COMPARISON OF ISOZYMES AMONG TYPHA SPECIES IN THE EASTERN UNITED STATES

Biochemical phenotsypes of four taxa of Typha from the eastern United States were determined by starch gel electrophoresis. The isozyme banding patterns of T. latifolia, T. angustifolia and T. domingensis are distinct and allow unambiguous species identification when morphological characters are inadequate or unsuitable. The fourth form, T. glauca, is not an F₁ hybrid, but it does appear to be intermediate between T. latifolia and T. angustifolia. The status of T. glauca and evolutionary relationships among the four forms may now be clarified by additional sampling because of the distinct and relatively invariant isozyme banding patterns which are described.     

Strength and physical fitness predict the perception of looming sounds

Listeners consistently perceive approaching sounds to be closer than they actually are and perceptually underestimate the time to arrival of looming sound sources. In a natural environment, this underestimation results in more time than expected to evade or engage the source and affords a “margin of safety” that may provide a selective advantage. However, a key component in the proposed evolutionary origins of the perceptual bias is the appropriate timing of anticipatory motor behaviors. Here we show that listeners with poorer physical fitness respond sooner to looming sounds and with a larger margin of safety than listeners with better physical fitness. The anticipatory perceptual bias for looming sounds is negatively correlated with physical strength and positively correlated with recovery heart rate (a measure of aerobic fitness). The results suggest that the auditory perception of looming sounds may be modulated by the response capacity of the motor system.     

Interaction of some polyhexamethylene biguanides and membrane phospholipids in Escherichia coli

The interaction between some polyhexamethylene biguanides and the cell envelope of Escherichia coli has been investigated. An amine-ended dimer, (AED, n = 2), a polydisperse mixture (ICI plc) available as the active ingredient of Vantocil IB, (PHMB, n = 5.5), and a high molecular weight fraction, (HMW, n = greater than or equal to 10) of PHMB were used. The sensitivity of batch cultures depleted of magnesium (M-dep), phosphorus (P-dep) or glycerol (C-dep) towards the biocides was assessed by monitoring the rate and extent of potassium ion leakage. P-dep suspensions were particularly resistant to all these agents and possessed less than half the quantity of phospholipid of other cell types. This was compensated for by a proportionate increase in fatty acid and neutral lipid content of the cells. The reduction in phospholipid content was accounted for by decreases in phosphatidylglycerol (PG) and phosphatidylethanolamine (PE). Diphosphatidylglycerol (DPG) and phosphatidylserine (PS) content of the cultures remained unaffected by the depleting nutrient. Fourier-transform n.m.r. spectroscopy was used to study proton nuclei during the interaction of HMW, AED and PHMB with various phospholipid-vesicle preparations. The results strongly suggest that the biocides acted preferentially on the acidic phospholipids PG and DPG, rather than towards PE or PS. Resistance of P-dep cultures therefore reflected reductions in PG content. A molecular basis for the interaction of these compounds and membranes is proposed.     

Cloning and expression of the Erwinia chrysanthemi asparaginase gene in Escherichia coli and Erwinia carotovora

A genomic library of Erwinia chrysanthemi DNA was constructed in bacteriophage lambda 1059 and recombinants expressing Er. chrysanthemi asparaginase detected using purified anti-asparaginase IgG. The gene was subcloned on a 4.7 kb EcoRI DNA restriction fragment into pUC9 to generate the recombinant plasmid pASN30. The position and orientation of the asparaginase structural gene was determined by subcloning. The enzyme was produced at high levels in Escherichia coli (5% of soluble protein) and was shown to be exported to the periplasmic space. Purified asparaginase from E. coli cells carrying pASN30 was indistinguishable from the Erwinia enzyme on the basis of specific activity [660-700 units (mg protein)-1], pI value (8.5), and subunit molecular weight (32 X 10(3]. Expression of the cloned gene was subject to glucose repression in E. coli but was not significantly repressed by glycerol. Recombinant plasmids, containing the asparaginase gene, when introduced into Erwinia carotovora, caused increased synthesis of the enzyme (2-4 fold higher than the current production strain).     

The cost of mutualism in a fly-fungus interaction

The movement ability of individuals has become increasingly important to a variety of ecological questions. In this study, I investigate how plant structure and changes in body size through development affect the movement ability of a predaceous stinkbug, Podisus maculiventris, on three species of goldenrod (Solidago spp.) representing a wide range of surface complexities. I adapt existing techniques for quantifying movement in two dimensions to the study of movement on natural plant structures in three dimensions. These experiments indicate that plant structure and insect size are significant factors affecting the movement ability of P. maculiventris. Changes in movement ability due to factors of ontogeny and different habitat structures suggest that the scale of an individual’s ambit or ecological sphere of influence may vary within its lifespan. Considering the influence of ontogeny and habitat structure on movement ability may be useful to investigations of population dynamics, foraging behavior, and pest management. Received: 14 July 1999 / Accepted: 23 March 2000     

Endless forms most stupid,icky, and small: The preponderance of noncharismatic invertebrates as integral to a biologically sound view of life

Big, beautiful organisms are useful for biological education, increasing evolution literacy, and biodiversity conservation. But if educators gloss over the ubiquity of streamlined and miniaturized organisms, they unwittingly leave students and the public vulnerable to the idea that the primary evolutionary plot of every metazoan lineage is “progressive” and "favors" complexity. We show that simple, small, and intriguingly repulsive invertebrate animals provide a counterpoint to misconceptions about evolution. Our examples can be immediately deployed in biology courses and outreach. This context emphasizes that chordates are not the pinnacle of evolution. Rather, in the evolution of animals, miniaturization, trait loss, and lack of perfection are at least as frequent as their opposites. Teaching about invertebrate animals in a “tree thinking” context uproots evolution misconceptions (for students and the public alike), provides a mental scaffold for understanding all animals, and helps to cultivate future ambassadors and experts on these little‐known, weird, and fascinating taxa.     

Fibrinogen and fibrin in strong magnetic fields. Complementary results and discussion

When fibrin polymerizes in a strong magnetic field, it can be highly oriented. The structural diffraction study of the oriented polymer becomes thus possible. The magnetic birefringence can also be used to study the development of the polymer Fibrinogen in solution is weakly oriented in high magnetic fields. In this work we present complementary results and discussion. The validity of the comparison of the orientation parameters of fibrinogen and fibrin with those of other orientable known biological structures is discussed. The orientation of fibrin formed from fibrin monomer solution is compared to that of fibrin formed by the action of thrombin on fibrinogen. The conditions to obtain highly oriented fibrin gels suitable for three dimensional structure studies are also briefly discussed.