- Volume 121, Issue 2, 1980

Studies on the metabolism of tryptophan in Pseudomonas aureofaciens ATCC 15926 revealed different metabolic routes for the l-and d-isomer besides the biosynthetic pathway for pyrrolnitrin synthesis. l-Tryptophan catabolism follows the aromatic route via anthranilic acid. Tryptophan 2,3-dioxygenase was induced by l-tryptophan. Kynureninase and anthranilate 1,2-dioxygenase were induced by l-tryptophan, l-kynurenine and anthranilic acid. Anthranilate 1,2-dioxygenase was absent from a mutant strain of P. aureofaciens ATCC 15926 which produced about 30-fold increased amounts of pyrrolnitrin. The K m values of tryptophan 2,3-dioxygenase and kynureninase did not differ substantially between the two strains. Kynurenine 3-monooxygenase, 3-hydroxyanthranilate 3,4-dioxygenase, tryptophanase and indolyl-3-alkane α-hydroxylase activities were not detected. d- and l-tryptophan were converted to indole-3-pyruvate by tryptophan amino-transferase and via indole-3-acetaldehyde to indole-3-acetic acid. This additional catabolic pathway as well as tryptophan racemase activity was constitutive and present in both strains.

A cell-free protein-synthesizing system from Streptomyces fradiae was developed by preparing ribosomes and an S-150 fraction with precautions to prevent protease action. Using this system, the ribosomes of this organism were shown to be susceptible to its own product, neomycin.

Glucosamine acted as a gratuitous catabolite repressor of maltose utilization in Saccharomyces cerevisiae. This repression was relieved in a linear manner as the maltose concentration was increased. Three mutants were isolated in which maltose utilization was no longer repressed by glucosamine. One of these mutants may be generally deficient in catabolite repression since it was not defective in glucosamine transport but was insensitive to glucosamine repression on all catabolite repressible carbon sources tested. Each mutant possessed a maltose uptake system which was notably less sensitive to glucose repression than that of the wild-type strain. These results are discussed in terms of a proposed model for regulation of maltose utilization in S. cerevisiae.

Five strains of Micrococcus, representing three species, accumulated trehalose when grown in the presence of glucose. Trehalose was not found in two Staphylococcus species or in Planococcus citreus.

Synchronized populations of Bacillus subtilis are maximally inducible for sporulation about 15 min after chromosome replication has started. However, the induction of serine protease, one of the earliest marker events in sporulation, is not related to the state of chromosome replication.

A bacterium named Fusobacterium polysaccharolyticum in an earlier paper produced spores and was reclassified as a clostridium. Although it appeared Gram-negative when stained, its cell wall structure was of the Gram-positive type.

A cytosolic extract from the cellular slime mould Dictyostelium discoideum contained an enzyme system that hydrolysed phosphatidylinositol. The route of degradation was exclusively by deacylation to glycerophosphoinositol. The hydrolysis was inhibited by phosphatidylethanolamine, the major phospholipid of the organism, which was also completely deacylated by myxamoebal extracts.

Crude enzyme preparations from Acetivibrio cellulolyticus converted ball-milled pulp, cotton batting, filter and tissue paper, a microcrystalline cellulose, carboxymethylcellulose, cellobiose and xylan to reducing sugars. The preparations showed maximum activity between pH 5 and 6 and at a temperature between 37 and 50 °C, depending on the substrate used. The enzyme activity was fairly stable at 2 °C for 4 weeks. The saccharifying ability of the preparation was comparable to that of commercially available cellulase preparations from Aspergillus niger and Trichoderma viride.

Partially purified bacterial extracts were prepared from segregated stalked and swarmer bacteria of Caulobacter crescentus and assayed for ATP-dependent deoxyribonuclease activity. This activity was found to be very low in the swarmer bacteria compared with a pure population of stalked cells or an asynchronous population of C. crescentus.

Mycobacterium rhodochrous strain 7EIC grows with dodecylcyclohexane at the expense of acetyl fragments released by β-oxidation of the side-chain. Cyclohexaneacetic acid, which is not amenable to β-oxidation and is not oxidized by this organism, accumulates in significant yield. In combination with Arthrobacter strain CA1, which degrades cyclohexaneacetic acid by a novel pathway, a stable mixed culture is established that is capable of the complete degradation of dodecylcyclohexane and related hydrocarbons.

A plasmid with a molecular mass of 1.4 × 106daltons has been identified in Staphylococcus aureus. This plasmid determines constitutive resistance to erythromycin and lincomycin and is the smallest naturally occurring element coding for antibiotic resistance in this species.