Digital Commons Network^™

Novel Aspects Of Ultrastructure In Two Species Of Cyanobacteria (Agmenellum Quadruplicatum, Mastigocladus Laminosus), Sandra Anne Nierzwicki-Bauer

Doctoral Dissertations

Novel aspects of morphology and ultrastructure were examined in two species of cyanobacteria. A complete, three-dimensional, ultrastructural reconstruction of the unicellular cyanobacterium Agmenellum quadruplicatum was carried out by means of high-voltage electron microscopy of thick sections and computer-aided reconstruction of serial thin sections. The photosynthetic thylakoid system consisted of 3-6 membrane sheets that traversed and were parallel to the long axis of the cell. These sheets were arranged as an anastomosing network of concentric shells. They coalesced and approached the cytoplasmic membrane at three peripheral loci along the entire length of the cell. The central cytoplasm of the cell was …

Biotransformation And Mutagenicity Of Benzidine, Melissa Lea Rochkind

Doctoral Dissertations

This study was undertaken to investigate whether the priority pollutant benzidine could be biotransformed by bacteria from natural environments and to determine what effect such biotransformation would have on the mutagenicity of the compound. Bacteria were collected from sites of toxic waste dumping and from estuarine, lake, and ocean locations. Sediment and water samples as well as bacterial isolates were incubated in media containing 100 (mu)g ml('-1 14)C(U)-benzidine (specific activity 6.76 mCi/mmol) supplemented with ammonia, phosphate and ferrous iron in aged seawater (salinity 26('o)/oo). Pure cultures were grown overnight in reduced-nutrient broth and washed prior to resuspending in the same …

The Effect Of Stringent Control On The Production Of Enterotoxin, Tryptophanase, And Beta-Galactosidase By Escherichia Coli In A Recycling Fermentor, Robin Leigh Eifert

Doctoral Dissertations

The recycling fermentor has been shown to be a good tool for studying microorganisms at very slow growth rates. Previous studies have determined that there are three distinct phases of growth based on biomass. Phase 3 has been shown to be initiated by the induction of the stringent response and to be regulated by the levels of guanosine 5'-diphosphate 3'-diphosphate (ppGpp) within the cell. By comparing the growth patterns of three enterotoxigenic Escherichia coli strains to that of E. coli strains of known rel genotypes, the Rel phenotypes of the enterotoxigenic strains were determined.

Both enterotoxin production and secretion in …