ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1991.tb02922.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Five different species of freshwater bacteria (Pseudomonassp.,Vibriosp.,Klebsiellasp.,Enterobactersp.,Serratiasp.) and a mixed natural population were used separately to inoculate cultures of axenic duckweed (Lemna minor). Inoculation withVibriosp. caused the final population density ofLemnaplants to be significantly greater after 52 d than that of either axenic controls orLemnainoculated with a mixed bacterial community. Inoculation withPseudomonassp. caused the final population density ofLemnato be significantly higher than with the mixed bacterial treatment. Inoculation ofLemnawithKlebsiellasp.,Enterobactersp. orSerratiasp. resulted in higher plant populations compared with controls, but these differences were not statistically significant. The presence of a mixed community of bacteria did not significantly affect the final population density ofLemnacompared with the controls. However,Lemnaplants inoculated with a natural population of bacteria showed significantly higher levels of senescence compared with the other five treatments and the controls. None of the five single bacterial taxa used appeared to have any significant effect of the sensescence of duckweed.

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1991.tb02923.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Thirty‐two of 38 cultures isolated from the nodules of pigeonpea plants were rapid growers. The generation time of rapid growers varied from 0·71 to 1·31 h and slow growers from 7·7 to 9·9 h. Rapid growers oxidized pentoses, hexoses, polyhydric alcohols (except dulcitol), tricarboxylic acid cycle intermediates (except citrate) and disaccharides more rapidly than slow growers; disaccharides were not oxidized by any of the slow growers. The Embden‐Meyerhof‐Parnas and Entner‐Doudoroff pathways and the tricarboxylic acid cycle were present in both rapid and slow growers, whereas the pentose‐phosphate pathway was present only in

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1991.tb02924.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Unhygienic conditions of a typical rural community in a developing country were simulated in the laboratory by inoculating fermented maize dough porridge withShigella flexneriand enterotoxigenicEscherichia coli(ETEC). The antimicrobial effects of the different processes involved in the preparation of fermented maize dough porridge were assessed. The soaking process reduced the pH but no antimicrobial effect against shigella and ETEC was noted. Unfermented maize dough did not inhibit any of the test strains. When the fermentation process had become established, half of the strains tested were inhibited by the fermented maize dough when examined 8 h after inoculation. Cooking the fermented maize dough into porridge reduced the antimicrobial effect but there was still significant inhibition of pathogens. This suggests that the antimicrobial effect of fermented maize dough is not due to pHper se.Fermentation of maize dough appears to be a useful strategy for reducing contamination of weaning foods bySh. flexneriand ETEC. The possible nature of the antimicrobial agent(s) produced during the fermentation of maize dough is discussed.

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1991.tb02925.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Plasmids associated with resistance to streptomycin, to streptomycin plus chloramphenicol or to tetracycline inStaphylococcus hyicusisolated from the skin of pigs have been compared, by restriction endonuclease digest patterns, with similar staphylococci from human sources and with published DNA base sequences. Several plasmids fromStaph. hyicushave proved to have a very similar structure to those described fromStaph. aureusbut others appeared very dissimilar. This confirms the opinion that staphylococci from animal skin share a pool of plasmids with those from human skin but may also possess some of quite different structure.

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1991.tb02926.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Whole‐cell hydrolysates ofBacteroides fragilis, the type species of the genusBacteroidesCastellani and Chalmers 1919, and the genetical closely related speciesB. vulgatus, B. ovatus, B. eggerthii, B. distasonis, B. uniformis, B. thetaiotaomicron, B. stercoris, B. merdae, andB. caccaewere used to determine characteristic carbohydrate patterns by capillary gas chromatography. On the basis of the chemical derivatization of the carbohydrates seven characteristic peaks for peracetylated aldononitriles and nine characteristic peaks for peracetylatedo‐methyloximes were selected from the carbohydrate fingerprints of the reference strains to prepare a dichotomous identification key. The classification of an unknown strain supposed to belong to the formerly called ‘Bacteroides fragilisgroup’is possible with this key. Some of the advantages of the technique were that the identification ofBacteroides fragilis‐like strains requires only 4–5 h after primary isolation and that the bacteria can be exposed to oxygen because viability of the organisms is not necessary. Sophisticated anaerobic techniques can therefore be avoided for ide

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1991.tb02927.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

A 1·5 kbEcoRI–BamHI restriction fragment fromMycobacterium tuberculosiswas found to hybridize specifically with genomic DNA fromM. tuberculosis‐complex organisms. Primers were designed from the terminal sequences of this fragment and used to amplify uniquelyM. tuberculosis‐group DNA in a polymerase chain reaction. It is suggested that a combination of these primers and probe will prove a useful tool for the early diagnosis of tuberculous infe

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1991.tb02928.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Two hundred and six strains of coagulase‐negativeStaphylococcusspecies were assessed for expression of glycocalyx on serum soft agar, india ink and adherence techniques. The organisms were maintained on trypticase soy agar plates at 4°C for 30 d (120 strains) or stored at ‐80°C in skim milk for 90 d (60 strains). Additionally, 26 milk samples from cows known to have excreted coagulase‐negative staphylococci were used to inoculate serum soft agar directly. Nine of 26 direct culture samples and 43 of 180 strains maintained for an extended period had diffuse‐type growth on serum soft agar. The proportion that exhibited an unstained halo by india ink was similar regardless of storage time. Slime production determined byin vitroadherence revealed a higher proportion of positive strains than had been predicted by serum soft agar or india ink techniques. More strains ofStaphylococcus chromogenes, Staph. epidermidis, Staph. hominis, Staph. simulansandStaph. warneriexpressed glycocalyx than other coagulase‐negativeStaphylococcusspecies. These results suggest that most coagulase‐negative staphylococci produce slime rather than a capsule. However, evidence for classical encapsulation was demonstrated in several strains by india ink. The finding thatStaphylococcusspecies other thanStaph. aureusisolated from bovine milk are capable of glycocalyx production may be of importance in investigations on the relationship between staphylococci and host defen

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1991.tb02929.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The effects of two calmodulin antagonists, trifluoperazine (TFP) and N‐(6‐aminohexyl)‐5‐chloro‐1‐naphthalene sulphonamide hydrochloride (W‐7) on L‐alanine‐induced germination ofBacillus cereusT spores were examined by measuring commitment to germination, decrease in optical density at 660 nm and phase‐contrast microscopy. The kinetics of optical density decrease suggested competitive inhibition of TFP or W‐7 with both L‐alanine and D‐alanine (L‐alanine analogue and germination inhibitor) as determined by Lineweaver‐Burk and Schild plots, respectively. Germination inhibition was pH‐dependent. The I50values for maximum decreasing rate of optical density in 10 mmol/l L‐alanine plus 5 mmol/l adenosine at pH 6·4 were 0·21 and 0·74 mmol/l for TFP and W‐7, respectively. Much less effect of N‐(6‐aminohexyl)‐l‐naphthalene sulphonamide hydrochloride than W‐7 lends support to the specificity of W‐7. The calmodulin antagonists were effective at a step in germination after commitment and loss of heat resistance. It is postulated that this process is necessary in the germination ofB. cereusT spores to convert phase‐bright spores to phase‐

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1991.tb02930.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Growth ofListeria monocytogenesat 4°C significantly increased its virulence for mice by the intravenous route and the effect was dose‐dependent. Virulence was apparent only at a dose of about or above 104viable listerias. At slightly lower doses of about 103, no such effect was observed. Growth at 4°C did not increase the virulence of the strains for mice by oral‐gastric challenge when given at doses of approximately

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1991.tb02931.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY