Salmonella scheme

Classification of bacterial viruses In the bacterial viruses, a formal classification scheme is rarely used. Rather, each bacterial virus is designated in terms of its principal bacterial host, followed by an arbitrary alphanumeric. Thus, we speak of T4 virus of Escherichia coli or P22 virus of Salmonella typhimurium. An overview of some of the major types of bacterial viruses is given later. We should note, however, that although a bacterial virus may be designated in reference to its principal host, the actual host range of the virus may be broader. Thus, bacteriophage Mu, generally studied with Escherichia coli, also infects Citrobacter and Salmonella. 

Finally, Droge and coworkers26 showed that the 2-aminoethyl phosphate-substituted KDO group is the lateral KDO unit of the branched trisaccharide (see Fig. 7), as follows. LPS from Salmonella minnesota mR3 was subjected to periodate oxidation. This sample, together with a control that had not been oxidized, was then mildly hydrolyzed with acid (pH = 3.4) during 1 h at 100°. Following removal of lipid A, both samples were analyzed by gel-filtration on Sephadex G-10, and paper electrophoresis. As expected, the ninhydrin-positive material obtained from the control sample was identical with KDO 7-(2-aminoethyl phosphate) (17) as previously identified. This spot was absent from the periodate-treated sample. Instead, an almost neutral, ninhydrin-positive spot was observed. This material (compound 26) was eluted, subjected to reduction with sodium [3H]borohydride, and hydrolyzed under strongly acidic conditions (see Scheme 11). Fol-... 

Salmonella typhimurium mutant.136-149 The defect of this mutant lies in the apparent KM (D-arabinose 5-phosphate) of its KDO 8-phosphate synthetase (compare this Section, 2). This KM increases more than 25-fold between 29 and 42°, so that the cells become increasingly dependent on exogenously supplied D-arabinose 5-phosphate as the growth temperature is raised. Cessation of LPS biosynthesis under nonper-missive conditions is accompanied by the accumulation of a KDO-de-ficient, precursor molecule.149 Lehmann150 and Rick and coworkers151 described studies directed at the isolation and chemical characterization of such lipid A precursors (for example, 133, Scheme 39). The... 

Scheme 9.11 Enzymatic transsialylation of four MPEG-DOXyl glycosides with sialidases from Vibrio cholerae and Salmonella typhimurium. V. cholerae sialylated in position 6 of the terminal monosaccharide units with yields of 12-17%, whereas S. typhimurium sialylated position 3 of the same monosaccharide units (yields 14-24%).

The first two steps in the biosynthesis of tryptophan in Salmonella typhimurium involve the enzyme complex anthranilate synthase-phosphoribosyltransferase, which is a tetramer having two subunits of each enzyme. The anthranilate synthase catalyzes reaction (7) and the phos-phoribosyltransferase catalyzes two reactions the N-terminal portion cleaves glutamine to glutamate giving NH3 for the anthranilate synthase, while the C-terminal portion catalyzes reaction (8).3,1,312 All these reactions require M2+ cations. Orotate phosphoribosyltransferase binds four Mn2+ ions in a cooperative fashion kinetic data have been interpreted in a scheme where both metal-free and metal-containing enzyme catalyze the reaction.313... 

The serogroup classification of Salmonella bacteria, according to the Kauffmann-White scheme (2), is based on the antigenic specificities which reside in the polysaccharide chain (the... 

The disaccharide epitope a-Tyv-(l —>3)-a-o- Man present in the D1 Salmonella serotype was synthesized as the pentenyl glycoside. The tyvelose donor 138 was prepared from ethyl l-thio-p-o-mannopyranoside 137 employing a single dideoxygenation step (Scheme 40). Glycosylation of 138 with the mannopyranosyl... 

Enterobactin was originally isolated from bacterial cultures of Salmonella typhimurium or Escherichia coll by lengthy extraction and chromatographic purification procedures giving yields in the region of 15 mg of product per litre of nutrient solution. Understandably, the exacting nature of this procedure has led to the development of a number of laboratory procedures to produce enterobactin synthetically. The most efficient of these makes use of the template effect (Section 3.9.1) involving the trimerisation of bulky triphenylmethyl substituted L-serine derivative about a tin atom (Scheme 3.28). 

