Characterization of a thermostable endoglucanase from Cellulomonas fimi ATCC484

Bacteria in the genus Cellulomonas are well known as secretors of a variety of mesophilic carbohydrate degrading enzymes (e.g., cellulases and hemicellulases), active against plant cell wall polysaccharides. Recent proteomic analysis of the mesophilic bacterium Cellulomonas fimi ATCC484 revealed uncharacterized enzymes for the hydrolysis of plant cell wall biomass. Celf_1230 (CfCel6C), a secreted protein of Cellulomonas fimi ATCC484, is a novel member of the GH6 family of cellulases that could be successfully expressed in Escherichia coli. This enzyme displayed very little enzymatic/hydrolytic activity at 30 °C, but showed an optimal activity around 65 °C, and exhibited a thermal denaturation temperature of 74 °C. In addition, it also strongly bound to filter paper despite having no recognizable carbohydrate binding module. Our experiments show that CfCel6C is a thermostable endoglucanase with activity on a variety of β-glucans produced by an organism that struggles to grow above 30 °C.

Isolation and characterisation of acid- and pepsin-soluble collagen from the skin of Cervus korean TEMMINCK var. mantchuricus Swinhoe

Acid-soluble collagen and pepsin-soluble collagen were extracted from the skin of deer, Cervus korean TEMMINCK var. mantchuricus Swinhoe. The two types of collagen were then characterised using sodium dodecyl sulfate–polyacrylamide gel electrophoresis, amino acid composition analysis, peptide hydrolysis patterns, thermal denaturation temperature, differential scanning calorimetry, Fourier transform infrared spectroscopy, and nuclear magnetic resonance imaging. The yield of pepsin-soluble collagen (9.62%) was greater than that of acid-soluble collagen (2.24%), but both types of collagen showed similar electrophoretic patterns with each other and with calf skin collagen. The peptide hydrolysis pattern results suggested that calf skin collagen and pepsin-soluble collagen from deer skin may be similar in terms of their primary structure. The thermal denaturation temperature of acid-soluble collagen and pepsin-soluble collagen were 36.67°C and 36.44°C, respectively, and their melting temperatures were 110°C and 120°C, respectively, which suggest high thermal stability. Fourier transform infrared showed a triple helical structure and nuclear magnetic resonance confirmed the presence of ‘hydration’ water. These results provide a basis for large-scale production and further application as alternatives to other mammalian collagens.

Similar C-phycocyanins from two strains of thermotolerant cyanophyte Mastigocladus laminosus

C-phycocyanin from two strains of the thermotolerant blue-green alga, Mastigocladus laminosus (NZ-DB2-m and I-30-m), that grow within different temperature ranges have been characterized with respect to aggregation, immunologic properties, subunit composition, and thermodenaturation. The critical thermal-denaturation temperature for phycocyanin from both strains of M. laminosus phycocyanin is 60 °C which is higher than that for mesophilic phycocyanin. Immunodiffusion studies have shown that these two strains of M. laminosus exhibit no antigenic differences and are closely related to the mesophilic Plectonema calothricoides and the thermophilic Synechococcus lividus (strain 3). Neither phenol nor α-naphthol has any effect on phycocyanin aggregation in these two strains of M. laminosus. There is also no enhancement of formation of large aggregates at their elevated temperature of cultivation. Furthermore, the phycocyanin of both strains of M. laminosus does not demonstrate any large amount of 19S or higher aggregates at any pH value. These observations suggest that the mode of adaptation of M. laminosus phycocyanin to high temperature is different from that previously encountered. It is also important to note that phycocyanin is essentially unchanged whether it is extracted from the same strain, M. laminosus (NZ-DB2-m), grown at either 50° or 37 °C.

Mesophilic mutants of an obligate psychrophile, Micrococcus cryophilus

Several mutants with elevated maximal growth temperature (MGT) were developed from an obligate psychrophile, Micrococcus cryophilus ATCC 15174, by ultraviolet irradiation. Two of the mutants, T8 and M19, have the most similar characteristics to those of their parent. The mutants lost the ability to grow well at 0 °C and showed changes in metabolic pathways while acquiring the ability to grow at elevated temperatures. Heat resistance and deoxyribonucleic acid thermal denaturation temperature were shown to be unrelated to maximum growth temperature. The significance of the mutants is discussed.

THERMAL DEPOLARIZATION OF FLUORESCENCE FROM POLYTENE CHROMOSOMES STAINED WITH ACRIDINE ORANGE

The degree of polarization of fluorescence from stretched Chironomus thummi polytene chromosomes, stained with low concentrations of acridine orange (AO), decreases with increasing temperature. The "half temperature" of this decrease (T½R) is lower than the expected DNA thermal denaturation temperature (Tm) by about 20°C. T½R is lowered as histone is removed from chromosomes. Balbiani ring regions of the fourth chromosome have T½R's much lower than other regions, and nearly as low as chromosomes which had been extensively pretreated with trypsin to remove histone and other proteins. Measurements of the thermal change in the rotational diffusion rate of AO in solution with DNA indicate that the temperature at which the DNA-AO bonding changes from a "rigid" to a "loose" mode varies with the GC percentage of the DNA, and in the same fashion as Tm, although 20°C lower.