We previously isolated a mutant of Escherichia coli that is preferentially affected in the synthesis of rRNA and has a mutation in the gene (accD) encoding a subunit of acetyl-CoA carboxylase. Using this mutant and other mutants of the pathway for fatty acid and phospholipid biosynthesis as well as cerulenin, a specific inhibitor of fatty acid synthesis, we show that (i) inhibition of fatty acid synthesis in the presence of both a carbon source and all 20 amino acids stimulates the accumulation of guanosine tetraphosphate (ppGpp) and leads to preferential inhibition ofrRNA synthesis, (ii) this ppGpp accumulation is spoT dependent, and (iii) the generation of the metabolic signal that stimulates this spoTmediated response probably does not depend on either phospholipid starvation or a significant reduction in the level of ATP.It is well known that amino acid starvation in Escherichia coli leads to accumulation of guanosine tetraphosphate (ppGpp) and cessation of rRNA synthesis. This (about 0.2-0.3 mM) medium. Samples (0.1 ml) were mixed with 10 ul of 11 M formic acid on ice, and cell debris and inorganic phosphate were removed as described (11). Equal volumes of these formic acid extracts were chromatographed in one or two dimensions on polyethyleneimine (PEI) cellulose TLC plates (11, 12). For quantification ofppGpp, an area equal in size to each ppGpp spot between ppGpp and GTP Abbreviations: ACP, acyl-carrier protein; ts, temperature sensitive.

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The purpose of this study is to evaluate the safety and effectiveness of nonablative laser treatment of facial rhytides (e.g., periorbital wrinkles) using the New Star Model 130 Nd:YAG laser system. Previous ablative laser skin resurfacing (LSR) using, for example, a pulsed or scanned CO2 laser has been accompanied by complications such as persistent erythema, dyspigmentation, scarring, and infection. A nonablative laser modality may be effective in reducing both the severity of wrinkles and the incidence of morbidity presently associated with LSR.