Characterization of an antigenically related family of cell-type specific proteins implicated in slug migration in Dictyostelium discoideum

The monoclonal antibody MUD50 recognizes a group of developmentally regulated proteins, which are almost exclusively expressed by prespore cells in developing aggregates of Dictyostelium discoideum. Some of these antigens are integrally associated with the cell membrane, as assessed by physical and detergent-fractionation procedures. The MUD50-reactive proteins are glycosylated and some are phosphorylated. Post-translational modification is the common antigenic feature that is recognized by the MUD50 antibody in these cell-type-specific proteins. A glycosylation-defective mutant, DL118, (modB) does not express the MUD50 epitope, but does express the MUD52 epitope, which is found on a different group of glycoproteins. Therefore, we conclude that MUD50 recognizes a particular carbohydrate epitope on a restricted group of proteins. These proteins are structurally diverse, but are apparently involved in the maintenance of structure and movement of the multicellular D. discoideum slug.     

Structural studies on cyanobacterial photosystem I

The cyanobacterial photosystem, I complex from Synechococcus sp. PCC6301 contains polypeptides of apparent M_r of 70,000, 18,000, 17,700, 16,000 and 10,000. Procedures were developed for the purification of the M_r 17,700 and 10,000 polypeptides. Amino acid analyses showed the absence of cystine and cysteine from these polypeptides. Amino-terminal sequences of 98 residues for the M_r 17,700 polypeptide and of 42 residues for the M_r 10,000 polypeptide were determined. Studies of pigment distribution within the photosystem I complex indicated that the binding of chlorophyll a and -carotene is in part dependent on the presence of these polypeptides.Abbreviations PSI photosystem I - P700 reaction center of PSI - SDS sodium dodecylsulfate - TBS tris-buffered saline - TTBS TBS containing Tween-20     

Sensitive, high-resolution chromatin and chromosome mapping in situ: presence and orientation of two closely integrated copies of EBV in a lymphoma line

Here we describe development and application of highly sensitive fluorescence methodology for localization of single-copy sequences in interphase nuclei and metaphase chromosomes by nonisotopic in situ hybridization. Application of this methodology to the investigation of Epstein-Barr virus integration in the Namalwa lymphoma cell line has revealed two EBV genomes closely integrated at the known site on chromosome 1. Detecting sequences as small as 5 kb, we further demonstrate resolution within interphase nuclei of two fragments of the viral genome spaced only 130 kb apart. Results indicate that the viral genomes are in opposite orientations and separated by roughly 340 kb of cellular DNA. This work demonstrates the feasibility and resolving power of interphase chromatin mapping to assess the proximity of closely spaced DNA sequences. Implications for virology, gene mapping, and investigation of nuclear organization are discussed.     

Role of chemical concentration and second carbon sources in acclimation of microbial communities for biodegradation

A study was conducted to determine the role of concentration of the test chemical, of a second organic compound, and of mutation in the acclimation period before the mineralization of organic compounds in sewage. The acclimation period for the mineralization in sewage of 2 micrograms of 4-nitrophenol (PNP) per liter increased from 6 to 12 days in the presence of 10 mg of 2,4-dinitrophenol per liter. The extension of the acclimation period was equivalent to the time required for mineralization of 2,4-dinitrophenol. In contrast, the time for acclimation for the degradation of 2 micrograms of PNP per liter was reduced when 10 or 100 mg of phenol per liter was added. Lower phenol levels increased the acclimation period to 8 days. The length of the acclimation period for PNP mineralization decreased as the initial concentration of PNP increased from 2 micrograms to 100 mg/liter. The acclimation period for phenol mineralization was lengthened as the phenol concentration increased from 100 to 1,400 mg/liter. The length of the acclimation period for PNP and phenol biodegradation was reproducible, but it varied among replicates for the biodegradation of other nitro-substituted compounds added to sewage or lake water, suggesting that a mutation was responsible for acclimation to these other compounds. The acclimation period may thus reflect the time required for the destruction of toxins, and it also may be affected by the concentration of the test compound or the presence of other substrates.     

