Metabolic Changes in Trichomonas gallinae Resulting from Growth in Various Carbohydrates*†

SYNOPSIS. The influence of the type of growth carbohydrate on the subsequent metabolic activity of Trichomonas gallinae was investigated. Washed suspensions of cells collected from CPL-glucose, CPL-maltose, CPL-galactose, and CPL-glucose-maltose media were examined in the Warburg respirometer for their ability to utilize glucose, maltose, and galactose. Comparisons of the metabolic parameters of substrate consumption, changes in glycogen content, and CO₂ and H₂ production were made. The pattern of utilization of the sugars, both qualitatively and quantitatively, depended upon the type of carbohydrate in the CPL medium used to culture the cells and upon the time of exposure of the cells to a particular sugar in the medium.     

Three-dimensional Structure of Thermolysin

The electron density map of thermolysin indicates how the polypeptide chain is displaced throughout the overall shape of the molecule.     

Climate change,chytridiomycosis or condition: an experimental test of amphibian survival

Variation in climatic temperature is frequently cited as playing a powerful role in driving host/pathogen dynamics, and as a consequence future patterns of disease are predicted to change owing to global warming. However, the preponderance of data is correlative and few quantitative tests exist that dissect the relative effects of changing temperature on host and pathogen responses. In this study, we experimentally tested the effect overwintering temperature had on the susceptibility of a vertebrate ectothermic host, the common toad Bufo bufo, to infection and mortality caused by Batrachochytrium dendrobatidis (Bd). We show that a ‘poor’ (warmer) overwintering regime increases the probability of infection, supporting the concept that the dynamics of infection are altered by changing environmental temperature profiles. We also show once established, the proliferation of Bd in the host was better in toadlets that experienced a ‘good’ (colder) winter. We find no relationship between survival and the different overwintering regimes or any consistent deleterious influence of disease on survival. Instead, survival is overwhelmingly predicted by measurements of condition (mass, mass lost over winter) that were not determined by overwintering temperature. We conclude that the survival of a cohort of overwintering toadlets is primarily driven by patterns of growth during the larval period rather than winter temperature or infectious disease.     

Pollination strategies in Cretan Arum lilies

Flowers of the genus Arum are known to attract dung‐breeding flies and beetles through olfactory deceit. In addition to this strategy, the genus has evolved several other pollination mechanisms. The present study aimed to characterize the pollination strategies of the Cretan Arum species by investigating the flowering phenology, thermogeny, inflorescence odours, and the pollinating fauna. The results obtained show that Arum cyrenaicum and Arum concinnatum emit a strong dung smell and exhibit the distinctive features associated with this pollination syndrome. Both species are highly thermogenic, have a similar odour profile and attract small‐bodied Diptera. Although sharing the same habitat, these two plant species are never found growing sympatrically as a result of the early blooming period of A. cyrenaicum. By contrast, Arum creticum and Arum idaeum have evolved a more traditional and mutually beneficial pollination mechanism. The stinking smell has been replaced by a more flower‐like odour that attracts bees (Lasioglossum sp.) and, occasionally, bugs (Dionconotus cruentatus). Although attracting the same pollinator, the main compound present in the odour of A. creticum is different from that of A. idaeum. Principal component analysis (PCA), based on physiologically active components of the flower odours determined by testing on the antenna of the Lasioglossum bee, revealed two different clusters, indicating that pollinators can potentially discriminate between the odours of the two species. A further PCA on the main floral odour volatiles as identified by gas chroatography‐mass spectroscopy from all the Arum species under investigation displayed odour‐based similarities and differences among the species. The PCA‐gas chomotography‐electroantennographic detection active peaks analysis showed that the two species, A. creticum and A. idaeum, form two groups and are clearly separated from A. cyrenaicum and A. concinnatum, which, conversely, cluster together. The evolutionary forces and selective pressures leading to diversification of pollination mechanisms in the Cretan Arum spp. are discussed. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 991–1001.     

The Location of the Transporting System for Inorganic Carbon and the Nature of the Form Translocated in Chlamydomonas reinhardtii

The permeability of the plasmalemma of Chlamydomonas reinhardtiicells was increased by treatment with poly-L-lysine or dimethylsulphoxideas indicated by 3-phosphoglyceric acid dependent O₂ evolution.These treatments decreased the ability of the cells to accumulateinorganic carbon internally and hence their photosynthetic affinityfor inorganic carbon in the medium. With saturating light andinorganic carbon, the photosynthetic rate was less affectedby the poly-L-lysine and dimethylsulphoxide treatments. Thusthe poly-L-lysine and dimethylsulphoxide did not alter the activityof the chloroplasts but rather made the intracellular inorganiccarbon pool more freely exchangeable with the medium. It isconcluded that the transporting system for inorganic carbonis located at the plasmalemma. Treatment with Diamox, an inhibitor of carbonic anhydrase, didnot affect photosynthetic rate and accumulation of inorganiccarbon when CO₂ was supplied but strongly inhibited both parameterswhen HCO^–₃ was supplied. In a mutant of Chlamydomonasreinhardtii lacking a cell wall, carbonic anhydrase leaks tothe medium and uptake of inorganic carbon is much faster whenCO₂ is supplied than when HCO^–₃ is supplied. These resultssuggest that CO₂ rather than HCO^–₃ is the inorganic carbonspecies that is actively translocated across the plasmalemma. Key words: Chlamydomonas, Inorganic carbon uptake     

A novel interaction of magnesium translocation with the supply of phosphorus to roots of grapevine (Vitis vinifera L.)*

Abstract. The role of phosphorus (P) in leaf magnesium (Mg) concentrations and photosynthesis was investigated in field and glasshouse experiments with grapevine (Vitis vinifera L., cvs. Chenin blane. Chardonnay, and Carignane). In the field, leaves of vines growing on soil with low available P exhibited symptoms of Mg deficiency and had low P and Mg concentrations. The rate of photosynthesis for leaves of untreated control vines was approximately 0.7 nmol CO₂ cm ² s ¹. When P fertilizer was applied to the soil, Mg deficiency symptoms were eliminated, and leaf P and Mg concentrations increased to above critical levels. When Mg was applied as a foliar spray, leaf Mg increased to above critical levels, but leaf P did not change significantly. In both experiments, the rate of photosynthesis increased to greater than 1.0 nmol CO₂ cm ² s ¹ after nutrient applications. Thus, under low soil P conditions, leaf photosynthesis was limited by leaf Mg concentrations. In glasshouse experiments in which vines were grown with and without P for three seasons, Mg accumulated in large roots of - P vines to approximately twice the concentration found in roots of + P vines. Analysis of the xylem exudate from detopped plants showed that Mg concentration in xylem sap of + P vines was twice as great as that in - P vines. When P was supplied to - P vines, the concentration of Mg increased to the concentration of + P vines within 2 days. The results show that the translocation of Mg from roots to shoots of grapevine is dependent upon P supply to the roots and suggest that Mg translocation is more sensitive than uptake to P supply.     

Feeding and growth of the isopod Asellus aquaticus on actinomycetes, considered as model filamentous bacteria

SUMMARY. Asellus aquaticus was fed for 49 days at 15°C on aquatic actinomycetes in the laboratory. Specific growth rates (wet weight) of animals initially 2.5mm in length ranged from 0.85 to 2.33% day⁻¹ on Micromonospora and Streptomyces S2 respectively. Asellus newly released from the brood-pouch (1.0 mm length) had a similar growth rate (2.74% day⁻¹) on Streptomyces S2. The growth rates of animals fed on actinomycetes were lower than those of animals feeding on macroscopic foods such as Elodea and decaying oak leaves, regardless of the initial size of the animal. However, it was concluded that actinomycetes, and by inference bacteria also, could maintain a population, albeit a slow-growing one, in a situation where macroscopic foods are largely absent.
The possible significance of hyphal diameter of micro-organisms in relation to assimilation from them is discussed. In this connection actinomycetes are considered as model filamentous bacteria.