摘要:

Cultures ofStreptomyces coelicolorA3 (2) produced actinorhodin in defined media with various carbon and nitrogen sources. Production occurred during biomass accumulation if assimilation of either the carbon or the nitrogen source limited the rate of growth. High growth rates tended to delay product synthesis until after biomass accumulation was complete, but fully biphasic fermentation profiles were achieved only with media supporting very rapid growth. The onset of actinorhodin production then coincided with a decline in the growth rate during transition of carbon-sufficient cultures to stationary phase. In cultures with maltose as a growth-limiting carbon source, depletion of phosphate increased the rate of actinorhodin biosynthesis, but did not alter the timing of its initiation. With defined media, the use of spores rather than vegetative mycelium as inocula reduced the overlap between trophophase and idiophase. The general guidelines for achieving biphasic production of actinorhodin inS.coelicolorA3 (2) cultures could be used to obtain trophophase–idiophase separation in cultures ofStreptomyces venezuelaeproducing chloramphenicol. However, the conditions needed to be modified to give optimized biphasic fermentations with individual strains. Under conditions favouring chloramphenicol production in a distinct idiophase, aromatic amine secondary metabolites in the same cultures ofS.venezuelaewere produced in a pattern that overlapped the trophophase, suggesting that conditions need to be tailored also to meet differences in the regulation of secondary metabolites.Key words:Streptomyces coelicolorA3 (2),Streptomyces venezuelae, actinorhodin, biphasic fermentations, chloramphenicol, inoculum shift down.

ISSN:0008-4166    

DOI:10.1139/m95-043

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

We tested the ability of hollow-fiber ultrafilters with molecular weight cut-offs (MWCOs) of 50 000, 13 000, and 6000 to remove and detect viral agents (phage T1, 50–150 nm; phage PP7, poliovirus, 28–30 nm) from ultrapure water, 0.85% saline with 1% trypticase soy broth, and Dulbecco's modified Eagle minimum essential medium with 10% fetal bovine serum (DMEM-10). Virus diluted in saline and DMEM-10 were tested to evaluate filter performance under conditions that minimize the adsorption of viral particles to the filter matrix. During filtration, the retentate was returned to the input reservoir, and the permeate was removed to a separate vessel. Thus, the virus concentration in the feed increased over the course of filtration. Filter performance was evaluated by comparing the concentration of infectious virus in the initial virus suspension with the virus concentration in the permeate and retentate. Very efficient removal of phages T1 and PP7 was observed with the filters with MWCOs of 13 000 and 6000 (titer reduction > 7 logs) for all three fluids tested. No poliovirus was detected in the permeate of the ultrafilters with MWCOs of 13 000 or 6000 (titer reduction > 6 logs). These results indicate that the ultrafilters with MWCOs of 13 000 and 6000 were very effective in removing small viral particles (25–30 nm) by size exclusion. The recovery efficiency of the virus in the retentate varied by fluid type. However, filtration with virus diluted in DMEM-10 resulted in consistent recovery of the viruses tested. The results suggest that these ultrafilters may have the dual potential of removing viral contaminants from fluids and concentrating virus in the retentate.Key words: virus removal, virus concentration, ultrafiltration membranes.

ISSN:0008-4166    

DOI:10.1139/m95-044

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Two strains, flocculating and nonflocculating, of the yeastKluyveromyces lactiswere grown in a Sabouraud's liquid medium containing 0.07 mM Ca. Treatment by ethylenediamine of isolated cell walls yielded three fractions: A, B, and C. Fraction A, soluble in ethylenediamine, contained phosphopeptidomannan-like hydrosoluble polymers; these constituted the external wall of the parietal layer. Phosphopeptidomannans have also been extracted from entire yeast cells autoclaved at 140 °C in a citrate buffer at pH 7.0. The flocculating and nonflocculating states of yeasts showed structural and quantitative variations in phosphopeptidomannans. The walls of the flocculating yeast cells contained higher amounts of peripheral polymers, the molecular masses of which were greater than those of nonflocculating yeast cells. These are the result of a more complex structure, due to the presence of a greater number of ramifications containing three or four mannose units. Analysis of the acetolysis products revealed in fact the release esentially of phosphorylated mannotriose and mannotetraose units by the flocculating yeast phosphopeptidomannans, while polymers of the nonflocculating yeast were characterized by the presence of mannobiose units. When such polymers were submitted to a β-elimination reaction, mannobiose and mannose units were liberated in such a ratio that mannobiose units appeared to be more numerous in flocculating yeast cells. A lectin extracted from the flocculating strain was incubated with erythrocytes activated by phophopeptidomannans derived from flocculating and nonflocculating yeasts and showed clearly that the more agglutinated erythrocytes were those activated by polymers derived from the flocculating yeast. The C fraction, insoluble in ethylenediamine, corresponded to the wall rigid matrix. The study of its chemical composition revealed no significative difference between the flocculating and the nonflocculating strains.Key words:Kluyveromyces lactis, phosphopeptidomannans, flocculation.[Journal translation]not available

