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To study the natural products produced by uncultured microorganisms, an environmental DNA (eDNA) cosmid library was constructed and screened for the heterologous production of small molecules. A blue clone, CSL51, found in the eDNA library produces deoxyviolacein and the broad spectrum antibiotic violacein. The full sequence of the 6.7 kb eDNA violacein gene cluster and the characterization of violacein and deoxyviolacein from an eDNA clone are reported here.

Bacillus cereus strain UW85 produces an antibiotic, designated zwittermicin A, that is associated with the ability of UW85 to suppress damping-off disease of alfalfa (Medicago sativa) caused by the oomycete pathogen, Phytophthora medicaginis, in a laboratory bioassay. We have identified certain culture conditions that promote or suppress zwittermicin A accumulation by UW85. Maximum accumulation was detected in supernatants of trypticase soy broth cultures after sporulation, which is when cultures of UW85 provide the greatest suppression of damping-off on alfalfa. Inorganic amendments to trypticase soy broth cultures had the following effects on zwittermicin A accumulation and disease suppression: phosphate (50 mM or more) reduced zwittermicin A accumulation and disease suppression; ferric iron (0.25–1.0 mM) enhanced zwittermicin A accumulaiton and disease suppression; micronutrients (manganese, boron, copper, molybdenum, zinc) had no effect on zwittermicin A accumulation or disease suppression. Cultures of UW85 grown in chemically defined minimal medium supplemented with casein hydrolysate or grown in defined medium containing the minimal requirements for growth supplemented with five amino acids (Gln, Arg, Met, Phe, Ile) accumulated zwittermicin A. In minimal medium, alfalfa seed exudate inhibited growth of UW85, whereas alfalfa sprout exudate enhanced zwittermicin A accumulation by 40%. These data indicate that the accumulation of zwittermicin A can be modulated by specific nutrients, inorganic compounds, and plant-derived factors. These results will facilitate the improvement of large-scale purification of zwittermicin A, suggest appropriate conditions under which to conduct further genetic and biochemical analyses, and further substantiate the association between antibiotic accumulation and disease suppression by UW85.

We present an approach to comparing the diversity and composition of bacterial communities from different habitats and for identifying which members of a community are most affected by an introduced bacterium. We use this method to explore both previously published and new data from field and growth chamber experiments in which we isolated heterotrophic bacteria from samples of root-free soil, roots of nontreated soybean seedlings, and from the roots of soybean seedlings grown from Bacillus cereus UW85n1–treated seeds. We characterize bacterial isolates for 40 physiological attributes, and grouped the isolates hierarchically using two-stage density-linkage cluster analysis. Multivariate analysis of variance and discriminant analysis of the relative frequencies of the clusters in the soil and rhizosphere habitats were then used to determine whether there were differences among the bacterial communities from the various habitats, and which of the clusters were most useful in discriminating among the communities. We used rarefied estimates of richness as a measure of community diversity in the various habitats. Introduction of UW85n1 affected the composition and/or diversity of rhizosphere communities in three of four experiments.

We have isolated two types of isolates having identical colony morphologies from stock cultures of two different Rhizobium meliloti strains. One isolate was agglutinated at a high-dilution titer (HA, highly agglutinable) of the alfalfa agglutinin and was sensitive to phage F20, and the other was agglutinated at a lower agglutinin titer (LA) and was sensitive to phage 16B. All LA isolates from the original slant produced nodules on alfalfa earlier than did HA strains from the original slant. When these HA and LA strains were mixed and used as the inoculum in both vermiculite and field soil in the laboratory, LA strains were always the predominant strains recovered from the nodules. LA strains were obtained from HA cells by selection for resistance to phage F20, and HA strains were obtained from LA cells by selection for resistance to phage 16B. All of the strains with the HA phenotype that were derived from LA strains by phage selection had the nodulation properties of the HA strains from the original slant. Two classes of strains with the LA phenotype were obtained from HA cells by phage selection. One was identical to the original LA strains from the slant, and the other had the nodulation properties of the HA strains. Thus, we have shown that some cell surface properties change the nodulation abilities of R. meliloti strains and, furthermore, that specific phages can be used to enrich for more competitive rhizobia.

