摘要:

Summary:The nature of the bacterial flora of trickling filters has been investigated. It consisted primarily of Gram‐negative, rod shaped bacteria closely related to the flora of fresh water. These bacteria were able to grow on nutrient agar at 22° and belonged mainly to the generaAchromobacter, Alcaligenes, Flavobacterium, PseudomonasandZoogloea. The results failed to confirm the importance previously attributed to coli‐aerogenes organisms, aerobic sporeformers and filamentous bacteria. The influence of homogenization on these findings is discussed. Further evaluation of the ecological importance of the various groups of bacteria was carried out by metabolic studies using synthetic se

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1964.tb04903.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Summary:Few arguments may be put forward in favour of the use ofEscherichia colias an indicator of the hygienic condition of preserved meat products. In products of this typeE. colioccurs only rarely. The proposal, which is supported by logical considerations and practical experience, to replace this organism byStreptococcus faecalisas an indicator of possible faecal contamination is strongly upheld by the authors. However, it is necessary to stress that the ubiquitous micro‐organism,Aerococcus viridans, occurs frequently in preserved meat products and, as it strongly resemblesStrep. faecalis, may cause difficulties in the hygienic evaluation of such foods. The morphological and biological characteristics found suitable for differentiating these two organisms are described. Results supporting the view thatAerococcus, PediococcusandGaffkyabe considered as distinct genera are also give

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1964.tb04904.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Summary:Lower members of the carboxylic fatty acid series, hydroxy acids, alcohols, amides, ureas, urethanes and some other low molecular weight compounds have been tested for bactericidal action onMycobacterium tuberculosisH37 Rv and BCG. The rate of bactericidal action of acetic acid is shown to be dependent on the concentration of undissociated acid. The bactericidal activity of normal fatty acids increases with increase in the length of the carbon chain. A comparison of the times required by equimolar solutions to sterilize a culture shows that maximum activity is reached at undecylic acid (C11). The bactericidal activity of corresponding acids, hydroxy acids and alcohols is compared.

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1964.tb04905.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Summary:The significance in food microbiology of the observation of Stapert, Sokolski&Northam (1962), that some bacteria occurring in water have such low heat resistances that they would be affected by the warm agar used for pouring plates, was tested. Forty‐two samples of 6 different foods stored for 7 days at 3° to enrich their psychrotrophic microflora, were examined using the same medium, but in thin poured plates and on spread plates, respectively, incubated at 14°. The logarithmic average count of the foods wasc.108/g and included about 60% Gram‐negative rods and 30% cocci. In 90% of the samples no differences were observed between the results from the two methods of counting. The slightly higher spread plate counts in the remaining instances could be accounted for by the increased disruption of bacterial agglomerations always observed in this procedure. Hence there is no reason to query the results of poured plate counts in general. Where it is yet probably safer to use spread plates, rigorous asepsis in pouring and storing should be observed to prevent the development of colonies of contaminants too small to be detected when the plates are inoculated, but leading to erroneous counts after incub

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1964.tb04906.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Summary:The new technique depends upon spreading bacterial cells over the surface of an agar medium in a Petri dish. The cells are heated, cooled, grown and countedin situ. The plates are preheated on the surface of a water bath and held for the required time on the surface of a second bath at the desired temperature. They are cooled by cold water jetted on to the base. The experimental control of factors affecting the accuracy of the method are discussed and applications suggested.

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1964.tb04907.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Summary:Actinomycetes isolated from nitrogen deficientAzotobacterplating medium were checked for antibiotic production on nitrogen deficient media and on these media with yeast extract or ammonium sulphate as nitrogen sources. In nitrogen deficient liquid media cobalt, molybdenum and citrate were required for growth and antibiotic formation. Evidence is presented that the antibiotics resulting from growth under these conditions are different from those produced when combined nitrogen is included in the medium, and it is suggested that this is an area for exploration for new antibiotics.

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1964.tb04908.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Summary:The preparation of plant tissue for examination by the fluorescent antibody technique is described. The procedures suggested are intended to overcome some of the major obstacles encountered and the efficacy of the method for plant investigations is upheld by its successful application in a simple test system.

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1964.tb04909.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Summary:An extensive investigation of 30 strains of bacteria which oxidize inorganic sulphur compounds led to the recognition of three major groups. A study of the occurrence of these groups in biological effluent systems suggested that the organisms generally believed to be responsible for the oxidation of thiosulphate and thiocyanate, the autotrophic thiobacilli, were absent in many instances. It is suggested that in these instances heterotrophic organisms, which are found throughout all the systems, may be responsible for the destruction of the sulphur compounds. A heterotrophic organism which destroys thiocyanate, but not thiosulphate, has been isolated.

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1964.tb04910.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Summary:The micro‐ecology of block cured, sliced, vacuum packed bacon has been studied during storage at 20 and 30°; high salt (8–12% NaCl, based on the aqueous phase) and low salt (5–7% NaCl) bacon were used. The dominant flora of all samples during the first 9 days' storage comprised catalase positive cocci. They persisted in the high salt bacon but, under lower salt conditions, group D streptococci and motile lactic acid bacteria became dominant.Of the chemical changes studied, proteolysis, lipolysis and reduction of nitrate and nitrite were due largely to coagulase negative subgroup II staphylococci. Micrococci which predominated at 20° were capable of reducing nitrate to nitrite but of only slightly increasing free amino or fatty acids.Inoculation of low count bacon with subgroup II staphylococci confirmed that this group was responsible for putrefaction in low salt bacon stored at temperatures above 20°. Similarly micrococci which tend to delay spoilage did not contribute much to the off odours and it was thought that the heterofermentative catalase negative organisms could contribute to typical sour

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1964.tb04911.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Summary:A collection of 185 isolates ofPseudomonas solanacearumhas been classified into 4 biotypes according to their capacity to oxidize 3 disaccharides (lactose, maltose and cellobiose) and 3 hexose alcohols (mannitol, sorbitol and dulcitol). Biotype 2 which oxidized the disaccharides but not the hexose alcohols appears to have a restricted host range; it was obtained solely from two plant hosts, potato and tomato, whereas biotype 1, which oxidized neither group of carbohydrates, and biotype 3 which oxidized both, were obtained from a diversity of plant hosts. A bacteriophage isolated from material infected with biotype 2 showed a high degree of specificity for isolates of biotype 2. The present known distribution of the 4 biotypes is given and their relationship to host range is discussed. A neotype culture forPs. solanacearumis proposed.

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1964.tb04912.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY