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Mannose- and Mannobiose-Specific Responses of the Insect-Associated Cellulolytic Bacterium Streptomyces sp. Strain SirexAA-E

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Title: Mannose- and Mannobiose-Specific Responses of the Insect-Associated Cellulolytic Bacterium Streptomyces sp. Strain SirexAA-E
Authors: Ohashi, Keisuke Browse this author
Hataya, Shogo Browse this author
Nakata, Akane Browse this author
Matsumoto, Kazuki Browse this author
Kato, Natsumi Browse this author
Sato, Wakana Browse this author
Carlos-Shanley, Camila Browse this author
Beebe, Emily T. Browse this author
Currie, Cameron R. Browse this author
Fox, Brian G. Browse this author
Takasuka, Taichi E. Browse this author →KAKEN DB
Keywords: Streptomyces sp. SirexAA-E
proteomics analysis
cellulose utilization
glycoside hydrolases
transcriptional regulation
Issue Date: 25-Jun-2021
Publisher: American Society for Microbiology
Journal Title: Applied and Environmental Microbiology
Volume: 87
Issue: 14
Start Page: e02719-20
Publisher DOI: 10.1128/AEM.02719-20
Abstract: The cellulolytic insect symbiont bacterium Streptomyces sp. strain SirexAA-E secretes a suite of carbohydrate-active enzymes (CAZymes), which are involved in the degradation of various polysaccharides in the plant cell wall, in response to the available carbon sources. Here, we examined a poorly understood response of this bacterium to mannan, one of the major plant cell wall components. SirexAA-E grew well on mannose, carboxymethyl cellulose (CMC), and locust bean gum (LBG) as sole carbon sources in the culture medium. The secreted proteins from each culture supematant were tested for their polysaccharide-degrading ability, and the composition of secreted CAZymes in each sample was determined by liquid chromatography-tandem mass spectrometry (LC-MS/ MS). The results indicated that mannose, LBG, and CMC induced the secretion of mannan and cellulose-degrading enzymes. Interestingly, two alpha-1,2-mannosidases were abundantly secreted during growth on mannose and LBG. Using genomic analysis, we found a unique 12-bp palindromic sequence motif at 4 locations in the SirexAA-E genome, two of which were found upstream of the above-mentioned alpha-1,2-mannosidase genes, along with a newly identified mannose and mannobiose-responsive transcriptional regulator, SsManR. Furthermore, the previously reported cellobiose-responsive repressor, SsCebR, was determined to also use mannobiose as an effector ligand. To test whether mannobiose induces the sets of genes under the control of the two regulators, SirexAA-E was grown on mannobiose, and the secretome composition was analyzed. As hypothesized, the composition of the mannobiose secretome combined sets of CAZymes found in both LBG and CMC secretomes, and thus they are likely under the regulation of both SsManR and SsCebR. IMPORTANCE Streptomyces sp. SirexAA-E, a microbial symbiont of biomass-harvesting insects, secretes a suite of polysaccharide-degrading enzymes dependent on the available carbon sources. However, the response of this bacterium to mannan has not been documented. In this study, we investigated the response of this bacterium to mannose, mannobiose, and galactomannan (LBG). By combining biochemical, proteomic, and genomic approaches, we discovered a novel mannose and mannobiose responsive transcriptional regulator, SsManR, which selectively regulates three alpha-1,2-mannosidasecoding genes. We also demonstrated that the previously described cellobiose responsive regulator, SsCebR, could use mannobiose as an effector ligand. Overall, our findings suggest that the Streptomyces sp. SirexAA-E responds to mannose and mannooligosaccharides through two different transcriptional repressors that regulate the secretion of the plant cell wall-degrading enzymes to extract carbon sources in the host environment.
Rights: Copyright © American Society for Microbiology
Type: article
Appears in Collections:国際連携研究教育局 : GI-CoRE (Global Institution for Collaborative Research and Education : GI-CoRE) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)
農学院・農学研究院 (Graduate School of Agriculture / Faculty of Agriculture) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 高須賀 太一

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