Effect of Iron and Salt on Prodigiosin Synthesis in Serratia marcescens
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 μg of Fe per ml for maximal growth and prodigiosin synthesis; Nima required 0.5 μg of Fe per ml. Three percent, but not 0.1%, sea salts inhibited prodigiosin synthesis in a complex medium containing up to 10 μg of Fe per ml. NaCl was the inhibitory sea salt component. The inhibition was not specific for NaCl; equimolar concentrations of Na2SO4, KCl, and K2SO4 also inhibited prodigiosin synthesis. Experiments with strains 264 and Nima and with mutant WF which cannot synthesize 4-methoxy-2-2′-bipyrrole-5-carboxyaldehyde (MBC), the bipyrrole moiety of prodigiosin, and with mutant 9-3-3 which cannot synthesize the monopyrrole moiety 2-methyl-3-amylpyrrole (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 MBC-synthesizing pathways.
Physical Sciences: Effect of Apollo 11 Lunar Samples on Terrestrial Microorganisms
No living organisms were found in the Apollo 11 lunar material by the biological quarantine team at the Manned Spacecraft Center, Houston1,2. The same result was obtained in our independent search for living organisms in 50 g of Apollo 11 bulk fines, although iron-containing artefacts superficially resembling microbial clones were seen3,4. Several plausible explanations can be offered for the failure to detect living organisms in this lunar material. First, no living organisms were present in the sample when tested. Second, living organisms were present but the media and environments in which they were placed were not suitable for growth. A third possibility is that living organisms were present in suitable media and environments but that the lunar material inhibited growth. Taylor et al.5 reported that aqueous extracts of lunar material markedly inhibited the growth and survival of Pseudomonas aeruginosa. We now report the results of experiments designed to test Apollo 11 lunar samples for inhibition of the growth of terrestrial microorganisms in conditions resembling as closely as possible those used in our earlier search for living organisms in Apollo 11 lunar material.
The Determination of Physicochemical Characteristics of Biodiesel and Its Blending Oils
The viscosity,combustion heat,sulfur content,carbon residue,ash,flash point,moisture and cetane value of biodiesel and its blending oils with diesel were determined.The influence of temperature on the viscosity was studied,and the physicochemical characteristics of biodiesel and its blending oils were compared with diesel.The results indicated that biodiesel and its blending oils had some superior performances and good application prospect.