Life without putrescine: disruption of the gene-encoding polyamine oxidase in Ustilago maydis odc mutants.

In previous communications the essential role of spermidine in Ustilago maydis was demonstrated by means of the disruption of the genes encoding ornithine decarboxylase (ODC) and spermidine synthase (SPE). However, the assignation of specific roles to each polyamine in different cellular functions was not possible because the spermidine added to satisfy the auxotrophic requirement of odc/spe double mutants is partly back converted into putrescine. In this study, we have approached this problem through the disruption of the gene-encoding polyamine oxidase (PAO), required for the conversion of spermidine into putrescine, and the construction of odc/pao double mutants that were unable to synthesize putrescine by either ornithine decarboxylation or retroconversion from spermidine.

Mechanism of Sterigmatocystin Biosynthesis Regulation by pH in Aspergillus nidulans.

External pH constitutes one of the most important environmental factors that control growth, metabolism and differentiation in microorganisms, including fungi. We have analyzed the effect of external pH on sterigmatocystin biosynthesis in Aspergillus nidulans. It was observed in repeated experiments that alkaline pH, in opposition to acid pH, increased sterigmatocystin production and the transcript levels of aflR, the master gene that regulates expression of the sterigmatocystin cluster in A.

[Exposure to aflatoxin B1 in experimental animals and its public health significance].

The presence of AFB1 in human beings was detected in Mexico in 1996 both as a mutation of the gene p53 in hepatocellular carcinomas in Monterrey, Mexico, and as the adduct AFB1-lysine in serum from patients in Matamoros, Mexico in 2003. Aflatoxin B1 has been classified as a carcinogenic agent to humans by the International Agency for Research on Cancer. The compound is a natural contaminant produced by Aspergillus flavus and/or A.

Biodiversity of Fusarium species in Mexico associated with ear rot in maize, and their identification using a phylogenetic approach.

Fusarium proliferatum, F. subglutinans, and F. verticillioides are known causes of ear and kernel rot in maize worldwide.

Regulatory considerations of aflatoxin contamination of food in Mexico.

Aflatoxins are potent mutagenic and carcinogenic compounds produced by some strains of Aspergillus flavus, A. nomius, and A. parasiticus that are commonly present in the environment.

[Inactivation of aflatoxin B1 and aflatoxicol through traditional "nixtamalización" of corn and their regeneration by acidification of corn dough].

Objective: To ratify the effect of traditional "nixtamalización" upon aflatoxin in corn, to identify the residual compound in dough, to evaluate its toxicity, and to verify the effect of acidic treatment on the regeneration of aflatoxin.

Material And Methods: Corn with and without aflatoxin was treated separately with lime and heat to obtain two types of dough. Aflatoxin and the residual compound were quantified by high pressure liquid chromatography (HPLC) and toxicity was evaluated in eight day old chicks.

Requirement of spermidine for developmental transitions in Aspergillus nidulans.

Deletion of the spermidine synthase gene in the fungus Aspergillus nidulans results in a strain, deltaspdA, which requires spermidine for growth and accumulates putrescine as the sole polyamine. Vegetative growth but not sporulation or sterigmatocystin production is observed when deltaspdA is grown on media supplemented with 0.05-0.