Ent-homocyclopiamine B, a Prenylated Indole Alkaloid of Biogenetic Interest from the Endophytic Fungus Penicillium concentricum.

Ent-homocyclopiamine B (1), a new prenylated indole alkaloid bearing an alicyclic nitro group along with 2-methylbutane-1,2,4-triol (2) were isolated from an endophytic fungus Penicillium concentricum of the liverwort Trichocolea tomentella (Trichocoleaceae). The structure of 1 was elucidated through extensive spectroscopic analyses and comparison with data reported for a structurally related nitro-bearing Penicillium metabolite, clopiamine C (3), which contain an indolizidine ring instead of the quinolizine ring in 1. The new compound, ent-homocyclopiamine B, exhibited slight growth inhibition against Gram-positive bacteria. Based on the reported biosynthesis of related compounds and the isolation of the mevalonic acid derived compound 2-methyl-1,2,4-butanetriol (2), we proposed that ent-homocylopiamine B (1) was biosynthesized from lysine and prenyl group-producing mevalonic pathway.

Micromonospora parathelypteridis sp. nov., an endophytic actinomycete with antifungal activity isolated from the root of Parathelypteris beddomei (Bak.) Ching.

A novel endophytic actinomycete with antifungal activity, designated strain NEAU-JXY5T, was isolated from the root of Parathelypteris beddomei (Bak.) Ching. Strain NEAU-JXY5T showed closest 16S rRNA gene sequence similarity to Micromonospora luteifusca GUI2T (99.31 %), and phylogenetically clustered with Micromonospora noduli GUI43T (99.24 %), 'Micromonospora lycii' NEAU-gq11 (99.19 %), 'Micromonospora zeae' NEAU-gq9 (99.12 %), Micromonospora saelicesensis Lupac 09T (98.97 %), Micromonospora vinacea GUI63T (98.96 %), 'Micromonospora jinlongensis' NEAU-GRX11 (98.91 %), Micromonospora profundi DS3010T (98.77 %), Micromonospora zamorensis CR38T (98.76 %), Micromonospora chokoriensis 2-19(6)T (98.71 %), Micromonospora lupini Lupac 14NT (98.69 %), Micromonospora ureilytica GUI23T (98.69 %), Micromonospora violae NEAU-zh8T (98.57 %) and Micromonospora taraxaci NEAU-P5T (98.37 %). Phylogenetic analysis based on gyrB gene sequences also indicated that the isolate clustered with the above strains except M. violae NEAU-zh8T. A combination of DNA-DNA hybridization results and some phenotypic characteristics indicated that the strain could be readily distinguished from these closest phylogenetic relatives. Therefore, it is concluded that strain NEAU-JXY5T represents a novel species of the genus Micromonospora, for which the name Micromonospora parathelypteridis sp. nov. is proposed. The type strain is NEAU-JXY5T (=CGMCC 4.7347T=DSM 103125T).

Rickettsial endosymbiont in the "early-diverging" streptophyte green alga Mesostigma viride.

A bacterial endosymbiont was unexpectedly found in the "axenic" culture strain of the streptophyte green alga Mesostigma viride (NIES-995). Phylogenetic analyses based on 16S rRNA gene sequences showed that the symbiont belongs to the order Rickettsiales, specifically to the recently designated clade "Candidatus Megaira," which is closely related to the well-known Rickettsia clade. Rickettsiales bacteria of the "Ca. Megaira" clade are found in a taxonomically diverse array of eukaryotic hosts, including chlorophycean green algae, several ciliate species, and invertebrates such as Hydra. Transmission electron microscopy, fluorescence in situ hybridi-zation, and SYBR Green I staining experiments revealed that the endosymbiont of M. viride NIES-995 is rod shaped, typically occurs in clusters, and is surrounded by a halo-like structure, presumably formed by secretory substances from the bacterium. Two additional M. viride strains (NIES-296 and NIES-475), but not SAG50-1, were found to house the rickettsial endosymbiont. Analyses of strain NIES-995 transcriptome data indicated the presence of at least 91 transcriptionally active genes of symbiont origins. These include genes for surface proteins (e.g., rOmpB) that are known to play key roles in bacterial attachment onto host eukaryotes in related Rickettsia species. The assembled M. viride transcriptome includes transcripts that code for a suite of predicted algal-derived proteins, such as Ku70, WASH, SCAR, and CDC42, which may be important in the formation of the algal-rickettsial association.

Distinctive bacterial communities in the rhizoplane of four tropical tree species.

It is known that the microbial community of the rhizosphere is not only influenced by factors such as root exudates, phenology, and nutrient uptake but also by the plant species. However, studies of bacterial communities associated with tropical rainforest tree root surfaces, or rhizoplane, are lacking. Here, we analyzed the bacterial community of root surfaces of four species of native trees, Agathis borneensis, Dipterocarpus kerrii, Dyera costulata, and Gnetum gnemon, and nearby bulk soils, in a rainforest arboretum in Malaysia, using 454 pyrosequencing of the 16S rRNA gene. The rhizoplane bacterial communities for each of the four tree species sampled clustered separately from one another on an ordination, suggesting that these assemblages are linked to chemical and biological characteristics of the host or possibly to the mycorrhizal fungi present. Bacterial communities of the rhizoplane had various similarities to surrounding bulk soils. Acidobacteria, Alphaproteobacteria, and Betaproteobacteria were dominant in rhizoplane communities and in bulk soils from the same depth (0-10 cm). In contrast, the relative abundance of certain bacterial lineages on the rhizoplane was different from that in bulk soils: Bacteroidetes and Betaproteobacteria, which are known as copiotrophs, were much more abundant in the rhizoplane in comparison to bulk soil. At the genus level, Burkholderia, Acidobacterium, Dyella, and Edaphobacter were more abundant in the rhizoplane. Burkholderia, which are known as both pathogens and mutualists of plants, were especially abundant on the rhizoplane of all tree species sampled. The Burkholderia species present included known mutualists of tropical crops and also known N fixers. The host-specific character of tropical tree rhizoplane bacterial communities may have implications for understanding nutrient cycling, recruitment, and structuring of tree species diversity in tropical forests. Such understanding may prove to be useful in both tropical forestry and conservation.