Debra A. Waters

Identification of genes involved in utilization of acetate and acetoin in Bacillus subtilis

The Bacillus subtilis ccpA gene has previously been shown to be involved in repression of amyE expression when cells are grown in excess glucose. The region of the B. subtilis chromosome downstream from ccpA was characterized to determine if additional genes involved in carbohydrate metabolism were present. Two open reading frames that exhibited sequence similarity to the Escherichia coli and B. subtilis motA and motB motility genes were found immediately downstream from ccpA; disruption of this region had no effect on growth, sporulation or motility. Two divergent transcriptional units containing the acsA and acuABC genes were also found in this region. The acsA gene encodes acetyl‐CoA synthetase, and inactivation of this gene resulted in loss of the ability to utilize acetate as a carbon source for growth or sporulation. Disruption of the acuABC genes resulted in poor growth or sporulation on acetoin or butanediol. The acsA and acuABC promoter sequences were identified by primer extension, and are in close proximity. Two sequences resembling the amyO regulatory target site necessary for glucose repression of amyE were identified in the acsA‐acuABC promoter regions.

Molecular Systematics of the Green Algae

Ranging from unicells to complex “plantlike” organisms that are adapted to habitats from subaerial or terrestrial to freshwater or marine, the green algae represent a diversity of life forms that offer a daunting challenge in the search for shared morphological characters. The ultrastuctural techniques that fueled the 1970s and early 1980s revolution in algal systematics revealed a suite of new morphological characters, but many were not global (i.e., present in all of the taxa). Controversy over the interpretation of the importance of ultrastructural features (e.g., of cell division versus flagellar apparatus) led to conflicting hypotheses. Also, different researchers studied different details of different taxa, and thus a data matrix reporting a complete set of morphological and ultrastructural characters over a wide range of algal taxa was not available. Thus, it is no wonder that many researchers interested in unraveling the mystery of green algal phylogeny embraced molecular systematics, hoping that its early promise of relatively simple access to ample global characters would lead, finally, to a “true” phylogeny. The extent to which this promise has been fulfilled, or is likely to be fulfilled, is the subject of this chapter.

Phragmoplast-mediated cytokinesis in trentepohlia : results of TEM and immunofluorescence cytochemistry

This paper reports transmission electron microscopy (TEM) and immunofluorescence evidence for phragmoplast-mediated cytokinesis in the green alga, Trentepohlia (Ulvophyceae, Chlorophyta). This type of cytokinesis is normally found only in land plants and some charophycean green algae. Earlier TEM work documented a phragmoplast in another trentepohlialean alga, Cephaleuros. Numerous molecular studies have shown that both Trentepohlia and Cephaleuros are clearly not in the charophycean (streptophyte) lineage of green algae. Also, details of vegetative cytokinesis in Trentepohlia and Cephaleuros indicate differences from the processes and structures observed in the streptophytes. Parallel evolution could be the explanation for a phragmoplast-mediated cytokinesis in both the chlorophycean Trentepohliales and the streptophyte lineage of charophycean green algae and land plants.