To facilitate efficient allelic exchange of genetic information into a wild-type strain background, we improved upon and merged approaches using a temperature-sensitive plasmid and a counter-selectable marker in the chromosome. We first constructed intermediate strains of Escherichia coli K12 in which we replaced wild-type chromosomal sequences, at either the fimB-A or lacZ-A loci, with a newly...

Large-molecular-weight plasmids were isolated from virulent and avirulent strains of Bacillus anthracis. Each strain contained a single plasmid species unique from the others with respect to molecular weight. Bacterial strains were cured of their resident extrachromosomal gene pools by sequential passage of cultures at 42.5 degrees C. Coincidental to the curing of plasmids was a loss of detecta...

Abstract The exponential rise in the Nigerian population has necessitated use of agrochemicals for enhanced agricultural yields to meet ever-rising demand food. However, such as organochlorine pesticides (OCPs) have caused several devastating health and ecological challenges. study was therefore aimed at assessing bioaccumulation OCPs associated parasitological microbial susceptibility P. obscu...

Large indigenous plasmids are a common feature in members of the genus Rhizobium, and their involvement in the control of symbiotic functions has been established. Studies on these rhizobial plasmids, called pSym plasmids, make up much of what is understood about the molecular and genetic basis of the N2-fixing symbiosis. The soybeans, generally nodulated by slow-growing rhizobia, are an econom...

About fifty indigenous clinical Klebsiella were isolated and identified on the basis of morphology, growth, and biochemical characteristics. Fifty two percent were identified as K. oxytoca, 42% as K. pneumoniae and 6% as K. ozaenae. All the isolates offered different resistance patterns (determined by medium incorporation-replica method) against antibiotics including ampicillin, streptomycin, g...

OBJECTIVES To investigate the role of a plasmid bearing the erm(B) gene on the prevalence of the macrolide, lincosamide and group B streptogramin (MLS(B)) phenotype of group A streptococci (GAS) and to characterize the plasmid and determine the clonal relation between the erythromycin-resistant isolates. METHODS Two hundred and five erythromycin-resistant GAS isolates were collected from 1990...

A bacterium was isolated from the soil of dumping ground for cattle yard waste by enrichment culture containing aflatoxin B1. This bacterium was closely related to Bacillus firmus that was found to be a non-pathogenic bacterium. The minimum inhibitory concentration of aflatoxin B1 to the bacterium was found to be 80 microg ml(-1) as measured by total viable count and soluble protein content met...

An assessment was made of the relative contributions of a spontaneous mutation to rifampin resistance and a cryptic plasmid, pTA2, to competitive nodulation of Medicago sativa by a strain of Rhizobium meliloti. This was facilitated by use of rifampin-resistant derivatives of this strain in which pTA2 was originally present, cured, or reintroduced. Both curing of pTA2 and spontaneous mutation to...