摘要:

Pseudomonas putidaML2 contains a large catabolic plasmid, pHMT112, carrying genes that encode the dioxygenase and dehydrogenase involved in the catabolism of benzene via theorthoor β-ketoadipate pathway. pHMT112 was derived from a larger and less stable plasmid inP.putidaML2 following growth on succinate as carbon and energy source but was, however, stably maintained inP.putidaeven in the absence of selection for growth on benzene. Cleavage sites for the restriction endonucleasesDraI,XbaI, andBamHI were mapped on the plasmid. A region of the plasmid, downstream of the benzene dioxygenase genes (bedC1C2BA), was found to encode thecis-benzene dihydrodiol dehydrogenase gene (bedD). RecombinantEscherichia colicontainingbedC1C2BADgenes was found to express benzene dioxygenase and dehydrogenase activity, indicated by the production of catechol when incubated in the presence of benzene. Hybridization using benzene dioxygenase genes as probes was used to construct a restriction map of the 35.5-kbXhoI–DraI fragment on which thebedoperon was located.Key words:Pseudomonas putida, catabolic plasmid, dioxygenase, dehydrogenase.

ISSN:0008-4166    

DOI:10.1139/m93-052

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

An entomogenous fungus,Entomophthora muscae, was studied morphologically with respect to the formation of primary and secondary conidia and germ tubes. The fungus penetrated the insect cuticle by germ tubes that were produced at the base of each conidium that penetrated directly through the cuticle. Fungal germ-tube formation and penetration of host integument were observed. The tough germ-tube penetration point seemed to provide abundant energy for the penetration of the host integument. Conidia not directly on the integument formed secondary conidia but were never observed to form germ tubes. Neither appressorium nor infection cushion was observed on the germ tubes.Key words:Entomophthora muscae, entomogenous fungus, insect mycosis, insect pathology, conidia.

ISSN:0008-4166    

DOI:10.1139/m93-053

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The ruminal fungiOrpinomyces joyoniistrain 19-2,Neocallimastix patriciarumstrain 27, andPiromyces communisstrain 22 were examined for their ability to digest cereal starch. All strains digested corn starch more readily than barley or wheat starch.Orpinomyces joyonii19-2 exhibited the greatest propensity to digest starch in wheat and barley, whereas the digestion of these starches byN.patriciarum27 andP.communis22 was limited. Media ammonia concentrations were lower when fungal growth was evident, suggesting that all strains assimilate ammonia. Fungi formed extensive rhizoidal systems on the endosperm of corn, butO.joyonii19-2 was the only strain to form such systems on the endosperm of wheat and barley. All strains penetrated the protein matrix of corn but did not penetrate starch granules. Starch granules from all three cereals were pitted, evidence of extensive digestion by extracellular amylases produced byO.joyonii19-2. Similar pitting was observed on the surface of corn starch granules digested byN.patriciarum27 andP.communis22, but not on wheat and barley starch granules. The ability of ruminal fungi to digest cereal grains depends on both the strain of fungus and the type of grain. The extent to which fungi digest cereal grain in the rumen remains to be determined.Key words: ruminal fungi, cereal grain, starch digestion, ruminant.

ISSN:0008-4166    

DOI:10.1139/m93-054

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Two chloramphenicol-producing strains ofStreptomyces venezuelaeaccumulated small amounts of polyhydroxybutyrate during exponential growth; the compound disappeared from the mycelium as the cultures entered stationary phase. Depletion of polyhydroxybutyrate coincided with chloramphenicol production but the amount of polymer stored in the mycelium was insufficient to supply the precursor requirement for biosynthesis of the antibiotic. Accumulation of polyhydroxybutyrate in theS.venezuelaestrains was appreciably lower than in two other streptomycetes examined. Glycogen and lipids accumulated in the mycelium ofS.venezuelae13s during the stationary phase, after nitrogen depletion; under the culture conditions used, they were the principal storage compounds inS.venezuelae. Trehalose was absent from the mycelium in vegetative cultures grown under nonsporulating conditions but it was abundant in spores obtained from submerged and surface cultures. Glycogen and polyhydroxybutyrate were absent from spores.Key words: storage compounds, biosynthesis, polyhydroxybutyrate, glycogen, trehalose, lipid.

