摘要:

Survival of a genetically‐markedAeromonas hydrophilawas monitored in water microcosms. There was no apparent loss of a marker plasmid which encoded thexylEreporter gene during prolonged incubation in lake water. Survival was best in sterile lake water but in sea water, cells died rapidly during the first 9 d, recovered up to day 12 and thereafter numbers fell up to 28 d accompanied by loss of the plasmid in a proportion of the cell

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1994.tb00921.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Benzyl thiocyanate, a specific stimulator of chlortetracycline biosynthesis, was transformed into dibenzyl disulphide byStreptomyces aureofaciens.The disulphide stimulated chlortetracycline production to a lesser extent than did benzyl thiocyanate.

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1994.tb00922.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Leuconostoc carnosumLA54A produces carnocin 54, a bacteriocin inhibitory toListeriaand closely related lactic acid bacteria. The effects of the pH of cell‐free LA54 culture supernatants on the antibacterial activity of carnocin 54 was assessed usingLeuc. mesenteroidesDSM 20343 and TA10C as indicator strains. Carnocin 54 showed greatest activity against both strains at pH 4.5. At pH 6.5, activity was reduced, especially againstLeuc. mesenteroidesTA10C. Scanning electron microscopy showed irregular and rough surfaces on bacteriocin‐treated cells at both pH val

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1994.tb00923.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Tubes of tomato juice agar were inoculated withClostridium sporogenesand anAspergillussp. and incubated aerobically. The clostridium only grew when theAspergilluswas present. pH and oxygen concentration were measured through the depths of the tubes. TheAspergillusgrew as a mat on the surface of the gel, removing oxygen and causing a local rise in pH. It was thought that the production of a microenvironment adjacent to the mycelial mat, consisting of raised pH and decreased oxygen concentration, enabled the clostridium to germinate and grow.

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1994.tb00924.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Listeria monocytogenestogether with Gram‐positive and Gram‐negative bacteria was grown in axenic cultures in meat juice under an atmosphere enriched with carbon dioxide at 4°C. The size of the final population of listeriae was determined by that of the initial inoculum. Growth ofL. monocytogenesceased with glucose depletion. Glucose‐6‐phosphate was not catabolized by listeriae. In aerobic axenic cultures generation times ofL. monocytogeneswere shorter and glucose depletion was faster than with a carbon dioxide‐enriched atmosphere. Oxidation of L‐ and D‐lactic to acetic acid was probably associated with the subsequent die‐off of

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1994.tb00925.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Yersinia enterocoliticaO : 3 was studied throughout two central composite designs to define the effects of temperature, pH and salt concentration on bacterial growth. Mathematical models were established by response surface methodology. The impedimetric technique was evaluated for its rapidity and ability to produce detection times related to bacterial metabolism. Finally, predicted values derived from model equations were compared with observed values obtained by plate counts.

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1994.tb00926.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

A method for developing a single‐transposon‐insertion mutant from a double‐insertion mutant inRhizobiumis described. An exopolysaccharide (EPS)‐defective mutant containing two Tn5‐lacZinsertions was complemented with cloned wild‐type DNA for EPS synthesis. One of the Tn5‐lacZinsertions from the mutant was transferred to the complementing plasmid by homologous recombination. The plasmid containing the Tn5‐lacZinsertion in the gene involved in EPS synthesis was transferred into the wild‐type strain and the Tn5‐lacZwas homogenized to obtain an EPS‐defective mutant with a sin

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1994.tb00927.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Unheated and heated (1 min at 121°C)Bacillus stearothermophilusspores were grown in non‐acidified (pH 7) and acidified recovery medium at different pH levels (6.7, 6.5, 6.2 and 5.9) using citric acid or glucono‐δ‐lactone (GDL) as acidulants. It was observed that the lower the pH, the lower the proportion of micro‐organisms which recovered. The level of recovery was not the same for both acidulants, meaning that at the same pH level citric acid showed a greater inhibitory effect that glucono‐δ‐lactone. Heat treatment sensitized spores to pH effect. A linear relationship of the behaviour of spores with each acidula

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1994.tb00928.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Activities of glycosidases (n= 8), esterases (n= 10), arylamidases (n= 63), acid phosphatase, alkaline phosphatase and phosphoamidase were tested in 47Borreliastrains. Forty‐four wereB. burgdorferistrains; 22 of which were isolated from human specimens (skin 13, cerebrospinal fluid six, and one each from blood, heart muscle and synovia), 13 were isolated from various organs of laboratory animals infected via tick bite or with human isolates, and nine from ticks. The remaining three were the relapsing fever strainsB. coriaceae,B. hermsii, andB. turicatae.Strains were of low and high passage but the number of subcultures did not influence the enzyme patterns obtained by utilization of chromogenic substrates of constitutive enzymes. Glycosidase activity was absent in almost all strains tested. Esterase activity was high on molecules of chain length 9 carbons. 2‐Naphthylamide derivatives were utilized by strains of human, rodent or tick origin in a range of 66.6 to 83.1%. Almost all strains utilized substrates for acid and alkaline phosphatase and phosphoamidase. Chymotrypsin activity was only found in three and two strains from specimens of human and rodent origin, respectively; and γ‐glutamyltransferase activity only in three human skin isolates. No strain tested displayed trypsin activity. Overall, the specific activities of constitutive enzymes of theBorreliastrains tested are widely similar. Thus, the enzyme profiles did not discriminate between human, animal and tick isolates, or between human isolates ofBorreliawhether cultivated from cerebrospinal fluid or from skin biopsy of Lyme borreliosis pa

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1994.tb00929.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AClostridiumspecies causing spoilage of vacuum‐packed refrigerated pork was isolated and characterized. The unknown organism differed phenotypically from other clostridial species usually associated with spoilage. Phylogenetic analyses based on 16S rRNA gene sequencing demonstrated that the psychrotroph represents a distinct line of descent within the genusClostridium.It is proposed that the organism be classified as a new species of the genusClostridium, Clostridium algidicarni

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1994.tb00930.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY