Use of lambda pMu bacteriophages to isolate lambda specialized transducing bacteriophages carrying genes for bacterial chemotaxis.

A general method for constructing lambda specialized transducing phages is described. The method, which is potentially applicable to any gene of Escherichia coli, is based on using Mu DNA homology to direct the integration of a lambda pMu phage near the genes whose transduction is desired. With this method we isolated a lambda transducing phage carrying all 10 genes in the che gene cluster (map location, 41.5 to 42.5 min). The products of the cheA and tar genes were identified by using transducing phages with amber mutations in these genes. It was established that tar codes for methyl-accepting chemotaxis protein II (molecular weight, 62,000) and that cheA codes for two polypeptides (molecular weights, 76,000 and 66,000). Possible origins of the two cheA polypeptides are discussed.     

Determination of protein synthesis initiation factor levels in crude lysates of Escherichia coli by a sensitive radioimmune assay.

Antisera specific for protein synthesis initiation factors IF1, IF2, and IF3 were prepared by immunizing rabbits. When crude cell lysates are analyzed by double immunodiffusion or by immunoelectrophoresis, each antiserum forms a single precipitin line antigenically identical to its cognate factor. The antisera do not crossreact with other initiation factors or with ribosomal proteins. A radioimmune assay was developed for each initiation factor by using the specific antisera and radioactive factors prepared by reductive alkylation with [¹⁴C]formaldehyde. The assays detect as little as 10 to 30 ng of factor. Initiation factor concentrations were measured in crude Escherichin coli MRE600 extracts prepared from cells grown exponentially in a rich medium. The three initiation factors are present in approximately stoichiometric amounts and comprise about 1% of the cell protein. The molar ratio of initiation factors to ribosomes is about 0.15, which corresponds to the concentration of native ribosomal subunits.     

Light and drug induced changes of epiphysial synaptic ribbons

Summary In the present investigation experiments were carried out to determine whether the functionally obscure synaptic ribbons of mammalian pinealocytes can be affected by acute changes in environmental lighting and which chemical processes may be involved in their regulation. Experiments carried out in male guinea-pigs have shown that the amounts of synaptic ribbons are immediately affected by changes in the lighting pattern. Extension of the light period reduced the normally occurring increase, whereas extension of the dark period inhibited the normally occurring decrease in the amount of synaptic ribbons. Results following injections of a number of drugs known to influence pineal function (noradrenaline, L-DOPA, propranolol, reserpine and p-chlorophenylalanine, respectively) suggest that synaptic ribbons may be directly or indirectly regulated by -adrenergic mechanisms.Dedicated to Professor Wolfgang Bargmann on the occasion of his 70th birthday.     

Scanning electron microscopy of surface and internal features of developing perithecia of Neurospora crassa.

Stages in the development of perithecia of Neurospora crassa, designated by the time elapsed after crossing, were investigated with the scanning electron microscope, from protoperithecia through perithecia. The usual examination of external features of whole specimens with this instrument was augmented by a freeze-fracture technique which allowed the viewing of development internally as well. Rapid increases in perithecial size soon after crossing were followed by the appearance, in section, of a centrum, at first undifferentiated but subsequently developing ascogenous hyphae. The perithecial beak appeared as a compact mass easily distinguishable in whole specimens from the surrounding hyphae by means of texture as well as shape. Two ascospores were photographed during emergence from an ostiole, but ostioles were found more frequently closed than open.     

Use of bacteriophage Mu to isolate deletions in the his-nif region of Klebsiella pneumoniae.

Klebsiella pneumoniae M5a1 is naturally resistant to infection by bacteriophage Mu. Mutants of K. pneumoniae sensitive to Mu infection were isolated and found to support both lytic and lysogenic development of Mu. K. pneumoniae lysogens containing a heat-inducible Mu prophage integrated in his were isolated. Strains carrying deletions extending from his into nif were obtained after heat treatment of these lysogens. Such deletions should be useful for determining the map order and cistronic organization of the nif genes.     

Greater goods: ethics,energy, and other-than-human speech

Renewable energy projects are ethically laudable for their cleansing intentions, but they also produce effects upon other-than-human beings in their orbit. Taking the case of Mexico's Isthmus of Tehuantepec, which is home to the densest concentration of on-shore wind parks anywhere in the world, and following Foucault's reading of the speech form ‘parrhesia’, this essay argues that the bodies of affected nonhuman beings, particularly those whose existence is actively balanced against a ‘greater good’ for humanity, enact a form of other-than-human speech, first in their threatened status and, secondly, through environmental management regimes that seek to synchronize human and nonhuman lives in settings of both local and global ecological failures.     

Symbiont community diversity is more variable in corals that respond poorly to stress

Coral reefs are declining globally as climate change and local water quality press environmental conditions beyond the physiological tolerances of holobionts—the collective of the host and its microbial symbionts. To assess the relationship between symbiont composition and holobiont stress tolerance, community diversity metrics were quantified for dinoflagellate endosymbionts (Family: Symbiodiniaceae) from eight Acropora millepora genets that thrived under or responded poorly to various stressors. These eight selected genets represent the upper and lower tails of the response distribution of 40 coral genets that were exposed to four stress treatments (and control conditions) in a 10‐day experiment. Specifically, four ‘best performer’ coral genets were analyzed at the end of the experiment because they survived high temperature, high pCO₂, bacterial exposure, or combined stressors, whereas four ‘worst performer’ genets were characterized because they experienced substantial mortality under these stressors. At the end of the experiment, seven of eight coral genets mainly hosted Cladocopium symbionts, whereas the eighth genet was dominated by both Cladocopium and Durusdinium symbionts. Symbiodiniaceae alpha and beta diversity were higher in worst performing genets than in best performing genets. Symbiont communities in worst performers also differed more after stress exposure relative to their controls (based on normalized proportional differences in beta diversity), than did best performers. A generalized joint attribute model estimated the influence of host genet and treatment on Symbiodiniaceae community composition and identified strong associations among particular symbionts and host genet performance, as well as weaker associations with treatment. Although dominant symbiont physiology and function contribute to host performance, these findings emphasize the importance of symbiont community diversity and stochasticity as components of host performance. Our findings also suggest that symbiont community diversity metrics may function as indicators of resilience and have potential applications in diverse disciplines from climate change adaptation to agriculture and medicine.