Maria Diaz-Torres

Identification and cloning of a mobile transposon fromAspergillus niger var.awamori

Aspergillus niger var.awamori contains multiple copies of a transposable element, Vader. This element was detected as a 437-bp insertion in four independently isolated spontaneous mutants of theniaD (nitrate reductase) gene. The Vader element is present in approximately 15 copies in bothA. niger var.awamori andA. niger. A single copy of Vader was detected from only one of the two laboratory strains ofA. nidulans which were also examined. Insertion of the Vader element into theniaD gene ofA. niger var.awamori caused a 2-bp duplication (TA) of the target sequence. The Vader element is flanked by a 44-bp inverted repeat. The genetic stabilities of the inserted Vader elements atniaD were examined by studying reversion frequencies resulting in colonies able to grow on nitrate as a sole nitrogen source. MutantsniaD392 andniaD436 reverted at a frequency of 9x10-3 and 4x10-2, respectively. Two of the mutants,niaD587 andniaD410, reverted at a lower frequency of 6x10-4.

Proteome analysis of biofilms: growth of Bacillus subtilis on solid medium as model.

Publisher Summary Bacillus subtilis mutant strains that show interesting phenotypes during growth on a solid medium compared to isogenic parental strains have been isolated. For some of these strains, such phenotypic differences have been difficult to detect in liquid media. Strains that are not readily amenable to genetic analysis have also been found. Bacillus subtilis can serve as a model for biofilm studies as it is the most well studied gram-positive organism and it has a completely sequenced genome. As far as growth on a solid medium, B. subtilis has been reported to undergo differential gene expression during colony formation. Bacillus subtilis has also shown solid media-dependent sporulation phenotypes and regulatory pathways. Peptide cell signaling factors have been identified in B. subtilis that stimulate various developmental pathways associated with the beginning of the stationary growth phase.