摘要:

A heterotrophicStreptomycessp. strain SH91 isolated from pig feces compost had the ability to oxidize hydrogen sulfide to odorless substances. With several purification steps including ion-exchange and hydrophobic chromatographies, the hydrogen sulfide oxidizing enzyme was purified to a homogeneous form. The molecular mass was estimated to be 37 kDa by SDS–PAGE. The optimum reaction pH and temperature were 6.5 and 30 °C, respectively. The enzyme was stable between pH 6.0 and 8.0 and up to 40 °C. The enzyme was activated by Ba2+, Mg2+, and Ca2+and inhibited by Mn2+, and Al3+. The main product was thiosulfate.Key words: hydrogen sulfide, heterotroph,Streptomyces, oxidizing enzyme, malodorous pollution.

ISSN:0008-4166    

DOI:10.1139/m97-157

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

The rumen contents of juvenile red deer (Cervus elaphus) were used as a source for the enrichment of obligately anaerobic glycerol-fermenting bacteria. Three bacterial strains were isolated from the 10−4dilution (isolates DR6A and DR6B) and 10−9dilution (isolate DR7) of the deer rumen contents. The isolates DR6A, DR6B, and DR7 produced ethanol (42 mM) and acetate (5 mM), propionate (31 mM) and acetate (42 mM), and formate (25 mM) and ethanol (38 mM), respectively, as the major glycerol fermentation products. Interestingly, acetate, propionate, and formate were observed to be the major glycerol fermentation products in mixed cultures obtained from the deer rumen. The three isolates were all shown to be related phylogenetically to the ruminal speciesClostridium clostridiiforme,Clostridium celerecrescens, andClostridium aerotoleranswithin the clostridial taxonomic cluster XIVa, on the basis of 16S rRNA gene sequence comparisons. But, because of phenotypic differences, each isolate is considered to be a new species within the genusClostridium, which has not been previously described or isolated from the rumen ecosystem.Key words: red deer, ecology, glycerol fermentation,Clostridium, rumen, 16S rRNA.

ISSN:0008-4166    

DOI:10.1139/m97-158

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

An enzyme hydrolyzing the condensation products of urea and formaldehyde (ureaform) was purified and characterized from a bacterium isolated from soil and described asOchrobactrum anthropiUF4. The enzyme designated as methylenediurea amidinohydrolase (methylenediurea deiminase) hydrolyzed ureaform condensation products of different length (methylenediurea, dimethylenetriurea, trimethylenetetraurea) to ammonium, formaldehyde, and urea at molar ratios of 2:1:1 (methylenediurea), 4:2:1 (dimethylenetriurea), and 6:3:1 (trimethylenetetraurea). Two other substrates, ureidoglycolate and allantoate, were also hydrolyzed, yielding glyoxylate and urea (ureidoglycolate) and glyoxylate, urea, and ammonium (allantoate), respectively. The molecular mass of the enzyme was determined by size exclusion chromatography to be 140 ± 25 kDa; the enzyme was composed of identical subunits of 38 ± 5 kDa, indicating that the native enzyme has a tetrameric structure. Growth of the bacterium in the presence of ureaform specifically induced the methylenediurea deiminase and no complete repression of enzyme synthesis by ammonium was observed.Key words: ureaformaldehyde, methylenediurea deiminase, fertilizer,Ochrobactrum anthropi.

ISSN:0008-4166    

DOI:10.1139/m97-159

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

The deduced product of thespa2gene ofStreptomyces ambofaciensis a homologue of RspA, involved in stationary-phase σsfactor regulation inEscherichia coli. This suggests that Spa2 could play a part in stationary-phase-associated differentiation inS.ambofaciens. The disruption ofspa2led to reductions in aerial mycelial development and associated spore pigmentation. The mutant phenotype reverted to the wild-type phenotype when the disruption construct spontaneously excised. Thespa2disruption had no detectable effect on growth rates in different media or antibiotic production and resistance. Whenspa2was placed on a multicopy plasmid, a severe defect in formation and pigmentation of aerial mycelium resulted. These results strongly suggest that Spa2 is involved in a complex manner in the morphological differentiation process.Key words:Streptomyces, differentiation, stationary-phase regulator.

