Comparative Physiology and Behaviour of the Mycoparasites Pythium acanthophoron, P. oligandrum and P. mycoparasiticum

Pythium acanthophoron (two isolates) was as aggressive as P. oligandrum in hyphal interactions with Fusarium oxysporum on water agar films. It caused rapid post-contact lysis or cytoplasmic coagulation of the host, and often branched and penetrated the host at contact points. P. acanthophoron grew across a range of fungi on pre-colonized agar plates; the range was narrower than for P. oligandrum but broader than for P. mycoparasiticum. In chemically defined liquid media, P. acanthophoron was unique among the six known mycoparasitic Pythium spp. in requiring organic nitrogen but not thiamine. It also grew on mannitol as the sole carbon source in the presence of calcium or sterols or both. However, individual isolates of the three mycoparasitic species showed different responses to calcium and the sterols ergosterol, cholesterol and beta-sitosterol when grown on mannitol. All three mycoparasites required components of molasses, carrot extract or sunflower seed extract to produce oogonia in culture; they formed few oogonia on potato extract, with or without dextrose, even when supplied with sterols. The three mycoparasites were less tolerant of high NaCl levels in culture than were three phytopathogens (P. aphanidermatum, P. ultimum, P. graminicola), in contrast to a previous report for P. oligandrum and P. ultimum. These in vitro studies suggest that P. acanthophoron has potential for use as a biocontrol agent instead of, or in addition to, P. oligandrum.     

Pathogenicity of Bacteria Symbiotically Associated with Insect Pathogenic Nematodes against the Greater Wax Moth,Galleria Mellonella (L.)

The bacterial symbionts isolated from the entomopathogenic nematodes were compared for their pathogenicity to last instar larvae of G. mellonella at both Phases I and II. Most bacterial symbionts at Phase I cause 100% mortality within 2-3 days post-injection with 1 times; 10 3 cells/larva. The pathogenicity of Phase I decreased in the following order: Xenorhabdus nematopbilus, Flavimonas oryzihabitans, Photorhabdus luminescens and Xenorhabdus bovienii with LD 50 values of 40, 55, 70 and 170 cells/larva. The injection of Phase II of the bacterial symbionts did not give 100% mortality even after 4 days post-injection. The time mortality response of G. mellonella larvae to both phases of the bacterial symbiont was significantly different usually at the two highest concentrations tested. The significancy in case of Phase I was in the following order from lowest to highest, F . oryzihabitans , X . nematophilus , P. luminescens and X. bovienii . It was 20.57, 23.96, 23.99 and 53.76 h, respectively. Also, F. oryzihabitans gave the lowest LT 50 value for its Phase II form. It was 36.85 h, and this is followed by X. bovienii , X. nematophilus , and P. luminescens , the LT 50 values of which were 69.29, 74.08 and 74.49 h, respectively. The results suggest that there is a direct correlation between toxin concentration and rate of killing the larvae. On the other hand, there is an inverse correlation between the LT 50 values and the injected concentration.     

Normal acute and chronic inflammatory responses in sphingosine kinase 1 knockout mice

Sphingosine-1-phosophate, generated from the phosphorylation of sphingosine by sphingosine kinase enzymes, is suggested to function as an intracellular second messenger for inflammatory mediators, including formyl peptide, C5a, and Fc. More recently, a role for sphingosine kinases during inflammation has also been proposed. Here we show that sphingosine kinase 1 knockout mice exhibit normal inflammatory cell recruitment during thioglycollate-induced peritonitis and that sphingosine kinase 1-null neutrophils respond normally to formyl peptide. In the collagen-induced arthritis model of rheumatoid arthritis, sphingosine kinase 1 knockout mice developed arthritis with normal incidence and severity. Our findings show that sphingosine kinase 1 is dispensable for inflammatory responses and support the need for more extensive studies of sphingosine kinases in inflammation.     

Entomopathogenic Nematodes, a Case Study: Introduction of Steinernema scapterisci in Florida

Steinernema scapterisci Nguyen & Smart (Rhabditida: Steinernematidae) was established in Florida in 1985 for the control of mole crickets, Scapteriscus spp. Infected hosts were collected in sound traps 23 km from the nearest release, indicating long-distance dispersal and area-wide establishment. In a subsequent pasture study, the nematode dispersed, on average, 60 m in 20 months; dispersal in some pastures was 150 m in 1 year. Establishment was not as successful on golf-courses; however, pest populations were reduced 27% in areas where the nematode persisted. Inoculative applications were successful at 10 of 29 sites in Florida, where sound traps attracted flying Scapteriscus to relatively small numbers of S. scapterisci infective juveniles. The differences in the susceptibility to the nematode for mole cricket life stages and species were determined in laboratory and field trials. The nematode became commercially available in 1993; commercial applications facilitate the establishment of S. scapterisci in many areas of the state.     

