Response of microbial populations to environmental disturbance

Taxonomic and genetic diversities of microbial communities disturbed by chemical pollutants were lower than in undisturbed reference communities. The dominant populations within the disturbed communities had enhanced physiological tolerances and substrate utilization capabilities, indicating that generalized physiological versatility is an adaptive characteristic of populations that successfully compete within disturbed communities.     

Morphology of a Virus of Blue-green Algae and Properties of Its Deoxyribonucleic Acid

The morphology of Safferman's virus of blue-green algae (phycovirus LPP-1) has been studied by electron microscopy and physicochemical methods. The virion has a short (100 to 200 A long, 150 A in diameter) forked tail, with an outer sheath, an inner core, and a capital attached to one of the vertices of a polyhedral head. The head capsid edge-to-edge distance is 600 A, based upon internal calibration of the magnification in electron micrographs by use of the line-line spacing of catalase crystals. Measurements of absorbancy and infectivity, and electron microscopy across the band of virus after zone centrifugation on a sucrose gradient, indicated that infectivity was correlated with the short-tailed particles described. The viral deoxyribonucleic acid (DNA) is linear, with a contour length of 13.2 +/- 0.5 mu, measured by the Kleinschmidt method. Its sedimentation coefficient, S(0) (20, w), is 33.4 +/- 0.7 S. These values are consistent with a molecular weight of 27 x 10(6) for the viral DNA. Based upon buoyant density in CsCl and thermal denaturation, the guanine-cytosine content of the DNA is 53%. The viral DNA was used as template for in vitro ribonucleic acid (RNA) synthesis by Escherichia coli RNA polymerase. This RNA annealed to 18% of the sequences in the viral DNA, 0.5% of the sequences in bacteriophage T7 DNA, and 0.25% of the sequences in Plectonema boryanum DNA, at saturating levels of RNA in the Hall-Nygaard hybridization assay. The lack of homology with T7 DNA is of interest because the two viruses are very similar morphologically. The lack of homology with host DNA suggests that this algal virus is a poor candidate for transduction.     

Bacteriophage T4D Head Morphogenesis. VIII. DNA-Protein Associations in Intermediate Head Structures That Accumulate in Gene 49? Mutant-Infected Cells

We have utilized the gene 49⁻ mutant-infected cells of bacteriophage T4D to accumulate large numbers of nucleic acid-protein intermediate head structures. These heads were used as substrates for experiments in the investigations of the mechanism of DNA packaging. Specifically, we have examined: (i) the susceptibility of the DNA in these structures to digestion by a variety of nucleases after a series of increasing temperature pulses from 25 to 100°C, (ii) the physicochemical characteristics of the DNA inside these heads, and (iii) the mechanism by which proteins are displaced from the interior of the head after treatment with basic proteins. We isolated DNA from these gene 49⁻ heads by use of gradient centrifugation procedures. The DNA had a molecular weight of 8 × 10⁶ and a density of 1.697 ± 0.005 g/cm³, and it contained a short resistant fraction (SRF) which, when associated with the gene 49⁻ heads, exhibited AT-protected regions that were not susceptible to micrococcal nuclease digestion. Such a fraction may contain pieces which are important in the initial association of the DNA with the prohead. Exposure of the gene 49⁻ intermediate capsid structures to basic proteins, such as bovine trypsin inhibitor, lysozyme, and l-polylysine-70, caused a displacement of an amorphous-appearing structure which may be a complex of the gene 49⁻ DNA and interior components of the capsid (e.g., internal proteins, polyamines). Our general conclusion is that in the gene 49⁻ intermediate head structures which are only partly filled with DNA, this DNA is held inside the head by strong electrostatic linkages with interior polypeptides and polyamines.     

Bacteriophage T4 head morphogenesis. VII. Terminal stages of head maturation.

