Our current knowledge of plant-microbe interactions indicate that populations inhabiting a host plant are not restricted to a single microbial species but comprise several genera and species. No one knows if communities inside plants interact, and it has been speculated that beneficial effects are the result of their combined activities. During an ecological study of nitrogen-fixing bacterial communities from Lupinus angustifolius collected in Spain, significant numbers of orangepigmented actinomycete colonies were isolated from surface-sterilized root nodules. The isolates were analysed by BOX-PCR fingerprinting revealing an unexpectedly high genetic variation. Selected strains were chosen for 16S rRNA gene sequencing and phylogenetic analyses confirmed that all strains isolated belonged to the genus Micromonospora and that some of them may represent new species. To determine the possibility that the isolates fixed atmospheric nitrogen, chosen strains were grown in nitrogen-free media, obtaining in some cases, significant growth when compared with the controls. These strains were further screened for the presence of the nifH gene encoding dinitrogenase reductase, a key enzyme in nitrogen fixation. The partial nifH-like gene sequences obtained showed a 99% similarity with the sequence of the nifH gene from Frankia alni ACN14a, an actinobacterium that induces nodulation and fixes nitrogen in symbiosis with Alnus. In addition, in situ hybridization was performed to determine if these microorganisms inhabit the inside of the nodules. This study strongly suggests that Micromonospora populations are natural inhabitants of nitrogen-fixing root nodules.

Abyssomicin I (1), a new modified polycyclic polyketide, was isolated from the culture extract of a soil-derived Streptomyces sp. The structure of 1 was elucidated by interpretation of NMR and other spectroscopic data. The stereochemistry of the new compound was assigned by NOE analysis, chemical derivatization, and application of the modified Mosher method. While 1 was inactive against bacteria and yeasts, the oxidized derivative 7 showed weak activities against gram-positive bacteria. Compounds 1 and 7 exhibited inhibitory effects on tumor cell invasion with IC(50) values of 11 and 0.21 μM, respectively.

A novel actinomycete strain, ABO T , isolated from copper-polluted sediments showed remarkable copper resistance as well as high bioaccumulation abilities. Classical taxonomic methods, including chemotaxonomy and molecular techniques, were used to characterize the isolate. Strain ABO T developed a honey-yellow substrate mycelium on all ISP media tested. Abundant, white, aerial mycelium was only formed on ISP 2, 5 and 7 and MM agar. Both types of hyphae fragmented into squarish rod-shaped elements. The aerial mycelium displayed spore-like structures with smooth surfaces in long, straight to flexuous chains. The organism has a type-IV cell wall lacking mycolic acids and type-A whole-cell sugar pattern (meso-diaminopimelic acid, arabinose and galactose) in addition to a phospholipid type-II profile. 16S rRNA gene sequence studies indicated that this organism is a member of the family Pseudonocardiaceae and that it forms a monophyletic clade with Amycolatopsis eurytherma NT202 T . The DNA-DNA relatedness of strain ABO T to A. eurytherma DSM 44348 T was 39.5 %. It is evident from these genotypic and phenotypic data that strain ABO T represents a novel species in the genus Amycolatopsis, for which the name proposed is Amycolatopsis tucumanensis sp. nov. The type strain is ABO T (5DSM 45259 T 5LMG 24814 T ).

The discovery that the actinobacterium Micromonospora inhabits nitrogen-fixing nodules raised questions as to its potential ecological role. The capacity of two Micromonospora strains to infect legumes other than their original host, Lupinus angustifolius, was investigated using Medicago and Trifolium as test plants. Compatible rhizobial strains were used for coinoculation of the plants because Micromonospora itself does not induce nodulation. Over 50% of nodules from each legume housed Micromonospora, and using 16S rRNA gene sequence identification, we verified that the reisolated strains corresponded to the microorganisms inoculated. Entry of the bacteria and colonization of the plant hosts were monitored using a GFP-tagged Lupac 08 mutant together with rhizobia, and by using immunogold labeling. Strain Lupac 08 was localized in plant tissues, confirming its capacity to enter and colonize all hosts. Based on studying three different plants, our results support a non-specific relationship between Micromonospora and legumes. Micromonospora Lupac 08, originally isolated from Lupinus re-enters root tissue, but only when coinoculated with the corresponding rhizobia. The ability of Micromonospora to infect and colonize different legume species and function as a potential plant-growth promoting bacterium is relevant because this microbe enhances the symbiosis without interfering with the host and its nodulating and nitrogen-fixing microbes.

c Micromonospora strains have been isolated from diverse niches, including soil, water, and marine sediments and root nodules of diverse symbiotic plants. In this work, we report the genome sequence of Micromonospora lupini Lupac 08 isolated from root nodules of the wild legume Lupinus angustifolious.T he genus Micromonospora is the type genus of the family Micromonosporaceae and includes microorganisms with potential biotechnological applications such as antibiotic producers, xylanolytic and cellulolytic strains, and degraders of natural rubber (2, 9). These bacteria are Gram positive, filamentous, and aerobic. Colonies are typically light orange, becoming red, brown, or purple with the production of single-spore sporangiophores. Micromonosporae have been isolated from soil, water, and marine sediments, and these microorganisms have recently been reported as natural inhabitants of root nodule tissues of legumes where this bacterium has been isolated from at least 20 different legume plant species, both wild and cultivated (1, 5) as well as from actinorhizal plants (7).Strain Lupac 08 was isolated from the root nodules of Lupinus angustifolius and identified using a combination of phylogenetic, chemotaxonomic, and morphological analyses that led to the description of Micromonospora lupini sp. nov. (6). Given the large number of Micromonospora strains recovered from symbiotic tissues, the genome of strain Lupac 08 was sequenced to obtain information about the potential ecological role of Micromonospora in interaction with legumes and actinorhizal plants.The genome sequence of M. lupini Lupac 08 was determined using the 454 FLX system and Titanium platform (454 Life Sciences). Highly pure genomic DNA samples from strain Lupac 08 were prepared and used to construct a GS FLX shotgun and a GS FLX long paired-end library. Sequences were assembled in 50 contigs and four scaffolds ranging from 583 to 7,083,659 bp using the GS De Novo Assembler (Newbler).The draft genome of M. lupini Lupac 08 has 7,327,024 bp with a GC content of 71.96%. Manual validation of the automatic annotation was performed using the MaGe (Magnifying Genomes) interface (8) and 7,054 protein-coding genes, 10 rRNA genes (3 genes for 5S rRNA, 4 genes for 16S rRNA, and 3 genes for 23S rRNA), and 77 tRNA genes were predicted.Preliminary information derived from the genomic data indicates that M. lupini Lupac 08 contains several genes encoding hydrolytic enzymes such as cellulases, amylases, xylanases, and pectinases that may have a role in the colonization process.Studies of bacterial secondary metabolism have largely targeted the discovery of new compounds and the mechanisms for their biosynthesis, but little is known about the ecological functions of secondary metabolites. These molecules may act as signals, pigments, lectins, and siderophores. As with most actinobacteria, M. lupini Lupac 08 is capable of producing bioactive molecules, and we recently confirmed the production of previously unknown molecules (3, 4). Preliminary data obtained from the g...