Immunohistochemistry combined with periodic acid-Schiff for bovine mammary gland with protothecal mastitis

Immunohistochemistry (IHC) of bovine cytokeratin combined with periodic acid-Schiff (PAS) was applied to study the pathogenesis, localization and distribution of Prototheca zopfii in bovine mammary protothecosis. The standard immunohistochemical procedure using anti-bovine cytokeratin was employed before and after PAS staining to optimize this combined method. The best results were obtained when IHC procedures were performed first. Most of the epithelial cells reacted strongly with the pancytokeratin antibody. Protothecal cell walls stained well with PAS. Algal organisms were present within the lumen and between the epithelial lining and basement membrane of the affected alveoli, but not inside the positive mammary epithelial cells. This combined staining method resulted in clear alveolar epithelial detail and good contrast between the epithelial cells and algae, and contributed to studying the pathogenesis of P. zopfii in mammary protothecosis.     

Incidence of Pentalonia nigronervosa coqueral (homoptera: Aphididae) and associated predators on banana plants in Egypt

The incidence of banana aphid, Pentalonia nigronervosa Coqueral and the coccinellid predators populations on banana plants cultivated at the Agricultural Research Centre Farm in El-Kanater El-Khayria, Qualiobia Governorate, Egypt (about 30 km North Cairo) had been studied. The population of this insect pest was relatively high during the cold and wet months (October, November, December, January and February), and found at its lowest level during the summer months. On the other hand, the numbers of aphid were higher on the mother plants than on the suckers. On mother plants, the population density was much higher on the lower parts of the plant than on the upper parts. The growth rate of aphid population infesting the mother plant of banana in season 2001, increased during the period from January to March and decreased from April to June. The population growth rate then increased from July to November then decreased in December. The same trend could be applied for the growth rate of aphid population in season 2002. At high growth rate it is advisable to use chemical control. The effect of weather factors on the population density of the banana aphid; the correlation between the total number of aphid and temperature or R.H. had been worked out. The coccinellid beetles were found on the banana plants during the warm period from March to August.     

Spp1 at the crossroads of H3K4me3 regulation and meiotic recombination

In Saccharomyces cerevisiae, all H3K4 methylation is performed by a single Set1 Complex (Set1C) that is composed of the catalytic (Set1) and seven other subunits (Swd1, Swd2, Swd3, Bre2, Sdc1, Spp1 and Shg1). It has been known for quite some time that trimethylated H3K4 (H3K4me3) is enriched in the vicinity of meiotic double-strand breaks (DSBs), but the link between H3K4me3 and the meiotic nuclease Spo11 was uncovered only recently. The PHD-containing subunit Spp1, by interacting with H3K4me3 and Mer2, was shown to promote the recruitment of potential meiotic DSB sites to the chromosomal axis allowing their subsequent cleavage by Spo11. Therefore, Spp1 emerged as a key regulator of the H3K4 trimethylation catalyzed by Set1C and of the formation of meiotic DSBs. These findings illustrate the remarkable multifunctionality of Spp1, which not only regulates the catalytic activity of the enzyme (Set1), but also interacts with the deposited mark, and mediates its biological effect (meiotic DSB formation) independently of the complex. As it was previously described for Swd2, and now for Spp1, we anticipate that other Set1C subunits, in addition to regulating H3K4 methylation, may participate in diverse biological functions inside or outside of the complex.     

Sugar Uptake and Utilisation during Adventitious Bud Differentiation on in Vitro Leaf Explants of ‘Wegierka Zwykła’ Plum (Prunus Domestica)

Leaf explants of plum Wegierka Zwyka were cultured on modified MS medium supplemented with 7.5 µM TDZ (thidiazuron) and 0.9 µM 2,4-D (2,4-dichlorophenoxyacetic acid), with the addition of either sucrose or glucose at a concentration of 2%, 3%, 4%, 5% or 6% (w/v). Regeneration was carried out in two steps: the first in darkness, the second in photoperiod conditions after subculture onto fresh medium. The study assessed the influence of the kind of sugar used and its concentration in the medium on organogenesis efficiency, and on sugar uptake from the medium. The results suggest that sucrose is a better carbon source than glucose for organogenesis of Wegierka Zwyka, even though at lower concentrations the efficiency of the sugars was comparable. With increasing concentration of sugars, the efficiency of organogenesis decreased, a relation more evident for media with glucose. In the first (dark) step of regeneration, the explants utilised less carbohydrates from the media than in the second step, when the main increase of explant weight took place. In the second phase, at 2–5% concentrations glucose uptake was higher than sucrose uptake.     

Analysis of sequences of two different classes of kinetoplast DNA minicircles of aLeishmania spp.

We have determined the nucleotide sequences of the minicircles representing a major (pLURkE3) and a minor (pLURkH13) class populations from the kinetoplast DNA ofLeishmania strain UR6. These minicircles have sequence organization similar to other kinetoplastid parasites, however, they have some unique structural features. These features include the following: (i) imperfect inverted repeat in the variable regions, similar to the conserved sequence elements of guide RNA genes in African trypanosomes, (ii) tandem and non-tandem direct repeats of 8 bp or longer scattered throughout the minicircles, (iii) non uniform strand distribution of bases throughout the minicircles and (iv) high TG content, more than half of the molecules being extremely (T + G) versus (A + C) strand biased. The heterogeneity of minicircle sequences in the variable regions may be exploited in developing recombinant DNA based diagnostic probes for detection and classification of Leishmania species. EMBL data base accession numbers X68026 and X68027. Part of this work was presented in the International Symposium on “Current Trends inLeishmania Research” held at Indian Institute of Chemical Biology, Calcutta on February 12–14, 1992.