Cytotoxic activity of lymphocytes. VI. Heterogeneity of cytotoxins in supernatants of mitogen-activated lymphocytes.

Two different lymphotoxins synthesized by human blood lymphocytes stimulated with phytohemagglutin (PHA) are described. The two toxins are called alpha-LT and beta-LT relative to their elution order on gel chromatography. Their m.w. are 75,000 and 45,000 daltons, respectively. Both toxins appear as early as 7 hr after the addition of PHA, with the amount of beta-toxin exceeding that of alpha-LT initially. Both toxins are differentiated from a third toxin (adherent cell toxin, ACT) made by plastic-adherent cells without requiring mitogen-stimulation. Depletion of macrophages or B cells does not affect the synthesis of either lymphotoxin. Monospecific antisera were elicited to alpha-LT. Antisera elicited to beta-LT also neutralized alpha-LT but to a significantly lesser degree. Alpha-LT appears to be the lymphotoxin described by most other workers. Beta-LT is unstable at 37 degrees C which may explain why the low m.w. lymphotoxin has not been described previously.     

Distribution of fitness effects of cross-species transformation reveals potential for fast adaptive evolution

Bacterial transformation, a common mechanism of horizontal gene transfer, can speed up adaptive evolution. How its costs and benefits depend on the growth environment is poorly understood. Here, we characterize the distributions of fitness effects (DFE) of transformation in different conditions and test whether they predict in which condition transformation is beneficial. To determine the DFEs, we generate hybrid libraries between the recipient Bacillus subtilis and different donor species and measure the selection coefficient of each hybrid strain. In complex medium, the donor Bacillus vallismortis confers larger fitness effects than the more closely related donor Bacillus spizizenii. For both donors, the DFEs show strong effect beneficial transfers, indicating potential for fast adaptive evolution. While some transfers of B. vallismortis DNA show pleiotropic effects, various transfers are beneficial only under a single growth condition, indicating that the recipient can benefit from a variety of donor genes to adapt to varying growth conditions. We scrutinize the predictive value of the DFEs by laboratory evolution under different growth conditions and show that the DFEs correctly predict the condition at which transformation confers a benefit. We conclude that transformation has a strong potential for speeding up adaptation to varying environments by profiting from a gene pool shared between closely related species.Subject terms: Molecular evolution, Bacterial genetics     

A critical role of RICK/RIP2 polyubiquitination in Nod-induced NF-kappaB activation

Nod1 and Nod2 are intracellular proteins that are involved in host recognition of specific bacterial molecules and are genetically associated with several inflammatory diseases. Nod1 and Nod2 stimulation activates NF-kappaB through RICK, a caspase-recruitment domain-containing kinase. However, the mechanism by which RICK activates NF-kappaB in response to Nod1 and Nod2 stimulation is unknown. Here we show that RICK is conjugated with lysine-63-linked polyubiquitin chains at lysine 209 (K209) located in its kinase domain upon Nod1 or Nod2 stimulation and by induced oligomerization of RICK. Polyubiquitination of RICK at K209 was essential for RICK-mediated IKK activation and cytokine/chemokine secretion. However, RICK polyubiquitination did not require the kinase activity of RICK or alter the interaction of RICK with NEMO, a regulatory subunit of IkappaB kinase (IKK). Instead, polyubiquitination of RICK was found to mediate the recruitment of TAK1, a kinase that was found to be essential for Nod1-induced signaling. Thus, RICK polyubiquitination links TAK1 to IKK complexes, a critical step in Nod1/Nod2-mediated NF-kappaB activation.     

Selenium improves photosynthesis and induces ultrastructural changes but does not alleviate cadmium-stress damages in tomato plants

Protoplasma - The application of Se to plants growing under Cd contamination may become an alternative strategy to minimize Cd damage. However, there is no specific information available regarding...     

Draft genome sequence of Bizionia argentinensis, isolated from Antarctic surface water

A psychrotolerant marine bacterial strain, designated JUB59(T), was isolated from Antarctic surface seawater and classified as a new species of the genus Bizionia. Here, we present the first draft genome sequence for this genus, which suggests interesting features such as UV resistance, hydrolytic exoenzymes, and nitrogen metabolism.     

Requirement for Par-6 and Bazooka in Drosophila border cell migration

Polarized epithelial cells convert into migratory invasive cells during a number of developmental processes, as well as when tumors metastasize. Much has been learned recently concerning the molecules and mechanisms that are responsible for generating and maintaining epithelial cell polarity. However, less is known about what becomes of epithelial polarity proteins when various cell types become migratory and invasive. Here, we report the localization of several apical epithelial proteins, Par-6, Par-3/Bazooka and aPKC, during border cell migration in the Drosophila ovary. All of these proteins remained asymmetrically distributed throughout migration. Moreover, depletion of either Par-6 or Par-3/Bazooka by RNAi resulted in disorganization of the border cell cluster and impaired migration. The distributions of several transmembrane proteins required for migration were abnormal following Par-6 or Par-3/Bazooka downregulation, possibly accounting for the migration defects. Taken together, these results indicate that cells need not lose apical/basal polarity in order to invade neighboring tissues and in some cases even require such polarity for proper motility.     

Comparison of Models Describing Light Dependence of N2 Fixation in Heterocystous Cyanobacteria

The abilities of four models to describe nitrogenase light-response curves were compared, using the heterocystous cyanobacterium Nodularia spumigena and a cyanobacterial bloom from the Baltic Sea as examples. All tested models gave a good fit of the data, and the rectangular hyperbola model is recommended for fitting nitrogenase-light response curves. This model describes an enzymatic process, while the others are empirical. It was possible to convert the process parameters between the four models and compare N₂ fixation with photosynthesis. The physiological meanings of the process parameters are discussed and compared to those of photosynthesis.