Spore formation by Bacillus polymyxa during the inhibition of polymyxin biosynthesis

When amino acids are added to the culture of Bacillus polymyxa growing under the conditions of active spore formation, the rate of polymyxin biosynthesis and the quantity of spores being formed decrease. All cells in the population start to produce spores under these conditions, but only some of them pass through all of the differentiation stages. Most of the cells remain in the state of prospores. Some cells which have started to differentiate are characterized by ultrastructural anomalies, do not form prospores and undergo early lysis.     

Phasmids as effective and simple tools for construction and analysis of gene libraries

Phasmid lambda pMYF131, a hybrid of phage lambda vectors and plasmid pUC19, was constructed. The phasmid and its derivatives were shown to be efficient vectors for construction and analysis of gene libraries in Escherichia coli cells. The lambda pMYF131 DNA molecule contains all the genes and regions essential for phage lytic development. The plasmid cannot be packaged either in the monomeric or the oligomeric form due to its specific length. Elongation of the DNA molecule by ligation with fragments of foreign DNA can make it packageable and this is easily detected by plaque formation. Hence, the procedures used to construct genomic libraries can be simplified by selection of only recombinant DNA molecules just at the time and on the basis of their packaging in vitro. The output of recombinant clones per vector molecule was several times higher for vector lambda pMYF131, compared to phage vector lambda L47.1AB, and attained 3 x 10(6) clones per micrograms DNA. Vector and recombinant phasmids can be obtained in large quantities in plasmid form. lambda pMYF131 contains nine unique restriction sites which allow the cloning of DNA fragments with blunt ends and of fragments with various types of cohesive ends, obtained by digestion with 14 prototype restriction enzymes. The maximal size of the cloned DNA fragments is approx. 20 kb for lambda pMYF131. Phasmid vectors were used to construct libraries of bovine, pig and quail genomes, and genomic libraries of 17 species of bacteria. Application of suitable methods allowed the identification 13 individual genes within these libraries.     

Faster induction of photosynthesis increases biomass and grain yield in glasshouse-grown transgenic Sorghum bicolor overexpressing Rieske FeS

Sorghum is one of the most important crops providing food and feed in many of the world's harsher environments. Sorghum utilizes the C₄ pathway of photosynthesis in which a biochemical carbon-concentrating mechanism results in high CO₂ assimilation rates. Overexpressing the Rieske FeS subunit of the Cytochrome b₆f complex was previously shown to increase the rate of photosynthetic electron transport and stimulate CO₂ assimilation in the model C₄ plant Setaria viridis. To test whether productivity of C₄ crops could be improved by Rieske overexpression, we created transgenic Sorghum bicolor Tx430 plants with increased Rieske content. The transgenic plants showed no marked changes in abundances of other photosynthetic proteins or chlorophyll content. The steady-state rates of electron transport and CO₂ assimilation did not differ between the plants with increased Rieske abundance and control plants, suggesting that Cytochrome b₆f is not the only factor limiting electron transport in sorghum at high light and high CO₂. However, faster responses of non-photochemical quenching as well as an elevated quantum yield of Photosystem II and an increased CO₂ assimilation rate were observed from the plants overexpressing Rieske during the photosynthetic induction, a process of activation of photosynthesis upon the dark–light transition. As a consequence, sorghum with increased Rieske content produced more biomass and grain when grown in glasshouse conditions. Our results indicate that increasing Rieske content has potential to boost productivity of sorghum and other C₄ crops by improving the efficiency of light utilization and conversion to biomass through the faster induction of photosynthesis.     

Sampling properties of DNA sequence data in phylogenetic analysis

We inferred phylogenetic trees from individual genes and random samples of nucleotides from the mitochondrial genomes of 10 vertebrates and compared the results to those obtained by analyzing the whole genomes. Individual genes are poor samples in that they infrequently lead to the whole-genome tree. A large number of nucleotide sites is needed to exactly determine the whole-genome tree. A relatively small number of sites, however, often results in a tree close to the whole-genome tree. We found that blocks of contiguous sites were less likely to lead to the whole-genome tree than samples composed of sites drawn individually from throughout the genome. Samples of contiguous sites are not representative of the entire genome, a condition that violates a basic assumption of the bootstrap method as it is applied in phylogenetic studies.      

