Ultrastructural aspects of wheat straw degradation by Phanerochaete chrysosporium and Trametes versicolor

The ultrastructural patterns characterizing wheat straw degradation by the ligninolytic fungi Phanerochaete chrysosporium and Trametes versicolor were studied. During fungal attack, the less lignified tissues were degraded first, whereas the xylematic and sclerenchymatic fibers underwent a delayed attack. In straw samples degraded by T. versicolor, partial delignification, defibrillation and swelling of cell walls, often causing separation between primary and secondary walls, were observed. By contrast, the formation of erosions and fissures, with minor lignin removal, characterized the attack to the cell wall by P. chrysosporium. At an advanced stage of decay, KMnO₄ staining demonstrated abundant electron-dense material around hyphae and in the proximity of the cell-wall surface. In the case of P. chrysosporium, spherical black bodies were found in the erosions and fissures produced during fungal attack.     

Allozyme variability and phylogenetic relationships in the cultivated potato (Solanum tuberosum) and related species

Gene frequencies at 13 isozyme loci were determined in three South American taxa of cultivated potatoes [the diploid group (gp.) Stenotomum, the diploid subgroups (subgp.) Goniocalyx, and the tetraploid gp. Andigena ofS. tuberosum], in the diploid weed speciesS. sparsipilum, and in most of the main cultivars now raised in the Northern Hemisphere (the tetraploid gp. Tuberosum ofS. tuberosum). High levels of genetic variability (mean number of alleles per locus, percentage of polymorphic loci, and mean heterozygosity) were detected, being higher in tetraploid potatoes. An equilibrium among the evolutionary factors which increase genetic variability and artificial selection for maximum yield would explain the high uniformity of heterozygosity values we observed in both Andigena (0.36 ± 0.02) and Tuberosum (0.38 ± 0.01) cultivars.—The low value of genetic distance (D = 0.044) between Stenotomum and Goniocalyx does not support the status of species forS. goniocalyx.—In most isozyme loci, the electromorphs of gp. Andigena were a combination of those found in both gp. Stenotomum andS. sparsipilum, suggesting an amphidiploid origin of gp. Andigena from that two diploid taxa. The presence in Andigena of unique electromorphs, which were lacking in both gp. Stenotomum andS. sparsipilum, suggests that other diploid species could be also implied in the origin of tetraploid Andean potatoes. Furthermore, since Andigena were more related to Stenotomum (D = 0.052) than toS. sparsipilum (D = 0.241), the autopolyploidization of Stenotomum individuals and the subsequent hybridization with gp. Andigena may also have occurred. Thus, our study suggests a multiple origin (amphidiploidy, autoploidy, and hybridization at tetraploid level) of gp. Andigena.—Most of the electromorphs of gp. Tuberosum were also found in gp. Andigena; both the direct derivation of that group from the Andean tetraploid potatoes and the repeated introgression provided by breeding programmes could explain this result. However, the allele c of Pgm-B, present in 30 out of 76 Tuberosum cultivars from Northern Hemisphere as well as in 3 Chilean Tuberosum cultivars, lacks in the 258 Andigena genotypes sampled, suggesting that Chilean germplasm could have taken part in the origin of at least the 39% of the potato cultivars from Europe and North America analyzed here.—The distanceWagner procedure provides an estimate of a 30% of heterogeneity in the evolutionary divergence shown by different groups of cultivated potatoes. Diploid groups show a higher (22.5%) evolutionary rate than tetraploids, which can be attributed to both tetrasomic inheritance and facultative autofecundation that exists in Andigena and Tuberosum groups. Thus, artificial selection acting since 10000 years has not resulted in a higher rate of molecular evolution at the isozyme level in the tetraploids.     

Assembly of Bacillus subtilis phage phi29. 1. Mutants in the cistrons coding for the structural proteins.

