Differential Roles of Five Fluffy Genes (flbA-flbE) in the Lifecycle In Vitro and In Vivo of the Insect-Pathogenic Fungus Beauveria bassiana.

The fluffy genes flbA-flbE are well-known players in the upstream developmental activation pathway that activates the key gene brlA of central developmental pathway (CDP) to initiate conidiation in Aspergillus nidulans. Here, we report insignificant roles of their orthologs in radial growth of Beauveria bassiana under normal culture conditions and different stresses although flbA and flbD were involved in respective responses to heat shock and H2O2. Aerial conidiation level was lowered in the deletion mutants of flbB and flbE (~15%) less than of flbA and flbC (~30%), in which the key CDP genes brlA and abaA were repressed consistently during normal incubation. The CDP-controlled blastospore production in submerged cultures mimicking insect hemolymph was abolished in the flbA mutant with brlA and abaA being sharply repressed, and decreased by 55% in the flbC mutant with only abaA being downregulated. The fungal virulence against a model insect was attenuated in the absence of flbA more than of flbC irrespective of normal cuticle infection or cuticle-bypassing infection (intrahemocoel injection). These findings unravel more important role of flbA than of flbC, but null roles of flbB/D/E, in B. bassiana's insect-pathogenic lifecycle and a scenario distinctive from that in A.nidulans.

Production of Blastospore of Entomopathogenic Beauveria bassiana in a Submerged Batch Culture.

The principal objective of this study was to determine the optimal liquid culture conditions in shake flasks for maximal sporulation of Beauveria bassiana. The optimal initial pH for the spore production of B. bassiana using Potato Dextrose Broth was 5.2. The screening in shake flasks of carbon and nitrogen sources resulted in the identification of an optimal medium based on 3% sucrose and 1% casamino acid, with a C : N ratio of 22 : 4. Using this medium, a production level of 5.65 × 10(7) spores per ml was obtained after 5 days of culture. Using 3% corn meal, 2% corn steep powder, and 2% rice bran, the maximum spore concentration of 8.54 × 10(8)/ml was achieved 8 days after inoculation at 25℃ in a rotary shaking incubator operated at 200 rpm. This represents a yield gain of approximately 2.89 times that of pre-optimization.

Production of Blastospore of Entomopathogenic Beauveria bassiana in a Submerged Batch Culture

The principal objective of this study was to determine the optimal liquid culture conditions in shake flasks for maximal sporulation of Beauveria bassiana. The optimal initial pH for the spore production of B. bassiana using Potato Dextrose Broth was 5.2. The screening in shake flasks of carbon and nitrogen sources resulted in the identification of an optimal medium based on 3% sucrose and 1% casamino acid, with a C : N ratio of 22 : 4. Using this medium, a production level of 5.65 x 107 spores per ml was obtained after 5 days of culture. Using 3% corn meal, 2% corn steep powder, and 2% rice bran, the maximum spore concentration of 8.54 x 108/ml was achieved 8 days after inoculation at 25degrees C in a rotary shaking incubator operated at 200 rpm. This represents a yield gain of approximately 2.89 times that of pre-optimization.