ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1993.tb00092.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThis paper presents circumstantial evidence that the mating system of the North American pocket gophers (Rodentia: Geomyidae) is a promiscuous one, with female choice at its base. A molecular marker (a length variant in the mitochondrial Control region [D‐loop]) is used to show mating asymmetry in a hybrid zone between the speciesThomomys bottaeandThomomys townsendiiin north‐eastern California. All hybrids result from abottaemother ×townsendiifather cross. Because of significant differences in body size and resulting burrow diameter,bottaefemales must have actively sought their respectivetownsendiimates for the asymmetry in mating to have occurred, signalling female choice in these subterranean mammals that are otherwise characterized by exclusive‐use territories, skewed adult sex ratio in favour of females, and high variance in male reproductive s

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1993.tb00093.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractContinuous‐flow column reactors were used to study the dynamics of plasmid exchange in a structured, thermodynamically open system containing eitherEnterobacter cloacaeorPseudomonas cepacia, both carrying the transmissible recombinant plasmid R388::Tn1721. Plasmid transfer rates were higher in vermiculite and sterile soil columns supplied with nutrient solution than those in sterile and non‐sterile soil columns without input of nutrient solution. For both species, donor and recipient strains took about 5 days to reach their maximum densities in effluents from the columns supplied with nutrient solution. After about 8 day s the donor and transconjugant populations of P.cepaciain the effluent solution decreased exponentially, whereasE. cloacaedonor, recipient and transconjugant strains maintained steady‐state concentrations. The difference between plasmid stability in the two species may have significant consequences in terms of releasing plasmid‐bearing genetically modified microorganisms into the natural environment. The plasmid is persistent in E.cloacaein non‐sterile soil even though its transfer to the marked recipient in non‐sterile soil

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1993.tb00094.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractDNA sequences of an intergenic spacer (IGS) and parts of genes in thenifcluster were amplified by the polymerase chain reaction (PCR) using two primers derived fromnifD‐andnifK‐conserved sequences. The PCR products were cleaved by ten 4–base cutting restriction enzymes and the restriction patterns were used as fingerprints to typeFrankiastrains. The feasability of this PCR‐RFLP method for typingFrankiastrains was investigated onFrankiareference strains belonging mainly to the Elaeagnaceae infectivity group but also on newFrankiaisolates and on other N2‐fixing microorganisms. By modulating the stringency of the amplifications, we showed the method allowed to target eitherFrankiastrains or the whole N2‐fixing microbial community. DNA digestion patterns were used to estimate the sequence divergence between theFrankia nifD‐Kfragment. The estimated relationships deduced from these genotypic data correlated well with establishedFrankiataxo

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1993.tb00095.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractIn this paper we report about a screening for streptothricin‐ (St)‐resistant phenotypes and genotypes among environmental bacteria from a St virgin area. St‐resistant bacteria were isolated from river water, sewage, manure and soil by selective plating. The resistance quotient was typical of an area without selective pressure. The occurrence of streptothricin acetyltransferase‐encoding determinants and their localization on a Tn7‐like transposon was tested by the application of a set of gene probes.Satgenes could be detected in 22.5% of the tested St‐resistant bacteria but in 100% of the checked Enterobacteriaceae. However, we could not detectsatgenes in St‐resistant bacteria from soil samples. Surprisingly thesatgenes were found to be located on conjugative or mobilizable plasmids for a rather high number of strains. The determined plasmid species and their restriction patterns showed a high degree of similarities to those observed from an area of strong selec

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1993.tb00096.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractRhizobium melilotistrains isolated from alfalfa plants grown in a mining recultivation field, in a model ecosystem (microcosm) and in soil core containers were characterized by two new taxonomic methods, fingerprinting and handprinting, using insertion sequence elements (IS) as hybridization probes. The diversity of strains within the field population could first be detected with IS‐fingerprinting, whereby nearly three times more groups ofRhizobium melilotistrains could be identified in comparison to the groups according to plasmid profiles. This complexity and diversity of the rhizobial population was also detected in microcosm studies. Strains identified among the field population were also detected in the microcosm studies. The persistence of rhizobia in soil was demonstrated in soil core samples held in a cold room for 2 years. A decrease in the genomic diversity of the R.melilotipopulation upon soil storage was observed. A novel monitoring method, IS‐handprinting, in which the presence of certain endogenous insertion elements within a strain is registered, was successfully employed to characterize genetically the fieldR. melilotistrains with simplicity and speed. In contrast to IS‐fingerprinting, IS‐handprinting is based on a simple plus‐or‐minus detection, which is sufficient for a taxonomic characterization. Both methods, using a non‐radioactive detection system, are sensitive enough to detect one copy of an insertion element in a strain's genome. IS‐fingerprinting, with its fine resolution, would be suitable for ecological studies of individual strains in any complex ecosystem, whereas IS‐handprinting would be suitable for monitoring strains and characterizing large n

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1993.tb00097.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractLuminescent strains ofPseudomonas fluorescens10586 were constructed in which luciferase production was constitutive by introduction ofVibrio fischeri luxABEgenes on the chromosome and on a multicopy plasmid. Light production in liquid batch culture was directly proportional to biomass concentration during exponential growth and enabled detection by luminometry of 1.7 × 103and 8.9 × 104cells/ml for the plasmid and chromosomally marked strains, respectively. Luminescent colonies of both strains were detectable by eye, enabling viable cell enumeration on solid media against a background of non‐luminescent strains. Following inoculation into sterile and non‐sterile soil lower levels of detection were increased but detection of 8.1–59 × 103and 2.2–30 × 103cells per g of soil was possible for plasmid and chromosomally marked strains. Maximum specific growth rate in liquid culture was unaffected by introduction ofluxmarker genes on the chromosome, but was reduced in the plasmid marked strain. The chromosomally encoded marker was stable in both liquid culture and in soil, but the plasmid was unstable during continuous subculturing in liquid medium and during growth in soil. The chromosomally encoded luminescence‐marker system therefore provides a convenient, non‐extractive technique for quantification of genetically modified soil mi

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1993.tb00098.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractAn efficient oligonucleotide typing method for the highly polymorphicMHC‐DRBgenes is described for artiodactyls like cattle, sheep and goat. By means of the polymerase chain reaction, the second exon ofMHC‐DRBis amplified as well as part of the adjacent intron containing a mixed simple repeat sequence. Using this primer combination we were able to amplify theMHC‐DRBexons 2 and adjacent introns from all of the investigated 10 species of the family of Bovidae and giraffes. Therefore, theDRBgenes of novel artiodactyl species can also be readily studied. Oligonucleotide probes specific for the polymorphisms of ungulateDRBgenes are used with which sequences differing in at least one single base can be distinguished. Exonic polymorphism was found to be correlated with the allele lengths and the patterns of the repeat structures. Hence oligonucleotide probes specific for different simple repeats and polymorphic positions serve also for typing across species barriers. The strict correlation of sequence length and exonic polymorphism permits a preselection of specific oligonucleotides for hybridization. Thus more than 20 alleles can already be differentiated from each of the three sp

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1993.tb00099.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1993.tb00100.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1993.tb00101.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY