摘要:

The aerobic decomposition of barley silage treated with two inoculants (LacA and LacB) containing mixtures ofLactobacillus plantarumandEnterococcus faeciumwas investigated over a 28-day period. Initially, yeast and bacterial populations were larger in silage inoculated with LacA than in silage treated with LacB or water alone (control). Differences in the succession of yeasts in silage treated with LacA were observed relative to the other two treatments. From silage treatment with LacA,Issatchenkia orientaliswas the most prevalent yeast taxon over all of the sample times, and the filamentous fungusMicroascus brevicauliswas also frequently isolated at later sample dates (14 days). In contrast,Saccharomyces exiguuswas the most prominent yeast recovered from silage treated with LacB and water alone on days 2 and 4, although it was supplanted byI.orientalisat later sample times. Successional trends of bacteria were similar for all three treatments.Lactobacillusspp. were initially the most prevalent bacteria isolated, followed byBacillusspp. (primarilyBacillus pumilus). However, the onset ofBacillusspp. prominence was faster in LacA silage, andKlebsiella planticolawas frequently recovered at later sample times (14 days). More filamentous fungi were recovered from LacA silage on media containing carboxylmethylcellulose, pectin, or xylan. The most commonly isolated taxa wereAbsidiasp.,Aspergillus flavus,Aspergillus fumigatus, Byssochlamys nivea,Monascus ruber,Penicillium brevicompactum,Pseudoallescheria boydii, andM. brevicaulis. The results of this study indicated that the two bacterial inoculants incorporated into barley at the time of ensilage affected the microbial ecology of silage decomposition following exposure to air. However, neither of the microbial inoculants effectively delayed aerobic spoilage of barley silage, and the rate of decomposition of silage treated with one of the inoculants (LacA) was actually enhanced.Key words: stability, yeasts, bacteria, fungi,Lactobacillus plantarum,Enterococcus faecium.

ISSN:0008-4166    

DOI:10.1139/w98-207

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

A simple defined basal medium is presented for the study of proteolytic activity, induction and repression, and protease purification withSerratia marcescens. Since the medium contains no protein, it does not interfere with or present artifact to protein assays, column chromatography, or electrophoresis. The medium consists of the basal salts and buffer medium of Bromke and Hammel (1979) plus a carbon-energy source such as glycerol, calcium chloride for the cation requirement for protease activity, and an amino acid, preferably leucine. Growth parameters and proteolytic activities are presented for unsupplemented medium and for the medium supplemented with each of 18 amino acids. Unsupplemented medium completes the logarithmic phase in 12.5 h of incubation and has a constitutive level of proteolytic activity. Supplementation with any amino acid, except cysteine and tryptophan, increases significantly the proteolytic activity, but has a varied effect on growth parameters.Key words:Serratia marcescens, growth, proteolytic activity, amino acids, leucine.

ISSN:0008-4166    

DOI:10.1139/w98-123

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

The growth kinetics of tanapox virus in owl monkey kidney cells was elucidated by single-step growth curves at multiplicities of 10, 1.0, and 0.1 plaque forming units (pfu) per cell at 37 and 33°C. Virus replicated equally well at both temperatures and produced a cytopathic effect that was characterized by densely packed rounded cells with retrogressed monolayer and granular vacuolated cytoplasm. Single-step growth curves revealed that the eclipse period varied from 24 h postinfection (hpi) at a multiplicity of infection of 10 pfu/cell to 48 hpi at 0.1 pfu/cell. The length of the latent period also varied from 36 hpi at 10 pfu/cell to 48 hpi at 0.1 pfu/cell. The intracellular virus, extracellular virus, and total virus titers reached their maximums relatively early at 10 pfu/cell as compared with 0.1 pfu/cell. About 78% of the mature progeny virion is retained intracellularly at 10 pfu/cell at 96 hpi. We conclude that tanapox virus replication is similar to other poxviruses, but the replication cycle is longer when compared with vaccinia virus.Key words: tanapox virus, single-step growth curve, eclipse period, latent period

ISSN:0008-4166    

DOI:10.1139/w98-212

出版商:NRC Research Press    

年代:1999

数据来源: NRC