Isolation of covalently closed circular deoxyribonucleic acid from Streptomyces coelicolor A3(2).

Covalently closed circular deoxyribonucleic acid (DNA) was isolated from two strains of Streptomyces coelicolor A3(2), representing two of the known fertility types. In each of the two strains circular DNA of about 20 times 10-6 daltons could be detected, amounting to about 1.5% of the total cellular DNA. The possible function of this DNA is discussed.     

Model-based prediction of the individual training intensity for the lower back muscles with application to physical rehabilitation

The individual adjustment of the training intensity during physical training of the lower back muscles plays a crucial role in strength rehabilitation of chronic low back pain patients. Since an one-repetition maximum test may increase injury risk and a common N-repetition maximum test with several trials is stressful for the patient and in many cases inaccurate, in this paper a model-based approach is proposed for predicting the N-repetition maximum. The individual training intensity represented by the N-repetition maximum is predicted by means of a biomechanical model together with fatigue parameters obtained from an isometric muscle contraction measurement.     

Extracellular Streptomyces lividans vesicles: composition,biogenesis and antimicrobial activity

We selected Streptomyces lividans to elucidate firstly the biogenesis and antimicrobial activities of extracellular vesicles that a filamentous and highly differentiated Gram‐positive bacterium produces. Vesicle types range in diameter from 110 to 230 nm and 20 to 60 nm, respectively; they assemble to clusters, and contain lipids and phospholipids allowing their in situ imaging by specific fluorescent dyes. The presence of the identified secondary metabolite undecylprodigiosin provokes red fluorescence of a portion of the heterogeneous vesicle populations facilitating in vivo monitoring. Protuberances containing vesicles generate at tips, and alongside of substrate hyphae, and enumerate during late vegetative growth to droplet‐like exudates. Owing to in situ imaging in the presence and absence of a green fluorescent vancomycin derivative, we conclude that protuberances comprising vesicles arise at sites with enhanced levels of peptidoglycan subunits [pentapeptide of lipid II (C55)‐linked disaccharides], and reduced levels of polymerized and cross‐linked peptidoglycan within hyphae. These sites correlate with enhanced levels of anionic phospholipids and lipids. Vesicles provoke pronounced damages of Aspergillus proliferans, Verticillium dahliae and induced clumping and distortion of Escherichia coli. These harmful effects are likely attributable to the action of the identified vesicular compounds including different enzyme types, components of signal transduction cascades and undecylprodigiosin. Based on our pioneering findings, we highlight novel clues with environmental implications and application potential.     

Ant Colonies Do Not Trade-Off Reproduction against Maintenance

The question on how individuals allocate resources into maintenance and reproduction is one of the central questions in life history theory. Yet, resource allocation into maintenance on the organismic level can only be measured indirectly. This is different in a social insect colony, a “superorganism” where workers represent the soma and the queen the germ line of the colony. Here, we investigate whether trade-offs exist between maintenance and reproduction on two levels of biological organization, queens and colonies, by following single-queen colonies of the ant Cardiocondyla obscurior throughout the entire lifespan of the queen. Our results show that maintenance and reproduction are positively correlated on the colony level, and we confirm results of an earlier study that found no trade-off on the individual (queen) level. We attribute this unexpected outcome to the existence of a positive feedback loop where investment into maintenance (workers) increases the rate of resource acquisition under laboratory conditions. Even though food was provided ad libitum, variation in productivity among the colonies suggests that resources can only be utilized and invested into additional maintenance and reproduction by the colony if enough workers are available. The resulting relationship between per-capita and colony productivity in our study fits well with other studies conducted in the field, where decreasing per-capita productivity and the leveling off of colony productivity have been linked to density dependent effects due to competition among colonies. This suggests that the absence of trade-offs in our laboratory study might also be prevalent under natural conditions, leading to a positive association of maintenance, (= growth) and reproduction. In this respect, insect colonies resemble indeterminate growing organisms.     

Bacteriocin and antibiotic resistance plasmids in Bacillus cereus and Bacillus subtilis.

A number of plasmids have been isolated as covalently closed circular DNAs from strains of Bacillus cereus and B. subtilis. From 12 out of 15 strains of B. cereus, plasmids could be isolated. Most of the B. cereus strains contained two or more plasmids. Their molecular weights ranged from 1.6 X 10(6) to 105 X 10(6). Bacteriocin production could be attributed to a 45 X 10(6)-dalton plasmid (pBC7) from B. cereus DSM 336, and tetracycline resistance to a 2.8 X 10(6) plasmid (pBC16) from B. cereus GP7. Two streptomycin-resistant strains of B. subtilis harbored plasmids of 5.2 X 10(6) and 9 X 10(6), respectively, which were, however, not correlated with the antibiotic resistance. The plasmid carrying resistance to tetracycline, pBC16, which was originally isolated from B. cereus, could be subsequently transformed in B. subtilis, where it is stably maintained.     