ISSN:0008-4166    

DOI:10.1139/m97-160

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

We studied, during a 2-year period, how the microbial stability of water changed when humus-rich lake water was filtered through the ground at a bank filtration water plant. The changes in microbial quality were followed as microbial numbers and growth activity. The filtration decreased microbial counts and growth ([3H]thymidine technique) in water up to 90%. The reduction in bacterial counts and growth depended on the filtration distance. The reduction was greatest between the lake and the first sampling point. Microbial numbers and growth declined steadily after infiltration with increased filtration distance. Viable counts of heterotrophic bacteria decreased faster than total bacterial counts along filtration. The microbial numbers and bacterial production in water followed seasonal changes in water temperature. Simultaneously with the microbial numbers, the concentrations of total organic carbon and assimilable organic carbon decreased during bank filtration. These results showed that microbial stability of humus-rich water was increased by filtration to a level generally found in natural groundwaters.Key words: bacteria, bank filtration, biological stability, drinking water, groundwater.

ISSN:0008-4166    

DOI:10.1139/m97-161

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

A full-scale nuclear fuel waste disposal container experiment was carried out 240 m below ground in an underground granitic rock research laboratory in Canada. An electric heater was surrounded by buffer material composed of sand and bentonite clay and provided heat equivalent to what is anticipated in a Canadian nuclear fuel waste repository. During the experiment, the heat caused a mass transport of water and moisture content gradients developed in the buffer ranging from 13% closest to the heater to 23% at the rock wall of the deposition hole. Upon decommissioning after 2.5 years, microorganisms could be cultured from all samples having a moisture content above 15% but not from samples with a moisture content below 15%. Heterotrophic aerobic and anaerobic bacteria were found in numbers ranging from 101to 106cells/g dry weight buffer. Approximately 102, or less, sulphate-reducing bacteria and methanogens per gram of dry weight buffer were also found. Identification of buffer population members was performed using Analytical Profile Index (API) strips for isolated bacteria and 16S rRNA gene sequencing for in situ samples. A total of 79 isolates from five buffer layers were identified with API strips as representing the beta, gamma and delta groups ofProteobacteriaand Gram-positive bacteria. Sixty-seven 16S rRNA clones that were obtained from three buffer layers were classified into 21 clone groups representing alpha and gamma groups ofProteobacteria, Gram-positive bacteria, and a yeast. Approximately 20% of the population comprised Gram-positive bacteria. Members of the generaAmycolatopsis,Bacillus, andNocardiapredominated. Among Gram-negative bacteria, the generaAcinetobacterandPseudomonaspredominated. Analysis of lipid biomarker signatures and in situ leucine uptake demonstrated that the buffer population was viable. The results suggest that a nuclear fuel waste buffer will be populated by active microorganisms only if the moisture content is above a value where free water is available for active life.Key words: 16S rRNA, bacteria, bentonite, nuclear fuel waste, phospholipid fatty acids, water activity.

ISSN:0008-4166    

DOI:10.1139/m97-162

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Transcription termination of T3 and SP6 DNA-dependent RNA polymerases have been studied on the DNA templates containing the threonine (thr) attenuator and its variants. Thethrattenuator is from the regulatory region of thethroperon ofEscherichia coli. The DNA template, encoding thethrattenuator, contains specific features of the rho-independent terminators. It comprises a dG + dC rich dyad symmetry, encoding a stem-and-loop RNA, which is followed by a poly(U) region at the 3′-end. Thirteen attenuator variants have been analyzed for their ability to terminate transcription and the results indicated that the structure as well as the sequence in the G + C rich region of RNA hairpin affect termination of both RNA polymerases. Also, a single base change in the A residues of the hairpin failed to influence termination, whereas changes in the poly(U) region significantly reduced the termination of both T3 and SP6 RNA polymerases. The requirement of a poly(U) region for termination by T3 and SP6 RNA polymerases was studied with nested deletion mutants in this region. The minimum number of U residues required for termination of SP6 and T3 RNA polymerases was five and three, respectively. However, both RNA polymerases needed at least eight U residues to reach a termination efficiency close to that achieved by wild-typethrattenuator encoding nine U residues. In addition, the orientation of the loop sequences of the RNA hairpin did not affect the transcription termination of either of the bacteriophage RNA polymerases.Key words: transcription termination, bacteriophage RNA polymerase.

