Relationship between thermotolerance and hydrophobin-like proteins in aerial conidia of Beauveria bassiana and Paecilomyces fumosoroseus as fungal biocontrol agents

• Published in: Journal of applied microbiology 2004-08, Vol.97 (2), p.323-331
• Main Authors: Ying, S.H, Feng, M.G
• Format: Article
• Language: English
• Subjects: Beauveria bassiana; Biological and medical sciences; Colony Count, Microbial; conidial thermotolerance; Electrophoresis, Polyacrylamide Gel; Formates - metabolism; Fundamental and applied biological sciences. Psychology; Fungal Proteins - physiology; Glucose - metabolism; Hot Temperature; hydrophobin‐like proteins; Hypocreales - growth & development; Hypocreales - physiology; microbial control; Microbiology; Paecilomyces - growth & development; Paecilomyces - physiology; Paecilomyces fumosoroseus; Pest Control, Biological; Starch - metabolism; Sucrose - metabolism
• ISSN: 1364-5072; 1365-2672
• DOI: 10.1111/j.1365-2672.2004.02311.x

Aims:  This study was to illustrate the relationship between the thermotolerance and the contents of hydrophobin‐like or formic‐acid‐extractable (FAE) proteins in aerial conidia of Beauveria bassiana and Paecilomyces fumosoroseus produced on rice‐based substrate. Methods and Results:  Survival indices of 11 isolates were separately assessed as a ratio of the viability of conidia after 3–150 min thermal stress at 48°C over that of unstressed conidia and fitted well to a survival model (r2 ≥ 0·97). For a given isolate, the fitted model generated an LT50, the time for 50% viability loss under the stress. The LT50s of six B. bassiana isolates (10·1–61·9 min) and five P. fumosoroseus isolates (2·8–6·2 min) were correlated (r2 = 0·81) with FAE protein contents (6·9–23·4 μg mg−1). The survival indices of a fixed B. bassiana isolate after 45‐min thermal stress at 48°C were also correlated to the FAE protein contents from conidia produced on glucose‐, sucrose‐, or starch‐based substrate (0·79 ≤ r2 ≤ 0·86). Three bands of 12·0, 15·0 and 17·5 kDa were recognized from SDS‐PAGE profiles of protein extracts from different isolates or from the fixed isolate grown on the three carbon sources, but the 12 kDa was less likely related to the thermotolerance. Conclusions:  Approximately 80% of variability in conidial thermotolerance was attributed to either 15·0‐ or 17·5‐kDa FAE protein or both. Significance and Impact of the Study:  The relationship between conidial thermotolerance and FAE protein contents implicates a new way to search for fungal biocontrol agents with more thermotolerance and environmental persistence.