Fungi produce numerous low molecular weight molecules endowed with a multitude of biological activities. However, mining the fullgenome sequences of fungi indicates that their potential to produce secondary metabolites is greatly underestimated. Because most of the biosynthesis gene clusters are silent under laboratory conditions, one of the major challenges is to understand the physiological conditions under which these genes are activated. Thus, we cocultivated the important model fungus Aspergillus nidulans with a collection of 58 soil-dwelling actinomycetes. By microarray analyses of both Aspergillus secondary metabolism and full-genome arrays and Northern blot and quantitative RT-PCR analyses, we demonstrate at the molecular level that a distinct fungal-bacterial interaction leads to the specific activation of fungal secondary metabolism genes. Most surprisingly, dialysis experiments and electron microscopy indicated that an intimate physical interaction of the bacterial and fungal mycelia is required to elicit the specific response. Gene knockout experiments provided evidence that one induced gene cluster codes for the long-sought after polyketide synthase (PKS) required for the biosynthesis of the archetypal polyketide orsellinic acid, the typical lichen metabolite lecanoric acid, and the cathepsin K inhibitors F-9775A and F-9775B. A phylogenetic analysis demonstrates that orthologs of this PKS are widespread in nature in all major fungal groups, including mycobionts of lichens. These results provide evidence of specific interaction among microorganisms belonging to different domains and support the hypothesis that not only diffusible signals but intimate physical interactions contribute to the communication among microorganisms and induction of otherwise silent biosynthesis genes.genome mining ͉ lecanoric acid ͉ orsellinic acid ͉ Streptomyces

Actinomycetes are considered an inexhaustible source of chemically diverse secondary metabolites. In addition to the genera Streptomyces, Micromonospora, and Actinoplanes, coryneform and nocardioform bacteria have been used in screening programs for new compounds of medical and biotechnological importance (5, 8).In the course of a program aimed at isolating actinomycetes that have potential for producing novel bioactive compounds, we isolated a large number of strains from different soils. In about 65 of these strains diaminobutyric acid (DAB) was the diagnostic diamino acid in the peptidoglycan. These strains had morphological and chemotaxonomic characteristics that placed them near the genera Agromyces and Clavibacter.In this paper we describe the isolation and characterization of two strains which differed markedly from the members of the genera Agromyces (27), Clavibacter, and Rathayibacter (26) that have been described. On the basis of our morphological, physiological, and biochemical data, as well as the results of our 16s ribosomal DNA (rDNA) analysis, we concluded that these strains belong to a new genus and species, for which we propose the name Agrococcus jenensis. These strains have been deposited in the German Collection of Microorganisms and MATERIALS AND METHODSBacterial strains and cultural conditions. Strain 2002-39/lT was isolated from a sample of frozen compost soil obtained near Jena, Germany, at a depth of about 10 cm. Isolation of this organism involved dilution plating on nutrient agar containing 2% peptone, a pancreatic digest (meat, fish), 0.5% NaCI, and 1.2% agar. Strain ST54 was isolated from the sandstone surface of the Alte Pinakothek building in Munich, Germany. The Agromyces and Cluvibacter type strains which we used in this study are listed in Table 1. General laboratory cultivation was performed on solid medium or in liquid rich (R) medium (25) containing 1% Bacto Peptone (Difco Laboratories), 0.5% yeast extract, 0.5% Casamino Acids, 0.2% meat extract, 0.5% malt extract, 0.2% glycerol, 0.1% MgSO, -7H,O, and 0.005% Tween 80 (pH 7.2) at 28°C.Morphological and physiological characteristics. Cell morphology was determined by examining cultures of different ages by phase-contrast microscopy. Colony morphology was studied by using a stereomicroscope. For scanning electron microscopy an 18-h-old culture of strain 2002-39/lT on an agar plate was suspended in a phosphate-buffered salt solution. The cells were fixed with 0 5 % glutaraldehyde, washed, and dehydrated in a series containing increasing concentrations of ethanol. After sputter coating with gold-palladium, the cells were observed with a Zeiss model 962 scanning electron microscope.

