Mixing patterns in Amazon lakes

The diel mixing patterns of two small floodplain lakes, Lago Jacaretinga in the Amazon drainage, and Lago Cristalino in the Rio Negro system, were investigated during both the high-water and low-water states of the Amazon River hydrograph. Measurements included temperature, oxygen, ammonia, phosphate, and chlorophyll. In both lakes thermal stratification developed during the day and was eroded at night. During the low-water period when the lakes were shallow, nocturnal circulation extended to the lake bottom, whereas when the lakes were deeper (greater than about 5 m), circulation did not reach the bottom and an anoxic hypolimnion developed. During the low-water period, percent of oxygen concentrations were relatively high but always less than saturation. Low oxygen concentrations were observed during the high-water period. At all times nocturnal mixing supplied a significant amount of oxygen to the lake ecosystems. Nighttime upward mixing of recycled nitrogen and phosphorus also appeared to be important nutrient sources for algal productivity.     

Plasmid-determined silver resistance in Pseudomonas stutzeri isolated from a silver mine.

A silver-resistant strain of Pseudomonas stutzeri was isolated from a silver mine. It harbored three plasmids, the largest of which (pKK1; molecular weight, 49.4 X 10(6)) specified silver resistance. Plasmid pKK1 was apparently nonconjugative but could be transferred to Pseudomonas putida by mobilization with plasmid R68.45.     

Organization of the ribosomal ribonucleic acid genes in various wild-type strains and wild-collected strains of Neurospora

Summary The organization of the ribosomal DNA (rDNA) repcat unit in the standard wild-type strain of Neurospora crassa, 74-OR23-1A, and in 30 other wild-type strains and wild-collected strains of N. crassa, N. tetrasperma, N. sitophila, N. intermedia, and N. discreta isolated from nature, was investigated by restriction enzyme digestion of genomic DNA, and probing of the Southern-blotted DNA fragments with specific cloned pieces of the rDNA unit from 74-OR23-1A. The size of the rDNA unit in 74-OR23-1A was shown to be 9.20 kilobase pairs (kb) from blotting data, and the average for all strains was 9.11+0.21 kb; standard error=0.038; coefficient of variation (C.V.)=2.34%. These data indicate that the rDNA repeat unit size has been highly conserved among the Neurospora strains investigated. However, while all strains have a conserved HindIII site near the 5 end of the 25 S rDNA coding sequence, a polymorphism in the number and/or position of HindIII sites in the nontranscribed spacer region was found between strains. The 74-OR23-1A strain has two HindIII sites in the spacer, while others have from 0 to at least 3. This restriction site polymorphism is strain-specific and not species-specific. It was confirmed for some strains by restriction analysis of clones containing most of the rDNA repeat unit. The current restriction map of the 74-OR23-1A rDNA repeat unit is presented.     

Mechanisms of genetic control of immune responses

The mechanisms underlying Ir gene control of CMI were addressed by examining the DTH and Tprlf responses specific for the synthetic polymers GT, GAT, and GA. We show that BALB/c mice (GAT/GA responders, GT nonresponders) primed with GT fail to develop DTH and Tprlf responses specific for GT, GAT, or GA. GAT immunization resulted in DTH responses that could be elicited not only with GAT and GA but also with GT, demonstrating that GT-specific T_DH are present in nonresponder mice. GT-specific DTH was transferred with Thy-1⁺ Lyt-1⁺2^–, H-2 Irestricted, nylon wool nonadherent cells. GA-primed BALB/c mice developed GAT- and GA-, but not GT-apecific DTH responses, indicating that GA and GT do not cross-react at the T-cell level. The ability of GAT [but not a mixture of GA plus GT, or GT electrostatically complexed to the immunogenic carrier MBSA (GT-MBSA)] to induce GT-specific DTH suggested a requirement for covalent linkage of stimulatory GA and nonstimulatory GT determinants present on the GAT molecule. Similarly, GT-specific in vitro Tprlf responses could be demonstrated in GAT-primed mice exhibiting significant levels of GT-specific DTH but not in GT- or GT-MBSA-primed mice. Tolerization experiments also suggested that GT-specific Th were involved in the development of GT-specific DTH in GAT-primed mice. The GT nonresponsiveness of BALB/c mice for DTH and Tprlf responses could not be reversed by treatments designed to abrogate Ts activity (priming with GT-MBSA and CY injection), nor could GT-primed cells be shown to inhibit the development or elicitation of GT-specific CMI in GAT-primed mice during the afferent and/or efferent stages of DTH. Our results suggest that GT nonresponsiveness does not result from the absence of GT-specific T cells or preferential induction of Ts. The results are discussed in the context of hole-in-the-repertoire and antigen presentation (determinant selection) models of Ir gene control.Abbreviations used in this paper APC antigen-presenting cells - BSA bovine serum albumin - BSS Mishell-Dutton balanced salt solution - CFA complete Freund's adjuvant - CMI cell-mediated immunity - CY cyclophosphamide - DTH delayed-type hypersensitivity - GA poly(Glu⁶⁰Ala⁴⁰) - GAT poly (Glu⁶⁰Ala³⁰Tyr¹⁰) - GT poly(Glu⁵⁰Tyr⁵⁰) - GT-MBSA GT complexed to methylated bovine serum albumin - It immune response - LN lymph node - PPD purified protein derivative of tuberculin - TDH DTH T cells - Th helper T cells - Tprlf T-cell proliferation - Ts suppressor T cells - TsF T-cell suppressor factor(s)     

