Biomedical subjects

W W Lanz

Publications and source records attributed to W W Lanz.

3 recordsLinked to original sources

PubMed1976

Timed-release capsule method for coliform enumeration.

Wax-coated capsules containing selective ingredients (brilliant green and oxgall) were added at the time of inoculation of most-probable-number media (modified lactose broths). The inhibitory ingredients gradually diffused from the capsules into the nonselective media, imparting selectivity to the media. Concentrations of brilliant green did not reach inhibitory levels until 2 or more h had elapsed, which permitted repair of some injured cells. Resuscitation of heat-injured Escherichia coli B cells occurred in the capsule-containing media, but not in conventional brilliant green bile 2% broth or violet red bile agar. No statistically significant differences were noted between coliform counts obtained on two groups of water samples by using the capsule, most-probable-number, membrane filtration, and pour plate methods. The capsule method could be used, however, as a combined presumptive and confirmed test for the examination of water. Improvements are needed to adapt the capsule method to the analysis of some categories of food.

Bacteriological Techniques↗

PubMed1975

Violet red bile 2 agar for stressed coliforms.

Counts on a new, autoclave-sterilizable violet red bile (VRB-2) agar were compared with counts on freshly boiled VRB agar. Yields on VRB-2 agar averaged 217, 180, 130, and 112% of counts obtained on the control medium for samples of water, cottage cheese, frozen vegetables, and raw milk, respectively. The general principle used for the development of VRB-2 agar could be applied to many other kinds of selective plating media.

Agar↗

PubMed1973

Characterization of esterases produced by a ruminal bacterium identified as Butyrivibrio fibrisolvens.

An obligately anaerobic ruminal bacterial isolate was selected from 18 tributyrin-degrading isolates and identified as Butyrivibrio fibrisolvens strain 53. The culture in late exponential phase contained enzymes which could be released by sonic disruption. These enzymes degraded substrates at a rate in the order 1-naphthyl acetate (NA) > 1-naphthyl butyrate > 1-naphthyl propionate but did not degrade 1-naphthyl palmitate or 1-naphthyl phosphate. The enzymes on NA were neither stimulated nor inhibited by CoCl(2), MgCl(2), and MnCl (each varied from 10(-6) to 10(-4) M). CaCl at 10(-3) M stimulated esterase activity by 16%. Aliphatic substrates were hydrolyzed at a rate in the order triacetin > tributyrin > tripropionin, and ethyl acetate > ethyl formate. Similarly, aromatic fluorescein diesters were degraded at a rate in the order acetyl > propionyl > caproyl > butyryl > capryl > lauryl. Polyacrylamide gel electrophoretic zymograms indicated that the enzyme composite contained cathodally migrating bands. By column chromatography, these enzymes were separated into six NA-degrading fractions. Fraction V contained an esterase which had an optimal temperature of 39 C, a K(m) of 7.6 x 10(-4) on NA, and a molecular weight of about 66,000. This enzyme was inhibited by paraoxon (41%, 10(-4) M), eserine (17%, 10(-2) M), NaF (17%, 10(-2) M), and diisopropyl fluorophosphate (62%, 10(-4) M) but not by 1-naphthyl N-methyl carbamate at 8.4 x 10(-4) M.

Anaerobiosis↗