Effect of blending lignin biopolymer on the biodegradability of polyolefin plastics

The ability of the lignin-degrading microorganism Phanerochaete chrysosporium to attack polyethylene and polypropylene was investigated using a series of polymer blends containing 10, 20 and 30% lignin obtained from the waste product of pulp and paper industry. In the cultivation medium, lignin peroxidase and Mn(II)peroxidase activities were detected. Degradation was verified by quantitative u.v. spectrophotometric analysis of the cultivation medium and by liberation of CO₂ from the blends. Measurement of the tensile strength after 30-days cultivation showed that the mechanical properties of the polymer blends were decreased during the biodegradation process. The isolation of oligomer fractions by tetrahydrofuran (THF) extraction of biodegraded polymers and their characterization by gel permeation chromatography (GPC), u.v. and Fourier transmission infrared (FTIR) spectroscopy indicates that biotransformation of the lignin component during the cultivation process initiates partial biodegradation of the synthetic polymer matrix.     

African swine fever virus IAP homologue inhibits caspase activation and promotes cell survival in mammalian cells

African swine fever virus (ASFV) A224L is a member of the inhibitor of apoptosis protein (IAP) family. We have investigated the antiapoptotic function of the viral IAP both in stably transfected cells and in ASFV-infected cells. A224L was able to substantially inhibit caspase activity and cell death induced by treatment with tumor necrosis factor alpha and cycloheximide or staurosporine when overexpressed in Vero cells by gene transfection. We have also observed that ASFV infection induces caspase activation and apoptosis in Vero cells. Furthermore, using a deletion mutant of ASFV lacking the A224L gene, we have shown that the viral IAP modulates the proteolytic processing of the effector cell death protease caspase-3 and the apoptosis which are induced in the infected cells. Our findings indicate that A224L interacts with the proteolytic fragment of caspase-3 and inhibits the activity of this protease during ASFV infection. These observations could indicate a conserved mechanism of action for ASFV IAP and other IAP family members to suppress apoptosis.     

Induction of mutations inSerratia marcescens by a proteosynthesis block

The formation of colour mutations ofSerratia marcescens by the action of chloramphenicol was studied. Pink variants were the commonest; the proportion of white variants was much smaller. Almost 100% mutations were formed in a two-day culture containing 100 μg. chloramphenicol/ml. Comparative experiments showed that the change in pigment formation was hereditary, i.e. that actual mutation, and not selection of chloramphenicol-resistant mutants, occurred. Mutation occurred both in strain 151 and strain HY. The resultant mutations remained constant throughout ten passages on normal nutrient medium. The minimum chloramphenicol concentration which produced an increase in the mutation frequency was 5 μg./ml. The combined effect of X-ray irradiation and chloramphenicol treatment somewhat stimulated the increase in the frequency of mutation as compared with cells which were only irradiated. The increase in the frequency of mutation was much slower on solid medium containing chloramphenicol.     

The genus Candida Berkhout

The properties of 53 fermentation type II strains of the genusCandida Berkhout were studied. The strains in question were originally identified asCandida tropicalis (Castellani) Berkhout,Candida pelliculosa Redaelli,Candida robusta Diddens et Lodder,Candida intermedia (Cif. et Ashf.) Langeron et Guerra,Candida langeroni Dietrichson,Candida obtusa (Dietrichson) v. Uden et Carmo Sousa and as various intermediate forms between these and other similar species. The classification criteria were extended by a number of very important characteristics, such as the degree of utilization of raffinose, the assimilation of lysine, xylose, cellobiose, maltotriose, maltotetraose and arabinose, virulence for mice, nutrient requirements, serological properties, etc. Actual classification was based on the numerical method of a similarity count. On the basis of this extension of the classification criteria, the characteristics of the speciesCandida tropicalis (Castellani) Berkhout andCandida pelliculosa Redaelli were defined in greater detail.Candida intermedia, evaluated on the basis of previously employed characteristics (lactose utilization, non-assimilation of KNO₃) does not appear to be a separate species, but a collection of different border-line forms of other species of this group.Candida robusta Diddens et Lodder is regarded as a member of the genusSaccharomyces, notCandida. The varietiesCandida tropicalis var.lambica andCandida pelliculosa var.cylindrica likewise do not seem to belong to the species concerned and will have to be studied in greater detail from the genetic aspect, in relation to other membrane-forming types ofCandida. The authors' extension of the classification criteria considerably reduced intraspecific variability, particularly in the speciesCandida tropicalis (Castellani) Berkhout, and led to greater accuracy in the practical diagnosis of this species, which is frequent in clinical material.     

Ecomorphological analysis as a complementary tool to detect changes in fish communities following major perturbations in two South African estuarine systems

Ecomorphological changes as a result of natural perturbations in estuarine fish communities were investigated in two South African estuaries (Swartvlei and East Kleinemonde), both before and after the loss of aquatic macrophyte beds in these systems. The fish communities were analysed using an ecomorphological diversity index (EMI) and the results compared to a traditional index, the Shannon-Wiener diversity index. The EMI revealed that the major changes in fish community composition recorded in both estuaries were associated with quantitative variations at the species level. Both estuaries essentially lost their macrophyte beds and ended up with the same type of bottom habitat (bare sediment). In both cases the fish morphological variability decreased immediately after aquatic macrophyte loss and then increased to end above the initial value. The ecomorphological analysis appeared to be sensitive to major ecological disturbances that occurred during the study period and this was confirmed by the morphospace configuration. The results indicate that the ecomorphology of the fish community responds to habitat changes and that this change corresponds to alterations in the representation of the different feeding types. These findings therefore contribute to the measurement of morphological changes in estuarine fish assemblages as a result of habitat changes within the ecosystem and we propose that ecomorphological analyses add another dimension to the information provided by existing diversity indices in studying changing fish communities.     

Protein phosphatases in higher plants: multiplicity of type 2A phosphatases in Arabidopsis thaliana

Two DNA fragments, AP-1 and AP-2, encoding amino acid sequences closely related to Ser/Thr protein phosphatases were amplified from Arabidopsis thaliana genomic DNA. Fragment AP-1 was used to screen. A. thaliana cDNA libraries and several positive clones were isolated. Clones EP8a and EP14a were sequenced and found to encode almost identical proteins (97% identity). Both proteins are 306 amino acids in length and are very similar (79–80% identity) to the mammalian isotypes of the catalytic subunit of protein phosphatase 2A. Therefore, they have been designated PP2A-1 and PP2A-2. A third cDNA clone, EP7, was isolated and sequenced. The polypeptide encoded (308 amino acids, lacking the initial Met codon) is 80% identical with human phosphatases 2A and was named PP2A-3. The PP2A-3 protein is extremely similar (95% identity) to the predicted protein from a cDNA clone previously found in Brassica napus. Southern blot analysis of genomic DNA using AP-1 and AP-2 probes, as well as probes derived from clones EP7, EP8a and EP14a strongly indicates that at least 6 genes closely related to type 2A phosphatases are present in the genome of A. thaliana. Northern blot analysis using the same set of probes demonstrates that, at the seedling stage, the mRNA levels for PP2A-1, PP2A-3 and the gene containing the AP-1 sequence are much higher than those of PP2A-2 and AP-2. These results demonstrate that a multiplicity of type 2A phosphatases might be differentially expressed in higher plants.