ISSN:0008-4166    

DOI:10.1139/m95-045

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

This study has shown that isolates ofRhizobium leguminosarumbiovartrifoliican be grouped on the basis of their randomly amplified polymorphic DNA (RAPD) fragment patterns. Evidence is presented that these groups are not entirely arbitrary but are consistent with other genetic and phenotypic characteristics. RAPD analysis has been used to assess the efficiency of a dispersion and differential centrifugation procedure used to extract bacteria from soil. Whilst the major groups ofRhizobiumisolates in soils were also found in the extracts, some of the others were missing. This is also reflected in the finding, made by measuring abundance of organisms, that as manyRhizobiumisolates are left in the residue as appear in the supernatant; more dispersion steps, possibly with different dispersants, are needed to maximize extraction. The technique has also demonstrated that dispersing soil by simply shaking it in water not only underestimates the numbers ofRhizobiumisolates present but also masks much of their diversity.Key words:Rhizobium, DNA amplification, random primers, bacterial extraction.

ISSN:0008-4166    

DOI:10.1139/m95-046

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

White-rot fungi degrade many hazardous organic compounds that are not readily degraded by other microorganisms. Some of these compounds are soil contaminants, so methods for using these fungi to decontaminate soil through either land farming or composting technologies are being developed. White-rot fungi normally colonize plants or plant residues (e.g., wood) and do not grow well in unamended soil, particularly if it is not sterilized. A practical method to promote their growth in soil, without the use of large quantities of amendments or inoculum, is presented. A variety of assays showed that growth of white-rot fungi in steamed soil is limited by availability of carbon and nitrogen sources, but not other nutrients. Ground alfalfa straw was a more effective inexpensive source of these nutrients than the other amendments that were tested. However, the fungi only sometimes colonized alfalfa-amended nonsterile soil, as a result of competition from other microorganisms. Consistently high growth of the white-rot fungi in alfalfa-amended soil could be induced by adjusting the moisture content, adding the fungicide benomyl, and inoculating with benomyl-resistant fungi. In soil so treated, degradation (mineralization) of pentachlorophenol was much more rapid than in untreated soil.Key words: white-rot fungi, bioremediation, growth, pentachlorophenol.

ISSN:0008-4166    

DOI:10.1139/m95-047

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Plasmids found in six strains ofThiobacillus ferrooxidanswere mapped and compared in an effort to detect the origin of replication. Four strains yielded an identical 9.8-kb plasmid, pTFI91. Restriction mapping and Southern blot hybridization analysis were used to confirm this finding. Dissimilar plasmids found in two other strains contained a conserved 2.2-kbSacI region common to pTFI91. DNA sequence analysis of this region showed structural features common to bacterial plasmid replicons. A comparison of the pTFI91 origin with those ofT.ferrooxidanspTF-FC2 and other broad host range vectors did not show significant homologous DNA sequences. To verify the replication function, a chloramphenicol acetyl transferase marker gene was ligated at the unique sites of pTFI91, and the plasmid was transformed intoEscherichia coliDH5α cells but no transformants were identified. To test the replication of pTFI91 independent of DNA polymerase I inE.coli, different restriction fragments of pTFI91 were cloned into pHSG398 (Cmr, ColEI origin) and transformed into thepolA1mutant SF800, but chloramphenicol-resistant transformants were not detected. Electrotransformation ofT.ferrooxidansTFI-70 andPseudomonas putidaATCC 19151 also failed to yield transformants. The results suggested that the pTFI91 plasmid replicon does not function either inE.colior inP.putida. Since pTFI91 contains the same origin of replication as other plasmids in several otherT.ferrooxidansstrains, this replicon may be commonly distributed inT.ferrooxidans.Key words: nucleotide sequence, origin of replication, plasmid DNA, replicon,Thiobacillus ferrooxidans.

