Aspergillus species, the primitive eukaryotic microbes were not considered of medical importance till the first report of Allergic bronchopulmonary Aspergillosis was described by Hinson et al. [1]. Subsequent severe outbreak of Turkey X disease in UK lead to identification of aflatoxin, the causative toxin as a fluorogenic polyketide compound with dicoumarin structure from Aspergillus flavus.

The morphological and taxonomical features of various Aspergillus species show some similar and some characteristic features. The medical importance of Aspergillus fumigatus, Aspergillus flavus and Aspergillus niger, also recently Aspergillus terreus is well established. The molecular complexity of Aspergillus species can be better explained by the genomic and proteomic profiles of Aspergillus species. The agricultural and economic importance of the Aspergillus species is due to their secondary metabolic pathways namely polyketide biosynthetic pathways. Aspergillus flavus and Aspergillus parasiticus through their potential to synthesise and secrete aflatoxins, contaminate a number of economically important agricultural crops such as groundnut, maize, cotton, spices and several nuts etc. However the biological role of polyketide biosynthetic pathway is not very well understood although some role in the developmental stage of the fungus is speculated [2].

The aflatoxin contamination of crops, food and feed negatively impact human and animal health. International Agency for Research in Cancer (IARC) classified aflatoxins in group 1 human carcinogens. The toxigenic, carcinogenic, terratogenic effects of aflatoxins are studied and reported from different countries. However the mechanism of action of these toxins at cellular and tissue level are necessary for a better understanding and to counter the toxic effect of these toxins.

Aspergillus species, like Aspergillus fumigates, Aspergillus flavus, Aspergillus niger and Aspergillus terreus are involved in a wide spectrum of clinical conditions such as ABPA, chronic necrotising aspergillosis, invasive aspergillosis, pulmonary hypersensitivity pneumonitis etc. Several immunodominant allergens, antigens, virulent factors are implicated in causing immunological reactions and clinical conditions. Host pathogen interaction studies in allergic and invasive diseases of aspergillosis established the innate role of lung surfactant proteins and their potential therapeutic use [3]. Besides a plethora of macromolecules, the causative organisms also secrete highly versatile polyketide toxins. A number of polyketide based biologically active, pharmaceutically important compounds are characterised so far. The biotechnological importance of these compounds are already being exploited with respect to A. niger, A. terreus, A. oryzae etc. Industrial importance of A. terreus is due to its potential to secrete statins, the first commercially available cholesterol lowering agent.

Contamination of a wide variety of agricultural crops, food and feed by aflatoxins is continuously being reported from different parts of the world. Food and Agricultural Organisation of the world estimates an approximately 25% of the world food crops are contaminated of which aflatoxin B1 is the major toxin. Based on scientific evidence of the carcinogenicity and toxicity of aflatoxins, USDA and FDA set cut of values of 20 ppb on foods. This scenario poses a major global scientific challenge for understanding the aflatoxin biosynthesis in order to develop preventive and management strategies for the toxigenic fungus and the toxin. Similarly specific, sensitive and affordable commercial diagnostic reagents are a necessity today for prevention and management of Aspergillus related diseases in humans and animals [4, 5].

Above challenges are being countered with the current knowledge of genomic and proteomic aspects of Aspergilli. Understanding on the aflatoxin biosynthetic pathway provides opportunities to explore novel polyketides of clinical and pharmaceutical importance for the benefit of mankind. However the goldmine of secondary metabolites of Aspergilli, basically polyketide compounds need to be further explored using advances in genetic manipulations.

Aflatoxin biosynthetic genes are organised in a 75 kb gene cluster in A. flavus and A. parasiticus along with transcription regulators. Although such gene clusters are present in some of the Asperillus species such as A. oryazae and A. sojae etc., aflatoxins are not synthesised by these species. In fact these species are being used in food industries and biotechnological production of industrially important compounds for several years.

In view of the hazardous impact of aflatoxigenic fungi on human health and agricultural crops, it is necessary to understand few important aspects of these toxins. Now genome sequencing data of several important Aspergillus species is available in public domain. Several studies are in progress to have a deeper insight into these important class of microbes. It is interesting to note some of the atoxigenic isolates of Aspergillus can limit the growth of aflatoxigenic isolates and function as biocontrol agents or biopesticides in the field against disease [6].

However in coming years we can anticipate effective methods of prevention and management of Aspergillus related diseases, aflatoxigenic fungi and aflatoxins in the world for improved quality of life. Further, the biotechnological potential of Aspergillii can be exploited better for the benefit of humans.