Development of sporeless/low sporing strains of Pleurotus through mutation

Summary The sporophores of Pleurotus are gymnocarpous and continuously release spores in the atmosphere causing respiratory allergies like hay fever and farmer’s lung disease among workers. The allergy is caused by the antigens present on the walls of the spores. Apart from this, during commercial production, these spores settle on the fruit bodies, germinate and form a velvety film which gives an unpleasant appearance to the mushrooms. The spores emitted may include new genotypes likely to attack wood or trees. Spore allergy is one of the most important limiting factors for the large scale cultivation of this species. Different approaches are being adopted at IIHR for the production of commercial sporeless/low-sporing strains of Pleurotus to alleviate the spore allergy problem. Attempts were made during the present investigation to produce sporeless or low-sporing mutants through u.v. mutation. Mutation of the mycelium did not yield the desired results. Mutation of the spores of Pleurotus sajor-caju yielded an extremely low-sporing mutant after 75 min exposure. The character has been found to be stable for more than 10 generations of subculturing.     

Fine-scale substrate use by a small sit-and-wait predator

Substrate choice is one of the most important decisions thatsit-and-wait predators must make. Not only may it dictate theprey available but also the cover for the predator which mayconceal it from prey or its own predators. However, while ona particular substrate the behavior and use of that substratemay vary widely. When naïve, newly emerged crab spiderlingsMisumena vatia (Thomisidae) occupied flowering goldenrod Solidagocanadensis, their behavior differed markedly on inflorescenceswith relatively sparse and densely packed flower heads as wellas on experimentally thinned and unthinned inflorescences. Initially,the spiderlings most often hunted at the thinned sites and hidamong the dense flower heads at the unthinned sites, a differencethat disappeared in all broods tested after 2–3 h, possiblybecause of the growing hunger of the initially concealed individuals.Prey capture (dance flies) in the thinned sites initially significantlyexceeded that in unthinned sites but subsequently did not differ.However, spiderlings encountered their principal predator, thejumping spider Pelegrina insignis, significantly more oftenon unthinned than thinned inflorescences. Even though usagepatterns initially differed strikingly, spiderlings did notdiffer in their rates of quitting the two types of sites. Theseresults suggest a trade-off between foraging and predator avoidancethat changes in response to increasing hunger over time.     

dbEST‐derived microsatellite markers in celery (Apium graveolens L. var. dulce)

We report on the development of 11 (from database expressed sequence tags) dbEST‐derived microsatellite markers in celery (Apium graveolens L. var. dulce). The sequences were obtained from DNA accessions available from GenBank and contained di‐, tri‐ and pentanucleotidic motifs. All the microsatellites were found in expressed sequence tags and they are expected to become useful tools for ecological, genetic and evolutionary studies, as well as for celery breeding. Polymorphism was explored in 16 celery commercial varieties, and marker transferability was tested on three accessions of celeriac (A. graveolens var. rapaceum). Primers and PCR conditions for microsatellite amplification are reported.     

Unloading of the soleus in tail-suspended rats increases the number of intrafusal fibers in muscle spindles

Transmission electron microscopy was used to study the ultrastructure of muscle spindles (encapsulated stretch receptors) in m. soleus of adult Wistar rats after repeated hindlimb unloading. It was shown that the unloaded soleus contained not only spindles with a typical number of intrafusal fibers (four) but also spindles with five or six fibers. The increase in the number of intrafusal fibers in muscle spindles of the unloaded animals is likely to be caused by the proliferation of their satellite cells (myoblasts).     

Transfer of reducing equivalents into mitochondria by the interconversions of proline and Δ1-pyrroline-5-carboxylate

Direct evidence is presented for a proline cycle using a cell-free experimental system which sequentially transfers ³H from [1-³H]glucose to NADP⁺ to Δ¹-pyrroline-5-carboxylate and yields [³H]proline. The formation of [³H]proline depends on the presence of NADP, Δ¹-pyrroline-5-carboxylate, and the enzymes glucose-6-phosphate dehydrogenase and Δ¹-pyrroline-5-carboxylate reductase. The production of [³H]proline from unlabeled proline in the presence of mitochondria provides direct evidence for one complete turn of a proline cycle which transfers reducing equivalents produced by glucose oxidation in the pentose pathway into mitochondria. In this cycle, proline is oxidized to Δ¹-pyrroline-5-carboxylate by mitochondrial proline oxidase. Δ¹-pyrroline-5-carboxylate is released from mitochondria and is recycled back to proline by Δ¹-pyrroline-5-carboxylate reductase with concomitant oxidation of NADPH. At the maximal rate observed, 60% of Δ¹-pyrroline-5-carboxylate produced is recycled back to proline. This cycle provides a mechanism for transferring reducing equivalents from NADPH into mitochondria and is linked to glucose oxidation in the pentose pathway by NADPH turnover.     

