M). Methscopolamine bromide is separated from neomycin sulfate and other formulation excipients by extraction into ethanol. The sample preparations are then concentrated and dissolved in water before chromatography.
View Article and Find Full Text PDFF'-episomes carrying the Salmonella typhimurium wild-type or attenuator-deleted histidine (his) operons were introduced into Escherichia coli strains containing relA or spoT single and double mutations known to affect guanosine 3'-diphosphate 5'-diphosphate (ppGpp) and guanosine 3'-triphosphate 5'-diphosphate (pppGpp) levels. Expression of the his operon and expression of the gene for 6-phosphogluconate dehydrogenase (gnd) were measured during balanced growth in amino acid-rich and minimal media. The data were consistent with the interpretation that ppGpp is a positive effector of his operon expression, whereas pppGpp is not an essential effector.
View Article and Find Full Text PDFThe need for greater interest and participation in hearing conservation on the part of otolaryngologists, audiologists, and others is growing. Ever increasing numbers of people are being handicapped by noise induced hearing impairment. This costly damage is not curable but is preventable.
View Article and Find Full Text PDFPurified native Hemophilus influenzae DNA is relatively insusceptible to nitrous acid (NA) mutagenesis in vitro, but is readily mutated following denaturation. NA mutagenicity for duplex DNA is significantly increased in the presence of various alcohols, glycols, phenols or primary amines. Phenol-extracted DNA contains dissociable contaminants of low molecular weight that enhance NA mutagenesis.
View Article and Find Full Text PDFA nonlethal concentration of H2O2 (0.05%) greatly enhances near-ultraviolet (NUV) inactivation of phage T7. Simultaneous treatment with H2O2 and NUV reduces the amount of DNA injected into the bacterial host, but not the number of phage adsorbed.
View Article and Find Full Text PDFBacillus brevis NRRL B-4389 produced extracellular maltase (alpha-glucosidase; EC 3.2.1.
View Article and Find Full Text PDFThis is a review that concentrates primarily on recent developments in the modification of conventional methods for recovery of injured coliforms and salmonellae; 43 of the 58 references were published in 1975 or later. The review encompasses four areas of activity: (a) most probable numbers procedures, (b) membrane filter procedures, (c) direct plating methods, and (d) the influence of other variables.
View Article and Find Full Text PDFA number of nitrosoureas and nitrosoamides have been compared with respect to mutagenicity for Salmonella typhimurium, in vitro cytotoxicity, in vivo toxicity and antitumor activity against murine L1210 leukemia, and chemical properties. Despite chemical similarities between the nitrosoureas and nitrosoamides, they show important differences in biological activity. Some of the nitrosoureas are very active antitumor agents, and they are less mutagenic than are the corresponding nitrosoamides, which lack antitumor activity.
View Article and Find Full Text PDFAn aryl-monoalkyl triazene, methyl-p-tolyl triazene (MTT) and a cyclic triazene (delta2-triazoline) are direct-acting mutagens for Salmonella typhimurium bacteria and for cell-free Hemophilus influenzae DNA. MTT causes reversion of the hisG46 base-substitution mutation, but no reversion of the hisD3052 frameshift mutation. Induced mutation frequency is not strongly influenced by modifications in the genetic background of the S.
View Article and Find Full Text PDFThe method of Hartman et al. for recovering stressed coliform bacteria was evaluated in a group study. The experimental medium, VRB-2, was more productive than VRB medium by 31% for raw milk, 70% for ice cream and 61% for cottage cheese.
View Article and Find Full Text PDFWild-type Salmonella typhimurium can use carnosine (beta-alanyl-L-histidine) as a source of histidine, but carnosine utilization is blocked in particular mutants defective in the constitutive enzyme peptidase D, the product of the pepD gene. Biochemical evidence for assigning carnosinase activity to peptidase D (a broad-specificity dipeptidase) includes: (i) coelution of carnosinase and dipeptidase activity from diethylaminoethyl-cellulose and Bio-Gel P-300 columns; (ii) coelectrophoresis of carnosinase and dipeptidase on polyacrylamide gels; and (iii) inactivation of carnosinase and dipeptidase activities at identical rates at both 4 and 42 degrees C. Genetic evidence indicates that mutations leading to loss of carnosinase activity map at pepD.
View Article and Find Full Text PDFAppl Environ Microbiol
March 1978
Gentamicin-thallous-carbonate (GTC) medium contained (per liter): 40.0 g of Trypticase soy agar, 5.0 g of KH(2)PO(4), 2.
View Article and Find Full Text PDFExpression of the histidine (his) operon in Salmonella typhimurium was found to be positively correlated with the intracellular level of guanosine tetraphosphate (ppGpp). Limitation for amino acids other than histidine elicited a histidine-independent metabolic regulation of the operon. In bacteria grown at decreased growth rates, his operon expression was metabolically regulated up to a point, after which further decreases in growth rate no longer resulted in further enhancement of operon expression.
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