Coexistence of succulent tree aloes: partitioning of bird pollinators by floral traits and flowering phenology

Coexistence among species that lack genetic barriers to hybridization usually depends on pre-mating isolating barriers. It has been difficult to explain coexistence among African Aloe species because they readily hybridize, often flower simultaneously and are mostly bird-pollinated. Here we show that co-flowering aloes in a succulent thicket community in South Africa partition the fauna of flower-visiting birds. Aloe species with small amounts of concentrated nectar in long corolla tubes were pollinated primarily by long-billed sunbirds. These species co-flowered with species with large amounts of dilute nectar in short corolla tubes which were pollinated primarily by short-billed, generalist nectarivores. Aloe species which share pollinators tend to have divergent flowering times and differences in pollen placement on birds. Without these isolating barriers, genetic dissolution of sympatric Aloe species would be likely.     

3-hydroxy fatty acids found in capsules of Cryptococcus neoformans

Using immunofluorescence confocal laser scanning microscopy, immunogold transmission electron microscopy and gas chromatography--mass spectrometry, we demonstrated the presence of 3-hydroxy fatty acids in Cryptococcus neoformans. Our results suggest that these oxylipins accumulate in capsules where they are released as hydrophobic droplets through tubular protuberances into the surrounding medium.     

The release of elongated, sheathed ascospores from bottle-shaped asci in Dipodascus geniculatus

Yeasts use different mechanisms to release ascospores of different lengths from bottle-shaped asci. Round to oval-shaped ascospores are enveloped in oxylipin-coated compressible sheaths, enabling ascospores to slide past each other when they reach the narrowing ascus neck. However, more elongated ascospores do not contain sheaths, but are linked by means of oxylipin-coated interlocked hooked ridges on the surfaces of neighboring ascospores, thereby keeping them aligned while they are pushed towards the ascus tip by turgor pressure. In this study, we found elongated, oxylipin-coated sheathed ascospores in Dipodascus geniculatus that are released effectively from bottle-shaped asci without alignment. This is possible because the ascus neck and opening have a diameter that is the same as the length of the ascospore, thus allowing the ascospores to turn sideways without blocking the ascus when they are released. We found that increased concentrations of acetylsalicylic acid inhibit both ascospore release and 3-hydroxy oxylipin production in this yeast, thereby implicating this oxylipin in sexual reproduction.     

Boza, a natural source of probiotic lactic acid bacteria

Aims: To evaluate the probiotic properties of strains isolated from boza, a traditional beverage produced from cereals. Methods and Results: The strains survived low pH conditions (pH 3·0), grew well at pH 9·0 and were not inhibited by the presence of 0·3% (w/v) oxbile. Cytotoxicity levels of the bacteriocins, expressed as CC₅₀, ranged from 38 to 3776 μg ml^?1. Bacteriocin bacST284BZ revealed high activity (EC₅₀ = 735 μg ml^?1) against herpes simplex virus type 1. Growth of Mycobacterium tuberculosis was 69% repressed after 5 days in the presence of bacST194BZ. Various levels of auto‐cell aggregation and co‐aggregation with Listeria innocua LMG 13568 were observed. Adhesion of the probiotic strains to HT‐29 cells ranged from 18 to 22%. Conclusions: Boza is a rich source of probiotic lactic acid bacteria. All strains survived conditions simulating the gastrointestinal tract and produced bacteriocins active against a number of pathogens. Adherence to HT‐29 and Caco‐2 cells was within the range reported for Lactobacillus rhamnosus GG, a well‐known probiotic. In addition, the high hydrophobicity readings recorded define the strains as good probiotics. Significance and Impact of the Study: Boza contains a number of different probiotic lactic acid bacteria and could be marketed as a functional food product.     

Distribution of 3-hydroxy oxylipins and acetylsalicylic acid sensitivity in Cryptococcus species

Using a well tested antibody specific for 3-hydroxy oxylipins, we mapped the presence of these oxylipins in selected Cryptococcus (Filobasidiella) species. Immunofluorescence microscopy studies revealed that these compounds are deposited on cell wall surfaces, appendages, and collarettes. In vitro studies revealed that growth of Cryptococcus species was inhibited by acetylsalicylic acid (which is known to inhibit mitochondrial function, including the production of 3-hydroxy oxylipins) at concentrations as low as 1 mmol/L. The results suggest that acetylsalicylic acid is effective in controlling the growth of tested pathogens, probably by targeting their mitochondria. This study further expands the known function of this anti-inflammatory drug as anti-fungal agent.     

Calcium alginate entrapment of the yeast Rhodosporidium toruloides for the kinetic resolution of 1,2-epoxyoctane

Resting cells of the yeast Rhodosporidium toruloides (UOFS Y-0471) were immobilised in calcium alginate beads for the enantioselective kinetic resolution of racemic-1,2-epoxyoctane. The initial activity exhibited by immobilised cells was almost 50% lower than that of the free counterpart but was extremely stable when compared to the free cells. The concentration of the immobilised biomass had no effect on apparent enzyme activity but did lead to a decrease in single cell activity. An increase in both the alginate and CaCl₂ concentrations used for bead preparation led to a decrease in enzyme stability. An increase in the alginate concentration led to an increase in bead diameter. The stoichiometric equation for cross-linking of alginate was only obeyed when CaCl₂ concentrations higher than 0.4 M were utilised for bead preparation.     

Mapping the distribution of 3-hydroxy oxylipins in the ascomycetous yeast Saturnispora saitoi

The distribution of 3-hydroxy oxylipins in Saturnispora saitoi was mapped using immunofluorescence microscopy. Fluorescence was observed on aggregating ascospores, indicating the presence of 3-hydroxy oxylipins on the surface or between ascospores. The oxylipin was identified as 3-hydroxy 9:1 using gas chromatography mass spectrometry. Furthermore, ultrastructural studies using scanning and transmission electron microscopy on ascospores revealed a clear equatorial ledge surrounding oval-shaped ascospores.     

Acetate enhances citric acid production by Yarrowia lipolytica when grown on sunflower oil

It was discovered that the addition of 10 g/l acetate to a medium containing 30 g/l sunflower oil caused a drastic increase in citric acid production by Yarrowia lipolytica UOFS Y-1701 i.e. from 0.5 g/l in the absence of acetate to 18.7 g/l in the presence of acetate. Similarly, the ratio of citric acid:isocitric acid increased significantly from 1.7:1 in the absence of acetate to 3.7:1 in the presence of acetate after 240 h of growth.