Characterization and localization of prodiginines from Streptomyces lividans suppressing Verticillium dahliae in the absence or presence of Arabidopsis thaliana

The ascomycete Verticillium dahliae causes worldwide vascular wilt of many field and horticultural plants. The melanized resting structures of this fungus, so-called microsclerotia, survive for many years in soils and continuously re-infect plants. Due to the absence of known fungicides, Verticillium wilt causes immense crop losses. We discovered that the Gram-positive, spore-forming soil bacterium Streptomyces lividans expresses members of the prodiginine family during co-cultivation with V. dahliae. Using HPLC and LC-MS analysis of cultures containing S. lividans alone or grown together with V. dahliae, we found that undecylprodigiosin [394.4 M+H](+) is highly abundant, and streptorubin B [392.4 M+H](+) is present in smaller amounts. Within co-cultures, the quantity of undecylprodigiosin increased considerably and pigment concentrated at and within fungal hyphae. The addition of purified undecylprodigiosin to growing V. dahliae hyphae strongly reduced microsclerotia formation. Undecylprodigiosin was also produced when S. lividans grew on the roots of developing Arabidopsis thaliana plants. Furthermore, the presence of the undecylprodigiosin producer led to an efficient reduction of V. dahliae hyphae and microsclerotia on plant-roots. Based on these novel findings and previous knowledge, we deduce that the prodiginine investigated leads to multiple cellular effects, which ultimately impair specific pathways for signal transduction and apoptosis of the fungal plant pathogen.     

The cellulolytic system of Streptomyces reticuli

The bacterium Streptomyces reticuli produces an unusual mycelia-associated cellulase (Avicelase, Cell) which is solely sufficient to degrade crystalline cellulose to cellobiose. The enzyme consists of a binding domain, one adjoining region with unknown function, and a catalytic domain belonging to the cellulase family E. During cultivation, the strain produces a specific protease which processes the Avicelase to a truncated enzyme lacking the binding domain. The cellulase synthesis is regulated by induction (Avicel) and repression (metabolizable sugars and glycerol).     

Social influence on age and reproduction: reduced lifespan and fecundity in multi-queen ant colonies

Evolutionary theories of ageing predict that life span increases with decreasing extrinsic mortality, and life span variation among queens in ant species seems to corroborate this prediction: queens, which are the only reproductive in a colony, live much longer than queens in multi-queen colonies. The latter often inhabit ephemeral nest sites and accordingly are assumed to experience a higher mortality risk. Yet, all prior studies compared queens from different single- and multi-queen species. Here, we demonstrate an effect of queen number on longevity and fecundity within a single, socially plastic species, where queens experience the similar level of extrinsic mortality. Queens from single- and two-queen colonies had significantly longer lifespan and higher fecundity than queens living in associations of eight queens. As queens also differ neither in morphology nor the mode of colony foundation, our study shows that the social environment itself strongly affects ageing rate.     

Architecture of the Streptomyces lividans DnaA protein-replication origin complexes

The Streptomyces oriC region contains two clusters of 19 DnaA boxes separated by a spacer (134 bp). The Streptomyces DnaA protein consists, like all other DnaA proteins, of four domains: domain III and the carboxyterminal part (domain IV) are responsible for binding of ATP and DNA, respectively. Binding of the DnaA protein to the entire oriC region analysed by electron microscopy showed that the DnaA protein forms separate complexes at each of the clusters of DnaA boxes, but not at the spacer separating them. In vivo mutational analysis revealed that the number of DnaA boxes and the presence of the spacer linking both groups of DnaA boxes seem to be important for a functional Streptomyces origin. We suggest that the arrangement of DnaA boxes allows the DNA-bound DnaA protein to induce bending and looping of the oriC region. As it was shown by electrophoretic mobility shift assay and "one hybrid system", two domains, I and III, facilitate interactions between DnaA molecules. We postulate that domain I and domain III could be involved in cooperativity at distant and at closely spaced DnaA boxes, respectively. The long domain II extends the range over which N termini (domain I) of DNA-bound DnaA protein can form dimers. Thus, interactions between DnaA molecules may bring two clusters of DnaA boxes separated by the spacer into functional contact by loop formation. Removal of the spacer region or deletion of domains I and II resulted, respectively, in nucleoprotein complexes which are not fully developed, or huge nucleoprotein aggregates.