Ecology and Population Biology of Aflatoxigenic Fungi in Soil

Soil serves as a reservoir for Aspergillus flavus and A. parasiticus, fungi that produce carcinogenic aflatoxins in agricultural commodities. Populations in soil are genetically diverse and individual genotypes show a clustered distribution pattern within fields. Surveys over large geographic regions suggest that climate and crop composition influence species density and aflatoxin‐producing potential. Aflatoxigenic fungi reside in soil as conidia, sclerotia and hyphae, which act as primary inocula for directly infecting peanuts or for infecting aerial crops (corn, cottonseed, tree nuts) through wind and insect dispersal. Infected crops periodically replenish soil populations during drought years.     

Comparison of the side-needle and knife techniques for inducing Aspergillus flavus infection and aflatoxin accumulation in corn hybrids

Evaluation of corn genotypes for resistance to aflatoxin accumulation has evolved over the past 30 years. Inoculation techniques have been developed to ensure that plants are exposed to Aspergillus flavus and resistant genotypes can be identified. We compared two inoculation techniques (side needle and knife) and different inoculation rates in Georgia and Mississippi. The relative performance of side-needle and knife inoculation techniques did not change or interact significantly across site years, suggesting that both the needle and knife are consistent inoculation techniques for discriminating between resistant and susceptible corn hybrids at the Mississippi State and Tifton locations.     

肾盂黄曲霉菌感染一例

黄曲霉菌属于曲霉科,是仅次于烟曲霉菌的第二大曲霉病诱发菌,多发于肺、鼻窦、眼,肾盂感染罕见.本例患者因黄曲霉菌感染肾盂诱发急性肾衰竭.使用两性霉素B局部及全身用药,治疗效果好,肾功能恢复.     

马尔尼菲篮状菌致病机制相关分子研究进展

马尔尼菲篮状菌是一种重要的条件致病菌,主要流行于泰国、印度、中国大陆、中国香港、中国台湾、越南等亚洲热带地区。过往其主要感染人群为HIV患者,而近几年,非HIV患者感染在逐年增多。马尔尼菲篮状菌的致病性与形态的转变、黑色素的形成、生化代谢产物的产生等相关。近几年,有关马尔尼菲篮状菌致病机制,尤其是调控形态转化的基因有较深入的研究。本文对近年来马尔尼菲篮状菌相关毒力基因尤其是在代谢产物、色素形成、形态学转变上的调控基因进行的总结及评述。     

Integration of Crop Management and Genetics for Control of Preharvest Aflatoxin Contamination of Corn

Aflatoxin contamination of corn in the field is influenced by several factors. In the southern U.S., insect populations are usually large every year. Drought caused by warmer and drier than normal weather is conducive to A. flavus infection and aflatoxin contamination of corn, Zea mays L. When loose‐husked hybrids are used in the southern U.S., they accentuate insect damage and aflatoxin contamination. The development and breeding of “southern‐type” hybrids is essential for control of preharvest aflatoxin contamination. Molecular biotechnology may make an impact on tackling the complexity of preharvest aflatoxin contamination of corn. Integration of crop management tactics and genetic strategies, conventional or molecular, may constrain the problem and help southern corn growers produce a quality, profitable crop.     

Unlocking the Secrets Behind Secondary Metabolism: A Review of Aspergillus flavus from Pathogenicity to Functional Genomics

Aspergillus flavus has received a considerable amount of attention due to its ability to produce aflatoxin, a secondary metabolite that is both immunosuppressive and carcinogenic to animals and humans. Research on aflatoxin over the last 40 years has made it one of the best studied fungal secondary metabolites. In spite of the large volume of research in this area, many unanswered questions remain concerning the genetic regulation of aflatoxin production and the molecular signals that intimately associate the synthesis of aflatoxin with specific environmental and nutritional conditions. It is anticipated that the tools now available in the field of genomics will build upon our existing knowledge and provide answers to some of these questions. Complete genome sequences are now available for a number of fungal species that are closely related to A. flavus. This information can be used along with current genomic analyses in A. flavus to more closely examine the biosynthesis and regulation of secondary metabolism. The intent of this review is to summarize the large body of knowledge that exists from many years of research on A. flavus, with the hope that this information in the light of new genomic studies may bring scientists closer to unraveling the web of regulatory circuits that govern aflatoxin biosynthesis. Specifically, scientific findings in the following areas will be presented: classification and phylogenetic analyses of A. flavus, population biology, ecology and pathogenicity in agricultural environments, classical genetics including linkage group and mutant analyses, gene clusters, regulation of aflatoxin biosynthesis, and genomics.     

南极海绵共附生真菌Talaromyces sp. HDN1820200次级代谢产物研究

目的对南极海绵共附生来源真菌Talaromyces sp.HDN1820200的次级代谢产物进行研究。方法对菌株发酵液粗提物利用柱层析(VLC,ODS)、凝胶分子筛(LH-20)以及半制备高效液相(MPLC)等方法进行次级代谢产物的分离纯化;利用现代波谱学方法(核磁共振NMR、圆二色谱ECD、红外光谱IR等)对化合物进行结构鉴定。结果分离鉴定了8个单体化合物:(2E,4E,6E)-4-methyldodeca-2,4,6-trienoic acid(1)、(2E,4Z,6E)-4-methyldodeca-2,4,6-trienoic acid(2)、Herbaridine B(3)、Kasanosin C(4)、Citrinolactone A(5)、Citreorosein(6)、1,5,8-trihydroxy-3-(hydroxymethyl)anthracene-9,10-dione(7)和Rugulosin B(8)。结论从南极海绵来源真菌Talaromyces sp.HDN1820200中分离得到了化合物1~8,其中化合物1和2为新化合物,属于脂肪酸类化合物,无明显细胞毒活性。     

Mimosa tenuiflora Aqueous Extract: Role of Condensed Tannins in Anti-Aflatoxin B1 Activity in Aspergillus flavus

Aflatoxin B1 (AFB1) is a potent carcinogenic mycotoxin that contaminates numerous crops pre- and post-harvest. To protect foods and feeds from such toxins without resorting to pesticides, the use of plant extracts has been increasingly studied. The most interesting candidate plants are those with strong antioxidative activity because oxidation reactions may interfere with AFB1 production. The present study investigates how an aqueous extract of Mimosa tenuiflora bark affects both the growth of Aspergillus flavus and AFB1 production. The results reveal a dose-dependent inhibition of toxin synthesis with no impact on fungal growth. AFB1 inhibition is related to a down-modulation of the cluster genes of the biosynthetic pathway and especially to the two internal regulators aflR and aflS. Its strong anti-oxidative activity also allows the aqueous extract to modulate the expression of genes involved in fungal oxidative-stress response, such as msnA, mtfA, atfA, or sod1. Finally, a bio-guided fractionation of the aqueous extract demonstrates that condensed tannins play a major role in the anti-aflatoxin activity of Mimosa tenuiflora bark.     

An unusual case of endocarditis in a dialysis patient.

A 53-year-old male on haemodialysis presented with 1 month ofright-sided pleuritic chest pain, low-grade fever and haemoptysis.He was on haemodialysis via arteriovenous fistula in the rightforearm for 3 years. He had recently completed interferon treatmentfor chronic hepatitis C. He had a 30-pack-year smoking history.Medications at presentation included moxifloxacin