Microbial communities in the saturated groundwater environment II: Diversity of bacterial communities in a Pleistocene sand aquifer and their in vitro activities

Bacterial cell numbers obtained from 103 water and sediment samples from a Pleistocene sandy aquifer in the Lower Rhine region (Bocholt, FRG) were determinated on P-agar and by direct count. Below 5 m under the surface, colony-forming unit (cfu) numbers in water samples were less than 100/ml, and in many cases less than 50/ml. In sediment samples, they were 10- to 100-fold higher (10²–10⁴ cfu/g dry wt), but changing markedly between different depths. Direct cell counts yielded numbers two to three orders of magnitude higher.About 2,700 strains of bacteria from 60 samples were isolated randomly and characterized by morphological and physiological properties. Of all the isolates, 71.6% were gram-negative, and 52.2% were gram-negative straight rods. Water communities, with one exception, had low proportions of gram-positive bacteria (<11%), whereas in all but one of the sediment communities percentages of gram-positive isolates were three- to sevenfold higher (35–43%). Water and sediment communities, as well as communities from different sampling sites and communities from different depths of the same sampling site, differed in their qualitative and quantitative morphotype composition and physiological capabilities.The in vitro activities of strains within a single community were quite different, indicating that each community is composed of many diverse bacteria, several having extremely different capabilities. Thus, each community has its own specific activity pattern. Gram-positive bacteria showed on an average lower total activities than did gram-negative bacteria. Grampositive bacteria as well as gram-negative bacteria from sediment had higher values of in vitro activities than the corresponding groups isolated from water. Many water and sediment bacteria preferred the same substrates which were utilized at high rates. However, there were differences in the degradation of the various other substrates present, and each community showed preferences for particular substrates, which they degraded best.The results of cell morphology and physiology studies indicated that all eight characterized communities were very different from one another and very diversely structured.     

Levels of pentose phosphate pathway enzymes fromCandida shehatae grown in continuous culture

Summary Candida shehatae exhibits different fermentative capacities when grown under different aeration conditions. These studies investigated the titers of xylose reductase, xylitol dehydrogenase, glucose-6-phosphate dehydrogenase and alcohol dehydrogenase in crude extracts ofCandida shehatae grown in continuous culture with various specific aeration rates. Carbon source, aeration rate, dilution rate and temperature were examined as variables. Xylose reductase and xylitol dehydrogenase were induced by xylose and were largely absent in glucose-grown cells. Alcohol dehydrogenae levels were higher in glucose-grown cells than in xylose-grown cells. The levels of this enzyme also correlated with the fermentative character of metabolism, having a low value under fully aerobic conditions, a high value under anaerobic conditions, and intermediate levels under various semi-aerobic conditions. Temperature had no effect on any enzyme level over the range of 20–30°C.Maintained in cooperation with the University of Wisconsin-Madison     

Interplasmidic illegitimate recombination in Bacillus subtilis

Summary The illegitimate recombination between Staphylococcus aureus plasmids pE194 (or pGG20, the hybrid between pE194 and Escherichia coli plasmid pBR322) and pBD17 (plasmid pUB110 without HpaII C-fragment) was studied in Bacillus subtilis. Cointegrates were generated with the frequency of 1–3x10^-8. Among 22 hybrids analysed 9 types of recombinants were found. Nucleotide sequences of all three parental plasmids were involved in intermolecular recombination. Nucleotide sequencing of recombinant DNA junctions revealed that in 8 cases recombination occurred between short homologous regions (9–15 bp). One recombinant was formed using nonhomologous sites. The similarity was demonstrated between nucleotide sequences of the recombination sites of two types of cointegrates and those used for pE194 integration into the B. subtilis chromosome. Possible mechanisms of illegitimate recombination are discussed.