ISSN:0008-4166    

DOI:10.1139/m95-048

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

A biosensor based onThiobacillus thioparuswas developed for the determination of thiosulfate and methanethiol.Thiobacillus thioparusis a chemoautotrophic bacterium and it oxidizes sulfur compounds to sulfuric acid. The sensor consisted of an oxygen electrode and immobilizedT.thioparus. When the sensor was used to determine thiosulfate, a linear relation between sensor output and concentration was obtained for the concentration range from 1 to 100 μM in a batch system and from 1 to 10 mM in a flow injection system. Output of the sensor was stable for more than 1 month. For methanethiol, the response of the sensor was measured for the concentration range from 0.2 to 3 mM in a flow injection system.Key words: microbial sensor, thiosulfate, methanethiol,Thiobacillus thioparusTK-m.

ISSN:0008-4166    

DOI:10.1139/m95-049

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Pseudomonas syringaecells starved in buffer released orcinol-reactive molecules and materials that absorbed ultraviolet light. The number of cells culturable in nutrient medium decreased more rapidly than the number of intact particles determined by microscopy. The results suggested that starvation resulted in the lysis of an increasing number of cells, and that a fraction of the intact particles were not culturable. Starvation also resulted in a decrease in the rate of oxygen consumption with acetate, glycerol, and succinate, but at different levels. Whereas the respiration of acetate and glycerol decreased concomitantly with culturability, the respiration of succinate decreased to levels similar to the concentration of intact cells, suggesting that all intact particles respired the succinate, but only the culturable cells respired the acetate and glycerol. The results suggest that measuring the activity of the electron-transport system can overestimate the viability of starved bacterial cells, and that complex metabolic activities such as the respiration of acetate and glycerol are probably better suited for the evaluation of this parameter.Key words:Pseudomonas syringae, starvation, culturability, viability, respiration.

ISSN:0008-4166    

DOI:10.1139/m95-050

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

A physical map was generated for the fowlpox virus Chick-N-Pox vaccine strain DNA genome forEcoRI,BamHI,NcoI, andPstI. The gel profiles resulting fromEcoRI,BamHI,BglII,NcoI,StyI,PstI, andPvuII digestions were analyzed by agarose and polyacrylamide gel electrophoresis. The size of the fowlpox virus genome was estimated from these digests to be 289–301 kb. Replication of fowlpox virus DNA in QT-35 cells was followed and indicated that viral DNA replication initiated at 6–8 h postinfection in these cells.Key words: physical mapping, fowlpox virus, QT-35 cells, DNA replication.

ISSN:0008-4166    

DOI:10.1139/m95-051

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Statistically determined values for the free energy and enthalpy change per equivalent accompanying the combustion of organic substances have been used to test the hypothesis that the free energy, enthalpy, and entropy changes accompanying anabolism are zero or nearly so. It is found that while this can be true in some cases, it is not always so, because the free energy and entropy changes per available electron accompanying biological combustion are different for different small molecular weight substrates although they are constant for cellular biomass. If the average energy change per equivalent accompanying the biological combustion of the cells is markedly different from that of the substrate, there will be a corresponding change in energy accompanying anabolism that is determined by the difference between them. The efficiency of available electron conservation is proposed as being preferable to free energy, enthalpy, and entropy efficiencies in that the latter parameters all have different values, whereas the former is common to all three of the latter. Free energy, enthalpy, and entropy efficiencies can be calculated from available electron conservation efficiencies if the biological combustion energies of the substrate, cells, and products are known per electron transferred. The methods described are applicable equally to aerobic and anaerobic growth process systems.Key words: yeast growth thermodynamics, electron conservation.

ISSN:0008-4166    

DOI:10.1139/m95-052

出版商:NRC Research Press    

年代:1995

数据来源: NRC