Thicno[2,3-/ pyrrolyl)-l-alaninc 217 and 4-(6//-sclcnolo[2,3-/ pyrrolyl)-l-alanine 218, have been synthesized via reactions of thicnol 2,3-/ ]pyrrolc 215 and selenolo[2,3-fc]pyrrole 216, respectively, with 1-serine (Scheme 43). The reactions are catalyzed by Salmonella typhimurium tryptophan synthase [59,60],... 

In our syntheses of Salmonella structures [10,13,19,21], the heptose derivative 1 was used as a precursor for all of the heptose residues found in the target molecules. An acceptor precursor for later formation of the (1 —> 7)-linkage was obtained by regioselective silylation of the primary hydroxyl group followed by benzoylation of OH-6 (Scheme 3). Van Boom et al. postpone the oxidation step... 

Derivative 13 was deprotected to give the triheptoside backbone of the Salmonella core [19], but the protecting pattern in 13 was also chosen to allow further synthesis of core structures. Thus, debenzylation of 13 to give the 2, 3, 4 -triol, followed by the orthoester protocol, once more gave a 3 -OH acceptor (14), which was reacted with methyl 2,3,4,6-tetra-O-benzyl-l-thio- -o-gluco-pyranoside and DMTST to give the tetrasaccharide 15 (Scheme 7). 

Compared to the Salmonella core, a totally different heptose part is found in the Haemophilus core, and new heptose acceptors allowing coupling in the 2-and the 4-position, and preferably also branched 2,3- and 3,4-structures, had to be constructed. Debenzylation of spacer derivative 9 (Scheme 6, p. 179) and iso-propylidenation of the resulting 2,3,4-triol gave a 4-OH acceptor (20) with the capacity to yield branched structures through later selective removal of the acetal. The same approach to 4-0-linked heptose derivatives has been used by van Boom et al. [51]. The isopropylidene group can also be introduced already at the hexose level before the carbon elongation reaction [5,28]. 

Direct -selective glycosylation was achieved as early as 1961 by Gorin and Perlinupon, using the bromide 4 [14]. In this case, silver oxide was used as the promoter and the presence of the 2,3-di-D-carbonyl group seems to be the critical feature for a successful -selective reaction. The same donor was used in a more efficient manner by Bebault and Dutton to prepare y0-Manl 4Rha, which corresponds to the disaccharide segment of a constituent of the Salmonella type D2 and E cell surfaces [15] (O Scheme 4). 

Very important early studies on transient adaptation to oxidative stress were performed by Spitz et al. [24] and by Laval [25]. After 4-6 h of temporary growth-arrest many cells exposed to 120-150 pM hydrogen peroxide, or 2-5 pmol 10 cells, undergo further changes that can be characterized as transient adaptation to oxidative stress (Scheme 2). In the mammalian fibroblasts we [15, 22, 23, 26-31] and others [24,25] have studied, maximal adaptation is seen approximately 18 h after initial exposure to hydrogen peroxide i.e., some 12-14 h after they exit from temporary growth-arrest. In bacteria such as E. Coli and salmonella maximal adaptation is seen 20-30 min after oxidant exposure [16,17,26], whereas yeast cells require some 45 min for maximal adaptation [18,26]. 

Premise 1. The Salmonella mutation test is a necessary component of genetic toxicity testing schemes. 

In this scheme a chemical Is subjected to an ln vitro battery of tests (the Salmonella assay and an assay for chromosome aberrations In mammalian cells In culture) to determine whether It Is a genotoxln In vitro and produces the type of genetic damage that can be detected by each of these assays. A positive result In one or both of the assays classifies the chemical as a genotoxln and the chemical Is then tested with a battery of In vivo assays. If both of the In vitro assays are negative, then the chemical Is tested In the appropriate battery of asays to detect nongenotoxlc carcinogens. 

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