Biomedical subjects

E D Jarvis

Publications and source records attributed to E D Jarvis.

23 records · Page 2Linked to original sources

PubMed1990

Genetic structure and DNA sequences at junctions involved in the rearrangements of Bacillus subtilis strains carrying the trpE26 mutation.

Studies on the region upstream to ribosomal operon rrnD of Bacillus subtilis led to the characterization of two of the four chromosomal junctions involved in the rearrangements (a translocation and an inversion) of the strains carrying the trpE26 mutation. Genetic analysis, by integrative mapping, showed linkage of rrnD to cysB and hisA (both on segment A) in the trpE26-type strains. Physical analysis showed that the region upstream to rrnD is now linked to the trpE-ilvA chromosome segment as demonstrated by analyzing restriction site-polymorphism between 168 and trpE26-type strains. Similar experiments confirmed the previous genetic data on linkage in these areas in strains carrying novel rearrangements derived from the trpE26-type strains: stable merodiploids and inversions. The nucleotide sequence of the area 5' to rrnD in both types of strains (168 and trpE26), the region downstream of the citG gene and the region carrying the trpE26 mutation (made available to us by D. Henner) provided evidence for the molecular basis of the differences in structure, allowed the identification of the break points and revealed the presence of a polypurine region upstream to rrnD as seen in other systems in B. subtilis. No extensive homology was found between pairs of junctions so far sequenced. The models proposed by C. Anagnostopoulos for the role of DNA sequences of intrachromosomal homology involved in the transfer of the trpE26 mutation and the formation of novel arrangements require therefore reevaluation.

Amino Acid Sequence↗

PubMed1988

Chromosomal organization of rRNA operons in Bacillus subtilis.

Integrative mapping with vectors containing ribosomal DNA sequences were used to complete the mapping of the 10 rRNA gene sets in the endospore forming bacterium Bacillus subtilis. Southern hybridizations allowed the assignment of nine operons to distinct BclI restriction fragments and their genetic locus identified by transductional crosses. Nine of the ten rRNA gene sets are located between 0 and 70 degrees on the genomic map. In the region surrounding cysA14, two sets of closely spaced tandem clusters are present. The first (rrnJ and rrnW) is located between purA16 and cysA14 closely linked to the latter; the second (rrnI, rrnH and rrnG) previously mapped within this area is located between attSPO2 and glpT6. The operons at or near the origin of replication (rrnO,rrnA and rrnJ,rrnW) represent "hot spots" of plasmid insertion.

Bacillus subtilis↗

PubMed1988

Instability of rRNA operons in Bacillus subtilis.

Many laboratory strains of Bacillus subtilis contain 9 rather than 10 rRNA operons due to deletions occurring within the rrnJ-rrnW or rrnI-rrnH-rrnG gene cluster. These operons are members of two sets of closely spaced clusters located in the cysA-aroI region. Analysis of rescued DNA from integrants with insertions into rrnG and rrnH indicated that these tandemly arranged operons allowed frequent deletions of an rrn operon equivalent. These events may arise spontaneously by intrachromosomal recombination or by simultaneous double crossovers with a multimeric integrative plasmid.

Bacillus subtilis↗

PubMed1986

Mapping of rRNA genes with integrable plasmids in Bacillus subtilis.

Integrable plasmids pGR102 and pWR103 containing ribosomal sequences from within the transcriptional units for 16S and 23S were used to transform Bacillus subtilis. To date, these plasmids integrated into 7 of 10 known rrn operons. Two such events occurred at unassigned operons, revealing a close linkage of the CAT gene of the plasmid to pha-1 situated between dal-1 and purB33 for rrnE and to thiA78 situated between glyB133 and re-12 for rrnD. All seven integration events that led to the loss of unique ribosomal BclI fragments can now be assigned to known rrn operons.

Bacillus subtilis↗

PubMedDate not supplied

Associative learning and stimulus novelty influence the song-induced expression of an immediate early gene in the canary forebrain.

To identify variables that affect immediate early gene (IEG) expression in the auditory telencephalon of songbirds, we developed a conditioning paradigm that trained adult male canaries to associate song with a mild shock. Learning of the association was measured by a bird's fear and avoidance responses. Birds exposed to paired song and shock were compared to yoked controls exposed to each stimulus alone or to both unpaired. Additional groups examined the effects of attention and stress, and of the novelty of the stimulus situation. In situ hybridization analysis of brain sections revealed an enhancement of ZENK expression in birds learning the association between song and shock above levels induced by song alone or yoked-unpaired song and shock. This effect was specifically seen in the caudomedial auditory telencephalon (NCM-HVCM). A comparison of the several control groups indicated that novelty of the song stimulus or of its pairing with shock were the main variables that predicted ZENK levels in NCM-HVCM. These observations are compatible with ZENK playing a role in the formation of song perceptual memories.

Animals↗