The intestinal absorption, distribution, and excretion of the major component of Firemaster BP-6,2,4,5,2',4',5'-hexabromobiphenyl, has been studied in the male rat. This polybrominated biphenyl was readily absorbed from the intestine, initially distributed throughout the body, and eventually stored primarily in the adipose tissue, was not subject to appreciable metabolism, and was excreted almost exclusively in the feces and at a very slow rate. Approximately 90% of an oral dose was absorbed from the intestine, and extrapolation of the rate of excretion to infinity indicates that less than 10% of the total dose would ever be excreted.

Five of the genes required for phosphorylative catabolism of glucose in Pseudomonas aeruginosa were ordered on two different chromosomal fragments. Analysis of a previously isolated 6.0-kb EcoRI fragment containing three structural genes showed that the genes were present on a 4.6-kb fragment in the order glucose-binding protein (gltB)-glucokinase (glk)-6-phosphogluconate dehydratase (edd). Two genes, glucose-6-phosphate dehydrogenase (zwf) and 2-keto-3-deoxy-6-phosphogluconate aldolase (eda), shown by transductional analysis to be linked to gltB and edd, were cloned on a separate 11-kb BamHI chromosomal DNA fragment and then subcloned and ordered on a 7-kb fragment. The 6.0-kb EcoRI fragment had been shown to complement a regulatory mutation, hexR, which caused noninducibility of four glucose catabolic enzymes. In this study, hexR was mapped coincident with edd. A second regulatory function, hexC, was cloned within a 0.6-kb fragment contiguous to the edd gene but containing none of the structural genes. The phenotypic effect of the hexC locus, when present on a multicopy plasmid, was elevated expression of glucokinase, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydratase, and 2-keto-3-deoxy-6-phosphogluconate aldolase activities in the absence of inducer.Glucose catabolism in Pseudomonas aeruginosa proceeds by either an oxidative or a phosphorylative pathway ( Fig. 1; reviewed in reference 24). In the direct phosphorylative pathway, glucose is transported into the cell by a periplasmic glucose-binding protein (GLTB)-dependent active transport system. Intracellular glucose is phosphorylated by glucokinase (GLK) and converted to 6-phosphogluconate (6PG) by glucose-6-phosphate dehydrogenase (ZWF). The 6PG from this pathway and from the oxidative pathway ( Fig. 1) is further metabolized to glyceraldehyde-3-phosphate and pyruvate by the Entner-Doudoroff enzymes 6PG dehydratase (EDD) and 2-keto-3-deoxy-6-phosphogluconate (KDPG) aldolase (EDA). GLK, ZWF, EDD, and EDA are strictly co-inducible, and 6PG is thought to serve as the physiological inducer (2,8,19). The glucose transport functions are separately regulated (20).All of the genes known to be required for direct phosphorylative catabolism of glucose to pyruvate and glyceraldehyde-3-phosphate are clustered in the 39-min region of the Pseudomonas aeruginosa chromosome (7,8,36 MATERIALS AND METHODS Bacterial strains and plasmids. All bacterial strains used in this study were derived from prototrophic P. aeruginosa PAO (16) and have been described previously. The edd lesions in strains PFB57 (edd-8 hexR1) and PFB2 (edd4 hexR2) have been described previously (2,8). Both of these mutant strains also were noninducible for the other glucose catabolic enzymes ZWF, GLK, and EDA (2, 8). We have designated these regulatory mutations hexRi and hexR2.Other strains used in this study were PFB9 (edd-1) and PFB52 (edd-2) (2), PFB362 (gltBi) (7), PRP444 (glk-1) (8), PFB98 (zwf-1) (36), PFB103 (zwf-2) (37), and PAO1838 (eda-9001 met-9020) (29).Plasmids in this study w...

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Crithidia fasciculata ribosomes were found to be 80S and to dissociate into 58 and 41S subunits; on 5 to 50% sucrose gradients, rRNA was separated into 25, 18, and 5S components. The molecular sizes of the heavier rRNA species, estimated by polyacrylamide gel electrophoresis were 1.24 and 0.84 M (X 10(6) daltons). The 25S RNA has a tendency to interact with the 18S RNA to give a complex that is difficult to separate by sucrose gradient centrifugation. The 25S RNA is also unstable and dissociates into 0.73 and 0.57 M components. The 18S RNA has molecular size (0.84 M) higher than the 0.7 M reported for most eukaryotes, but similar to that of Euglena and Amoeba. Ribosomal RNA hybridized 0.29% of the nuclear DNA. Mitochondrial RNA, extracted by a rapid procedure was resolved into 16 and 5S components in sucrose gradients.