Summary. Glutaraldehyde in 2% aqueous alkaline solution is rapidly bactericidal and sporicidal, killing 99.99% of the spores of Bacillus anthracis and Clostridium tetani in 15 and 30 min, respectively. It exhibits some degree of tuberculocidal activity, but it appears to be inferior to several other disinfectants when challenged with a large inoculum. Fungicidal action has been demonstrated but not assessed quantitatively. Evidence is presented to show that biocidal activity depends on the availability of two free aldehyde groups in the molecule.

SUMMARYA streptomycin-resistant strain of Staphylococcus aureus, which requires haemin for aerobic growth, grew either aerobically or anaerobically in the absence of haemin provided the medium was supplemented with acetate or pyruvate; growth with these organic acids was increased by uracil and purines. The parent drug-sensitive strain grew aerobically without haemin but when grown anaerobically required either uracil or acetate or pyruvate. With both strains mevalonate replaced acetate and was about ten times more active.The products of glucose fermentation by both strains showed no gross difference, lactate being predominant (about 85 yo of the glucose carbon) ;only small amounts of acetate were detected. Under aerobic conditions suspensions of the parent strain oxidized glucose to acetate which accumulated. The mutant strain oxidized glucose to acetate only when previously grown with haemin or when haemin was added to the suspension of organisms. When the organism was grown with acetate in place of haemin, lactate was the predominant product. The ability of the mutant to form sufficient acetate from glucose for biosynthetic purposes is apparently dependent on a functional electron transport chain involving haemoproteins. A nicotinamide-adenine dinucleotide-linked lactate dehydrogenase and a pyruvate oxidizing system are present in extracts of both organisms. The activity of these enzymes in the mutant strain was similar whether the organisms were grown on haemin or acetate,

SUMMARY:Mutants of Aspergillus niger, Wisconsin strain 724, were produced by multiple X-ray and ultraviolet irradiation. The mutants differed from the parent strain culturally and in citric acid production. Comparison between the yields of citric acid from the parent strain and mutants showed significant increases with the latter. In crude sugar media, such as ferrocyanide-treated brown sugar, yields of citric acid equivalent to 80 yo of the sugar fermented were obtained in aerated culture, whereas only 21 yo was obtained with the parent strain.

SUMMARY: A method for isolating and identifying high acid-yielding mutants of Aspergillus niger is described. This involves cultivation of the organisms on absorbent paper soaked in an indicator medium. The advantages of the technique and the criteria used for selecting biochemically interesting mutants are briefly described. The greater acid production of mutants selected by paper culture has been confirmed by comparing yields of citric acid in surface and submerged fermentations with those given by the wild type strain.The selection of acid-producing fungi described by Foster & Davis (1949) and modified by Quilico, Panizzi & Visconti (1949) has been used frequently for isolating fungi showing marked differences in acid production. Their methods of cultivation on indicator media are unsatisfactory for selection of colonies which produce large amounts of acid because of the extensive diffusion of the acid zones around the colonies. With such strains large quantities of media are required since each colony to be screened would have to be tested on a separate agar plate, and there is no simple means of determining whether such colonies arise from one or more spores. METHODSThe irradiation techniques used, and a description of the mutant strains isolated by the technique to be described, are given in the following paper (Gardner, James & Rubbo, 1956). Paper culture selection techniqueThe method depends on the ability of Aspergillus niger to grow as compact discrete colonies surrounded by clearly defined acid zones on absorbent paper previously soaked in liquid culture medium. There are a number of ways of carrying out this paper culture technique, and these can be modified to suit the purpose of the experiment. So far the following procedure has been used. Circular sheets of Eucalypt viscose pulp, 1 mm. thick and 10 in. in diameter were marked with pencil in fifty 1 in. squares and soaked in liquid medium (see below). The moistened paper was supported at four points in a 10 in. Petri dish containing 5 ml. 20 % (vlv) glycerol in water to prevent drying of the paper during incubation. The dish and its contents were autoclaved at 116" (10 lb./sq.in. pressure) for 15 min. The medium contained (g./l.) : cane molasses (56%, w/v, sucrose), 40; KH,PO,, 1.0; MgS04.7H,0, 0.25; NH,NO,, 2.5. To every 100 ml. of this medium (adjusted to pH 5.0) 10 ml. of bromcresol green G . Microb. XIV 1 . 5

1. A small but serious outbreak of Ps. aeruginosa infection in a premature baby ward has been described.2. Heavy contamination of the suction apparatus and tubing was demonstrated to be the main reservoir of infection.3. It was also shown that this apparatus could disseminate the organism as an aerosol.4. The measures adopted to eliminate the source and prevent dissemination of the infectious agent have been described.