A DNA-modification methylase from Bacillus stearothermophilus V.

A type II modification methylase (M BstVI) was partially purified from the thermophilic bacterium Bacillus stearothermophilus V. The methylase catalyses the transfer of methyl groups from S-adenosyl-L-methionine to unmodified double-stranded DNA. The product of methylation was identified by paper chromatography as N6-methyladenine. Since M BstVI protects DNA against cleavage by BstVI and XhoI restriction endonucleases, it follows that it methylates the adenine residue in the sequence 5'-C-T-C-G-A-G-3'.     

Degradation of diarylethane structures by Pseudomonas fluorescens biovar I

Pseudomonas fluorescens biovar I was isolated from a pulp mill effluent based on its ability to grow on synthetic media containing 1,2-diarylethane structures as the sole carbon and energy source. Analysis of samples taken from cultures of this strain in benzoin or 4,4-dimethoxybenzoin (anisoin), showed that cleavage between the two aliphatic carbons takes place prior to ring fission. Intermonomeric cleavage was also obtained with crude extracts. Substrates of this reaction were only those 1,2-diarylethane compounds that supported growth of the bacterium. The purification and partial characterization of an enzyme that catalyzes the NADH-dependent reduction of the carbonyl group of benzoin and anisoin is also reported.     

Cryogenic changes in seminal protein of cattle and buffalo

The effect of subzero temperatures on the electrophoretic pattern of seminal plasma protein of cattle and buffalo was studied. The profiles of the seminal proteins of these two closely related species differed considerably. Cattle had 11 proteins in the anodic system (pH 8.6) and none in the cathodic system (pH 4.3), while buffalo have 19 in the anodic system (pH 8.6) and 2 proteins in the cathodic system (pH 4.3). Freezing of semen at -5 degrees C for 24 h caused aggregation of seminal proteins in both species. A higher aggregation and loss of proteins were observed when freezing was done in liquid nitrogen at -196 degrees C. The effect was more pronounced in buffalo than in cattle. Loss of more seminal plasma proteins due to cryoinjury in buffalo semen may account for its poorer freezability than that of cattle semen.     

Measurement of bacterial growth rates in subsurface sediments using the incorporation of tritiated thymidine into DNA

Microbial growth rates in subsurface sediment from three sites were measured using incorporation of tritiated thymidine into DNA. Sampling sites included Lula, Oklahoma, Traverse City, Michigan, and Summit Lake, Wisconsin. Application of the thymidine method to subsurface sediments required (1) thymidine concentrations greater than 125 nM, (2) incubation periods of less than 4 hours, (3) addition of SDS and EDTA for optimum macromolecular extraction, and (4) DNA purification, in order to accurately measure the rate of thymidine incorporation into DNA. Macromolecule extraction recoveries, as well as the percentage of tritium label incorporated into the DNA fraction, were variable and largely dependent upon sediment composition. In general, sandy sediments yielded higher extraction recoveries and demonstrated a larger percentage of label incorporated into DNA than sediments that contained a high silt-clay component. Reported results also indicate that the acid-base hydrolysis procedure routinely used for macromolecular fractionation in water samples may not be routinely applicable to the modified sediment procedure where addition of SDS and EDTA are required for macromolecule extraction. Growth rates exhibited by subsurface communities are relatively slow, ranging from 5.1 to 10.2×10⁵ cells g^–1 day^–1. These rates are 2–1,000-fold lower than growth rates measured in surface sediments. These data lend support to the supposition that subsurface microbial communities are nutritionally stressed.     

Microfungus-yeast mixed cultures in the degradation of amylaceous wastes. I: Interactions affecting amylolytic activity

Summary Some possible criteria in selection of amylolytic microorganisms for their mixed culture with non-amylolytic yeasts are discussed, and the growth of several microfungus-yeast mixed cultures on mussel processing wastes are studied.     

In vitro propagation ofMitragyna parvifolia Korth.

