The spo-87 mutation is one of two sporulation mutations originally used to define the spUJ locus of Bacillus subtiIis. We now show that it blocks sporulation after completion of prespore engulfment (stage 111). Surprisingly, the operon is expressed vegetatively, probably from a @*-dependent promoter, and its expression is shut down at the transcriptional level at about the onset of sporulation. DNA sequencing reveals that the locus defined by sp0-87, which we now designate spIIIJ, consists of a bicistronic operon. However, only the first gene is essential for sporulation; the function of the second cistron is cryptic. The predicted SpoIIIJ product has an M, of 29409. It probably forms a lipoprotein and is rich in basic and hydrophobic amino acids. Mutations in spoIIIJ abolish the transcription of prespore-specific genes transcribed by the nC form of RNA polymerase but not transcription of the spoIIIG gene encoding oc. The SpoIIIJ product could be involved in a signal transduction pathway coupling gene expression in the prespore to events in the mother cell, or it could be necessary for essential metabolic interactions between the two cells.

Studies of developmental biology are often facilitated by diagram “models” that summarize the current understanding of underlying mechanisms. The increasing complexity of our understanding of development necessitates computational models that can extend these representations to include their dynamic behavior. Here we present a prototype model of C. elegans vulval precursor cell fate specification that represents many processes crucial for this developmental event but that are hard to integrate using other modeling methodologies. We demonstrate the integrative capabilities of our methodology by comprehensively incorporating the contents of three seminal papers, showing that this methodology can lead to comprehensive models of developmental biology. The prototype computational model was built and is run using a language (Live Sequence Charts) and tool (the Play-Engine) that facilitate the same conceptual processes biologists use to construct and probe diagram-type models. We demonstrate that this modeling approach permits rigorous tests of mutual consistency between experimental data and mechanistic hypotheses and can identify specific conflicting results, providing a useful approach to probe developmental systems.

This study evaluates an iterative design experiment in an introductory lab course in which instruction was restructured and uncertainty in lab activities was increased. It is proposed that these changes to the rhetorical context helped motivate and shape more authentic engagement in scientific argumentation.

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The spoIIA locus of Bacillus licheniformis was cloned into the phage vector 4105J9; selection was based on the ability of the clone to complement mutations in both the first and the last of the spoIIA genes of B. subtilis. The B . licheniformis DNA was subcloned into M13 and sequenced; it includes three genes of identical lengths to those of B. subtilis. The average interspecies difference in nucleotide sequence is 24%; C occurs at the third position of codons 55% more often in the B. fichenvormis than in the B . subtilis sequence. The average difference in predicted amino acid sequence is 11 %, but the distribution of these differences is far from random, and there are several long stretches of amino acid sequence that are identical in the two organisms. The distribution of non-conservative amino acid changes between the species is also strikingly non-random; no such changes are found in those regions in which missense mutations are known in B. subtilis. Each species has an open reading frame 5' of the spoIIAA gene, but the predicted amino acid sequence, and the distribution of differences between the two species in both nucleotides and predicted amino acids, suggest that these open reading frames are not expressed. Both species have regions 3' of the open reading frames which resemble rhoindependent terminators of transcription, but that in B. licheniformis is longer and could form a more elaborate secondary structure than that in B. subtifis.