ISSN:0008-4166    

DOI:10.1139/m97-163

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Bacteriophages specific forPseudomonas aeruginosaandEscherichia coliwere examined for their ability to multiply in stationary phase hosts. Four out of five bacteriophages tested, includingE.colibacteriophage T7M, were able to multiply in stationary phase hosts. The bacteriophage ACQ had a mean burst size of approximately 1000 in exponential phaseP.aeruginosahosts and 102 in starved hosts, with corresponding latent periods that increased from 65 to 210 min. The bacteriophage UT1 had a mean burst size of approximately 211 in exponential phaseP.aeruginosahosts and 11 in starved hosts, with latent periods that increased from a mean of 90 min in exponential phase hosts to 165 min in starved hosts. Bacteriophage multiplication occurred whether or not the hosts had entered stationary phase, either because the cultures had been incubated for 24 h or were starved. Significantly, bacteriophage multiplication occurred inP.aeruginosa, which had been starved for periods of 24 h, several weeks, or 5 years. Only oneP.aeruginosavirus, BLB, was found to be incapable of multiplication in stationary phase hosts. These results reveal that starvation does not offer bacterial hosts refuge from bacteriophage infection and suggest that bacteriophages will be responsible for significant bacterial mortality in most natural ecosystems.Key words: bacteriophage multiplication, stationary phase, starvation.

ISSN:0008-4166    

DOI:10.1139/m97-164

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Erwinia carotovorasubsp.betavasculorumEcb168 causes vascular necrosis and root rot of sugar beet and produces an antibiotic(s) that is antagonistic against otherErwiniaspp. EcbI−mutants of Ecb168, each containing a single transposon insertion in theecbIgene (forErwinia carotovorasubsp.betavasculoruminducer), do not produce detectable levels of extracellular protease or antibiotic(s), and express less pectate lyase activity and virulence than the wild-type strain. A plasmid containing the clonedecbIgene complemented the EcbI−mutants for these phenotypes. Protease production by EcbI−mutants grown on agar surfaces was restored by neighboring cells ofEscherichia colicontainingecbI. Production of a diffusibleN-acylhomoserine lactone autoinducer by wild-type Ecb168 was detected with indicator strains ofE.coliandAgrobacterium tumefaciens. EcbI−mutant strains did not produce an autoinducer detected by the indicator strains. Antibiotic production by EcbI−mutants was restored by cell-free culture supernatants of Ecb168 orE.colicontaining a clonedecbIgene. The predicted amino acid sequence of EcbI is similar to those of CarI, ExpI, and HslI, three LuxI homologs required for production of a diffusibleN-acylhomoserine lactone autoinducer inErwinia carotovorasubsp.carotovora. AluxRhomolog, termedecbR(forErwinia carotovorasubsp.betavasculorumregulator), is convergently transcribed and overlaps withecbIby 17 bp at their 3′ ends. These results are consistent with the hypothesis that a quorum-sensing system related to the prototypicluxI–luxRgene pair controls antibiotic and exoenzyme production inErwinia carotovorasubsp.betavasculorum.Key words: quorum sensing, β-lactam, gene regulation.

ISSN:0008-4166    

DOI:10.1139/m97-165

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Resting cells ofPseudomonasstrain LB400, grown on biphenyl, transformed 80, 50, and 17% of Aroclor 1242, 1254, and 1260, respectively. Resting cells grown on glucose or glycerol also transformed these polychlorinated biphenyl (PCB) mixtures to the extent of 60, 35, and 9% for Aroclors 1242, 1254, and 1260, respectively. Time courses of the transformation of the separated individual congeners in the Aroclors were plotted and used to determine the transformation rate constants (k). By analysis of the rate constants, it was concluded that the order of degradation of the different congeners in an Aroclor were similar regardless of the growth substrate. In general,kvalues for the conversion of a particular congener were lower for cells grown on glucose or glycerol compared with cells grown on biphenyl. Generally,kvalues for the transformation of the same congener in different Aroclors were not the same: rate constants had highest values for the congener in Aroclor 1242 and lowest values in Aroclor 1260. The data allowed congeners to be grouped according to their relative rates of degradation. The ratio ofkvalues for transformation of individual congeners in Aroclors by cells grown on biphenyl and glucose were not constant.Key words:Pseudomonasstrain LB400, polychlorinated biphenyls, Aroclors, transformation, resting cells.

ISSN:0008-4166    

DOI:10.1139/m97-166

出版商:NRC Research Press    

年代:1997

数据来源: NRC