The effect of mutations in the cistrons coding for the phage structural proteins has been studied by analyzing the phage-related structures accumulated after restrictive infection. Infection with susmutants in cistron 8, lacking both the major head and the fiber protein, does not produce any phage-related structure, suggesting a single route for the assembly of phage phi29; infection with ts mutants in this cistron produces isometric particles. Mutants is cistron 9, coding for the tail protein, TP1, produce DNA-free prolate heads with an internal core; these particles are abortive and contain the head proteins HPO, HP1 and HP3, the upper collar protein NP2 and the nonstructural proteins p7, p15 and p16. Mutants in cistron 10, coding for the upper collar protein, NP2, produce DNA-free isometric heads also with an internal core; they contain the head proteins and the nonstructural protein p7, suggesting that this protein forms the internal core. Mutants in cistrons 11 and 12, coding for the lower collar protein, NP3, and the neck appendages, NP1, respectively, give rise to the formation of DNA-containing normal capsids and DNA-free prolate particles, more rounded at the corners than the normal capsids and with an internal core; the DNA-containing 11-particles are formed by the head proteins and the upper collar protein; the DNA-free 11-particles contain, besides these proteins, the nonstructural protein p7 and a small amount of proteins p15 and 16. The DNA-containing 12-particles have all the normal phage structural proteins except the neck appendages, formed by protein NP1; the DNA-free particles are similar to the DNA-free 11-particles. After restricitive infection mutant sus14(1241) has a delayed lysis phenotype and produces a phage burst higher than normal, after artificial lysis. It produces DNA-containing particles, identical to wild-type phage, which have all the normal phage structural proteins, and DNA-free prolate particles, more rounded at the corners than the final phage particles and with an internal core; the last particles contain the same proteins as the DNA-free 11 or 12-particles. These particles could represent a prohead state, ready for DNA encapsulation. None of the DNA-containing particles have the nonstructural proteins p7, p15 or p16, suggesting that these proteins are released from the proheads upon DNA encapsulation.     

A family with a satellited Yq chromosome

Summary A large pedigree with a satellited Yq chromosome is described, Q, C, and NOR banding were performed. Family C proband suffers from a Klinefelter syndrome.     

Deoxyribonuclease activities in Myxococcus coralloides D

Myxococcus coralloides D produced cell-bound deoxyribonucleases (DNases) during the exponential phase of growth in liquid medium. DNase activity was much higher than that detected in other myxobacterial strains and was fractionated into three different peaks by filtration through Sephadex G-200. The DNases were named G, M and P. The optimum temperatures were 37 degrees C, 33 degrees C and 25 degrees C respectively, although high activities were recorded over the temperature range 20-45 degrees C. The pH range of high activity was between 6.0 and 9.0, with an optimum for each DNase at 8.0. DNases M and P were strongly inhibited by low concentrations of NaCl, but activity of DNase G was less affected by NaCl. The three activities required divalent metal ions as cofactors (especially Mg2+ and Mn2+); however, other metal ions (Fe2+, Ni2+, Zn2+) were inhibitors. The molecular weights were estimated by gel filtration chromatography and SDS-PAGE as 44 kDa (DNase G), 49 kDa (DNase M) and 39 kDa (DNase P).     

Substrate specificity and properties of the aryl-alcohol oxidase from the ligninolytic fungus Pleurotus eryngii.

The production in a 5-1 fermenter of the extracellular enzymes laccase and aryl-alcohol oxidase by the fungus Pleurotus eryngii was studied. The latter enzyme has been purified 50-fold by Sephacryl S-200 and Mono Q chromatography. Purified aryl-alcohol oxidase is a unique flavoprotein with 15% carbohydrate content, a molecular mass of 72.6 kDa (SDS/PAGE) and a pI of 3.9. The enzyme presents wide specificity, showing activity on benzyl, cinnamyl, naphthyl and aliphatic unsaturated alcohols. Neither activity nor inhibition of veratryl alcohol oxidation was found with saturated alcohols, but competitive inhibition was produced by aromatic compounds which were not aryl-alcohol oxidase substrates, such as phenol or 3-phenyl-1-propanol. From these results, it was apparent that a double bond conjugated with a primary alcohol is necessary for substrate recognition by aryl-alcohol oxidase, and that activity is increased by the presence of additional conjugated double bonds and electron donor groups. Both affinity and maximal velocity during enzymic oxidation of methoxybenzyl alcohols were affected in a similar way by ring substituents, increasing from benzyl alcohol (Km = 0.84 mM, Vmax = 52 U/mg) to 4-methoxybenzyl alcohol (Km = 0.04 mM, Vmax = 208 U/mg). Aryl-alcohol oxidase presents also a low oxidase activity with aromatic aldehydes, but the highest activity was found in the presence of electron-withdrawing groups.     

A new microtitration method for the enumeration of contagious bovine pleuropneumonia (CBPP) vaccines.

A new method is proposed for the microtitration of CBPP vaccines by performing eight parallel endpoint two-fold dilutions. When performed on a 96-well plate, it gives a titre with a precision of +/- 0.2 log10. By comparison, the established method, performed in tubes, gives a precision of only +/- 0.6 log10. The adaptation to microtitre plates allows much more economical culture of larger numbers of samples. Statistical analysis permits determination of vial-to-vial homogeneity of a batch and calculation of a titre with a precision of +/- 0.09 log10. The new method may be applied for the titration of mycoplasmas.