title: Digestion of Yeasts and Beta-1,3-Glucanases in Mosquito Larvae: Physiological and Biochemical Considerations.
abstract: Aedes aegypti larvae ingest several kinds of microorganisms. In spite of studies regarding mosquito digestion, little is known about the nutritional utilization of ingested cells by larvae. We investigated the effects of using yeasts as the sole nutrient source for A. aegypti larvae. We also assessed the role of beta-1,3-glucanases in digestion of live yeast cells. Beta-1,3-glucanases are enzymes which hydrolyze the cell wall beta-1,3-glucan polyssacharide. Larvae were fed with cat food (controls), live or autoclaved Saccharomyces cerevisiae cells and larval weight, time for pupation and adult emergence, larval and pupal mortality were measured. The presence of S. cerevisiae cells inside the larval gut was demonstrated by light microscopy. Beta-1,3-glucanase was measured in dissected larval samples. Viability assays were performed with live yeast cells and larval gut homogenates, with or without addition of competing beta-1,3-glucan. A. aegypti larvae fed with yeast cells were heavier at the 4th instar and showed complete development with normal mortality rates. Yeast cells were efficiently ingested by larvae and quickly killed (10% death in 2 h, 100% in 48 h). Larvae showed beta-1,3-glucanase in head, gut and rest of body. Gut beta-1,3-glucanase was not derived from ingested yeast cells. Gut and rest of body activity was not affected by the yeast diet, but head homogenates showed a lower activity in animals fed with autoclaved S. cerevisiae cells. The enzymatic lysis of live S. cerevisiae cells was demonstrated using gut homogenates, and this activity was abolished when excess beta-1,3-glucan was added to assays. These results show that live yeast cells are efficiently ingested and hydrolyzed by A. aegypti larvae, which are able to fully-develop on a diet based exclusively on these organisms. Beta-1,3-glucanase seems to be essential for yeast lytic activity of A. aegypti larvae, which possess significant amounts of these enzyme in all parts investigated.
authors.affiliation: Laboratory of Insect Biochemistry and Physiology, Oswaldo Cruz Institute, FIOCRUZ, 4365 Brasil Av, Leonidas Deane Building, room 207, Manguinhos, Rio de Janeiro, Brazil, 21040-360.
authors.forename: Raquel Santos
authors.initials: RS
authors.lastname: Souza
authors.affiliation: Laboratory of Insect Biochemistry and Physiology, Oswaldo Cruz Institute, FIOCRUZ, 4365 Brasil Av, Leonidas Deane Building, room 207, Manguinhos, Rio de Janeiro, Brazil, 21040-360.
authors.forename: Hector Manuel
authors.initials: HM
authors.lastname: Diaz-Albiter
authors.affiliation: Institute of Integrative Biology, Biosciences Building, University of Liverpool, Crown Street, Liverpool, L69 7ZB, United Kingdom.
authors.forename: Vivian Maureen
authors.initials: VM
authors.lastname: Dillon
authors.affiliation: Division of Biomedical and Life Sciences, Furness Building, Lancaster University, Bailrigg, Lancaster, LA1 4YG, United Kingdom.|National Institute of Science and Technology for Molecular Entomology, 373 Carlos Chagas Filho Av., Center for Health Science, Building D, Basement, room 5, Cidade Universitária, Rio de Janeiro, Brazil, 21941-590.
authors.forename: Rod J
authors.initials: RJ
authors.lastname: Dillon
authors.affiliation: Laboratory of Insect Biochemistry and Physiology, Oswaldo Cruz Institute, FIOCRUZ, 4365 Brasil Av, Leonidas Deane Building, room 207, Manguinhos, Rio de Janeiro, Brazil, 21040-360.|National Institute of Science and Technology for Molecular Entomology, 373 Carlos Chagas Filho Av., Center for Health Science, Building D, Basement, room 5, Cidade Universitária, Rio de Janeiro, Brazil, 21941-590.
authors.forename: Fernando Ariel
authors.initials: FA
authors.lastname: Genta
mesh_terms: D000330:Aedes / Q000254:growth & development*; D000818:Animals; D043326:Glucan 1,3-beta-Glucosidase / Q000378:metabolism*; D007814:Larva / Q000201:enzymology*; D012441:Saccharomyces cerevisiae / Q000201:enzymology*
chemical_list: D043326:Glucan 1,3-beta-Glucosidase; C117648:beta-1,3-exoglucanase