Paterson, R. R. M.

Mycological Research

Universidade do Minho: RepositoriUM

Mycological Research News1This issue of Mycological Research News features : In this issue; The coronomycin producer: a case of mistakenidentity?; Long-range self-organization in Dictyostelium ; and Resistance variation in natural pathosystems.Thirteen research papers are included in this part, seven concerning the phylogenetic relationships of plant pathogens:a new invasive Phytophthora on trees, variation and mating systems in P. ramorum, the status of the Microdochium nivalevarieties, the position of Pseudocercospora cladosporioides on olives, Verticillium s. lat., an ancestral powdery mildew, anda consideration of Sawadaea spp. along with their maple hosts. Other papers report on parthensomes in corticioid fungi,collembola grazing, the cultivation of Cordyceps unilateralis, genetic diversity in Entomophaga maimaiga, the gold contentof macromycetes, and a fossil Aspergillus species from Tertiary amber.The following new scientiﬁc names are introduced: Caespitotheca gen. nov. ; Aspergillus collembolorum, andPhytophthora kernoviae spp. nov. ; and C. forestalis (syn. Uncinula forestalis), and Microdochium majus (syn. Fusariumnivale var. majus) combs. nov.doi:10.1017/S0953756205213692IN THIS ISSUEThe ﬁrst two papers concern Phytophthora specieswhich are important pathogens of trees and orna-mentals. The new species P. kernoviae described fromsouth-west England causes bleeding lesions on beechand stem necrosis of rhododendron (pp. 853–859). Inaddition, new information on the morphology andmating behaviour of the severe pathogen P. ramorum,causal agent of sudden oak death in North America butalso present on a range of trees and ornamental shrubsin Europe, is presented based on studies of strains fromEurope and North America. All but one Europeanisolate belonged to mating type A1, while A1 and A2mating types were both well-represented in NorthAmerica; some morphological diﬀerences were alsoobserved (pp. 860–871).Microdochium nivale has long been recognized ashaving two varieties, var. majus and var. nivale. Now,phylogenetic analysis of sequences of the EF-1 alphagene, leave no doubt that the varieties merit recognitionat species rank, a decision supported by diﬀerences inthe sizes and septation of the conidia and also inpathogenicity (pp. 872–880). Molecular phylogeneticstudies using three genes show that Pseudocercosporacladosporioides, causal agent of Cercospora leaf spot ofolives, is correctly placed in that genus; further, thepopulations are genetically rather homogenous, at leastin Spain, suggesting spraying may be eﬃcacious incontrolling the disease (pp. 881–888). Molecular andimmunochemical studies on 12 species placed inVerticillium s. lat. support the revised classiﬁcationsinto diﬀerent genera, and crossed electrophoresesclarify the relationships of Verticillium s. str. speciesand also support the recognition of V. longisporum asa separate species (pp. 889–902). Amongst the pow-dery mildews, molecular phylogenetic studies usingsequences from three rDNA regions show thatUncinulaforestalis is ancestral and the divergence may haveoccurred in the late Cretaceous; the new genericname Caespitotheca is introduced for the species(pp. 903–911). In addition, molecular phylogeneticstudies on Sawadaea species placed them in sevenclades, correlated with diﬀerent sections of the hostgenus Acer and two geographical groupings; asthe radiations in Acer occurred before those ofSawadaea, it is suggested that some of the speciesmay have jumped onto maples from other hosts(pp. 912–922).Septal ultrastructure is a key character in under-standing phylogenetic relationships of basidiomycetesin particular. Electron microscopical studies of sevencorticioid fungi showed all to have perforate parenthe-somes, indicating that they do not belong to thecantharelloid or hymenochaetoid clades, and thatan earlier report of imperforate parenthosomes inPhanerochaete was incorrect (pp. 923–926).1 MycologicalResearchNews is compiled byDavidL.Hawksworth,Executive Editor Mycological Research, The Yellow House, CalleAguila 12, Colonia La Maliciosa, Mataelpino, ES-28492 Madrid,Spain. (tel/fax: [+34] 91 857 3640; e-mail : myconova@terra.es), towhom suggestions for inclusion and items for consideration should besent. Unsigned items are by the Executive Editor.Mycol. Res. 109 (8): 849–851 (August 2005). f The British Mycological Society 849Printed in the United Kingdom.The eﬀects of grazing of a collembolan onHypholomafasciculare have been examined experimentally onwood blocks; coverage was drastically reduced andfewer mycelial cords were formed (pp. 927–935). Acollembolan of Tertiary age entombed in Baltic amberhas been found to be heavily infected by an Aspergillusspecies