ISSN:0008-4166    

DOI:10.1139/m93-055

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Iron-oxidizing autotrophs and acidophilic heterotrophs were quantified at an incubation temperature of 18 °C in several samples obtained from the bioleaching areas of two uranium mines in Ontario, Canada. All samples were mine-water samples with temperatures in the range 13–18 °C. Iron-oxidizing autotrophs ranged from 2683 ± 377 to 245 000 ± 20 205 colony-forming units∙mL−1and were always numerically superior to acidophilic heterotrophs, which ranged from 40 ± 8 to 9650 ± 161 colony-forming units∙mL−1. For each sample, approximately 20 isolates of each nutritional group were examined for the ability to grow at temperatures of 4, 18, 21, and 37 °C, respectively; overall, 559 isolates of iron-oxidizing bacteria (predominantlyThiobacillus ferrooxidans) and 252 acidophilic heterotrophic isolates were examined and categorized as 'broader temperature range psychrotrophs,' 'narrower temperature range psychrotrophs,' 'intermediates,' or mesophiles. Although psychrotrophic representatives of both groups were abundant, no psychrophiles were recovered from any of the samples. For the iron oxidizers, the temperature growth profiles of the isolates were similar from sample to sample. For the acidophilic heterotrophs, the temperature growth profiles varied considerably among samples.Key words: psychrotrophs;Thiobacillus ferrooxidans; uranium mi

ISSN:0008-4166    

DOI:10.1139/m93-056

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Phage infectingActinomadura verrucosospora,Actinomadura pusilla, andNocardiopsis flavawere isolated from mulches applied to avocado trees at the University of Western Australia experimental plots. The physiochemical properties, plaque morphology, host range, and particle morphology of the phage isolated are described. Taxonomic implications of the reactions of some cell wall chemotype III actinomycetes toActinomaduraphage are also discussed.Key words:Actinomaduraphage.

ISSN:0008-4166    

DOI:10.1139/m93-057

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Recent food-borne outbreaks of human listeriosis as well as numerous sporadic cases have been mainly caused byListeria monocytogenesserovar 4b strains. Thus, it was of interest to find out whether a certain clone or a certain few clones were responsible for these cases and especially for outbreaks., We used pulsed-field gel electrophoresis of large chromosomal DNA restriction fragments generated byApaI,SmaI, orNotI to analyse 75L.monocytogenesstrains isolated during six major and eight smaller recent listeriosis outbreaks. These strains could be divided into 20 different genomic varieties. Thirteen of 14 strains isolated during major epidemics in Switzerland (1983–1987), the United States (California, 1985) and Denmark (1985–1987) demonstrated indistinguishable DNA restriction patterns. In contrast, strains responsible for the outbreaks in Canada (Nova Scotia, 1981), the United States (Massachusetts, 1983), France (Anjou, 1975–1976), New Zealand (1969), and Austria (1986) and some smaller outbreaks in France (1987, 1988, 1989) were each characterized by particular combinations of DNA restriction patterns. Seventy-seven percent of the tested strains could be classified into the previously describedApaI group A (Broschet al. 1991), demonstrating a very close genomic relatedness. Because 49% of the epidemic strains selected for this study belonged to phagovar 2389/2425/3274/2671/47/108/340 or 2389/47/108/340, fifty-six additional strains of these phagovars, isolated from various origins, were also typed to determine whether differences in DNA restriction profiles between epidemic and randomly selected strains of the same phagovars could be pointed out. Variations in DNA patterns appeared more frequently within randomly selected strains than within epidemic strains.Key words:Listeria monocytogenes, listeriosis, typing, pulsed-field gel electrophoresis, epidemic.

