Enumeration and Identification of Bacillus cereus in Foods: I. 24-Hour Presumptive Test Medium

An egg yolk-polymyxin medium (KG) for rapid enumeration of Bacillus cereus is described. The test is presumptive in that differentiation of B. cereus (and closely related organisms) from other species is based on the formation of turbidity in the agar surrounding the colonies of the cereus group organisms. The medium is formulated to encourage sporulation and release of free spores for serological confirmatory tests within the 24-hr incubation period. The production of turbidity in egg yolk and free-spore production by 25 strains of B. cereus on KG agar were measured. The recovery of food poisoning strains of B. cereus inoculated into nonsterile food slurries was assessed. A comparison of KG agar and mannitol-egg yolk-polymyxin-agar indicated that the two media were comparable in their abilities to recover low levels of B. cereus from naturally contaminated foods. Since KG agar enhances spore formation by B. cereus, thus permitting early serological testing, its use in screening food products is advocated.     

Biochemical heterogeneity of the Sanfilippo syndrome: preliminary characterization of two deficient factors

Fibroblasts cultured from the skin of Sanfilippo patients show excessive accumulation and prolonged turnover time of sulfated mucopolysaccharide. This abnormality can be corrected by a macromolecular factor contained in the secretions of fibroblasts of differing genotype, as well as in normal human urine. By cross-correction tests, the Sanfilippo fibroblasts can be subdivided into two groups, each deficient in a different factor. Analytical polyacrylamide gel electrophoresis shows the two factors, which are probably proteins, to have a similar molecular weight (ca. 200,000) but to differ in charge at pH 8.5.     

Tryptophan-dependent indoleacetic-acid biosynthesis from indole,demonstrated by double-labelling experiments

Summary ³H-serine+¹⁴C-indole were administered to tips of sterily-grown pea seedlings and of non-sterile oat coleoptiles. The Try and IAA produced were extracted and purified by paper chromatography, and their ³H/¹⁴C ratios were determined. The ³H/¹⁴C ratio of IAA was lower than the ³H/¹⁴C ratio of Try. However, the same decrease of the IAA ³H/¹⁴C ratio was found when ³H, ¹⁴C-Try was supplied instead of ³H-serine+¹⁴C-indole. This result supports the view that Try is the native IAA precursor and that no significant bypass from indole to IAA exists in the plant material used.Abbreviations IAA indole-3-acetic acid - IPyA indole-3-pyruvic acid - Try tryptophan     

NUCLEOLAR-DERIVED RIBONUCLEIC ACID IN CHROMOSOMES, NUCLEAR SAP, AND CYTOPLASM OF CHIRONOMUS TENTANS SALIVARY GLAND CELLS

The distribution of monodisperse high molecular weight RNA (38, 30, 28, 23, and 18S RNA) was studied in the salivary gland cells of Chironomus tentans. RNA labeled in vitro and in vivo with tritiated cytidine and uridine was isolated from microdissected nucleoli, chromosomes, nuclear sap, and cytoplasm and analyzed by electrophoresis on agarose-acrylamide composite gels. As shown earlier, the nucleoli contain labeled 38, 30, and 23S RNA. In the chromosomes, labeled 18S RNA was found in addition to the 30 and 23S RNA previously reported. The nuclear sap contains labeled 30 and 18S RNA, and the cytoplasm labeled 28 and 18S RNA. On the basis of the present and earlier analyses, it was concluded that the chromosomal monodisperse high molecular weight RNA fractions (a) show a genuine chromosomal localization and are not due to unspecific contamination, (b) are not artefacts caused by in vitro conditions, but are present also in vivo, and (c) are very likely related to nucleolar and cytoplasmic (pre)ribosomal RNA. The 30 and 23S RNA components are likely to be precursors to 28 and 18S ribosomal RNA. The order of appearance of the monodisperse high molecular weight RNA fractions in the nucleus is in turn and order: (a) nucleolus, (b) chromosomes, and (c) nuclear sap. Since both 23 and 18S RNA are present in the chromosomes, the conversion to 18S RNA may take place there. On the other hand, 30S RNA is only found in the nucleus while 28S RNA can only be detected in the cytoplasm, suggesting that this conversion takes place in connection with the exit of the molecule from the nucleus.