which is described as new (pp. 956–960).Macromycetes have been analyzed for their contents ofnumerous metals, but gold is rarely considered; ananalysis of material of 89 species of ectomycorrhizaland saprobic fungi found the highest values in eachcategory in Boletus edulis and Morchella esculenta,respectively (pp. 951–955). A method to facilitate thecultivation of Cordyceps unilateralis, which producesanti-malarial red naphthoquinones, has been devel-oped (pp. 936–940). In the entomopathogenEntomophaga maimaiga, which is speciﬁc to gypsymoth, AFLP analyses show the original Asian popula-tions to be the most polymorphic, with few polymor-phic loci occurring in North America – a resultconsistent with the species being introduced there(pp. 941–950).doi:10.1017/S0953756205223699THE CORONOMYCIN PRODUCER : A CASE OF MISTAKEN IDENTITY?A mistake is revealed in the paper of Ezra et al. (2004)where an obvious Penicillium is called a Streptomyces.It is diﬃcult to believe that this could be the case, and itgives me no pleasure in it being highlighted. However,‘ for the sake of science’ it is important that it is. This isclearly of relevance where secondary metabolites ofhuge potential signiﬁcance are involved such as theso-called coronamycins. In addition, these reportsinﬂuence which organisms are investigated for naturalproduct discovery. A number of important additionalissues are raised. For example, the crucial role oftaxonomic specialists to natural product discovery, andover-reliance on PCR methodology.I have discussed this case with other experts fromboth sides of the mycological and bacteriologicalfence, and we all agree that the organism is: (1) not aStreptomyces ; and (2) a Penicillium. However, closeexamination of the published images reveals someactinomycete-like bacterial ﬁlaments in the background.The culture was evidently mixed, so it is unclear if thecoronamycins were produced by the fungus, the bac-terium, both, or partly by one and then modiﬁed bythe other. Obviously the cultures were not puriﬁedby the use of appropriate media. This case demon-strates the importance of having taxonomists check thepurity of cultures, although the scale of this mistake islarger than usual. Strobel’s defence (Strobel, Ezra &Castillo 2004), based on Gram staining and nuclearobservations, is not convincing as the results wereambiguous, and the stain was not devised for fungiin any case.Caveletti & Monciardini (2004) were also convincedthat the organism in question is not what was claimed,and attention has been drawn to other biochemicalmethods that can be used to distinguish fungi fromother organisms (Paterson 2005). Now that it is realizedthat Ezra et al.’s cultures may have contained ‘ invis-ible ’ bacterial contaminants, DNA from those mayhave been inadvertently ampliﬁed by PCR, so generat-ing bogus PCR results with respect to the verticillatefungus present. The problem of contaminants andmisidentiﬁcations in fungal DNA sequence databanksis known, and has been the subject of recent debateelsewhere (Hawksworth 2004). The key to resolvinguncertainties such as that of the coronamycin producingorganism(s) is the deposit of voucher cultures in publicfungal genetic resource collections so they can bechecked by other researchers (Ryan & Smith 2004).Sadly, in this case cultures were only deposited in‘Montana State University Mycological culture collec-tion’, where Ezra et al. are based, and subcultures arenot being made available because of the potentialeconomic value of the strain. In response to my requestfor a culture, Gary Strobel (pers. comm.) commented:‘Unfortunately, the p-25 organism is licensed andpatented to a company in Calif [sic !] and I am notat liberty to freely send the isolate to anyone otherthan the company’. More speciﬁc identiﬁcation of thetwo organisms present is therefore impossible at thistime.Perhaps journals will need to specify the publiccollections in which vouchers must have been depositedprior to papers being accepted for publication toresolve this pernicious problem; futher, researchersmust decide whether they want to place their work inthe public domain through publication in refereedjournals, or make them available on an exclusive basisto a particular company for commercial exploitation;they cannot have it both ways.Cavaletti, L. & Monciardini, P. (2004) Congruence between strainmorphology and the 16S rRNA gene sequence. Microbiology 150 :3093–3094.Ezra, D., Castillo, U. F., Strobel, G. A., Hess, W. M., Porter, H.,Jensen, J. B., Condron, M. A. M., Teplow, D. B., Sears, J.,Maranta, M., Hunter, M., Weber, B. & Yaver, D. (2004)Coronamycins, peptide antibiotics produced by a verticillateStreptomyces sp. (MSU-2110) endophytic on Monstera sp.Microbiology 150 : 785–793.Hawksworth, D. L. (2004) ‘Misidentiﬁcations’ in fungal DNAsequence databanks. New Phytologist 161 : 13–15.Paterson, R. R. M. (2005) Fungus or bacterium and vice versa?Microbiology 151 : 641.Mycological Research News 850Ryan, M. J. & Smith, D. (2004) Fungal genetic resource centres andthe genomic challenge. Mycological Research 108 : 1351–1362.Strobel, G. A., Ezra, D. & Castillo, U. (2004) A question concerningthe identity of Streptomyces sp. MSU-2110. Microbiology 150 :3094–3096.R. Russell M. PatersonMicoteca de Universidade do Minho, Centro de EngenhariaBiologica, Campus de Gualtar, 4710-057 Braga, Portugal.E-mail : russell.paterson@deb.uminho.ptdoi:10.1017/S0953756205233695LONG-RANGE SELF-ORGANIZATION IN DICTYOSTELIUMJust how the separate amoeboid cells of the slime-mould Dictyostelium discoideum organize themselvesinto multicellular structures has long fascinated devel-opmental biologists. It has been known that nutrient-deprived amoebae aggregate as a result of chemicalattraction (chemotaxis). The chemotaxis is throughwaves of adenosine 3k5k-cyclic monophosphate (cyclicAMP, cAMP) relayed from cell to cell, cores of out-wardly rotating spiral waves self-organizing. However,the control mechanism for the system was unknown.Now, using seven mutants in the cAMP/protein kinaseA pathway, Sawai, Thomason & Cox (2005) have beenable to shed new light on this fascinating phenom-enon. The mutants exhibited periodic signalling, butdid not develop long-range self-organizing territories,and numerous separate spiral cores or cells were pro-duced; the development of the cores is well-illustratedphotographically and in a supplementary video avail-able on-line. The regA and erkB mutants displayedaround two- and four-fold increases in the number ofsingularities, respectively. The chemotaxic wavesarising from diﬀerent sources ‘collide and anihilateeach other before they can propagate very far ’, sopreventing normal self-organization.This study is claimed to be the ﬁrst amongst livingorganisms demonstrating at the genetic level spon-taneous symmetry-breaking in a self-organizing sys-tem. It is speculated that similar autoregulatorysystems may operate in systems as disparate as heartmuscle to prevent deleterious occurrences of spiralwaves. Another example of the potential value of fungias model systems for investigating fundamental bio-logical processes, as stressed in Mycological Researchlast year (Gow 2004).Gow, N. A. R. (2004) New angles in mycology: studies in directionalgrowth and directional motility. Mycological Research 108 : 5–13.Sawai, S., Thomason, P. A. & Cox, E. C. (2005) An autoregulatorycircuit for long-range self-organization in Dictyostelium cell popu-lations. Nature 433 : 323–326.doi:10.1017/S0953756205243691RESISTANCE VARIATION IN NATURAL PATHOSYSTEMSNatural host-pathogen systems have received scantattention fromplant pathologists andothermycologists,the pioneering work of Jeremy J. Burdon and co-workers being a notable exception (e.g. Burdon 1987,Thrall & Burdon 2000). Now a study has been carriedout on the Plantago lanceolata – Podosphaera planta-ginis pathosystem in south-west Finland where the hostpopulations are isolated and only a small proportionof the populations is generally infected by the pow-dery mildew at any one time (Laine 2004). During thethree-year study, the fungus infected only 2–5% ofthe populations, and some were infected one year andnot the next, with new infections also occurring.Inoculation experiments were conducted using fourisolates of the fungus and revealed 16 resistant pheno-types amongst 64 plants tested. Some populationsbelong to a single resistance type, while in others onlyhalf showed identical resistance responses. No associ-ation between resistant populations and geographicallocation was found. The author suggests that the highlevels of resistance in the host populations retards thespread of the fungus and so decreases the possibility ofregional epidemics. It will be interesting to see whetherthis proves to be general model for natural pathosys-tems where fungus and host have co-existed forextended periods of time.Burdon, J. J. (1987) Diseases and Plant Population Biology.Cambridge University Press, Cambridge, UK.Laine, A.-L. (2004) Resistance variation within and among hostpopulations in a plant-pathogen metapopulation: implicationsfor regional pathogen dynamics. Journal of Ecology 92 : 990–1000.Thrall, P. H. & Burdon, J. J. (2000) Eﬀect of resistance variation in anatural plant host-pathogen metapopulation on disease dynamics.Plant Pathology 49 : 767–773.Mycological Research News 851

The coronamycin producer: a case of mistaken identity?

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The coronamycin producer: a case of mistaken identity?

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