A stock culture of Rhizobium meliloti 102F51 contains colonies of two distinct phenotypes (Handelsman et al., J. Bacteriol. 157:703-707, 1984); one colony type is agglutinated by high dilutions of the alfalfa agglutinin, is sensitive to phage F20, and is resistant to phage 16B, and the other is agglutinated only by low dilutions of the alfalfa agglutinin, is resistant to phage F20, and is sensitive to phage 16B. Cells of the latter phenotype have an inner-membrane-bound galactosyltransferase activity that transfers galactose from UDP-galactose to a water-insoluble anionic polymer. This enzymatic activity is absent in cells of the first phenotype. All of the phage 16B-resistant mutants selected from a sensitive strain were agglutinated by high dilutions of the alfalfa agglutinin, were sensitive to phage F20, and lacked galactosyltransferase activity. The galactose-containing polymer prepared in vitro was immunologically cross-reactive with the cell surface.

TERATOMAS arising from the stomach have been the subject of two published reports. Selman,1 in 1943, reported the case of an infant who was submitted to surgery at the age of 4 months because of an abdominal mass occupying the upper left quadrant. At operation, a fibrocystic mass 6 in. in diameter was disclosed, arising on a broad base from the anterior wall of the stomach. Removal of the mass and the portion of stomach wall from which it arose effected a cure. The tumor contained a variety of tissues, including skin and appendages, connective tissue, and colonic mucosa. It was a benign, complex teratoma. Selman's survey of the literature failed to disclose any previous case described by those interested in teratomas or benign gastric tumors.Large, Williams, and Neel encountered a similar tumor in a 7-month-old infant, in 1952.2 This child's hemoglobin was 4 gm. per 100

Symbiosis is receiving increased attention among all aspects of biology because of the unifying themes it helps construct across ecological, evolutionary, developmental, semiochemical, and pest management theory. Insects show a vast array of symbiotic relationships with a wide diversity of microorganisms. These relationships may confer a variety of benefits to the host (macrosymbiont), such as direct or indirect nutrition, ability to counter the defenses of plant or animal hosts, protection from natural enemies, improved development and reproduction, and communication. Benefits to the microsymbiont (including a broad range of fungi, bacteria, mites, nematodes, etc.) often include transport, protection from antagonists, and protection from environmental extremes. Symbiotic relationships may be mutualistic, commensal, competitive, or parasitic. In many cases, individual relationships may include both beneficial and detrimental effects to each partner during various phases of their life histories or as environmental conditions change. The outcomes of insect–microbial interactions are often strongly mediated by other symbionts and by features of the external and internal environment. These outcomes can also have important effects on human well being and environmental quality, by affecting agriculture, human health, natural resources, and the impacts of invasive species. We argue that, for many systems, our understanding of symbiotic relationships will advance most rapidly where context dependency and multipartite membership are integrated into existing conceptual frameworks. Furthermore, the contribution of entomological studies to overall symbiosis theory will be greatest where preoccupation with strict definitions and artificial boundaries is minimized, and integration of emerging molecular and quantitative techniques is maximized. We highlight symbiotic relations involving bark beetles to illustrate examples of the above trends.

Zwittermicin A acts synergistically with the insecticidal activity of Bacillus thuringiensis subsp. kurstaki Berliner against gypsy moth (Lymantria dispar (L.)) larvae. The objective of this study was to assess the influence of insect source and diet on this synergy. Zwittermicin A increased the mortality caused by B. thuringiensis subsp. kurstaki in gypsy moths collected from four population sources feeding on artificial diet, and on larvae feeding on four tree species, in a dose-dependent manner. Zwittermicin A did not cause mortality of L. dispar when applied alone. The ability of zwittermicin A to act synergistically with B. thuringiensis subsp. kurstaki did not differ greatly among these four populations, although mortality was slightly lower in a field-collected population from Michigan. Zwittermicin A increased the activity of B. thuringiensis subsp. kurstaki on L. dispar feeding on white oak, aspen, larch, and willow. Larval mortality was directly proportional to the concentration of zwittermicin A applied to foliage, although the synergistic effect of zwittermicin A differed among host species. These results suggest strategies for employing synergists in the application and resistance management of microbial pesticides.