The high speed production of fluid segments for the highly parallelized cultivation of monoclonal cell populations was carried out by the use of microchip segmentor modules. Aqueous fluid segments, embedded in a non-miscible carrier liquid, were produced with frequencies up to 30 s(-1) and showed a high homogeneity in size. This corresponds with the production of about 2.5 million samples per day. The segment volumes can be adapted between about 4 nl and 100 nl. The typical segment size for cultivation experiments is in the range between 40 nl and 80 nl. Nutrient medium can be applied instead of pure water. It is possible to aliquot a cell suspension in such a way that most of the aqueous fluid segments contain only one cell. In model experiments with four microbial species chip-produced aliquots of 60 nl, each containing one or a few cells, were incubated in Teflon capillary tubes. Rapid growth of the microcultures was observed. Cell densities were found to be as high as in conventional shake flask cultures.

New gram-positive bacteria were isolated from 1-year-old sludge from a wastewater treatment plant. The isolates are coccoid to rod-shaped, nonmotile aerobes that form neither spores nor mycelia. They are characterized by a peptidoglycan with directly cross-linked rneso-diaminopimelic acid (type Aly), by the presence of menaquinone MK-S(H,), and by the lack of mycolic acids. The strains have complex fatty acid patterns with i-C16:o and straight-chain saturated and unsaturated fatty acids as major components. The G+C content of the DNA is 70 mol%. The results of chemotaxonomic studies and a 16s ribosomal DNA sequence comparison support our proposal to assign these bacteria to a new genus, the genus Janibacter gen. nov.; the type species is Junibucter Zirnosus sp. nov., and the type strain of J. Zirnosus is strain HKI 83 (= DSM 11140).Both spore-forming and asporogenous actinomycetes have been screened during the last few years for useful bioactive compounds (13,39). The asporogenous organisms play important roles in mineralization of environmentally hazardous chemicals, such as polycyclic aromatic hydrocarbons (22), and in biotechnological production of natural products (23,26,29).To isolate new actinomycetes with new biological activities, we investigated several samples of soil, sludge, and sewage waste. A total of 168 strains were isolated from a 1-year-old sludge sample collected from a wastewater treatment plant. Two of these isolates were found to be markedly different from the other isolates and from previously described genera in their chemotaxonomic and their physiological features. In this paper these two strains are characterized phenotypically and phylogenetically. Below we propose the creation of a new genus, the genus Janibacter gen. nov., with one species, Janibacter limosus sp. nov., for these organisms. MATERIALS AND METHODSBacterial strains and cultural conditions. Strains HKI 83T (T = type strain) and HKI 84 were isolated from a 1-year-old sludge sample from the wastewater treatment plant near Jena, Thuringia, Germany, by the dilution plate technique on plate count agar (Difco Laboratories, Detroit, Mich.). General laboratory cultivation was performed at 28°C on solid rich medium (R medium) or in liquid R medium (43), which contained 1% (wtivol) Bacto Peptone (Difco), 0.5% (wt/vol) yeast extract, 0.5% (wt/vol) Casamino Acids, 0.2% (wthol) meat extract, 0.5% (wt/vol) malt extract, 0.2% (wtivol) glycerol. 0.1% (wt/vol) MgSO, -7H,O, and 0.005% (wt/vol) Tween 80 (pH 7.2). To determine the cellular fatty acids, strains were cultivated for 24 h in liquid tryptic soy broth (Difco) at 28°C.Morphological and physiological characteristics. Colony morphology on R medium and cell morphology at different ages were determined by stereomicroscopy and phase-contrast microscopy (Olympus, Tokyo, Japan). Nitrate reductase activity, urease activity, indole production, methyl red and Voges-Proskauer reactions, hydrogen sulfide production, and hydrolysis of esculin and Tween 80 were determined as described by Lanyi (...

The taxonomic position, growth characteristics and antibiotic resistance properties of a slightly yellow-pigmented bacterial strain, designated R26 T , isolated from the midgut of the mosquito Anopheles gambiae, were studied. The isolate produced rod-shaped cells, which stained Gram-negative.