Differences in the natural-abundance carbon stable isotopic compositions between products from aerobic cultures of Escherichia coli K-12 were measured. Respired CO2 was 3.4%o depleted in 13C relative to the glucose used as the carbon source, whereas the acetate was 12.3%o enriched in 13C. The acetate 13C enrichment was solely in the carboxyl group. Even though the total cellular carbon was only 0.6%o depleted in '3C, intracellular components exhibited a significant isotopic heterogeneity. The protein and lipid fractions were-1.1 and-2.7%o, respectively. Aspartic and glutamic acids were-1.6 and +2.7%o, respectively, yet citrate was isotopically identical to the glucose. Probable sites of carbon isotopic fractionation include the enzyme, phosphotransacetylase, and the Krebs cycle.
Penicillium simplicissimum, isolated from weathering basalt, produced citric acid when grown in a glucose-mineral salts medium with basalt, granite, granodiorite, rhyolite, andesite, peridotite, dunite, or quartzite. After 7 days' growth as much as 31 percent of the silicon, 11 percent of the aluminum, 64 percent of the iron, and 59 percent of the magnesium in some of the rocks were solubilized, and a number of rocks showed altered infrared absorption in the silicon-oxygen vibration region.
Serratia marcescens wild-types ATCC 264 and Nima grew but did not synthesize prodigiosin in a glycerol-alanine medium containing 10 ng of Fe per ml. Wild-type 264 required the addition of 0.2 Ag of Fe per ml for maximal growth and prodigiosin synthesis; Nima required 0.5 ,g of Fe per ml. Three percent, but not 0.1%, sea salts inhibited prodigiosin synthesis in a complex medium containing up to 10 ,g of Fe per ml. NaCl was the inhibitory sea salt component. The inhibition was not specific for NaCl; equimolar concentrations of Na2SO4, KCl, and K2SO also inhibited prodigiosin synthesis. Experiments with strains 264 and Nima and with mutant WF which cannot synthesize 4-methoxy-2-2'bipyrrole-5-carboxaldehyde (MBC), the bipyrrole moiety of prodigiosin, and with mutant 9-3-3 which cannot synthesize the monopyrrole moiety 2-methyl-3amylpyrrole (MAP) showed that both MBC synthesis and the reaction condensing MAP and MBC to form prodigiosin were relatively more sensitive to NaCl inhibition than the MAP-synthesizing step. The capacity of whole cells to condense MAP and MBC was present, but inactive, in cells grown in NaCl; removal of the NaCl from non-proliferating salt-grown cells restored the activity. Other evidence suggests the existence of a common precursor to the MAP-and MBCsynthesizing pathways.Apollo 11 lunar material in a medium containing 0.1% (wt/vol) sea salts had no detectable effect on the growth of a number of terrestrial microorganisms (12). However, fluorescent pigment formation by Pseudomonas aeruginosa ATCC 15422 was inhibited, whereas synthesis of the red pigment prodigiosin by Serratia marcescens ATCC 264 was stimulated. These effects were traced to iron leached from the lunar material. It was also observed that increasing the concentration of sea salts in the growth medium from 0.1 to 3% prevented prodigiosin synthesis in the presence of lunar material. Although iron is required for prodigiosin synthesis (1, 2, 5), only Waring and Werkman (13) have reported quantitative data. In addition, the literature appears devoid of any reports on salt inhibition of prodigiosin biosynthesis. This paper reports the results of further studies on the iron requirements for growth and prodigiosin synthesis in S. marcescens, identification of NaCl as the component in sea salt responsible for inhibition of prodigiosin synthesis, and the location and apparent mechanism of action of the NaCl block in the terminal biosynthetic pathway of the pigment. MATERIALS AND METHODSOrganisms. The wild-type strains of S. marcescens used in this study were ATCC 264 (obtained from H. S. Ginoza) and Nima (kindly supplied by R. P. Williams). Mutants 9-3-3 and WF were also supplied by R. P. Williams. Mutant 9-3-3 is blocked in the synthesis of the volatile monopyrrole moiety of prodigiosin, 2-methyl-3-amylpyrrole (MAP), but produces the stable bipyrrole moiety, 4-methoxy-2-2'-bipyrrole-5-carboxaldehyde (MBC). Mutant WF is blocked in the synthesis of MBC, but produces MAP. Both mutants and the two wild types can couple MBC and MAP to form ...
Fecal coliforms growing in a selective lactose-based broth medium at 44.5°C generate a change in the electrical impendance of the culture relative to a sterile control when populations reach 106 to 107 per ml. The ratio of these changes was measured automatically, and the data were processed by computer. A linear relation was found between the logio of the number of fecal coliforms in an inoculum and the time required for an electrical impedance ratio signal to be detected. Pure culture inocula consisting of 100 fecal coliforms in log phase or stationary phase were detected in 6.5 and 7.7 h, respectively. Standard curves of logio fecal coliforms in wastewater inocula versus detection time, based on samples collected at a sewage treatment plant over a 4-month period, were found to vary from one another with time. Nevertheless, detection times were rapid and ranged from 5.8 to 7.9 h for 200 fecal coliforms to 8.7 to 11.4 h for 1 fecal colifonn. Variations in detection times for a given number of fecal coliforms were also found among sewage treatment plants. A strategy is proposed which takes these variations into account and allows for rapid, automated enumeration of fecal coliforms in wastewater by the electrical impedance ratio technique.
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