Species currently classified within the cyanobacterial genus Microcoleus were determined to fall into two distinct clades in a 16S rDNA phylogeny, one containing taxa within the Oscillatoriaceae, the other containing taxa within the Phormidiaceae. The two lineages were confirmed in an analysis of the 16S-23S internal transcribed spacer (ITS) region sequences and secondary structures. The type species for Microcoleus is M. vaginatus Gomont, and this taxon belongs in the Oscillatoriaceae. Consequently, Microcoleus taxa in the Phormidiaceae must be placed in separate genera, and we propose the new genus Coleofasciculus to contain marine taxa currently placed in Microcoleus. The type species for Coleofasciculus is the well-studied and widespread marine mat-forming species Microcoleus chthonoplastes (Mert.) Zanardini ex Gomont. Other characters separating the two families include type of cell division and thylakoid structure.

Filamentous nonheterocytous cyanobacteria have been recognized as key ecosystem players in terms of soil stabilization, carbon sequestration, and water retention. Although the ecological importance of this group is well understood, its taxonomy is understudied. Microcoleus, Schizothrix, and Leptolyngbya, the most common cyanobacterial genera reported from soils, have all been found to be polyphyletic and in need of revision. In this study, strains morphologically corresponding to M. steenstrupii were isolated from North American desert soils. This species has been found to be polyphyletic, forming several distinct clades in numerous analyses. Three desert soil strains were analysed using ecological and geographical information, detailed morphological investigations, and DNA sequence data of the 16S rRNA gene and associated 16S-23S internal transcribed spacer. On the basis of this polyphasic characterization, we concluded that they represented the genus Symplocastrum. Until now, this cyanobacterial genus was poorly understood and lacked molecular definition. A more precise description of Symplocastrum is provided, including its phylogenetic position based on 16S rRNA gene sequence. Two new species are described (S. flechtnerae, S. torsivum) and Schizothrix californica is transferred to Symplocastrum. Phylogenetic placement of Symplocastrum is a critical component of the revisionary work underway in the nonheterocytous filamentous cyanobacteria and will lead to further revisionary work in this problematic group. Furthermore, with increasing taxonomic clarification of these filamentous taxa, ecological studies will have greater resolution and accuracy.

Entamoeba histolytica is an intestinal parasite that infects 50–100 million people and causes up to 55,000 deaths annually. The transmissive form of E. histolytica is the cyst, with a single infected individual passing up to 45 million cysts per day, making cyst production an attractive target for infection control. Lectins and chitin are secreted to form the cyst wall, although little is known about the underlying membrane trafficking processes supporting encystation. As E. histolytica does not readily form cysts in vitro, we assessed membrane trafficking gene expression during encystation in the closely related model Entamoeba invadens. Genes involved in secretion are up-regulated during cyst formation, as are some trans-Golgi network-to-endosome trafficking genes. Furthermore, endocytic and general trafficking genes are up-regulated in the mature cyst, potentially preserved as mRNA in preparation for excystation. Two divergent dynamin-related proteins found in Entamoeba are predominantly expressed during cyst formation. Phylogenetic analyses indicate that they are paralogous to, but quite distinct from, classical dynamins found in human, suggesting that they may be potential drug targets to block encystation. The membrane-trafficking machinery is clearly regulated during encystation, providing an additional facet to understanding this crucial parasitic process.

Heat shock protein genes led to the discovery of mitosomes in Entamoeba histolytica, but mitosomes have not been described for any other Entamoeba species, nor have they been identified in the cyst stage. Here, we show that the distantly related reptilian pathogen Entamoeba invadens contains mitosomes, in both trophozoites and cysts, suggesting all Entamoeba species contain these organelles.