Demonstration of afferent connections of the forebrain in Emys orbicularis turtles by the peroxidase method

The transport of horseradish peroxidase (HRP) out of the injection site in the dorsal ventricular ridge was studied in turtles Emys orbicularis. Labeled cells in the forebrain were observed in the paleostriatum among fibers of the lateral forebrain bundle. In the thalamus most of cells containing the granular HRP reaction product were located in the n. rotundus, n. reuniens and perirotundal nuclei (n. dorso-medialis anterior, n. magnocellularis thalami, n (centralis) lateralis, n. dorso-medialis). Fewer labeled cells were revealed in the n. anterior and n. ventralis. The density of labeled cells in the majority of all thalamic nuclei increased if the HRP was extended from the dorsal ventricular ridge into the neostriatum and the pallial thickening with adjacent general cortex. HRP positive cells in the pretectal area, nuclei of the posterior commissura and mesencephalic ventro-lateral tegmentum were observed only in cases when the enzyme was diffused from the injection site into the neostriatum, while the HRP retrograde transport to n. geniculatus lateralis, pars dorsalis was revealed only when HRP was extended into the pallial thickening and adjacent general cortex. Ascending connections of the paleostriatum, thalamic nuclei and mesencephalic tegmentum with telencephalic structures, mainly with the dorsal ventricular ridge, were discussed.     

Actinomyces thermovulgaris endospores

It has been established for the first time that autolysis observed when Actinomyces thermovulgaris T-54 is cultivated on liquid media of various composition is caused by the formation of submerged spores. These, in contrast to exospores of the majority of the actinomycetes, are endospores according to their structure and the following criteria: thermostability, the presence of dipicolinic acid, the structure of ultrathin cross-sections studied by electron microscopy, the resistance to novobiocin.     

Functional redundancy between flavodiiron proteins and NDH‐1 in Synechocystis sp. PCC 6803

In oxygenic photosynthetic organisms, excluding angiosperms, flavodiiron proteins (FDPs) catalyze light‐dependent reduction of O₂ to H₂O. This alleviates electron pressure on the photosynthetic apparatus and protects it from photodamage. In Synechocystis sp. PCC 6803, four FDP isoforms function as hetero‐oligomers of Flv1 and Flv3 and/or Flv2 and Flv4. An alternative electron transport pathway mediated by the NAD(P)H dehydrogenase‐like complex (NDH‐1) also contributes to redox hemostasis and the photoprotection of photosynthesis. Four NDH‐1 types have been characterized in cyanobacteria: NDH‐1₁ and NDH‐1₂, which function in respiration; and NDH‐1₃ and NDH‐1₄, which function in CO₂ uptake. All four types are involved in cyclic electron transport. Along with single FDP mutants (?flv1 and Δflv3) and the double NDH‐1 mutants (?d1d2, which is deficient in NDH‐1_1,2 and ?d3d4, which is deficient in NDH‐1_3,4), we studied triple mutants lacking one of Flv1 or Flv3, and NDH‐1_1,2 or NDH‐1_3,4. We show that the presence of either Flv1/3 or NDH‐1_1,2, but not NDH‐1_3,4, is indispensable for survival during changes in growth conditions from high CO₂/moderate light to low CO₂/high light. Our results show functional redundancy between FDPs and NDH‐1_1,2 under the studied conditions. We suggest that ferredoxin probably functions as a primary electron donor to both Flv1/3 and NDH‐1_1,2, allowing their functions to be dynamically coordinated for efficient oxidation of photosystem I and for photoprotection under variable CO₂ and light availability.