Difference in keratinase activity of dermatophytes at different environmental conditions is an attribute of adaptation to parasitism Anima Sharma, 1 Subhash Chandra 2 and Meenakshi Sharma 3 1 Department of Biotechnology, Mahatma Gandhi Institute of Applied Sciences, Jaipur, Rajasthan, India, 2 Department of Biotechnology and Allied Sciences, Jayoti Vidyapeeth WomenÕs University, Jaipur, Rajasthan, India and 3 Department of Botany, University of Rajasthan, Jaipur, Rajasthan, India Summary Dermatophytes are a group of morphologically and physiologically related moulds, which cause well-defined infection called dermatophytosis. The enzymatic ability of fungi to decompose keratin has long been interpreted as a key innovation in the evolution of animal dermatology. In the present study, keratinase activity profile among Trichophyton mentagrophytes, Trichophyton rubrum, Microsporum canis and Microsporum gypseum isolated on keratin substrates such as human hair, human nail and chicken feather at variable environmental conditions of temperature, pH and metal ions was elucidated. All the above-mentioned fungal strains were isolated from soil using To-KA-Va baiting technique and keratinolytic activity was measured spectrophotometrically. In the temperature range of 30–40 °C and slightly alkaline pH (7.0–8.0), Trichophyton produced the highest activity of keratinase. It can be presumed that high enzyme production of Trichophyton species at normal body temperature range and pH could be an attribute for obligate anthropization in some dermatophytes. Key words: Dermatophytosis, keratin, hair, nail, chicken feather, dermatophytes. Introduction In ancient times, vertebrates developed a special protein known as keratin. This protein is used by numerous groups of animals as a structural element. Due to the strength and stability of keratin, very few organisms are able to break it down and utilise it as source of nutrition. Only a few insects, bacteria, actinomycetes and fungi can use the keratin as the sole source of carbon and nitrogen. The enzymatic ability of fungi to decompose keratin has long been interpreted as a key innovation in the evolution of animal dermatology. Dermatophytes are a group of morphologically and physiologically related moulds, which cause well-defined infection called dermatophytosis; it can also be called Tinea or Ringworm. 1 Humid weather, over population and poor hygienic conditions are conducive to the growth of dermato- phytes. The dermatophytes have the ability to invade keratinized tissue (skin, hair, and nails), but are usually restricted to the non-living cornified layer of the epidermis because of their inability to penetrate viable tissue of an immunocompetent host. Acid proteinases, elastase, keratinases and other proteinases reportedly act as virulence factors. Keratinases are the key enzymes in fungal invasion of skin and have been mostly studied in dermatophyte species belonging to the Trichophyton and Microsporum genera, some pathogenic yeasts as Candida albicans and also some other fungi and bacteria. 2 Due to the fact that any fungus may incite an infectious disease in a host with altered immunity, organisms that were once harmless now have the potential to be pathogenic. 3 However, the metabolic products can cause allergic and inflammatory responses in the host. 4 The breakdown of the keratinised cells is due to the enzyme keratinase produced by these organisms. Certain strain of Microsporum and Tricho- phyton species produces enzymes, which are able to Correspondence: Dr A. Sharma, Associate Professor of Biotechnology, Department of Biotechnology, Mahatma Gandhi Institute of Applied Sci- ences, JECRC Campus, Tonk Road, Jaipur-302033, Rajasthan, India. Tel.: +91 953 037 4771. Fax: +91 141 512 2449. E-mail: dranima.biotech@gmail.com Accepted for publication 22 September 2011 Original article Ó 2011 Blackwell Verlag GmbH doi:10.1111/j.1439-0507.2011.02133.x mycoses Diagnosis,Therapy and Prophylaxis of Fungal Diseases