摘要:

Phototrophic bacteria were observed forming a brown layer, at the interface between aerobic and anaerobic waters, in a stratified tropical lagoon (Bietri Bay, 5°15′ N, 4 °W, Ivory Coast). Within the brown layer (3.2–4 m depth), a stratification of different genera was observed. In the upper part purple bacteria developed, whereas green and brownChlorobiaceaeabounded mostly in a lower layer (3.5–4 m depth). Among the purple bacteria, some species were isolated and identified asRhodopseudomonas palustris,Chromatium violascens,Chr.vinosum, andChr.gracile. The green and brown sulfur bacteria were related toChlorobium vibrioformeandChl.phaeobacteroides.Chlorobium phaeobacteroideswas the most abundant organism in the whole brown layer as well as in the deepest layer. As the phototrophic bacteria isolated were able to grow at different salt concentrations, the stratification observed could be explained by the gradients of sulfide and light. As shown by experimental data, purple bacteria grew under microaerobic conditions and used light intensities higher than green and brown sulfur bacteria whose growths were highly dependent on strict anaerobic conditions. During the dry season, holomixis involved the disappearance of the brown layer. Some phototrophic bacteria were found in the oxygenated water column. However, only brownChlorobiumwas isolated. Although this species was found in a microaerobic environment in Bietri Bay, it never grew under microaerobic conditions in the synthetic media. This bacterium (Chlorobium phaeobacteroidesstrain BI 28) was able to use thiosulfate, as didChl.vibrioformeisolated from the brown layer.

ISSN:0008-4166    

DOI:10.1139/m84-042

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Bacterization of soybean seeds or roots withRhizobium japonicumsignificantly reduced charcoal rot disease caused byMacrophomina phaseolina.Rhizobium japonicuminhibited the growth ofM.phaseolinaon both liquid and solid media. Replacement of nutrient medium with culture filtrate ofR.japonicumsignificantly reduced mycelial growth ofM.phaseolina. Whole culture extracts ofR.japonicumyielded a toxic substance which was identified as rhizobitoxine after chromatographic, ultraviolet, and infrared spectrophotometric analyses. This compound also was detected in the roots of soybean inoculated with eitherR.japonicumalone or in combination ofR.japonicumandM.phaseolina. Dosage response curves with rhizobitoxine showed it to be antifungal. The possible role of rhizobitoxine in protecting soybean roots fromM.phaseolinainfection is discussed.

ISSN:0008-4166    

DOI:10.1139/m84-043

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Cell surface characteristics of threeMortierellaspecies differing in their response to a mycoparasite,Piptocephalis virginiana, were examined. Their cell wall composition was typical of mucoraceous fungi with chitin and chitosan as major polysaccharides. Electron microscopy revealed that the mycoparasite penetrated and formed haustoria in the hyphae of susceptible hosts,M.pusillaandM.isabellina. The failure of the parasite to establish contact and penetrate a hypha of the nonhost,M.candelabrum, was not due to cell wall thickness, rigidity, or chitin contents. Markedly different protein patterns obtained from crude alkali extracts of host and nonhost cell walls by sodium dodecyl sulfate – polyacrylamide gel electrophoresis might explain the difference in host and nonhost response to the mycoparasite. Whereas most of the bands differed only in intensity after staining with either Coomassie blue or periodic acid – Schiff reagent, there were two distinct bands of glycoproteins (76 000 and 74 000) observed in the host species which were absent in the nonhost species.

ISSN:0008-4166    

DOI:10.1139/m84-044

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Exogenous proline betaine (stachydrine orN-dimethylproline) or γ-butyrobetaine (γ-trimethylaminobutyrate), at a concentration as low as 1 mM, were found to stimulate the growth rate ofKlebsiella pneumoniae, wild type M5A1, in media of inhibitory osmotic strength (0.8 MNaCl). Simultaneously, nitrogen fixation by whole cells, a process particularly sensitive to osmotic stress, was strongly enhanced by these compounds. However, in the absence of sodium chloride, both the growth and nitrogen fixation were not affected by the addition of the methylammonium derivatives in the medium. The sensitivity of the nitrogen fixation to osmotic stress was used as a bioassay to evaluate the potentiality of osmoprotective compound in relation to the number of methyl groups on the nitrogen atom of glycine, proline, and γ-aminobutyrate. Experiments with sarcosine (monomethylglycine), dimethylglycine, and glycine betaine (trimethylglycine), or experiments with mono- and di-methylproline or γ-mono-, γ-di-, γ-tri-methylaminobutyrate, indicated that the greatest stress tolerance was always obtained with the moreN-methylated compounds.

ISSN:0008-4166    

DOI:10.1139/m84-045

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Three-dimensional models of the relationships among fluorescent pseudomonads were prepared from appropriately transformed percent DNA homology values. The transformation selected wasf(x) = ((1 – HOM/HOM)200, where HOM = fractional DNA homology and 200 is a scaling factor. Model accuracy was quite good as a plot of transformed DNA homology values versus model distances was essentially linear for homology values greater than 30%. The model suggested that bacterial strains within the fluorescent pseudomonads appear to be related in a three-dimensional continuum with no clear and easy "natural" demarcation into groups (i.e., species).

