Alves Sérgio Batista, Rossi Luciana Savoi, Lopes Rogério Biaggioni, Tamai Marco Antonio, Pereira Roberto M
Departamento de Entomologia, Fitopatologia e Zoologia Agrícola, ESALQ/USP, Caixa Postal 9, Piracicaba, SP 13418-900, Brazil.
J Invertebr Pathol. 2002 Oct;81(2):70-7. doi: 10.1016/s0022-2011(02)00147-7.
Beauveria bassiana colonizes insect hosts initially through a yeast phase, which is common in some artificial liquid cultures, but not reported on artificial solid media. We describe a yeast-like phase for B. bassiana isolate 447 (ATCC 20872) on MacConkey agar and its virulence toward Diatraea saccharalis and Tetranychus urticae. The yeast-like cells of B. bassiana developed by budding from germinating conidia after 24-h incubation. Cells were typically 5-10 microm and fungal colonies were initially circular and mucoid, but later were covered with mycelia and conidia. Ability to produce yeast-like cells on MacConkey medium was relatively common among different B. bassiana isolates, but growth rate and timing of yeast-like cell production also varied. Metarhizium anisopliae and Paecilomyces spp. isolates did not grow as yeast-like cells on MacConkey medium. Yeast-like cells of B. bassiana 447 were more virulent against D. saccharalis than conidia when 10(7)cells/ml were used. At 10(8)cells/ml, the estimated mean survival time was 5.4 days for the yeast suspension and 7.7 days for the conidial suspension, perhaps due to faster germination. The LC(50) was also lower for yeast than conidial suspensions. Yeast-like cells and conidia had similar virulence against T. urticae; the average mortalities with yeast-like cells and conidia were, respectively, 42.8 and 45.0%, with 10(7)cells/ml, and 77.8 and 74.4%, with 10(8)cells/ml. The estimated mean survival times were 3.6 and 3.9 for yeast and conidial suspensions, respectively. The bioassay results demonstrate the yeast-like structures produced on MacConkey agar are effective as inoculum for B. bassiana applications against arthropod pests, and possibly superior to conidia against some species. Obtaining well-defined yeast phase cultures of entomopathogenic hyphomycetes may be an important step in studies of the biology and nutrition, pathogenesis, and the genetic manipulation of these fungi.
球孢白僵菌最初通过酵母阶段定殖昆虫宿主，这在一些人工液体培养中很常见，但在人工固体培养基上未见报道。我们描述了球孢白僵菌菌株447（ATCC 20872）在麦康凯琼脂上的酵母样阶段及其对甘蔗二点螟和二斑叶螨的毒力。球孢白僵菌的酵母样细胞在培养24小时后从萌发的分生孢子出芽发育而来。细胞通常为5 - 10微米，真菌菌落最初是圆形且呈黏液状，但后来被菌丝体和分生孢子覆盖。在麦康凯培养基上产生酵母样细胞的能力在不同的球孢白僵菌分离株中相对常见，但酵母样细胞的生长速率和产生时间也有所不同。金龟子绿僵菌和拟青霉属分离株在麦康凯培养基上不会以酵母样细胞形式生长。当使用10⁷个细胞/毫升时，球孢白僵菌447的酵母样细胞对甘蔗二点螟的毒力比分生孢子更强。在10⁸个细胞/毫升时，酵母悬浮液的估计平均存活时间为5.4天，分生孢子悬浮液为7.7天，这可能是由于萌发更快。酵母悬浮液的半数致死浓度（LC₅₀）也比分生孢子悬浮液低。酵母样细胞和分生孢子对二斑叶螨的毒力相似；使用10⁷个细胞/毫升时，酵母样细胞和分生孢子的平均死亡率分别为42.8%和45.0%，使用10⁸个细胞/毫升时分别为77.8%和74.4%。酵母和分生孢子悬浮液的估计平均存活时间分别为3.6天和3.9天。生物测定结果表明，在麦康凯琼脂上产生的酵母样结构可作为球孢白僵菌用于防治节肢动物害虫的有效接种物，并且可能对某些物种比分生孢子更具优势。获得明确的昆虫病原丝状真菌酵母阶段培养物可能是这些真菌生物学和营养、致病机制以及基因操作研究中的重要一步。
