The evolution of self-fertility inCrepis tectorum (Asteraceae)

The extent of self-fertility was examined in 16 populations ofCrepis tectorum. A hypothesis that a weedy habit favours autogamy was only partly supported. Low levels of self-fertility characterized non-weedy populations from calcareous grasslands (alvars) on the Baltic island in Öland. By contrast, plants in nearly all weed populations studied were more or less self-fertile. However, the trend towards autogamy may have occurred independently of the trend towards a weedy habit, as shown by moderately to high levels of self-fertility in alvar populations from two other Baltic islands. In the weed group, there was a tendency for plants from two field populations to be more autogamous than plants from more ruderal habitats. There was an association between self-fertility and small, inconspicious heads in the alvar group but the association was weaker when weed populations were also considered. The relatively wide heads characterizing the ruderal weed populations may, at least partly, be an indirect effect of increases in overall plant size and/or in the size of the fruit associated with each flower.     

Inducible reactivation of UV-irradiated cholera phage e5 in Vibrio cholerae MAK757

Summary The survival of UV-irradiated cholera phage e5 was found to increase when the host cells, Vibrio cholerae MAK757, were exposed to a low dose of UV irradiation before phage infection (Weigle reactivation), indicating the existence of a UV-inducible DNA repair pathway (SOS repair) in V. cholerae MAK757. The induction signal generated by UV irradiation was transient in nature and lasted about 20–30 min at 37°C. Maximal weigle reactivation of the phage was obtained when the host cells were irradiated with a UV dose of 16 J/m². V. cholerae MAK757 was also found to possess efficient photoreactivation and host cell reactivation of UV-damaged DNA in phage e5.     

Isolation and characterization of mutants deleted for the sulA-ompA region of the Escherichia coli K-12 chromosome

Abstract We have isolated mutants deleted for different segments of the sulA-ompA region of the Escherichia coli K-12 chromosome using gene fusion techniques. Genetic and physical analysis showed that the deletions ranged from 500 to more than 4000 base pairs (bp) Strains were found in which all, or part, of the sulA and ompA genes had been deleted.     

A versatile primer for DNA sequencing in the M13mp2 cloning system

A primer for DNA sequencing by the chain-termination method in the M13mp2 cloning system was constructed and amplified. The primer was isolated as an EcoRI/AluI restriction fragment. After conversion of the AluI end into an EcoRI end the fragment was cloned in pBR325 from which it can be recovered by cleavage with EcoRI. The primer hybridizes to the single-stranded DNA of the mature M13mp2 phage next to the site of insertion thereby directing DNA synthesis along the inserted DNA.     

Yards,corridors, and mosaics: How to burn a boreal forest

Ethnographic studies have established that, until shortly after World War II, Indians in northern Alberta regularly and systematically fired habitats to influence the local distribution and relative abundance of plant and animal resources. In ways similar to what has been reported for hunter-gatherers in other regions, this pyrotechnology contributed to an overall fire mosaic that, in this case, formerly characterized northern boreal forests. Crosscultural comparisons of these practices with those in other parts of North America, as well as in several parts of Australia, illustrate functionally parallel strategies in the ways that hunter- gatherers employed habitat fires, specifically in the maintenance of fire yards and fire corridors in widely separated and different kinds of biological zones.We would like to thank Ross Wein tor his comments and suggestions on this paper, especially his ideas about the characteristics of fire mosaics as they would occur under natural conditions in boreal forests. We are also indebted to several granting agencies for funds that supported our earlier research. They include the Social Sciences and Humanities Research Council, the Museum of Man, Fire Science Center (University of New Brunswick), the Boreal Institute for Northern Studies (University of Alberta), the Australian Institute for Aboriginal Studies, and the Northern Australian Research Unit (Australian National University).     

Isolation and characterization of a virulent phage for Rhodobacter sphaeroides

A new virulent bacteriophage, termed øRsV, was isolated from a local sewage plant on the facultative phototrophic bacterium Rhodobacter sphaeroides DSM 159 as the host organism. Electron microscopic studies revealed that in general morphology phage øRsV resembles the T-even Escherichia coli phages. The host range of phage øRsV was restricted to strains of R. sphaeroides. E. coli strains B and K 12 were not infected. The phage genome was characterized on the basis of thermal denaturation profiles and restriction analyses indicating that it consists of about 160 kb of double-stranded DNA lacking cohesive ends. The G+C content was determined to be 46.8 mol%.