摘要:

TheProteobacteriaare physiologically and morphologically diverse, although they form a coherent set of four main lineages on phylogenetic analysis of ribosomal RNA. A rational and consistent taxonomic arrangement bringing today's phenotypic and phylogenetic conclusions about them into register is not yet possible. It is also difficult to understand the selective forces involved in their evolution that fostered such diversity. This latter problem is addressed in this essay and is based on the assumption that bacterial evolution could only have occurred in ecological consortia whose products of metabolism modified the environment, provided nutrition, and have a basis for selection of new capabilities.Key words:Proteobacteria, bacterial diversity, bacterial evolution, ecological selection.

ISSN:0008-4166    

DOI:10.1139/m91-001

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The gene coding for the 12-kDa protein (MPB57) ofMycobacterium bovisBCG has recently been cloned and sequenced (R. Yamaguchi, K. Matsuo, A. Yamazaki, S. Nagai, K. Terasaka, and T. Yamada. 1988. FEBS Lett. 240:115–117).To map linear B-cell epitopes by ß-galactosidase fusion proteins, we have constructed convenient vectors (pUR278S, pUR288S, and pUR289S) with theSmaI site. Based on recognition by polyclonal antibodies, two epitope regions on the MPB57 protein were identified, both of which corresponded to the amino acid sequences Glu20to Val45(26 residues, epitope I region) and Ile78to Leu86(9 residues, epitope II). Complementary oligonucleotides encoding epitope II were synthesized, polymerized by a ligase reaction, inserted into the native MPB57 protein gene, and expressed inEscherichia coli, giving rise to epitope-inserted proteins. Their stability and potential uses are described.Key words: epitope, fusion protein, repeat sequence, subunit vaccine.

ISSN:0008-4166    

DOI:10.1139/m91-002

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Petromyces albertensisproduced xylitol andD-xylulose when cultivated on a medium containingD-xylose. These fermentative products were identified by high-performance liquid chromatography. A large amount of xylitol was obtained from aD-xylose medium containing ammonium acetate and yeast extract at an initial pH of 7.0. Maximum production of xylitol and of the enzymes concerned with its production was observed after 10 days of cultivation. AD-xylose (100 g/L) medium supplemented with 1% (v/v) methanol gave the highest yields of xylitol (39.8 g/L) andD-xylulose (2.8 g/L).Key words:Petromyces albertensis,D-xylulose, xylitol.

ISSN:0008-4166    

DOI:10.1139/m91-003

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Five intracellular proteases from sporulating cells ofClostridium perfringenstype A were identified and three could be separated by DEAE–Sephacel. Two, I-A and I-B, had caseinolytic activity and one, I-C, was only active onN-benzoyl-DL-arginine-p-nitroanilide. I-A and I-B could each be further separated by Sephacryl S-300 into I-A-1 and I-A-2 and I-B-1 and I-B-2, respectively. I-A-1, a chymotrypsin-like enzyme, was the major intracellular protease, constituting 74% of the intracellular caseinolytic activity. In addition to cytoplasmic proteases both trypsin and chymotrypsin-like enzyme activity was associated with the membrane fraction. I-A-1 had a molecular weight of 330 000, with subunits of 120 000 and 138 000. I-A-1 cleaved a 1200 molecular weight peptide fromC.perfringensenterotoxin. Early sporulating cell extracts ofC.perfringenscontained three presumptive enterotoxin precursors, which disappeared following treatment with I-A. Such cells also contained at least 10 spore coat related proteins, only one (51 500 molecular weight) of which was sensitive to I-A-1. The results indicate a possible role for the major intracellular protease in the processing ofC.perfringensenterotoxin and a less important role, if any, in spore coat formation.Key words:Clostridium perfringens, protease, spores, sporulation.

ISSN:0008-4166    

DOI:10.1139/m91-004

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Four surface proteins of the phytopathogenic MollicuteSpiroplasma citriwere characterized using monospecific polyclonal antisera. Antiserum specific for P29 (spiralin) caused growth inhibition, spiral deformation, and metabolism inhibition, while anti-P89, anti-P77, anti-P58, and preimmune sera did not. In Triton X-114 phase partitioning, P29, P89, and one of two P77 bands were hydrophobic, indicating the probability that they are integral membrane proteins. P58 partitioned into the hydrophilic phase and may be an extrinsic membrane protein. A second band which reacts with anti-P77 serum was also hydrophilic. Treatment of the two P77 components with trypsin and chymotrypsin resulted in very different polypeptide patterns, suggesting that the two bands represent unrelated proteins. These results demonstrate the variability in hydrophobicity among surface-exposed proteins inS.citriand describe procedures that should prove useful for characterizing and separating other proteins of interest in spiroplasmas.Key words:Spiroplasma, mollicute, surface proteins, serology, Triton X-114.

ISSN:0008-4166    

DOI:10.1139/m91-005

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

A total of 377 heterotrophic bacteria were isolated on nonselective medium from the rhizoplanes of five species of conifer. The species were western hemlock (Tsuga heterophylla), Douglas-fir (Pseudotsuga menziesii), lodgepole pine (Pinus contorta), white spruce (Picea glauca), and western red cedar (Thuja plicata). Twenty-eight strains from this population were identified as presumptive agrobacteria. All proved nontumourigenic. Principal-component analysis indicated that the strains, which had clustered into two discrete groups, had intermediate biovar characteristics. Cluster 1 was predominately biovar 3/2 in character, cluster 2 was predominately biovar 2/3. All the presumptive agrobacteria were distributed randomly with respect to the tree species. This study demonstrates that agrobacteria, although atypical, do occur in forest soils and attests to the ubiquity of the genus in soil.Key words:Agrobacterium, biovars, crown gall, conifers.

