G. San-Blas & R. A. Calderone, Eds., Caister Academic Press, Wymondham, UK, 2004, ISBN 0-9542464-7-0, 371 pp, £99.00
A male medical mycologist in the context of discussing the role of the hyphae in the pathogenesis of fungal infections once mused at a public lecture whether it was just men who presumed that you needed something long and thin to achieve penetration! Pathogenic Fungi: Structural Biology and Taxonomy is a recent collection of reviews that I thought might aim in part to address the questions around the long-debated issue of the relationship between the shape of a fungus and its ability to cause disease. Indeed, the first of the two sections is headed ‘Fungal dimorphism and pathogenicity’. In actuality, the contributions to that debate are relatively limited in this volume. There are chapters on the structure and composition of the fungal cell wall by Rafael Sentendreu and colleagues, and the biosynthesis of the fungal cell wall by Ruiz-Herrera and some of the same colleagues, which are detailed and worthy but which do not directly address issues of pathogenicity. These first two chapters are perhaps too reliant on older references (I calculated that 37% of all references were published before 1990) and whereas historical context is always important, one expects such reviews to be biased toward recent results.
Berman & Gow's excellent review of the cell cycle of fungal pathogens also only links the subject to pathogenesis briefly—in a section with the statement, that changes in cell shape or dimorphic behaviour ‘has often been considered to be an important virulence factor’. It is really left to Tamaki Cho to detail some of the very exciting work going on: characterizing how the multitude of genes involved in morphogenesis in Candida albicans also play a role in virulence. For example, how mutants in the proteinase genes SAP4, 5 and 6 and the septin proteins CDC10 and 11 produce hyphae but have reduced invasiveness. This is starting to confirm what many had long suspected, that infection by C. albicans, at least, is the result of a complex interplay of factors of which morphogenesis per se plays only a part, and possibly a limited part. San-Blas & Nino-Vegas have written a chapter on morphogenesis in ‘Other agents of systemic mycoses’ which focuses on the endemic pathogens. Aspergillus spp. are not given specific space in this volume, which I am sure is not for lack of material. Whereas a lot of discussion in this chapter is of older data, or findings only indirectly or presumed to be related to pathogenesis, the roles of catalases and calcium binding proteins in the intracellular survival of Histoplasma capsulatum make fascinating reading. Hazan & Liu's comparison of the conservation of morphogenesis in four different pathogens, including two plant pathogens, is an elegant and productive approach. It makes use of the fact that in fungi, such as the corn smut pathogen Ustilago maydis, morphology (and indeed reproductive mode) and infection are linked. San-Blas & Murgich's chapter on mathematical and computational modelling of fungal shape might have been better placed earlier in the volume, but is a welcome break from DNA-based approaches. It is nice to see Bartnicki-Garcia's wonderfully intuitive models of morphogenesis in hyphae being developed and Franklin Harold's exhortations against the trend towards the reductionism of molecular biology being given an airing.
In the second part, it is back to molecules and Mendoza & Silva's timely and informal accounts of the role of DNA analysis in the effective identification and classification or reclassification of the unculturable ‘fungi’ Lacazia loboi and Rhinosporidium seeberi. After Pneumocystis carinii came into the fungal fold, R. seeberi went out and Lobo loboi received a new name, perhaps a case of lost one, won one and drew one! Jianping Xu's chapter on fungal gene genealogy covers Cryptococcus neoformans well, but perhaps misses the opportunity to cover the work of John Taylor, Dee Carter and many others on Histoplasma and Coccidioides. The account by Prieto and others on the alkali-extractable and water-soluble polysaccharides (F1SS) that concluded the volume was interesting, but in places deteriorated into a list of fungal taxa and what was or was not known about their cell wall carbohydrates. Furthermore, I am not convinced that this volume was the place for no less than 10 pages of the 37 different patterns of sugar residues found in a variety of fungal cell walls.
Overall this volume was, as many such books are, a mixed bag and one to which some chapters will be turned to more often than others. The attempt to knit together morphology and new taxonomic tools was perhaps just about successful, although to be fair, it is not always possible to commission a series of chapters on perfectly complementing subjects that generate a harmonious whole. As to my initial interest in discovering the ultimate answers to the millennium-old questions about what fungal shape has to do with fungal infection, I think that I may have to wait a few more years.