Unraveling predatory-prey interactions between bacteria

It is known for decades that certain bacteria are capable to use other bacteria as nutrient sources. As a matter of fact, predatory behavior is not uncommon in prokaryotes. Predatory bacteria were found both in terrestrial and in aquatic habitats. To date, however, only a few of these micropredators have been thoroughly characterized with regard to their ecology and predation strategies. In this study, various aspects of the predatory behavior of the hitherto hardly investigated genera Lysobacter and Cupriavidus should be explored. The first goal was to develop tools for investigating the predatory performance of Lysobacter and Cupriavidus strains under laboratory conditions. Since predatory bacteria pursue many different hunting strategies, the design of a generally applicable assay was challenging. Available predation assays are tailored to predator-specific features, such as growth rate, motility and prey range. The best characterized facultative predators are myxobacteria and several predation assays have been established for this bacterial group. Because myxobacterial predation assays were found to be not suitable for testing of Lysobacter and Cupriavidus strains, an alternative predation assay was developed that provides quantitative data on the reduction of bacterial prey and the concomitant growth of the predator. For this purpose, as prey, soil bacteria that produce distinctive pigments or harbor specific antibiotic resistant gene were selected. Following a defined period in which the prey bacteria were incubated together with the predator, the individual populations could easily be distinguished based on the colors of their colonies or antibiotic resistance after plating. With CFU-based predation assay the predatory activity of both genera was verified. Lysobacter spp. and Cupriavidus spp. were shown to consume both Gram-negative and Gram-positive bacteria. The second aim was to identify factors that trigger and promote predatory activity. Using the CFU-based predation assay, it was confirmed that the selected Lysobacter spp. were effectively feeding on both Gram-positive and Gram-negative prey under nutrient-deficient conditions.Seit Jahrzehnten ist bekannt, dass bestimmte Bakterien in der Lage sind, ihresgleichen als Nahrungsquelle zu nutzen. Tatsächlich ist räuberisches Verhalten bei Prokaryoten nicht ungewöhnlich. Räuberische Bakterien konnten sowohl in terrestrischen wie auch in aquatischen Habitaten nachgewiesen werden. Bislang sind jedoch nur wenige dieser Mikroprädatoren hinsichtlich ihrer Ökologie und ihres Jagdverhaltens näher charakterisiert worden. In dieser Arbeit sollten verschiedene Aspekte des räuberischen Verhaltens der bislang kaum beachteten Gattungen Lysobacter und Cupriavidus erforscht werden. Das erste Ziel war die Entwicklung von Methoden, um das räuberische Verhalten von Lysobacter- und Cupriavidus-Stämmen unter Laborbedingungen untersuchen zu können. Da räuberische Bakterien unterschiedliche Jagdstrategien verfolgen, stellte die Entwicklung eines allgemein einsetzbaren Assays eine Herausforderung dar. Verfügbare Prädationsassays sind i.d.R. auf spezifische Räuber zugeschnitten. Sie sind auf die jeweilige Wachstumsrate, Motilität und das Beutespektrum optimiert. Die am besten charakterisierten fakultativen Räuber sind Myxobakterien, für die auch zahlreiche Prädationsassays etabliert worden sind. Da sich diese Assays für die Testung von Lysobacter- und Cupriavidus-Stämmen als ungeeignet erwiesen haben, wurde ein alternativer Assay entwickelt, mit dem quantitative Daten zur Tötung der bakteriellen Beute und zeitgleich zum damit einhergehenden Wachstum des Räubers erhoben werden können. Zu diesem Zweck wurden Bodenbakterien, die bestimmte Pigmente produzieren oder spezifische Antibiotika-resistente Gene haben, als Beute ausgewählt. Beute und Räuber wurden über einen definierten Zeitraum zusammen inkubiert. Nach Ausplattierung konnten die einzelnen Populationen leicht auf Grund der Koloniefarbe oder Antibiotikaresistenz unterschieden werden. Mit dem CFU-basierten Prädationsassay wurde die räuberische Aktivität beider Gattungen verifiziert. Lysobacter spp. und Cupriavidus spp. fraßen sowohl Gram negative als auch Gram positive Bakterien

Micromonospora schwarzwaldensis sp. nov., a producer of telomycin, isolated from soil

