An alternate method of calculating the heat of growth of Escherichia coli K-12 on succinic acid

The DeltaH(f) (0) unit weight of a complex substance such as a biological macromolecule is almost always obtained by means of combustion analysis. In theory, this can also be done by summing the DeltaH(f) (0) values for the monomers comprising the macromolecule plus the enthalpic energies involved in their polymerization. The enthalpy of formation of one unit-carbon formula weight of dried Escherichia coli K-12 cells was determined by summing the values of the enthalpies of formation of the quantities of monomers in the major classes of macromolecules substances comprising the cellular biomass and the enthalpic energies involved in their polymerizations. To this value was added the enthalpy of formation of the cellular ions in their aqueous standard states, per unit-carbon formula weight of cellular substance and the enthalpy change with respect to the ionization of the protein amino acid side chains. If it is assumed that the cellular fabric is insoluble and that the ions are soluble, the sum of the enthalpies of formation of all the cellular components should closely approximate the enthalpy of formation of one unit-carbon formula weight equivalent of living cells. Using this value, a calculation of the enthalpy change accompanying anabolism shows this latter to be effectively zero, indicating that the heat of growth (anabolism plus catabolism) is equal to that calculated for catabolism alone. This conclusion is in accord with those of several investigators who have used manometry or direct calorimetry.     

Rapid determination of plasmid-carrying yeast cells by using an imaging sensor system

A novel imaging sensor system for the determination of plasmid carrying yeast cells was developed. The sensor system consisted of an Silicon Intensifier Target (SIT) video camera, a fluorescent microscope, and a personal computer system equipped with an image memory board. This system was based on the fact that the membrane integrity of only plasmid-carrying cells is lost following cell growth in 5-fluoro-orotic acid (5-FOA) containing medium, and consequently these target cell can be stained with fluorescent probes and detected. In this study, plasmid-carrying cells were detected and their fraction determined in a mixture of both plasmid-carring and plasmid-free cells. A good correlation was observed between the values determined by this sensor system and the conventional method in the 30%-80% range, and one assay was possible within 4 h. This sensor system could be used for the monitoring of plasmid-carrying fraction in recombinant yeast cells during cultivation.     

Process development with nitrogenase-producing Escherichia coli C-M74 (pUS1) CellS

A process for the continuous fermentation of the genetically modified, nitrogenase-producing Escherichia coli C-M74 (pUS1)-strain has been developed. This strain, which is able to fix molecular nitrogen, has the nifgenes of the bacterium Klebsiella pneumoniae. Cell growth and nitrogenase activity of the enzyme have been optimized both in batch and continuous fermentations. For the fermentations, trial runs were performed by cultivating the E. coli cells in 50-ml culture bottles. The medium composition was varied in order to provide high biomass production and nitrogenase activity. For an effective fermentation control, an on-line analysis was built up for the substrates ammonium and glucose. Other medium components such as ampicillin, citric acid, acetic acid, nitrogenase activity, and protein were measured by using different off-line methods. Modern optical methods like in-line microfluorometry for monitoring the culture fluorescence and laser flow cytometry for the estimation of DNA and protein content were also employed. Plasmid stability was also determined.     

Extrachromosomal human immunodeficiency virus type-1 DNA can initiate a spreading infection of HL-60 cells

In this report, we describe a human immunodeficiency virus type-1 (HIV-1)-infected promyelocytic cell line, OM, derived from HL-60 cells. Although the OM cell line was biologically cloned twice, the pattern of HIV-1 expression during culture appeared analogous to a classical acute spreading infection and was inhibited by both azidothymidine and recombinant soluble CD4 treatment. The number of OM cells actually expressing HIV-1 at the beginning of culture was 0%, reached a peak of nearly 100% at 6 weeks, and then fell to less than 10% HIV-1+ cells by 10 weeks. Clonal analysis of the surviving cells verified that stable HIV-1+ OM cells resulted from the spreading infection. Southern analysis confirmed the transmission of HIV-1 through these OM cultures and the occurrence of stable clones which resulted. The initial percentage of OM cells actually harboring the HIV-1 genome was less than 0.1%, indicating nonfaithful transmission of an unintegrated HIV-1 genome during clonal expansion. These results demonstrate that extrachromosomal HIV-1 DNA can contribute to the spread of HIV-1 infection and give rise to cells which have stably integrated HIV-1 provirus.     