Multiple shoot formation and their elongation from excised apical vegetative shoots of a 40-year old-tree ofMitragyna parvifolia Korth. was achieved in Murashige and Skoog's medium supplemented with 4.44 M benzyl adenine. The in vitro regenerated shoots rooted when cultured on modified Murashige and Skoog's medium containing low inorganic salts and the three auxins. Regeneration by this method was suitable for mass propagation of the plant.     

New prospects for deducing the evolutionary history of metabolic pathways in prokaryotes: Aromatic biosynthesis as a case-in-point

Metabolic pathways of prokaryotes are more biochemically diverse than is generally recognized. Distinctive biochemical features are shared by phylogenetic clusters. The hierarchical levels of characterstate clustering depends upon evolutionary events which fortuitously became fixed in the genome of a common ancestor. Prokaryotes can now be ordered on a phylogenetic tree. This allows the evolutionary steps that underlie the construction and regulation of appropriately complex biochemical pathways to be traced in an evolutionary progression of prokaryote types that house these pathways. Essentially the approach is to deduce ancestral character states at ever deeper phylogenetic levels, utilizing logical principles of maximum parsimony. The current perspective on the evolution of the biochemical pathway for biosynthesis of aromatic amino acids is developed as a case-in-point model for analyses that should be feasible with many major metabolic systems. Phenylalanine biosynthesis probably arose prior to the addition of branches leading to tyrosine and tryptophan. An evolutionary scenario is developed that begins with non-enzymatic reactions which may have operated in primitive systems, followed by the evolution of an enzymatic system that pre-dated the divergence of major lineages of modern eubacteria (Gram-positive bacteria, Gram-negative purple bacteria, and cyanobacteria).Florida Agricultural Experiment Station, Journal Series No. 8251.     

Nitroso-aldicarb induces sister-chromatid exchanges in human lymphocytes in vitro

Nitroso-aldicarb was tested for its ability to induce sister-chromatid exchanges (SCE) and cell-cycle delay in human peripheral blood lymphocytes in vitro. This derivative of aldicarb induced a dose-dependent increase in SCE values per cell. In addition, a slight decrease in the successive mitotic progression of cells in culture was observed.     

Response of aromatic-pathway enzymes to changing physiological states of growth in suspension cultures of Nicotiana silvestris

The activity levels of enzymes of aromatic amino acid biosynthesis respond to changing physiological states of growth, as illustrated by results obtained from suspension-cultured cells of Nicotiana silvestris Speg. et Comes line ANS 1 (2N=24). The experimental system provides a foundation for interpretations about overall regulation of enzyme levels in relationship to growth physiology. Levels of activity for shikimate dehydrogenase (EC 1.1.1.25), prephenate aminotransferase and arogenate dehydrogenase were followed throughout a growth cycle obtained by a conventional subculture protocol. Enzyme date were also obtained from cell cultures maintained in continuous exponential growth for greater than 10 generations (EE cells). Both shikimate dehydrogenase and prephenate aminotransferase exhibited elevated stationary-phase levels of enzyme, much of which was carried over into a subsequent subculture. At least 4 generations of exponential growth were required before diminution of the latter two enzymes to the levels characteristic of truly exponential-phase growth (EE cells) occurred. This is reminiscent of the overall behavior of 3-deoxy-D- arabino -heptulosonate 7-phosphate (DAHP) synthase (EC 4.1.2.15), specifically attributed to the properties of the cytosolic isozyme species (DAHP synthase-Co). Elevation of arogenate dehydrogenase also occurred in stationary-phase cells, but diminished rapidly during lag phase to reach the level characteristic of EE cells.     

Effects of social isolation and crowding upon adrenocortical reactivity and behavior in the rat

The effects of social isolation and crowding on adrenocortical function and upon behavioral responsiveness to electric shock have been studied in male and female rats. All female experimental groups showed higher corticosterone levels and heavier adrenals than their male counterparts. The major effect of housing condition concerned the corticosterone response to stress, while basal hormone concentration was not modified. Socially housed rats showed a more intense adrenocortical response and also a greater behavioral reactivity to electric shock than the isolates.