Molecular phylogeny of the higher and lower taxonomy of the Fusarium genus and differences in the evolutionary histories of multiple genes

<p>Abstract</p> <p>Background</p> <p>Species of the <it>Fusarium </it>genus are important fungi which is associated with health hazards in human and animals. The taxonomy of this genus has been a subject of controversy for many years. Although many researchers have applied molecular phylogenetic analysis to examine the taxonomy of <it>Fusarium </it>species, their phylogenetic relationships remain unclear only few comprehensive phylogenetic analyses of the <it>Fusarium </it>genus and a lack of suitable nucleotides and amino acid substitution rates. A previous stugy with whole genome comparison among <it>Fusairum </it>species revealed the possibility that each gene in <it>Fusarium </it>genomes has a unique evolutionary history, and such gene may bring difficulty to the reconstruction of phylogenetic tree of <it>Fusarium</it>. There is a need not only to check substitution rates of genes but also to perform the exact evaluation of each gene-evolution.</p> <p>Results</p> <p>We performed phylogenetic analyses based on the nucleotide sequences of the rDNA cluster region (rDNA cluster), and the β-tubulin gene (<it>β-tub</it>), the elongation factor 1α gene (<it>EF-1α</it>), and the aminoadipate reductase gene (<it>lys2</it>). Although incongruence of the tree topologies between <it>lys2 </it>and the other genes was detected, all genes supported the classification of <it>Fusarium </it>species into 7 major clades, I to VII. To obtain a reliable phylogeny for <it>Fusarium </it>species, we excluded the <it>lys2 </it>sequences from our dataset, and re-constructed a maximum likelihood (ML) tree based on the combined data of the rDNA cluster, <it>β-tub</it>, and <it>EF-1α</it>. Our ML tree indicated some interesting relationships in the higher and lower taxa of <it>Fusarium </it>species and related genera. Moreover, we observed a novel evolutionary history of <it>lys2</it>. We suggest that the unique tree topologies of <it>lys2 </it>are not due to an analytical artefact, but due to differences in the evolutionary history of genomes caused by positive selection of particular lineages.</p> <p>Conclusion</p> <p>This study showed the reliable species tree of the higher and lower taxonomy in the lineage of the <it>Fusarium </it>genus. Our ML tree clearly indicated 7 major clades within the <it>Fusarium </it>genus. Furthermore, this study reported differences in the evolutionary histories among multiple genes within this genus for the first time.</p

Mycotoxin contamination in foodstuffs and feeds-health concerns in Thailand

Many studies on mycotoxins have been carried out in various parts of the world. Thailand is one of many tropical countries to continuously encounter problems associated with mycotoxin contamination in foodstuffs and animal feed, and faces health concerns associated with humans and animals. This review has gathered background information from mycotoxin studies in Thailand in order to update the information on mycotoxin issues from 1967 until the present. The first report of mycotoxin contamination in animal feed was published in 1983. Among the various known mycotoxins, aflatoxins (AF) have been the main concern in human foodstuffs and animal feed, followed by deoxynivalenol(DON), fumonisin (FUM) and trichothecene (T) toxins respectively, while zearalenone (ZEA) has primarily been a concern regarding animal feed in Thailand. Hepatocellular carcinoma has been reported in association with patients consuming foods contaminated with AF. In addition, the standard limit of total aflatoxin (TAF) for foodstuffs has been set at 20 μg/kg in Thailand. It is therefore necessary to improve the control strategies and regulations for all mycotoxins in human foodstuffs and animal feed in Thailand

Development of an Analytical Method for Simultaneous Determination of the Modified Forms of 4,15-Diacetoxyscirpenol and their Occurrence in Japanese Retail Food

4,15-Diacetoxyscirpenol (4,15-DAS) is a type A trichothecene mycotoxin produced by Fusarium species. Four modified forms of 4,15-DAS including 7-hydroxydiacetoxyscirpenol, 7,8-dihydroxydiacetoxyscirpenol, 4&beta;,8&alpha;,15-triacetoxy-3&alpha;,7&alpha;-dihydroxy-12,13-epoxytrichothec-9-ene and 4,15-diacetylnivalenol were purified from cultures of F. equiseti. An analytical method using a multifunctional column has been developed for the simultaneous determination of 4,15-DAS, its four modified forms, T-2 toxin, HT-2 toxin and neosolaniol in cereals. The performance of the current method was evaluated, and a total of 248 samples of five different commodities were analyzed for over two years by this method. 4,15-DAS was detected in Job&rsquo;s tears products, corn flour and azuki bean, but it was not found in wheat flour or rye flour. The four modified forms of 4,15-DAS were detected in samples of Job&rsquo;s tears products, contaminated by 4,15-DAS. This is the first report on quantification of the modified forms of 4,15-DAS in cereals

Inhibitory Activities of Blasticidin S Derivatives on Aflatoxin Production by Aspergillus Flavus

Blasticidin S (BcS) is a protein synthesis inhibitor which shows strong growth inhibitory activity against a number of microorganisms. However, BcS inhibited aflatoxin production by Aspergillus flavus without affecting its growth. In order to obtain information about the structure–activity relationship of BcS as an aflatoxin production inhibitor, BcS derivatives were prepared and their aflatoxin production inhibitory activities were evaluated. Among five derivatives, blasticidin S carboxymethyl ester, deaminohydroxyblasticidin S, and pyrimidinoblasticidin S showed inhibitory activity, while the others did not. The IC50 value for aflatoxin production of the carboxymethyl ester derivative was one-fifth of that of BcS although their antimicrobial activities were almost the same. These results indicate that the inhibitory activity of BcS against aflatoxin production was enhanced by esterification of its carboxyl group and that the carboxymethyl ester derivative might be more suitable for practical use than BcS because of the specificity of the carboxymethyl ester derivative, which inhibited aflatoxin production more than BcS