title: Aeromonas chitinase degrades chironomid egg masses.
abstract: Chironomids are freshwater insects that undergo a complete metamorphosis of four life stages. Chironomid egg masses can be degraded by Vibrio cholerae and some Aeromonas species. Egg mass degradation by V. cholerae requires haemagglutinin protease activity. Our aim was to identify the egg mass degrading (EMD) factor secreted by Aeromonas dhkanesis 3K1C15. Following the hypothesis that the EMD factor of A. dhkanesis is also a protease, secreted proteases were screened, but none of them proved to have the same properties as the EMD factor. Using conventional protein purification methods, we found that the active fraction included chitinases. We further confirmed chitin as a building block of the egg masses. Interestingly, by supplementing bacterial growth media with chitin, we observed unexpected EMD factor activity in Aeromonas isolates that initially were not able to degrade egg masses. Accordingly, we concluded that although strain 3K1C15 secretes chitinases constitutively, most Aeromonas strains secrete chitinases inductively. Induction of chitinases in nature presumably occurs when bacteria are attached to the egg mass habitat, in which chitin is abundant. Considering that chitinases are highly conserved across bacteria phyla, we assume that the role of this enzyme in the bacteria-insect interplay could be wider than is currently thought.
authors.affiliation: Department of Evolutionary and Environmental Biology, Faculty of Natural Sciences, University of Haifa, Haifa, Israel.
authors.forename: Sivan
authors.initials: S
authors.lastname: Laviad
authors.affiliation: Department of Biology and Environment, Faculty of Natural Sciences, University of Haifa, Oranim, Israel.|Protein Purification Center, Ramat Yohanan, Israel.
authors.forename: Amnon
authors.initials: A
authors.lastname: Golan
authors.affiliation: Department of Evolutionary and Environmental Biology, Faculty of Natural Sciences, University of Haifa, Haifa, Israel.
authors.forename: Tamar
authors.initials: T
authors.lastname: Shaked
authors.affiliation: Nesin Central Laboratory, Mekorot National Water Co. Ltd., Jordan District, Nazareth Illit, Israel.
authors.forename: Dalit
authors.initials: D
authors.lastname: Vaizel-Ohayon
authors.affiliation: Department of Evolutionary and Environmental Biology, Faculty of Natural Sciences, University of Haifa, Haifa, Israel.|Department of Biology and Environment, Faculty of Natural Sciences, University of Haifa, Oranim, Israel.
authors.forename: Malka
authors.initials: M
authors.lastname: Halpern
authors.affiliation: Department of Evolutionary and Environmental Biology, Faculty of Natural Sciences, University of Haifa, Haifa, Israel.|Department of Biology and Environment, Faculty of Natural Sciences, University of Haifa, Oranim, Israel.
authors.forename: Elah
authors.initials: E
authors.lastname: Pick
mesh_terms: D000333:Aeromonas / Q000201:enzymology* / Q000378:metabolism*; D000818:Animals; D001711:Biotransformation; D002686:Chitin / Q000378:metabolism*; D002688:Chitinases / Q000378:metabolism*; D007313:Insecta; D015053:Zygote / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D002686:Chitin; D002688:Chitinases