Protists have divergent effects on bacterial diversity along a productivity gradient

Productivity and predation are thought to be crucial drivers of bacterial diversity. We tested how the productivity–diversity of a natural bacterial community is modified by the presence of protist predators with different feeding preferences. In the absence of predators, there was a unimodal relationship between bacterial diversity and productivity. We found that three protist species (Bodo, Spumella and Cyclidium) had widely divergent effects on bacterial diversity across the productivity gradient. Bodo and Cyclidium had little effect on the shape of the productivity–diversity gradient, while Spumella flattened the relationship. We explain these results in terms of the feeding preferences of these predators.     

Chlorophyllb-containing oxygenic photosynthetic prokaryotes: Oxychlorobacteria (Prochlorophytes)

The major ultrastructural and pigment characteristics of three chlorophyllb-containing photosynthetic prokaryote genera,Prochloron, Prochlorothrix, andProchlorococcus, are summarized. Aspects of their ecology are reviewed, as are also the major findings of comparisons among the three genera, and between them and the cyanobacteria, based on analyses of nucleotide sequences. The information summarized is discussed to assess how closely the three genera are related and whether they form a natural taxonomic grouping within the cyanobacteria. It is concluded that, although much of the evidence points to substantial differences among the three genera, the convenience of keeping them together as a group, namely, Oxychlorobacteria (formerly Prochlorophyta), outweighs certain inconsistencies revealed by analysis of a range of objective criteria. Current views on the possible significance of the group to considerations of the evolution of green chloroplasts are also presented.     

WHO Expert Committee on Biological Standardization: highlights of the 50th meeting, October 1999.

Biological medicines, which include vaccines, blood products and biological therapeutics, have historically played a dominant role in improving world health and are expected to make an increasingly important contribution to public health in the 21st century. Recent scientific and biotechnological developments have opened the way to novel products, new production methods and to highly sensitive assay procedures. However, the nature of biologicals, and especially new vaccines, blood products and therapeutics, raises particular questions regarding their standardization and quality control. These relate both to efficacy and to safety not only for the individual recipient but also for the population at large. Such advances highlight the complex issues surrounding standardization and control of biologicals, issues that need to be addressed on an international level.