title: Genomic characterization of a fructophilic bee symbiont Lactobacillus kunkeei reveals its niche-specific adaptation.
abstract: Lactobacillus kunkeei is classified as a sole obligate fructophilic lactic acid bacterium that is found in fructose-rich niches, including the guts of honeybees. The species is differentiated from other lactobacilli based on its poor growth with glucose, enhanced growth in the presence of oxygen and other electron acceptors, and production of high concentrations of acetate from the metabolism of glucose. These characteristics are similar to phylogenetically distant Fructobacillus spp. In the present study, the genomic structure of L. kunkeei was characterized by using 16 different strains, and it had significantly less genes and smaller genomes when compared with other lactobacilli. Functional gene classification revealed that L. kunkeei had lost genes specifically involved in carbohydrate transport and metabolism. The species also lacked most of the genes for respiration, although growth was enhanced in the presence of oxygen. The adhE gene of L. kunkeei, encoding a bifunctional alcohol dehydrogenase (ADH)/aldehyde dehydrogenase (ALDH) protein, lacked the part encoding the ADH domain, which is reported here for the first time in lactic acid bacteria. The deletion resulted in the lack of ADH activity, implying a requirement for electron acceptors in glucose assimilation. These results clearly indicated that L. kunkeei had undergone a specific reductive evolution in order to adapt to fructose-rich environments. The reduction characteristics were similar to those of Fructobacillus spp., but distinct from other lactobacilli with small genomes, such as Lactobacillus gasseri and Lactobacillus vaginalis. Fructose-richness thus induced an environment-specific gene reduction in phylogenetically distant microorganisms.
authors: Department of Food and Cosmetic Science, Tokyo University of Agriculture, Hokkaido, Japan.
authors: Shintaro
authors: S
authors: Maeno
authors: Department of Computational Biology and Medical Sciences, Graduate School of Frontier Science, The University of Tokyo, Chiba, Japan; Center for Information Biology, National Institute of Genetics, Shizuoka, Japan.
authors: Yasuhiro
authors: Y
authors: Tanizawa
authors: Genome Research Center, NODAI Research Institute, Tokyo University of Agriculture, Tokyo, Japan.
authors: Yu
authors: Y
authors: Kanesaki
authors: Genome Research Center, NODAI Research Institute, Tokyo University of Agriculture, Tokyo, Japan.
authors: Eri
authors: E
authors: Kubota
authors: Functional Foods Forum, University of Turku, Turku, Finland.
authors: Himanshu
authors: H
authors: Kumar
authors: Department of Microbiology, University of Stellenbosch, Stellenbosch, South Africa.
authors: Leon
authors: L
authors: Dicks
authors: Functional Foods Forum, University of Turku, Turku, Finland.
authors: Seppo
authors: S
authors: Salminen
authors: Department of Food and Cosmetic Science, Tokyo University of Agriculture, Hokkaido, Japan.
authors: Junichi
authors: J
authors: Nakagawa
authors: Center for Information Biology, National Institute of Genetics, Shizuoka, Japan; RIKEN Center for Sustainable Resource Science, Kanagawa, Japan.
authors: Masanori
authors: M
authors: Arita
authors: Department of Food and Cosmetic Science, Tokyo University of Agriculture, Hokkaido, Japan. Electronic address: a3endou@bioindustry.nodai.ac.jp.
authors: Akihito
authors: A
authors: Endo
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics; D000426:Alcohol Dehydrogenase / Q000235:genetics; D000445:Aldehyde Oxidoreductases / Q000235:genetics; D000818:Animals; D001516:Bees / Q000382:microbiology*; D050260:Carbohydrate Metabolism / Q000235:genetics*; D004269:DNA, Bacterial / Q000235:genetics; D005632:Fructose / Q000378:metabolism*; D016680:Genome, Bacterial / Q000235:genetics*; D007778:Lactobacillus / Q000145:classification / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*
chemical_list: D004269:DNA, Bacterial; D005632:Fructose; D000426:Alcohol Dehydrogenase; D000445:Aldehyde Oxidoreductases
keywords: Comparative genomics; Fructobacillus; Fructophilic lactic acid bacteria; Lactobacillus kunkeei; adhE