, AND HERMAN C. LICHSTEIN. Biotin transport and accumulation by cells of Lactobacillus plantarum. I. General properties of the system. J. Bacteriol. 90:843-852. 1965.-Resting cells of Lactobacillus plantarum were saturated with bound biotin by incubation in phosphate buffer with biotin and glucose for 2 hr. This bound biotin was stable to wide changes in temperature, pH, and reaction time. Free biotin could be eluted from the cells by suspending them in cold water or saline. Immersing the cells in boiling water for 30 sec released all free biotin. Recoveries of added biotin exceeded 92%. Free biotin uptake by bound biotin-saturated cells occurred by two mechanisms. One process was independent from temperature (Qlo, 1.25), pH, cellular metabolism, and inhibition by iodoacetate. The other mechanism was dependent upon temperature (Qlo, 2.58; optimum, 37 C), pH (optimum, 7.5), and active cellular metabolism, and was inhibited by iodoacetate. Activation energies of 3,700 and 13,800 cal per mole, respectively, were observed for glucose-independent and-dependent free biotin uptake. Both processes exhibited approximately the same degree of inhibition by homobiotin. Higher concentrations of homobiotin were required to inhibit growth than to inhibit free biotin uptake. Intracellular-extracellular ratios as high as 600 were established in the absence of glucose, whereas ratios of nearly 4,000 occurred in the presence of glucose. MATERIALS AND METHODS Organism and growth conditions. L. plantarum strain 17-5, which was employed in all studies, was maintained in stab culture on APT medium (Case Laboratories, Chicago, Ill.) by serial transfer every 2 to 4 weeks, incubated at 30 C overnight, and then refrigerated. Cells for experimental use were grown in the medium of Wright and Skeggs (1944) containing 5 X 10-4,ug of biotin per ml; the medium was modified by the substitution of cysteine for cystine, and the addition of folic acid (0.5 mg per liter) to improve growth. NaCl was omitted because the Difco Vitamin Free Casamoin Acids used as a source of amino acids contains 38% NaCl. Glucose was sterilized separately by auto-843

Colonoscopy has been advocated by some investigators as the most appropriate means of screening asymptomatic patients with a positive family history of colorectal cancer. However, results of such screening have been widely disparate. The purpose of this study was to evaluate the yield of colonoscopy in a cohort of completely asymptomatic individuals with one or two first-degree relatives with a history of colorectal cancer and to compare this yield with that of colonoscopy in a group of patients with apparent anal bleeding. Patients with possible genetic disorders, such as familial polyposis, were excluded. A total of 160 asymptomatic patients and a comparison group of 137 patients with nonacute anorectal bleeding underwent colonoscopy. Colonoscopy was completed in 143 of the 160 study patients (89 percent) and in all of the comparison patients and did not result in any complications. Twenty-two adenomas were found in 17 study patients (10.6 percent); 16 of the 22 adenomas were less than 1 cm in size. In the comparison group, eight adenomas were identified (5.8 percent of patients). No cancers were identified. The difference in polyp frequency between groups was not significant. The relatively low yield of colorectal neoplasms discovered at colonoscopy in this study may in part be due to the small sample size or to the strict criteria used to define these asymptomatic patients but does not lend strong support to the notion that colonoscopy is an appropriate first step in screening the asymptomatic patient with one or two first-degree relatives with colon cancer.

The effect of phenolic compounds, ethyl alcohol, and sodium metabisulphite on the lytic activity of virulent bacteriophage PL-1 on a Lactobacillus casei S strain isolated from a lactic acid beverage fermentation was investigated. Catechin, caffeic, and gallic acids, commercially produced red, white, and champagne tannins, ethyl alcohol, and sodium metabisulphite inhibited plaque formation. Catechin, caffeic, and gallic acids were the most effective inhibitors of plaque formation. Commercially supplied oenocyanin was not effective.

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, AND HERMAN C. LICHSTEIN. Biotin transport and accumulation by cells of Lactobacillus plantarum. II. Kinetics of the system. J. Bacteriol. 90:853-856. 1965.-Bound biotin-saturated cells of Lactobacillus plantarum accumulated free biotin by a time-dependent process exhibiting substrate saturation phenomena in the presence and absence of glucose. Apparent Km and Vmax values determined in the presence and absence of glucose, respectively, from Lineweaver-Burk plots were found to be 31.5 and 7.72 m,um (K.) and 9.72 and 3.26 ,u,umoles per mg per min (Vm.). Free biotin transport per se appeared to be an energyindependent, mediated process, whereas the accumulation of large intracellular vitamin concentrations was energy-dependent. Internal free biotin was quantitatively converted to bound biotin. The rate and extent of bound biotin formation was slower than free biotin uptake, and dependent upon intracellular free biotin levels up to a saturating concentration.