Monitoring hairy-root growth by image analysis

Hairy roots, incited byAgrobacterium rhizogenes, form a useful system for analysing the expression and phenotypic effects of foreign genes in plant root tissue. Image analysis offers a non-invasive method of describing their growth in culture. Images of pea (coarse) andBrassica (fine) hairy roots were captured, processed and analysed without difficulty using a commercially available image analysis system. The value of this method in monitoring intermediate changes in growth pattern was illustrated by following the changes in five putatively chlorsulfuron-resistantBrassicc hairy-root lines cultured with and without a selective level of chlorsulfuron. Areas of hairy-root research where this technique will be particularly useful are discussed.     

Projection of Monte Carlo and molecular dynamics trajectories onto the normal mode axes: human lysozyme

A method is presented to describe the internal motions of proteins obtained from molecular dynamics or Monte Carlo simulations as motions of normal mode variables. This method calculates normal mode variables by projecting trajectories of these simulations onto the axes of normal modes and expresses the trajectories as a linear combination of normal mode variables. This method is applied to the result of the molecular dynamics and the Monte Carlo simulations of human lysozyme. The motion of the lowest frequency mode extracted from the simulations represents the hinge bending motion very faithfully. Analysis of the obtained motions of the normal mode variables provides an explanation of the anharmonic aspects of protein dynamics as due first to the anharmonicity of the actual potential energy surface near a minimum and second to trans-minimum conformational changes.     

Dna Ploidy Studies of Benign and Malignant Tumours: Comparison of Flow Cytometry and Image Analysis Techniques Using Two Types of Cytological Specimen

DNA ploidy studies were carried out on Feulgen stained smears and cytocentrifuge preparations from 35 malignant tumours and four benign neoplasms using the CAS image analyser. The smears were prepared from scrapings from fresh tumour tissue whereas the cytocentrifuge preparations were prepared from single nuclear suspensions from paraffin-embedded cell blocks from the same tumour. Histograms obtained by image analysis of the tumour scrapes were compared with those obtained on the cytocentrifuge preparations. Concordant results were obtained in four benign tumours (100%) and 32 malignant tumours (91%). The results obtained by image analysis were also compared with results obtained by flow cytometry of the tumour tissue. Discordant results were obtained for three malignant tumours. Possible reasons for the discrepancy include sampling error, tumour heterogeneity and selective loss of cell populations during processing.     

Lithic microwear analysis in archeology

Stone tools are the most durable and ubiquitous residue of prehistoric hominid activity. For this reason, archeologists attempt to learn as much as possible about hominid behavior from the analysis of lithic artifacts. Lithic microwear analysis reconstructs aspects of stone-tool use from patterned variation in the traces of microscopic wear on those tools. The analysis of lithic microwear traces has increased our understanding of how stone tools were used in contexts ranging from the early Pleistocene to the ethnographic present.     

Morphological adaptions of Quercus ilex leaves in the Castelporziano forest

The annual course of vegetative growth of the most representative species of a Quercus ilex L. forest in Castelporziano (Latium, Italy) was studied through periodical analysis of selected ecophysiological leaf indexes, for the period 1987–1990. The results demonstrate that the local climate facilitates continuous vegetative activity of the sclerophyllous species without a latent phase. The variable morphology of sun and shade leaves of Q. ilex illustrates the plant's response to environmental stress.     

Microsite differentiation in a Mediterranean oak savanna

Abstract. Microscale variation of vegetation was studied in a Mediterranean oak savanna dominated by annual plants at Neve Ya'ar Experimental Station, in the lower Galilee of Israel. Species presence/absence data were recorded in 20 cm x 20 cm quadrats on a 500-quadrat transect. These data were ordinated with Detrended Correspondence Analysis. Soil nitrate, phosphorous, potassium, pH, soil moisture and salinity were determined at 2-m intervals on the 100-m transect, at monthly intervals from November 1981 to April 1982. Litter cover and canopy shade were surveyed in October 1981 and April 1982. A sharp rise in available nitrate occurred in November, following the first winter rains. Patterns in herbaceous vegetation, as expressed by sample ordination scores, correlated best with litter cover in October. This suggested that vegetation pattern in this community may be strongly influenced by environmental conditions at the time of seedling germination and establishment.