Genetic isolation and evolutionary history of oases populations of the Baja California killifish,Fundulus lima

The Baja California killifish, Fundulus lima, is found in six desert oases of the southern Baja California Peninsula, Mexico. The recent introduction of exotic fishes, particularly redbelly tilapia, have impacted the ecology of Fundulus lima such that it is now endangered. Plans of relocating F. lima to bodies of freshwater that are free of exotics have been proposed, however little is know about the genetic identity of the current populations. In this study, we examined the mitochondrial control region of F. lima samples from 4 oases, and in addition, compared these samples to their sister species, the California killifish F.␣parvipinnis. Using a combination of phylogenetic and coalescent approaches, we were able to determine that the two subspecies of the California killifish, F. p.␣brevis, and F. p. parvipinnis, and F. lima form an unresolved trichotomy that diverged between 200,000 years and 400,000 years ago. The one F. lima individual that we were able to collect in the southernmost oasis grouped with the southern subspecies of the California killifish, F. parvipinnis brevis. In contrast, we found that the 3 northern oases grouped together in a “Fundulus lima” clade. Each oasis is genetically distinct, yet there is no evidence of a␣marked genetic bottleneck in any populations (Haplotype diversity between 0.5 and 0.8). Future relocation plans will therefore need to be done cautiously to preserve the genetic identity of the original populations.     

Exploring polymorphisms in B-DNA helical conformations

The traditional mesoscopic paradigm represents DNA as a series of base-pair steps whose energy response to equilibrium perturbations is elastic, with harmonic oscillations (defining local stiffness) around a single equilibrium conformation. In addition, base sequence effects are often analysed as a succession of independent XpY base-pair steps (i.e. a nearest-neighbour (NN) model with only 10 unique cases). Unfortunately, recent massive simulations carried out by the ABC consortium suggest that the real picture of DNA flexibility may be much more complex. The paradigm of DNA flexibility therefore needs to be revisited. In this article, we explore in detail one of the most obvious violations of the elastic NN model of flexibility: the bimodal distributions of some helical parameters. We perform here an in-depth statistical analysis of a very large set of MD trajectories and also of experimental structures, which lead to very solid evidence of bimodality. We then suggest ways to improve mesoscopic models to account for this deviation from the elastic regime.     

Immunological behavior of two alloforms of ATPase fromMicrococcus lysodeikticus

Antisera were raised in rabbits to two alloforms of ATPase isolated from two substrains ofMicrococcus lysodeikticus. These alloforms show a similar amino acid composition but differ in the associated carbohydrate components. Similarities and differences in the immunological behavior of the two forms have been assessed by immunodiffusion, immunoelectrophoresis, and crossed immunoelectrophoresis. The ATPase forms show a great extent of homology as might be expected from their relatedness in amino acid composition. Differences in immunological properties are also evident. They do not seem primarily to reflect the differences in the glycan constituents, but do result from the polymorphism of the purified ATPase molecule of each form. This heterogeneity (microheterogeneity) is a consequence of the lability of the ATPase molecule and influences its behavior as antigen and immunogen.     

R( − )pantoyllactone-β-d-glucopyranoside: Characterization of a metabolite from rice seedlings

A new derivative of pantoic acid, R( - ) pantoyllactone-β-d glucopyranoside, has been isolated from rice seedlings and its structure determined. β-Glucosidase hydrolysed it to -glucose and R( - )pantoyllactone. Alkaline hydrolysis converted it to the salt of 2-R( - )pantoic acid β- -glucopyranoside. It accumulated in rice shoots but not in roots.     

Influence of the incorporation of cholesterol on the doubling time and on the arrhenius and hill plots of two membrane-bound enzymes ofEscherichia coli K12

Escherichia coli was grown at 37°C with increasing cholesterol concentrations in the growth medium. Under these conditions, it was shown that neither the phospholipid species nor the fatty acid composition were affected by the incorporation of cholesterol. On the other hand, the doubling time (t_d) was increased; two membrane-bound enzymes, (Ca⁺⁺)-ATPase and D-lactate-dehydrogenase, were modified in the temperature-dependence activities, and the (Ca^±±)-ATPase changed its Hill coefficient for the inhibition by Na⁺. This last parameter was the most sensitive in detecting very low cholesterol incorporations to the cytoplasmic membranes.