Ribonucleases in Nicotiana tabacum leaf extracts treated with phenol

When tobacco leaf extracts are treated with phenol, ca 20% of the ribonuclease (RNase) activity survives and can be measured when the phenol is removed. After purification, the resistant RNase is inactivated by phenol; this suggests that tobacco leaves contain material that protects the RNase. Phenol-resistant RNase may be one of the TMV-RNA inactivating systems present in phenol extracts of tobacco leaves.     

A molecular dynamics study of the stoichiometric complex formed by poly (alpha, L-glutamate) and octyltrimethylammonium ions in chloroform solution.

We present a molecular dynamics simulation at 300 K in explicit solvent environment of chloroform of the stoichiometric complex formed by poly(alpha,L-glutamate) and octyltrimethylammonium ions. We observed that the alpha-helix conformation of the polypeptide chain remains stable during a 2-ns run. The surfactant ions predominantly adopted an extended conformation that is stabilized by favorable interactions with the organic solvent. Analysis of the organization of the surfactant with respect to the polypeptide chain indicated that each octyltrimethylammonium cation was preferentially bound to more than one carboxylate group. It was found that the most populated arrangement was that with the surfactant cations interacting with two carboxylate groups simultaneously.     

Effect of thiostrepton and 3′-terminal fragments of aminoacyl-tRNA on EF-Tu and ribosome-dependent GTP hydrolysis

The effect of the antibiotics thiostrepton and micrococcin on EF-T_u-catalyzed (ribosome-dependent) GTP hydrolysis in the presence of A-Phe, C-A-Phe, or C-C-A-Phe (related to the sequence of the 3′-terminus of aminoacyl-tRNA)(System I) or by methanol (‘uncoupled GTPase’, System II) was investigated. In System I, thiostrepton increases the binding affinities of the effectors to the EF-T_u·GTP·70 S ribosome complex, as well as the extent of the GTP hydrolysis, while the K^GTP_m is virtually unchanged. Similarly, in the uncoupled system (System II) and in the absence of effectors, thiostrepton significantly increases V^GTP_max, whereas K^GTP_m remains unaffected. Micrococcin is without any effect in both systems. The ‘uncoupled GTPase’ (in System II) is also strongly inhibited by C-A-Phe. The results indicate the crucial role of the EF-T_u site which binds the aminoacylated C-C-A terminus of aminoacyl-tRNA in promoting GTP hydrolysis. It follows that the binding of the model effectors (such as C-C-A-Phe) to that site is favorably influenced by the interaction of thiostrepton with the 50 S ribosomal subunit, whereas thiostrepton, per se, does not influence the affinity of EF-T_u for GTP.     

Survival of Escherichia coli in the environment: fundamental and public health aspects

In this review, our current understanding of the species Escherichia coli and its persistence in the open environment is examined. E. coli consists of six different subgroups, which are separable by genomic analyses. Strains within each subgroup occupy various ecological niches, and can be broadly characterized by either commensalistic or different pathogenic behaviour. In relevant cases, genomic islands can be pinpointed that underpin the behaviour. Thus, genomic islands of, on the one hand, broad environmental significance, and, on the other hand, virulence, are highlighted in the context of E. coli survival in its niches. A focus is further placed on experimental studies on the survival of the different types of E. coli in soil, manure and water. Overall, the data suggest that E. coli can persist, for varying periods of time, in such terrestrial and aquatic habitats. In particular, the considerable persistence of the pathogenic E. coli O157:H7 is of importance, as its acid tolerance may be expected to confer a fitness asset in the more acidic environments. In this context, the extent to which E. coli interacts with its human/animal host and the organism''s survivability in natural environments are compared. In addition, the effect of the diversity and community structure of the indigenous microbiota on the fate of invading E. coli populations in the open environment is discussed. Such a relationship is of importance to our knowledge of both public and environmental health.     

Two lignans from Litsea grandis and L. gracilipes

Two lignans, grandisin and (+)-eudesmin have been isolated from Litsea grandis and L. gracilipes respectively.