Shape, size and density of daytime surface swarms of the euphausiid Meganyctiphanes norvegica in the Bay of Fundy

Daytime surface swarms of ^{Meganyctiphanes norvegica} in the Bayof Fundy were examined using a variety of techniques to providemeasurements of their shapes, sizes and densities. Shapes andsizes were determined from two aerial photographs: swarms werespherical, ribbon-like or amorphous. were up to 28 6 m longand ranged in area from 0.4–111 7 m². Densities were measuredby a bag-sampling device which gave figures of up to 41 000animals m^–3 by photographic methods which gave figuresof up to 770 000 animals m^–3 and by a plankton net whichgave maximum values of six animals m^–3 Using the photographicmethod the maximum euphausud biomass was estimated to be 154kg m^–3 within swarms and the largest swarm measured wasestimated to contain up to 2 1 tonnes of M. norvegica. Meanpatch biomass estimates for the two aerial photographs rangedfrom 77.8–778 g m^–3 and 15 6–155.6 g m^–3which are similar to figures obtained by other authors usingintegrating sampling techniques at depth.     

Thermoregulatory physiology of the carpenter bee,Xylocopa varipuncta

Summary The carpenter beesXylocopa varipuncta maintain thoracic temperatures of 33.0°C to 46.5°C during continuous free flight from 12°C to 40°C. Since the thoracic temperature excess is not constant (decreasing from 24°C at low air temperatures to 6°C at high) the bees are thermoregulating. We document physiological transfer of relatively large amounts of heat to the abdomen and to the head during pre-flight warm-up and during artificial thoracic heating. Most of the temperature increase of the head is due to passive conduction, while that of the abdomen is due to active physiological heat transfer despite a series of convolutions of the aorta in the petiole that anatomically conform to a counter-current heat exchanger. Although the thermoregulatory mechanisms during flight are far from clarified, our data suggest that thermoregulation involves a strong reliance on active convective cooling through increased flight speed.     

Dopamine- and octopamine-sensitive adenylate cyclase in the brain of adultCulex pipiens mosquitoes

The effects of dopamine and octopamine on adenylate cyclase activity were studied on the head homogenate of adult Culex pipiens mosquitoes in vitro. Both dopamine and octopamine were shown to increase the cyclic AMP content in the homogenate. The antagonist haloperidol blocked the production of cyclic AMP induced from dopamine but had no effect on the production of cyclic AMP induced by octopamine at the concentrations tested. The opiate agonist etorphine was ineffective at reducing cyclic AMP levels induced by either dopamine or octopamine at the concentrations tested.     

Dinitrogen fixation by obligate and facultative anaerobic bacteria in association with cellulolytic fungi

The anaerobic bacteriumClostridium butyricum is the major contributor to nitrogen gains by a cellulolytic/nitrogen-fixing population isolated from straw. Growth of the anaerobe is supported by the products of fungal cellulases. The facultative anaerobeEnterobacter cloacae does not make a significant direct contribution to nitrogen fixation but in association withC. butyricum allows the anaerobe to grow under aerobic conditions. The major function ofE. cloacae is though to be provision of oxygen-depleted microsites.     

