The Aerogenic Response of Escherichia coli and Strains of Aerobacter in EC Broth and Selected Sugar Broths at Elevated Temperatures

Gas formation by 116 strains of Escherichia coli and 104 strains of Aerobacter was determined in a specially constructed and accurately controlled water bath employing EC, lactose, maltose, sucrose, glucose, levulose, and galactose broths at temperatures ranging from 44.5 to 46.5 C.

Greatest gas activity occurred in EC broth. In the range 44.9 to 45.5 C over 92% of the E. coli cultures formed gas, but the Aerobacter strains dropped from 68 to 2%. A natural point of separation of the two groups occurred at 45.5 C.

Inhibition of the gas-forming mechanism rather than death is the universal response of the Escherichia organisms to these temperatures. The inhibition increases with rising temperatures and is readily reversible. At 46.5 C, 64.5% of all the Escherichia cultures were inhibited and 69.1% of all the cultures were actually viable.

In EC broth it was found that as a group atypical E. coli (-+--) were the most resistant gas-positive types. Least resistant in EC broth was a group of known typical fecal isolates of E. coli (++--). Of intermediate resistance between the two groups was the large body of typical E. coli (++--) organisms.

Certain individual strains of E. coli excelled in the production of gas in the variety of sugar broths tested at elevated temperatures. The Aerobacter strains did not exhibit this property.

Finally it is suggested that elevated temperature incubation studies of this type be conducted in critically controlled water baths with an ascertained accuracy in the vicinity of 45.5 ± 0.1 C under full load.

     

Some Seismic Profiles near the Western End of the Puerto Rico Trench

A cooperative program of seismic refraction profiling was completed in the vicinity of the Puerto Rico Trench by Hudson Laboratories, Woods Hole, Lamont, and Texas A. & M. Profiles completed near the western end of the Trench were analyzed at Hudson Laboratories. Five seismic layers are indicated below the water layer. The thickness/velocity relationships are as follows: 5.1 km of 1.5 km/sec. (water); 1 km of 1.7 km/sec. (sediment); 1.5 km of 3 km/sec. (metamorphics?); 2 km of 5.5 km/sec. (basement); and 2 km of 7.1 km/sec. (high speed basement). Below these, typical Moho velocities of 8.1 km/sec. were measured. Total depth to Moho ranges from 9 to 12 km below sea level, the greatest variation occurring in the basement layers. The least depth was measured 65 miles north of the Puerto Rico Trench.     

The choline acetyltransferase of human placenta

1. Various methods for the extraction of choline acetyltransferase (acetyl-CoA-choline O-acetyltransferase, EC 2.3.1.6) from immature human placenta (18-28 weeks of gestation) are described. 2. The crude enzyme was found to be stable at -18 degrees and +4 degrees under a variety of conditions. 3. Purification methods, including ammonium sulphate fractionation, gel filtration on various grades of Sephadex and DEAE-Sephadex fractionation, have yielded a preparation of high specific activity.     

OXIDATIVE AND HYDROLYTIC ENZYMES IN THE NEPHRON OF NECTURUS MACULOSUS : Histochemical, Biochemical, and Electron Microscopical Studies

The distribution of oxidative and hydrolytic enzyme activities along the nephron of Necturus maculosus Rafinesque was studied histochemically. The proximal tubule possessed all the demonstrable enzyme activities associated with the hexose-monophosphate shunt and glycolysis, but lacked detectable succinic dehydrogenase and cytochrome oxidase activities. Krebs cycle enzymes other than succinic dehydrogenase were easily detectable. The distal tubule, on the other hand, possessed no detectable hexose-monophosphate shunt enzyme activities, but all demonstrable glycolytic and Krebs cycle enzymes and cytochrome oxidase were present in high activity. These data indicate that the proximal tubule of Necturus probably cannot depend, as can the distal tubule, on the Krebs cycle and cytochrome system to provide energy for its transport processes, an inference supported, in general, by available physiological evidence. The question of the importance of the hexose shunt to proximal tubular function arises. Evidence is presented that the proximal tubular blood supply is primarily venous in nature, a hypothesis which would correlate well with its anaerobic metabolic pattern. In addition, the absence of cytochrome oxidase and succinic dehydrogenase from the proximal tubular cells implies either that they possess very few mitochondria, or that their mitochondria have a very unusual enzymatic pattern. Electron microscopical observations and data obtained from the measurement of the enzyme activities of homogenates of Necturus kidney are presented which indicate that the second hypothesis is more probably correct.