Several aspects of the terminal stages of T4 head maturation were investigated using ts and am mutants blocked at single steps of the assembly pathway. We had previously found that cells infected with mutants of gene 13, e.g., tsN38 and amE609, accumulated both stable (10 to 20%)- and fragile (80%)-filled head precursors (Hamilton and Luftig, 1972). Here we showed the following for such gene 13-defective, mutant-infected cells. (i) Using thin-section analysis the pool of phage precursor structures observed under nonpermissive conditions was one-third of that observed when the cells were cultured under permissive conditions. (ii) In order for complete conversion of the precursors into viable phage to occur, there were apparent requirements of metabolic energy, protein, and DNA synthesis. (iii) The intracellular DNA pool under nonpermissive conditions exhibited a 50% distribution between 63S (mature size) and 200 S (concatenate size) DNA, with the latter DNA serving as a precursor pool. Further, this DNA pool when spread onto a protein monolayer exhibited a dispersed array of DNA, strands around a core, which was less dense than that found for the greater than 1,000S DNA concatenate isolated from gene 49-defective infected cells. (iv) When precuations were taken to stabilize the head precursors, such as lysis of the cells into glutaraldehyde, there was a 30% increase in the yield of 1,200S filled heads. Correlating these results and previous results concerning gene 49-defective unfilled heads, we propose that there are several forms of gene 13 fragile head precursors which serve as intermediates between gene 49 unfilled heads and gene 13 stable filled heads. We cannot, however, rule out the possibility that all gene 13-defective heads represent a single class of unstable particles, which decay slowly. In either case, we have shown that gene 13-defective particles are unstable to some degree inside the cell and are highly unstable outside the cell; yet all particles can still be efficiently converted to phage in vivo.     

Characterization of extracellular vesicle miRNA identified in peripheral blood of chronic pancreatitis patients

Molecular and Cellular Biochemistry - Plasma-derived extracellular vesicles (EV) can serve as markers of cell damage/disease but can also have therapeutic utility depending on the nature of their...     

66 Architectural role of HMO1 in bending,bridging, and compacting DNA

HMO1 proteins are abundant Saccharomyces cerevisiae (yeast) High Mobility Group Box (HMGB) protein (Kamau, Bauerla & Grove, 2004). HMGB proteins are nuclear proteins which are known to be architectural proteins (Travers, 2003). HMO1 possesses two HMGB box domains. It has been reported that double box HMGB proteins induce strong bends upon binding to DNA. It is also believed that they play an essential role in reorganizing chromatin and, therefore, are likely to be involved in gene activation. To characterize DNA binding we combine single molecule stretching experiments and AFM imaging of HMO1 proteins bound to DNA. By stretching DNA bound to HMO1, we determine the dissociation constant, measure protein induced average DNA bending angles, and determine the rate at which torsional constraint of the DNA is released by the protein. To further investigate the local nature of the binding, AFM images of HMO1-DNA complexes are imaged, and we probe the behavior of these complexes as a function of protein concentration. The results show that at lower concentrations, HMO1 preferentially binds to the ends of the double helix and links to the separate DNA strands. At higher concentrations HMO1 induces formation of a complex network that reorganizes DNA. Although HMG nuclear proteins are under intense investigation, little is known about HMO1. Our studies suggest that HMO1 proteins may facilitate interactions between multiple DNA molecules.     

Two new gonad-infecting philometrids (Nematoda: Philometridae) from the yellowedge grouper Hyporthodus flavolimbatus (Serranidae) and the great northern tilefish Lopholatilus chamaeleonticeps (Malacanthidae) in the northern Gulf of Mexico

Based on light and scanning electron microscopical studies, two new gonad-infecting species of Philometra Costa, 1845 (Nematoda: Philometridae) are described from marine perciform fishes in the northern Gulf of Mexico: P. hyporthodi n. sp. from the ovary of the yellowedge grouper Hyporthodus flavolimbatus (Poey) (Serranidae) and P. lopholatili n. sp. from the ovary of the great northern tilefish Lopholatilus chamaeleonticeps Goode & Bean (Malacanthidae). Philometra hyporthodi is mainly characterised by the body length of both the males (3.62–4.07 mm) and gravid female (105 mm), the length of the spicules (135–138 μm) and the presence of dorsal transverse lamella-like structures on the distal portion of the gubernaculum. Philometra lopholatili is distinguished by the presence of a distinct dorsal protuberance consisting of two dorsolateral lamellated parts separated from each other by a smooth median field, an uninterrupted mound on the male caudal extremity, the length of the spicules (165–189 μm) and the body length of the males (2.19–2.34 mm) and gravid female (280 mm). Philometra lopholatili is the first representative of the genus and the second philometrid species reported from fishes of the family Malacanthidae.