Transformation ofBacillus spp.: An examination of the transformation ofBacillus protoplasts by plasmids pUB110 and pHV33

The protoplasting and transformation techniques described by Chang and Cohen [5] have been modified by the inclusion of mutanolysin and these techniques have been used to prepare protoplasts of a number ofBacillus spp. Cells of some, however, remained resistant to cell wall hydrolysis by both mutanolysin and lysozyme. Protoplasts were prepared from sixBacillus species, including a strain ofB. subtilis, and transformed with the plasmid pUB110. Transformation with the shuttle vector pHV33 was, however, less successful and antibiotic-resistant protoplasts, although detected, either failed to regenerate their osmotic stability or rapidly lost their antibiotic resistance.     

Bacillus thuringiensis and control of plant pests

Summary The feasibility ofB. thuringiensis as an economic insect control agent is dependent upon various factors. Consideration of three situations. whereB. thuringiensis could be used illustrates the interaction of these factors, and their contribution to determining the success or failure of the organism as an insecticide. Apple crops suffer from attack by a complex of insect pests, many of which are very susceptible to theB. thuringiensis toxin. However chemical control methods are preferred by growers in order to satisfy the consumers' demand for top quality blemish-free fruit. By contrast cotton growers are beset with problems of pest resistance to chemical insecticides. This problem is tackled by using pest management strategies which orchestrate all possible methods of control. Such a situation is ideally suited toB. thuringiensis products, but as yet they have proven to be of inadequate efficacy. The softwood forest industry is an example whereB. thuringiensis is both needed and effective. The pest complex is relatively simple, and there is public concern about the health risks of chemical sprays. Recent developments of high performance formulations means thatB. thuringiensis is an economic, cost-effective, biological alternative to chemical control for forestry pests.

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Resumen La posibilidad de utilizarB. thuringiensis para el control de insectos de una forma económica depende de varios factores. La consideración de tres situaciones distintas en las queB. thuringiensis puede ser utilizado ilustra la interacción de estos factores y su contribución al éxito o fracaso del organismo como insecticida. El cultivo de manzanas sufre el ataque de una serie de plagas de insectos, muchas de las cuales son susceptibles a la toxina deB. thuringiensis. Sin embargo, los agricultores prefieren utilizar métodos de control químico a fin de satisfacer la demanda del consumidor por un fruto de primera calidad sin marcas ni señales. Por el contrario, los cultivadores de algodon estan sensibilizados a los problemas de la aparición de plagas resistentes a los insecticidas químicos. Este problema se ha abordado utilizando sistemas de control integrado que aglutinan todos los posibles métodos de control. Esta situación parece la ideal para el uso de productos a base deB. thuringiensis, pero hasta ahora estos han resultado ser poco eficaces. La industria de la madera blanda constituye en ejemplo en el cualB. thuringiensis es a la vez necesario y efectivo. Las plagas en cuestión forman un sistema relativamente simple y los efectos de los sprays químicos sobre la salud pública son causa de preocupación. Los desarrollos recientes en formulaciones de elevada eficacia convierten aB. thuringiensis en una alternativa biológica económicamente factible frente al control químico de plagas forestales.

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Résumé La possibilité d'utiliser économiquementB. thuringiensis dans la lutte contre les insectes nuisibles dépend de facteurs divers. L'examen de trois situations dans lesquellesB. thuringiensis peut être utilisé illustre l'interaction de ces facteurs et leur contribution dans le succès ou l'échec de cet organisme comme insecticide. Les récoltes de pommes sont menacées par les attaques d'un mélange complexe d'insectes, dont beaucoup sont sensibles à la toxine deB. thuringiensis. Cependant, les horticulteurs préfèrent les méthodes chimiques à cause de l'exigence des consommateurs pour des fruits de haute qualité et sans aucune tache. Par contre, les cultivateurs de coton sont obsédés par les problèmes de résistance aux insecticides chimiques. Ce problème est affronté par des stratégies faisant appel à tous les moyens de lutte possibles. C'est une situation convenant bien aux produits qui contiennentB. thuringiensis, mais jusqu'ici ces produits se sont montrés inefficaces. L'industrie du bois tendre forestier est toutefois un exemple de cas oùB. thuringiensis est à la fois nécessaire et efficace. En effet, le complexe des insectes agressifs est relativement simple et il existe en outre une prévention du public contre les risques sanitaires des pulvérisations de produits chimiques. La mise au point récente de formulations à haute performance démontre queB. thuringiensis est, pour la lutte contre les insectes nuisibles des forêts, une alternative économique et bon-marché.

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Invited paper presented at the VII International Conference on the Global Impacts of Applied Microbiology, Helsiki, 12–16 August 1985. Session 8