ISSN:0008-4166    

DOI:10.1139/m91-006

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The effect of NH4NO3on the expression of take-all in wheat and on the ability of fluorescent pseudomonad bacteria to decrease the growth of the pathogen and the symptoms of the disease was examined in a nitrogen-deficient acidic soil from Western Australia. Application of NH4NO3increased the fresh weight of shoots, decreased root weight and length, and offset some of the deleterious effects of infection. Inoculation withGaeumannomyces graminisvar.tricitireduced shoot weight and root weight and length at all but the highest level of applied nitrogen. Fluorescent pseudomonads applied to wheat seed (at approximately 108colony-forming units/seed) reduced seed germination and failed to reduce the severity of take-all expressed as weight or length of shoots or N content. Although the density of black runner hyphae ofG.graminisvar.tricitiwas reduced at 40 days and the proportion of root colonized by the pathogen was lower at 28 days with bacterization under severe nitrogen deficiency, no effect of the bacteria was observed if N was added.Key words:Gaeumannomyces graminisvar.triciti, fluorescent pseudomonads, wheat, nitrogen.

ISSN:0008-4166    

DOI:10.1139/m91-007

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The role of motility and extracellular polysaccharide production in nodulation competitiveness ofRhizobium frediiwas examined. Transposon Tn5was used to mutagenize strain USDA208, and mutants with reduced motility on semisolid agar medium were isolated. One such mutant, 208M3, migrated to only one-seventh the distance of the parental strain. Solid medium amended with triphenyltetrazolium chloride was used to identify mutants altered in extracellular polysaccharide production. Type 1 colonies, typified by mutant 208T13, were heavily mucoid, while type 2 colonies, represented by mutant 208T3, were dry and nonmucoid. Compared with strain USDA208, these mutants produced 4- to 5-fold more extracellular polysaccharide and 20% as much extracellular polysaccharide, respectively. Marker exchange of 208T3 genomic DNA containing Tn5into strain USDA208 resulted in a mutant, 208K1, that produced extracellular polysaccharide levels similar to mutant 208T3. Mutants 208M3, 208T3, and 208T13 contained single Tn5insertions. All formed pink nodules on 'Peking' soybean that were structurally indistinguishable and contained proteins with similar profiles. Rates of nodulation were similar in the mutants and the parental strain. Mutants 208M3 and 208T13 were as competitive against an isolate ofBradyrhizobium japonicumserogroup 123 as was strain USDA208. In contrast, mutants 208T3 and 208K1 were competitively superior.Key words: nodulation competition, motility, extracellular polysaccharide,Rhizobium.

ISSN:0008-4166    

DOI:10.1139/m91-008

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The association of a 20-MDa plasmid with nalidixic acid resistant (Nalr) strains ofShigella dysenteriae1 has been examined. The plasmid, which is readily transferable, does not itself code for nalidixic acid resistance but offers a survival advantage to its host under nalidixic acid stress. The plasmid-containing cultures ofS.dysenteriae1 produced Nalrmutantsin vitroat a frequency 1000-fold higher than their plasmidless parent strains, after two exposures to nalidixic acid. Using a similar procedure, mutants resistant to other antibiotics such as chloramphenicol, tetracycline, or ciprofloxacin could not be isolated. The genome ofS.dysenteriae1 appears to carry a heavy load of the insertion sequence IS1. The propensity of the plasmid-containing strains to readily mutate to nalidixic acid resistance and its possible relevance to the observed association of the plasmid with Nalrclinical isolates is discussed.Key words:Shigella, nalidixic acid, plasmid, shigellosis.

ISSN:0008-4166    

DOI:10.1139/m91-009

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

We followed the diel and summer variations of bacterioplankton production (estimated from [3H] thymidine incorporation) and abundance (direct count with 4′,6-diamidino-2-phenylindole staining) at four depths in a Canadian Shield humic lake. We found production to be highest and most variable in the epilimnion, but the differences between production estimates made at different times were statistically significant in only 5 out of 16 cases. Production differed significantly among depths in 14 out of 18 trials. The renewal time of the bacterial community varied between 1 and 20 days. Bacterioplankton production and primary production were uncorrelated (r = 0.225;p > 0.2), but bacterial production and chlorophyllaconcentration were positively correlated (r = 0.816;p < 0.005). Small coccis (~0.3 – ~0.8 μm) represented between 52 and 80% of the bacterial cells in all the samples. There was no correspondence between bacterial production and frequency of dividing cells. Bacterial production and abundance varied inversely throughout the season, bacteria being two to three times less concentrated in the spring, whereas production was two to three times higher. We found no correlation between bacterioplankton production and abundance (r = 0.012;p > 0.5). Our results demonstrate the importance of small-scale sampling and the difficulty with which bacterioplankton production, its spatiotemporal variations, and the relationships between bacteria and phytoplankton can be predicted.Key words: bacterioplankton, abundance, production, spatiotemporal variations, bacterioplankton–phytoplankton relationships.

ISSN:0008-4166    

DOI:10.1139/m91-010

出版商:NRC Research Press    

年代:1991

数据来源: NRC