Chitinolytic activity at low temperature of an Antarctic strain (A3) of Verticillium lecanii.
The chitinolytic activity of Verticillium cfr. lecanii A3, a strain isolated from continental Antarctica, was compared to those of two selected strains of Trichoderma harzianum. After 72 h of incubation at 25 degrees C in media containing chitin as the sole carbon source, all strains showed the same enzyme activity (ca. 230 mU/ml); at 15 degrees C, the levels of enzyme activity of the three strains were similar to those obtained at 25 degrees C. At 5 degrees C, in contrast, the activity of V. lecanii was ca. 4 times higher than those of both strains of T. harzianum (203 and 57 mU/ml, respectively; incubation time 144 h). The chitinase of V. lecanii, purified by preparative isoelectric focusing and ion-exchange chromatography, was shown to be a glycoprotein with apparent molecular weight of 45 kDa and isoelectric point of 4.9. The enzyme was active over a broad range of temperatures (5-60 degrees C): at 5 degrees C, its relative activity was still 50% of that recorded at 40 degrees C (optimal temperature). V. lecanii and its purified chitinase showed clear inhibitory effects on the growth of some test moulds such as Mucor plumbeus, Cladosporium cladosporioides, Aspergillus versicolor and Penicillium verrucosum: observations under the light and scanning electron microscopes revealed that growth inhibition was accompanied by mycelial damage and cell lysis.
Dipartimento di Agrobiologia e Agrochimica, University of Tuscia, Viterbo, Italy.
M
M
Fenice
L
L
Selbmann
R
R
Di Giambattista
F
F
Federici
D000864:Antarctic Regions; D000935:Antifungal Agents / Q000378:metabolism*; D001230:Aspergillus / Q000187:drug effects; D002686:Chitin / Q000378:metabolism*; D002688:Chitinases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D002963:Cladosporium / Q000187:drug effects; D003470:Culture Media; D005516:Food Microbiology; D006863:Hydrogen-Ion Concentration; D008855:Microscopy, Electron, Scanning; D009089:Mucor / Q000187:drug effects; D010407:Penicillium / Q000187:drug effects; D013696:Temperature; D014242:Trichoderma / Q000378:metabolism; D020172:Verticillium / Q000201:enzymology* / Q000648:ultrastructure
D000935:Antifungal Agents; D003470:Culture Media; D002686:Chitin; D002688:Chitinases