摘要:

Tryptophan‐catabolic variants, tan 4b and 18ac, ofBradyrhizobium japonicumUSDA 26 were isolated from enrichment cultures in nitrogen (N)‐limited media containing either ammonium or glutamate. Presence of exogenous tryptophan (trp) in the medium led to sparse restricted growth and elicited selective growth of tan‐coloured variants over that of parental USDA 26. A 36% increase in cellular uptake‐accumulation of the ammonia analogue [14C]‐methylamine was found withtrp‐induced tan 18ac cells over that measured with either ammonium‐induced tan 18ac ortrp‐induced tan 4b. The assimilation patterns of uniformly labelled [14C]‐glutamate also differed when tan 18ac was compared with tan 4b. These studies of tan variants isolated from enrichment cultures suggest that bradyrhizobial populations can be manipulated by changing the N sources that l

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1991.tb03788.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Sixteen strains of atypical (catalase‐weak or negative), hippurate‐hydrolysing campylobacters from paediatric blood and faecal cultures were identified by DNA–DNA slot hybridization. All were closely related ( 67%) toCampylobacter jejuniand representative strains had G + C contents of 30 ± 1 mol%. Numerical analysis of chromosomal DNAHaeIII digest patterns revealed two clusters of strains at the 55%S level corresponding toC. jejunisubsp.jejuniandC. jejunisubsp.doylei; most strains belonged to the latter subspecies. No two strains had identical patterns but within each subspecies two subgroups were identifiable, corresponding to Lior biotypes I and II. Southern blot hybridization analysis with a 16 + 23S rRNA cistron probe fromEscherichia colialso showed differences between the various strains, and in a numerical analysis three groupings were formed at 70%S corresponding toC. jejunisubsp.jejuniLior biotypes I and II, andC. jejunisubsp.doylei. Four of the subspeciesdoyleistrains contained a 3·4‐MDa plasmid. These analyses showed that catalase‐negativeC. jejunisubsp.jejuniwere genomically distinguishable fromC. jejunisubsp.doyleias were Lior biotypes within subsp.jejuni. Ability to produce catalase is not a feature common to allC. jejunistrains, and our results confirm that some strains of subspeciesjejunimay be negative in that character although typical in other respects. DNA pattern heterogeneity was consistent with serological differences betw

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1991.tb03789.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Glutamate starch penicillin (GSP) medium was used for the simultaneous isolation ofPseudomonasandAeromonas. Modifications to reduce the number ofPseudomonasand background flora and to improve the recovery ofAeromonasfrom water samples are described. The original medium was modified by adding glucose and ampicillin. The addition of 10 μg/l of C‐glucose to the medium (SGAP‐10C) permitted better recuperation of stressed cells of aeromonads and the ampicillin reduced the numbers ofPseudomonas. The best temperature for the recovery of aquatic aeromonads was 28°C. The recovery of different species ofAeromonason SGAP‐10C was 93%. The selectivity of the medium was validated because 95·5% of 28 colonies tested with anAeromonas‐like morphology belonged to the genusAeromonas. Moreover, when 45 strains of different genera were cultured on the medium, onlyVibrio alginolyticuspresented a confusing morphology. When the SGAP‐10C was compared with GSP with 45 river samples, the new medium gave a significantly better recovery ofAeromonasspp., especially when large numbers ofPseudomonasspp. were present. SGAP‐10C used at 28°C and 48 h was an efficient selective medium for the isolation ofAeromonasfr

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1991.tb03790.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Cytotoxic activity assays of Gram‐negative, heterotrophic bacteria are often laborious and time consuming. The objective of this study was to developin situprocedures for testing potential cytotoxic activities of heterotrophic bacteria isolated from drinking water systems. Water samples were passed through 0·45 μm membrane filters which were then placed upon appropriate media and incubated. After incubation, each membrane filter was transferred to the surface of Y‐1 mouse adrenal cells overlaid with 1% agar. The filters were removed after exposure for 15 min. The Y‐1 cells were then incubated at 37°C in 2·5% CO2for an additional 24 h. The release of putative cytotoxic and cytotonic products from the bacterial colonies was recognized by zones of cellular lysis and injury of Y‐1 cells that appeared immediately beneath the membrane. Cytotoxic strains ofAeromonas, Vibrio, Escherichia, andLegionellaspp. were readily recognized by this method. About 1% of the bacteria isolated from drinking water also released cytotoxic products. This frequency was dependent upon the primary medium used and the density of bacteria present. The majority of cytotoxic strains isolated from drinking water also expressed protease activity (95%) and haemolytic activity (70%). Thisin situmembrane filter procedure is a facile method for simultaneously testing many different bacteri

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1991.tb03791.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY