LOCATION OF ENZYMES IN <i>AZOTOBACTER AGILIS</i>

Robrish, Stanley A. (University of California, Davis) and Allen G. Marr . Location of enzymes in Azotobacter agilis . J. Bacteriol. 83: 158–168. 1962.—If the cells of Azotobacter agilis are disrupted by osmotic shock, respiratory enzymes and the compounds characteristic of cell wall and cytoplasmic membrane are recovered almost completely in large particles. The large particles obtained by osmotic shock were found by electron microscopy to consist of cell wall, cell membrane, and an internal membrane appearing as either vesicles or tubules in section. These envelopes are free of all the soluble cytoplasmic material and are essentially free of ribosomes. Small particles obtained by osmotic shock are ribosomes; small particles obtained by sonic oscillation consist of both ribosomes and amorphous material, presumably fragments of the envelope.</jats:p

Acid Production from Glucose and Sucrose by Growing Cultures of Caries-Conducive Streptococci

Acid production was determined for several strains of caries-conducive streptococci growing on glucose and sucrose. The yield of acid per mol of sucrose was the same as that from two hexose units. It was determined by macroscopic and microscopic observations of the culture that extracellular polymer was formed from sucrose during growth, but the amount of sucrose diverted to polymer formation was less than that anticipated from visual observations. </jats:p

Distribution of Enzymes Forming Polysaccharide from Sucrose and the Composition of Extracellular Polysaccharide Synthesized by <i>Streptococcus mutans</i>

The distribution of polysaccharide-forming activity from sucrose was investigated in cultures of three strains of Streptococcus mutans by using an assay which conveniently determines total polysaccharide. The enzymatic activity for polysaccharide formation from sucrose is almost exclusively extracellular. The ratio of the fructan to glucan in the polysaccharide differs among the three strains investigated. The enzymatic activity for the formation of polysaccharide from sucrose has been shown to be bound to the cell-free polymer itself. </jats:p

Metabolism of sucrose and its five isomers by Fusobacteriummortiferum. Microbiology 148:843

Fusobacterium mortiferum utilizes sucrose [glucose-fructose in α(1 2) linkage] and its five isomeric α-D-glucosyl-D-fructoses as energy sources for growth. Sucrose-grown cells are induced for both sucrose-6-phosphate hydrolase (S6PH) and fructokinase (FK), but the two enzymes are not expressed above constitutive levels during growth on the isomeric compounds. Extracts of cells grown previously on the sucrose isomers trehalulose α(1 1), turanose α(1 3), maltulose α(1 4), leucrose α(1 5) and palatinose α(1 6) contained high levels of an NAD M plus metal-dependent phospho-α-glucosidase (MalH). The latter enzyme was not induced during growth on sucrose. MalH catalysed the hydrolysis of the 6&apos;-phosphorylated derivatives of the five isomers to yield glucose 6-phosphate and fructose, but sucrose 6-phosphate itself was not a substrate. Unexpectedly, MalH hydrolysed both α-and β-linked stereomers of the chromogenic analogue p-nitrophenyl glucoside 6-phosphate. The gene malH is adjacent to malB and malR, which encode an EII(CB) component of the phosphoenolpyruvate-dependent sugar :phosphotransferase system and a putative regulatory protein, respectively. The authors suggest that for F. mortiferum, the products of malB and malH catalyse the phosphorylative translocation and intracellular hydrolysis of the five isomers of sucrose and of related α-linked glucosides. Genes homologous to malB and malH are present in both Klebsiella pneumoniae and the enterohaemorrhagic strain Escherichia coli O157 :H7. Both these organisms grew well on sucrose, but only K. pneumoniae exhibited growth on the isomeric compounds