A Gram-positive, spore-forming actinomycete strain (HKI0641T) was isolated from a soil sample collected in the Black Forest, Germany. During a screening for antimicrobial natural products this bacterium was identified as a producer of the antibiotic telomycin. Morphological characteristics and chemotaxonomic data suggested that the strain belongs to the genus Micromonospora. The peptidoglycan contains meso-diaminopimelic acid, and the fatty acid profile consists predominantly of anteiso-C15:0, iso-C15:0, iso-C16:0 and C16:0. MK-10(H4), MK-10(H2) and MK-10 were identified as the major menaquinones. To determine the taxonomic positioning of strain HKI0641T, we computed a binary tanglegram of two rooted phylogenetic trees that were based upon 16S rRNA and gyrB gene sequences, respectively. The comparative analysis of the two common classification methods strongly supported the phylogenetic affiliation with the genus Micromonospora, but it also revealed discrepancies in the assignment at the level of the genomic species. 16S rRNA gene sequence analysis identified M. coxensis DSM 45161T (99.1%) and M. marina DSM 45555T (99.0%) as the nearest taxonomic neighbours, whereas the gyrB sequence of strain HKI0641T indicated a closer relationship to M. aurantiaca DSM 43813T (95.1%). By means of DNA-DNA hybridization experiments, it was possible to resolve this issue and to clearly differentiate strain HKI0641T from other Micromonospora species. The type strains of the aforementioned Micromonospora species could be further distinguished from strain HKI0641T by several phenotypic properties, such as colony colour, NaCl tolerance and the utilization of carbon sources. The isolate was therefore assigned to a new species, for which the name Micromonospora schwarzwaldensis sp. nov. is proposed. The type strain is HKI0641T (= DSM 45708T = CIP 110415T).Fil: Vela Gurovic, Maria Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Instituto de Química del Sur; Argentina. Hans-Knöll-Institute; AlemaniaFil: Müller, Sebastian. Hans-Knöll-Institute; AlemaniaFil: Domin, Nicole. Hans-Knöll-Institute; AlemaniaFil: Seccareccia, Ivana. Hans-Knöll-Institute; AlemaniaFil: Nietzsche, Sandor. University Hospital Jena; AlemaniaFil: Martin, Karin. Hans-Knöll-Institute; AlemaniaFil: Nett, Markus. Hans-Knöll-Institute; Alemani

Estimation of the Genetic Diversity in Tetraploid Alfalfa Populations Based on RAPD Markers for Breeding Purposes

Alfalfa is an autotetraploid, allogamous and heterozygous forage legume, whose varieties are synthetic populations. Due to the complex nature of the species, information about genetic diversity of germplasm used in any alfalfa breeding program is most beneficial. The genetic diversity of five alfalfa varieties, involved in progeny tests at Institute of Field and Vegetable Crops, was characterized based on RAPD markers. A total of 60 primers were screened, out of which 17 were selected for the analysis of genetic diversity. A total of 156 polymorphic bands were generated, with 10.6 bands per primer. Number and percentage of polymorphic loci, effective number of alleles, expected heterozygosity and Shannon's information index were used to estimate genetic variation. Variety Zuzana had the highest values for all tested parameters, exhibiting the highest level of variation, whereas variety RSI 20 exhibited the lowest. Analysis of molecular variance (AMOVA) showed that 88.39% of the total genetic variation was attributed to intra-varietal variance. The cluster analysis for individual samples and varieties revealed differences in their population structures: variety Zuzana showed a very high level of genetic variation, Banat and Ghareh were divided in subpopulations, while Pecy and RSI 20 were relatively uniform. Ways of exploiting the investigated germplasm in the breeding programs are suggested in this paper, depending on their population structure and diversity. The RAPD analysis shows potential to be applied in analysis of parental populations in semi-hybrid alfalfa breeding program in both, development of new homogenous germplasm, and identification of promising, complementary germplasm

Variochelins, Lipopeptide Siderophores from <i>Variovorax boronicumulans</i> Discovered by Genome Mining

Photoreactive siderophores have a major impact on the growth of planktonic organisms. To date, these molecules have mainly been reported from marine bacteria, although evidence is now accumulating that some terrestrial bacteria also harbor the biosynthetic potential for their production. In this paper, we describe the genomics-driven discovery and characterization of variochelins, lipopeptide siderophores from the bacterium <i>Variovorax boronicumulans</i>, which thrives in soil and freshwater habitats. Variochelins are different from most other lipopeptide siderophores in that their biosynthesis involves a polyketide synthase. We demonstrate that the ferric iron complex of variochelin A possesses photoreactive properties and present the MS-derived structures of two degradation products that emerge upon light exposure