ISSN:0008-4166    

DOI:10.1139/m84-046

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The extracellular and cell-bound cellulase (CM-cellulase) elaborated by the rumen bacteriumRuminococcus albusSY3 in synthetic medium was an endo-(1 → 4)-β-glucanase in that (i) it produced a rapid fall in the degree of polymerisation (1900 → 300) of H3PO4-swollen cellulose, while causing only 0.5% hydrolysis, and (ii) it released large amounts of cellotriose and smaller amounts of cellotetraose from H3PO4-swollen cellulose. The enzyme appeared in a wide range of molecular weights, which varied according to the culture conditions, but nevertheless focused at pH 6.0–6.1 in all cases in a pH gradient supported in a polyacrylamide gel. Cell-bound enzyme, which was of very large molecular weight (> 1.5 × 106), was excluded from the polyacrylamide gel. Under certain conditions, cellulose swollen in H3PO4was hydrolysed extensively, but highly ordered cellulosic substrates were poorly hydrolysed. The enzyme acted synergistically with an endwise-acting cellobiohydrolase from the fungusTrichoderma koningiiin solubilizing a microcystalline wood α-cellulose preparation (Avicel): the same cooperation was not apparent when Avicel was swollen in H3PO4or when cellulose in the form of cotton fibre was used.

ISSN:0008-4166    

DOI:10.1139/m84-047

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

To isolate intact flagella with basal complexes fromVibrio cholerae, a rhamnolipid hemolysin fromPseudomonas aeruginosawas used to disrupt the cell envelope and flagellar sheath. The nonionic detergent, Triton X-100, provided similar results forCampylobacter fetus. Each of these basal complexes possessed, in addition to the four classical rings, concentric membrane rings (CMR's) similar to those found inAquaspirillum serpens. Through the use of stereo imaging (which allows structures to be visualized in three dimensions) of thin sections of cells which had been sequentially treated with a number of envelope perturbants (i.e., ethylenediaminetetraacetate, lysozyme, Triton X-100, rhamnolipid hemolysin, and sodium dodecyl sulfate), we have progressively exposed the component parts of the basal organelles inV.choleraeandC.fetus. Since the action of these envelope perturbants has been well documented, we have been able to determine the associations of the exposed portions of the flagellar basal complex and the layer of the cell envelope in which they would normally reside. From our observations we have concluded that in bothV.choleraeandC.fetusthe L ring is embedded in the outer membrane and the P ring is associated with the peptidoglycan. The CMR's are bracketed by the L and P rings and are sandwiched between the outer membrane and the peptidoglycan. Elements of both the S and M rings appear to be associated with the plasma membrane.

ISSN:0008-4166    

DOI:10.1139/m84-048

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

An environmental isolate (13-1BB) ofSalmonella enteritidisserogroup C1was inoculated into sterile Potomac River water microcosms to observe survival and culturability of the organism by employing acridine orange direct count, fluorescent antibody direct count, direct viable count, plate count on veal infusion agar and xylose lysine decarboxylase agar, and indirect enumeration by the most-probable-number method (MPN), using media selective forSalmonella. Loss of culturability on laboratory media was observed within 48 h. However, cultures could be "resuscitated" and cultured on solid media, following addition of nutrients to the microcosms. Cells, resuscitated 4 days after apparent "die-off" (0 colony-forming units (cfu)/mL) using plate count techniques, yielded numbers of cfu in the same order of magnitude as had been observed before the onset of nutrient limitation. Microscopic techniques for direct viable counting indicated that viability is maintained for as long as 60 days after depletion of nutrients, although attempts to culture these cells, by addition of nutrient, after 21 days yielded apparently sterile plates. Thus, longer periods of "dormancy" appear to require conditions other than simple nutrient addition for resumption of cell growth and division.

ISSN:0008-4166    

DOI:10.1139/m84-049

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Two families ofEscherichia colimutants with altered outer membrane protein components were examined for sensitivity to freezing and thawing and other stresses. A mutant unable to make the lipoprotein (lpo) was extremely sensitive to freezing and thawing in water or saline and to challenge with detergent, while the mutant unable to make the porin proteins (ompB) was more resistant than the isogenic wild type; strains unable to make thetsxandompA proteins were slightly more sensitive to the stresses. Similarly, thelpodeficient strain exhibited more and theompB less wall and membrane damage than the wild-type strains. Little difference in the extent of wall damage, but more membrane damage, was seen for the twotsxand theompA strains when compared with the wild-type strain. The roles of the specific proteins in determining sensitivity to freeze–thaw are discussed.

ISSN:0008-4166    

DOI:10.1139/m84-050

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The uptake and incorporation of macromolecular precursors in germinatingSaccharomyces cerevisiaeascospores were investigated. Addition of cycloheximide at various times during germination revealed that protein synthesis can occur within 20 min after the spores are shifted to glucose-containing media. The time of initiation of uptake and incorporation of several amino acids differed; this can be attributed to differing amino acid pool levels in the spores, as well as differing transport activities. Two-dimensional gel electrophoresis of proteins labeled with [35S]methionine for various 20-min periods after germination began showed at least one protein whose synthesis begins well after the bulk of the proteins.

ISSN:0008-4166    

DOI:10.1139/m84-051

出版商:NRC Research Press    

年代:1984

数据来源: NRC