Biomedical subjects

L Thorne

Publications and source records attributed to L Thorne.

21 records · Page 2Linked to original sources

PubMed1988

Structural relatedness between mosquitocidal endotoxins of Bacillus thuringiensis subsp. israelensis.

A mosquitocidal toxin gene, cloned from Bacillus thuringiensis subsp. israelensis, was introduced into mutant crystal-negative B. thuringiensis subsp. israelensis cells. Partial toxicity to mosquitos was restored. The 58-kilodalton cloned gene product is a minor protein component of B. thuringiensis subsp. israelensis crystals and is structurally related to a major, 135-kilodalton crystal toxin.

Animals↗

PubMed1987

Clustering of mutations blocking synthesis of xanthan gum by Xanthomonas campestris.

Mutations that block the synthesis of xanthan gum by Xanthomonas campestris B1459S-4L-II were isolated as nonmucoid colonies after treatment with ethyl methanesulfonate. Complete libraries of DNA fragments from wild-type X. campestris were cloned into Escherichia coli by using a broad-host-range cosmid vector and then transferred into each mutant strain by conjugal mating. Cloned fragments that restored xanthan gum synthesis (Xgs+; mucoidy) were compared according to restriction pattern, DNA sequence homology, and complementation of a subset of Xgs- mutations. Groups of clones that contained overlapping homologous DNA were found to complement specific Xgs- mutations. The results suggest clustering of the genetic loci involved in xanthan synthesis. The clustering occurred within three unlinked regions. Two forms of complementation were observed. In most instances, independently isolated cosmid clones that complemented a single mutation were found to be partially homologous. Less frequent was the second form of complementation, in which two cosmid clones that lacked any homologous sequences restored the mucoid phenotype to a single mutant. Finally, xanthan production was measured for wild-type X. campestris carrying multiple plasmid copies of the cloned xanthan genes.

Cloning, Molecular↗

PubMed1986

Structural similarity between the lepidoptera- and diptera-specific insecticidal endotoxin genes of Bacillus thuringiensis subsp. "kurstaki" and "israelensis".

A gene from Bacillus thuringiensis subsp. "israelensis" was cloned from the large plasmids of this subspecies and was shown to code for a mosquitocidal polypeptide. The gene could be expressed in either Escherichia coli, Bacillus subtilis, or B. thuringiensis subsp. "israelensis" to produce the larvicidal activity. Similarly, a Lepidoptera-specific toxin gene from B. thuringiensis subsp. "kurstaki" was also cloned and expressed in E. coli and B. subtilis. Both cloned genes were sequenced and subjected to computer analysis. A long open translational reading frame coded for the B. thuringiensis subsp. "kurstaki" gene product. However, the B. thuringiensis subsp. "israelensis" clone was composed of two adjacent open reading frames oriented as if they were in a transcriptional operon. The products of the cloned genes retained their specificity for either Lepidoptera or Diptera. The control regions immediately preceding the toxin genes of both B. thuringiensis subspecies showed considerable DNA homology, most likely because both toxins are expressed only during sporulation. In addition, the deduced amino acid sequences from the two contiguous B. thuringiensis subsp. "israelensis" genes bore a striking resemblance to the deduced amino acid sequence from the single larger B. thuringiensis subsp. "kurstaki" gene, as if these two arrangements were evolutionarily related.

Amino Acid Sequence↗