Emergence of putative energy parasites within Clostridia revealed by genome analysis of a novel endosymbiotic clade.

The Clostridia is a dominant bacterial class in the guts of various animals and are considered to nutritionally contribute to the animal host. Here, we discovered clostridial endosymbionts of cellulolytic protists in termite guts, which have never been reported with evidence. We obtained (near-)complete genome sequences of three endosymbiotic Clostridia, each associated with a different parabasalid protist species with various infection rates: Trichonympha agilis, Pseudotrichonympha grassii, and Devescovina sp. All these protists are previously known to harbor permanently-associated, mutualistic Endomicrobia or Bacteroidales that supplement nitrogenous compounds. The genomes of the endosymbiotic Clostridia were small in size (1.0-1.3 Mbp) and exhibited signatures of an obligately-intracellular parasite, such as an extremely limited capability to synthesize amino acids, cofactors, and nucleotides and a disrupted glycolytic pathway with no known net ATP-generating system. Instead, the genomes encoded ATP/ADP translocase and, interestingly, regulatory proteins that are unique to eukaryotes in general and are possibly used to interfere with host cellular processes. These three genomes formed a clade with metagenome-assembled genomes (MAGs) derived from the guts of other animals, including human and ruminants, and the MAGs shared the characteristics of parasites. Gene flux analysis suggested that the acquisition of the ATP/ADP translocase gene in a common ancestor was probably key to the emergence of this parasitic clade. Taken together, we provide novel insights into the multilayered symbiotic system in the termite gut by adding the presence of parasitism and present an example of the emergence of putative energy parasites from a dominant gut bacterial clade.

Structures of antimutagenic constituents in the peels of Citrus limon.

The methanolic extracts from the peels of Citrus limon were found to show antimutagenic effects against 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole, and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in the Ames test. From the methanolic extracts, four new coumarins (wakayamalimonol A-D) and a new furanocoumarin (wakayamalimonol E) were isolated together with fifteen known compounds. The absolute stereostructures of the new compounds were determined by chemical synthesis and the modified Mosher's method. Among the isolated constituents, coumarins, furanocoumarins, and limonoids showed antimutagenic effects in the Ames test. One of the major constituent, limonin, showed significant antimutagenic effects against mitomycinC and PhIP in the micronucleus test in vivo.

Magnolol and honokiol prevent learning and memory impairment and cholinergic deficit in SAMP8 mice.

The therapeutic use of neurotrophic factors to treat neurodegenerative disorders, including Alzheimer's disease, is considered feasible. Magnolol and honokiol, constituents of the Magnolia plant, are small organic compounds with neurotrophic activity. We investigated whether magnolol and honokiol can prevent age-related learning and memory impairment and cholinergic deficits in senescence-accelerated mice (SAM). Magnolol (1, 10 mg/kg) or honokiol (0.1, 1 mg/kg) were orally administered to SAMP8 mice once a day for 14 days in 2-month-old mice. Learning and memory performance were evaluated by passive avoidance tests and location and object novelty recognition tests. SAMP8 mice showed significant impairment of learning and memory at 4 and 6 months of age. This age-related learning and memory impairment was prevented by pretreatment with either magnolol (10 mg/kg) or honokiol (1 mg/kg). Cholinergic neuron densities in the medial septum and vertical limb of the diagonal band of the forebrain were evaluated by an immunohistochemical analysis of choline acetyltransferase (ChAT). SAMP8 mice showed a significant cholinergic deficit at 6 months of age. These age-related cholinergic deficits were prevented by treatment with either magnolol (10 mg/kg) or honokiol (1 mg/kg). Moreover, SAMP8 mice showed decreased activity of Akt, a member of the prosurvival pathway, in the forebrain at 2 months of age. A 14-day treatment with either magnolol (10 mg/kg) or honokiol (1 mg/kg) enhanced phosphorylation of Akt in the forebrain at 2 months of age. These results suggest that magnolol and honokiol prevent age-related learning and memory impairment by preserving cholinergic neurons in the forebrain. These compounds may have potential therapeutic applications to various neurodegenerative disorders.