Section B. Bacteriology and mycology applied to dairying

Abstract

Reviews of the progress of dairy sciencepreformed enzymes, are added to chemically defined substrates, giving clear-cut results. A clockwork automatic bacteriological inoculating device has been devised by Fuson & Marcus (20). An ingenious device(2i), patented in the U.S.A., for counting bacterial colonies, consists of a fountain pen connected to an electro-magnetic counter which registers each time the pen touches the Petri dish or roll-tube. Hannay (22) has described a new type of laterally illuminated colony counting chamber. British Standards for Petri dishes (23) have been issued recently. A microtechnique for the growth of many cultures, particularly for assay work, in one Petri dish has been developed by Turner-Graff(24). Newbould's(25) roll-tube spinner is designed to use cheap, easily obtainable vials or bottles. A suggestion contributing, in the long run, to economy is that of using rigid, seamless tubes of Kraft paper instead of the paper wrappings commonly used for individual sterile pipettes (26); Lack (27) has described a hot box for microcultures, which dispenses with a water jacket since the heating element consists of glass electrothermal heating tape. From America have come details of a simple large-scale anaerobic culture apparatus (28) utilizing a milk can as the main container, and of the uses to which spun glass (29) may be put as an air-filtering medium for bacteriological purposes.The text of the papers read, and the discussion, at a Symposium of the Institute of Biology in London in 1951 have been published under the title Freezing and Drying^); diversity of opinion and lack of collaboration and understanding between bacteriologist and vacuum engineer was apparent concerning even such vital factors as the plugs for drying tubes. Fry & Greaves (31), working mainly with a paracolon bacillus over a 3-year period, have shown that the nature of the suspending medium is one of the most important factors determining the survival rate of bacteria dried in vacuo; the addition of 5-10% of glucose or lactose increased the percentage survival. Young cultures were less resistant to drying than older cultures, but the cell concentration appeared to be of little consequence. ' Mist desiccans' (1 part broth, 3 parts serum with 7-5% added glucose) proved a satisfactory suspending medium for sensitive organisms such as Neisseria gonorrhoea. Briggs' observations (32) on the freeze-drying of lactobacilli are in almost complete agreement with those of Fry & Greaves; using strains of Lactobacillus acidophilus and L. bulgaricus, which were particularly sensitive to freeze-drying, she obtained with her suspending media survival rates of over 10% after 18 months' storage; her work is being continued with other species of lactobacilli subsequently tested to determine whether selection has taken place, although this should not be a danger except where very low survival rates are experienced. Sharpe (33) has tested the precipitin and agglutination reactions of cultures of L. acidophilus and L. bulgaricus which had b...

Section B. Bacteriology and mycology applied to dairying

“…aerogenes were most frequently encountered in Thomas's studies of ropy milk(U6,ll7), in which water supplies were found to be the chief source of the organisms. Sundman's work (118,119) confirms that of Jones in part, since she demonstrated the protein character of a slime produced by strains of Str. cremoris from Finnish ropy sour milk, differing from the polysaccharide slime produced by Str.…”