In vitro construction of a recombinant adenovirus Ad2:Ad5

A hybrid virus containing the left half of the Ad5 genome and the right half of the Ad2 genome has been constructed by ligating together in vitro the BamHI.-A fragment of Ad5 (map co-ordinates 0–59.5) to the-SawHI-A fragment of Ad2 (map coordinates 59.5–100), and using this DNA to transfect susceptible cells. Viable progeny virus has been obtained which grows as well as the parental virus without any requirement for helper virus, and probably contains a hybrid hexon polypeptide consisting of the major part of the Ad5 hexon with an Ad2 carboxy terminus.     

Photosensory transduction in the flagellated alga, Euglena gracilis. III. Induction of Ca2+-dependent responses by monovalent cation ionophores

(1) The effects of monovalent cation ionophores (valinomycin and gramicidin), a protonophore (nigericin) and extracellular pH change on the motility and blue light-induced photobehavior (step-down photophobic response) of Euglena were investigated. (2) Monovalent cation ionophores, but not the protonophore, can both partially suppress photobehavior and, under appropriate conditions, induce a change in flagellar activity (and thus cell movement) that appears identical to that associated with the photobehavior. (3) Valinomycin, at low extracellular KCl, delays the induction of photobehavior and also induces a light-independent elevation in the frequency of directional changes in the cells' swimming path. Both effects are suppressed by elevation in extracellular KCl. (4) Gramicidin, in the presence of the anion tetraphenylborate, suppresses photobehavior. The same combination, if applied in the presence of elevated extracellular NaCl, induces a light-independent cell tumbling and elevation in the frequency of directional changes in the cells' swimming path. The induced behavior is dependent on the extracellular Na concentration, requires the presence of extracellular Ca²⁺ and is blocked by La³⁺. (5) Photobehavior is observed over the pH range 3.5–8.2 and fluence/response relationships for photobehavior are not significantly different over the pH range 5.5–8.2. (6) The results provide a link between the previously reported effects of Ca²⁺ ionophores, and the effects of monovalent cations and monovalent cation-transport inhibitor on motility and photobehavior.     

Assimilation of ammonia inParacoccus denitrificans

Two pathways serve for assimilation of ammonia inParacoccus denitrificans. Glutamate dehydrogenase (NADP⁺) catalyzes the assimilation at a high NH₄ ⁺ concentration. If nitrate serves as the nitrogen source, glutamate is synthesized by glutamate-ammonia ligase and glutamate synthase (NADPH). At a very low NH₄ ⁺ concentration, all three enzymes are synthesized simultaneously. No direct relationship exists between glutamate dehydrogenase (NADP⁺) and glutamate-ammonia ligase inP. denitrificans, while the glutamate synthase (NADPH) activity changes in parallel with that of the latter enzyme. Ammonia does not influence the induction or repression of glutamate dehydrogenase (NADP⁺). The inner concentration of metabolites indicates a possible repression of glutamate dehydrogenase (NADP⁺) by the high concentration of glutamine or its metabolic products as in the case when NH₄ ⁺ is formed by assimilative nitrate reduction. No direct effect of the intermediates of nitrate assimilation on the synthesis of glutamate dehydrogenase (NADP⁺) was observed.     

Spontaneous occurrence of heat-stable somatic antigen variants in Bacillus thuringiensis

Heat-stable somatic antigen (HSSA) variants were isolated from Bacillus thuringiensis strain T84A1-A by antiserum-mediated selection. Substantial differences in HSSAs were clearly shown between variants and the parent strain by HSSA agglutination tests, Ouchterlony tests and precipitin-halo-formation (PHF) tests of extracellular HSSAs, although a 'one way'cross-reaction was evident. The frequency of HSSA variants in the population was < 10^-4, as determined by PHF tests on antiserum-agar plates. Heat-stable somatic antigen variants showed no alteration in flagellar antigenic structure and in 30 phenotypic characteristics. The insecticidal activity of HSSA variants was on the level with that of the parent strain, when tested with larvae of three lepidopterous species.     

Nitrogen fixation by the benthic freshwater cyanobacterium Lyngbya wollei

The ability of the benthic cyanobacterium Lyngbya wollei to fix nitrogen was studied using field samples and axenic cultures. L. wollei was collected and isolated from Lake Okeechobee, Florida, where it forms extensive mats. Rates of acetylene reduction up to 39.1 nmol mg dry wt⁻¹ h⁻¹ were observed for field samples. The maximum observed rate of acetylene reduction in axenic laboratory cultures was 200 nmol mg dry wt⁻¹ h⁻¹. Aerobic conditions limited nitrogen fixation activity, but dark/light cycles promoted the development of activity. Reduced oxygen levels appeared to be required for the development of significant levels of nitrogenase activity. The level of irradiance also had a significant impact on the level of activity. The potential significance of nitrogen fixation to Lyngbya production is discussed.     

A study of methods for in situ X-ray energy dispersive analysis of polyphosphate bodies in Plectonema boryanum

A variety of preparative methods for in situ X-ray energy dispersive analysis were tested to determine their effects on the elemental composition of polyphosphate bodies in P. boryanum. The bodies were found to contain large amounts of P and K and small amounts of Ca and Mg. Air drying, freeze-drying and freeze-drying from a liquid nitrogen slush all gave similar results. Fixation of the cells in glutaraldehyde and/or OsO₄ resulted in loss of the K and enhancement of the Ca peak. Magnesium was lost during embedding in epoxy.