ISSN:0008-4166    

DOI:10.1139/m93-058

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Polymerase chain reaction amplification was used to compare different regions of the cytochromec3gene from nine strains ofDesulfovibrio vulgaris, to examine homology within the species. Six 30-base polymerase chain reaction primers and three probes were synthesized on the basis of the published nucleic acid sequence of the cytochromec3gene fromD.vulgaris, NCIMB 8303. Amplifications were performed on genomic DNA isolated from NCIMB 8303 as well as eight other strains. Six strains, NCIMB 8302, 8305, 8306, 8311, 11779, and DSM 2119, showed amplification products of equal size and quantity to those of strain 8303. Two other strains, NCIMB 8456 and DSM 1744, either showed reduced levels or no detectable amplification products. These results were confirmed by hybridization of amplified DNA to radiolabeled probes specific for each product. DNA sequencing of a 145-bp polymerase chain reaction fragment from strains NCIMB 8302, 8303, 11779, and DSM 2119 revealed complete sequence homology between these strains, whereas slight differences were seen with strain NCIMB 8456. Amino acid sequencing of the first 20 residues of cytochromec3purified from strains NCIMB 8456 and 8303 also showed differences in the two proteins. In contrast to the results obtained with strain NCIMB 8456, limited homology was observed between the first 20 amino acid residues of cytochromec3from strain DSM 1744 and strain NCIMB 8303.Key words: cytochromec3,Desulfovibrio, polymerase chain reaction amplification, taxonomy.

ISSN:0008-4166    

DOI:10.1139/m93-059

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

A study was made of 113 bacterial isolates from root nodules of peas, lentils, red clover, and French beans, which had been grown in the same soil. Plasmid band profiles visualized in Eckhardt gels were analysed in relation to DNA hybridization patterns obtained by probing restricted total cellular DNA in Southern blots.Rhizobium leguminosarumchromosomal probes (plac12, pCOS309.1) and various symbiotic plasmid (nodgene region) probes were used. Dominant plasmid DNA hybridization patterns and more frequent combinations of plasmid patterns and chromosomal types were found among the isolates of each host plant species; the occurrence of alternative combinations indicated that genetic transfer and recombination among members of this soil population had taken place. About 40% of all isolates belonged to the same chromosomal type. Isolates of the same chromosomal type were often found with cryptic plasmids of the same size in different host plant species. Although isolates could not be assigned to their respective plant host groups using chromosomal probes alone, this was generally possible using symbiotic plasmid probes and the results were in complete accordance with plant tests. However, there was a group of bean isolates in which no homology to any of theR.leguminosarumprobes was detected under the conditions of high stringency used. Other exceptional isolates of beans conformed in probe tests and subsequent plant host specificity tests better to biovarsviciaeortrifoliithan to biovarphaseoli; thus, the nodulation of beans (i.e.,Phaseolus vulgaris) in the field appears less subject to stringent control of specificity than that of other host plant species. It was also noted that thenodgene regions probed showed greater diversity in isolates of biovarsviciaeandtrifoliithan in biovarphaseoli.Key words:Rhizobium leguminosarum, genetic diversity, plasmid, DNA hybridization, restriction fragment length polymorphism.

ISSN:0008-4166    

DOI:10.1139/m93-060

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Several saprophytic fluorescent pseudomonads that are aggressive root colonizers express similar specific activities of superoxide dismutase during growth in liquid culture. The pseudomonads have the potential to produce hydrogen peroxide sensitive and hydrogen peroxide insensitive isoforms of superoxide dismutase with distinct mobilities in nondenaturing polyacrylamide gel electrophoresis. Synthesis of the hydrogen peroxide insensitive form is enhanced by limited iron availability, by exposure to Mn2+, and to a lesser extent by external sources of superoxide anion. UnlikePseudomonas aeruginosa, a root-colonizing strain ofPseudomonas putidadid not show regulation of isoform pattern by phosphate availability. A plasmid potentially encoding the pseudomonad hydrogen peroxide sensitive form complemented the superoxide dismutase deficiency in a mutant ofEscherichia colilacking expression of both Fe and Mn genes. Contact between the plant root and pseudomonad orE.colicells that lack or express superoxide dismutase did not influence superoxide anion production from root surface enzymes. The pseudomonad and the superoxide dismutase deficient and producingE.colistrains survived exposure to the root equally well. Only the hydrogen peroxide sensitive isoform of superoxide dismutase was detected inP.putidacells associated with bean root surfaces.Key words: pseudomonads, activated oxygen, root surface colonization.

ISSN:0008-4166    

DOI:10.1139/m93-061

出版商:NRC Research Press    

年代:1993

数据来源: NRC