Genetic differentiation in Aspidosperma polyneuron (Apocynaceae) over a short geographic distance as assessed by AFLP markers

Studies on intraspecific variation can contribute to the development of conservation strategies by identifying units of conservation for threatened species. Aspidosperma polyneuron is a tropical tree of seasonal semideciduous forests that is currently endangered and protected because it has been heavily logged for lumber, although it was once common in Brazil and neighboring countries. We investigated genetic structure in two samples of A. polyneuron collected from steep hillsides and from flat areas of a natural forest fragment in northern Paraná State, Brazil. Seven AFLP primer combinations yielded 200 markers, with a polymorphic rate of 88.5% for samples from the flat area and 99% for samples from the high declivity area. Total genetic diversity (H(T)) was 0.387, while the genetic diversity within the populations (H(S)) was 0.307 and 0.372, for samples from the flat and the high declivity areas, respectively. Genetic differentiation between samples was high, with a mean F(ST) of 0.265 and a genetic distance of 0.148, indicative of a high degree of genetic structure over a short distance. Principal coordinate analysis separated the samples into three groups of individuals; the first group included individuals from the high declivity area, the second group consisted of individuals only from the flat area, and the third group had individuals from both areas. Bayesian analysis also showed K = 3 clusters. The unexpected high level of intraspecific variation of A. polyneuron in this small forest fragment should be taken into account when evaluating the genetic impact of forest degradation on this species in other semideciduous forest fragments.     

Ultrastructure of contact-chemoreceptor sensilla found among the genae of female Gasterophilus nasalis

Scanning electron microscopy was used to observe contact-chemoreceptor sensilla in the genae of the anterior vestigial mouthparts of female Gasterophilus nasalis. These were of the uniporous trichoid type and were surrounded by mechanosensory aporous trichoid sensilla of variable size. Contact-chemoreceptor sensilla could be involved in detecting different chemical substances, including the equine kairomones that stimulate females to lay eggs on the hair of the host and/or the short-range sexual pheromones used in precopulatory courtship. The probable functions of these sensilla are discussed with reference to the current literature on the sensorial organs of muscomorphid dipterans.     

Purification and molecular characterization of antibacterial compounds produced by Lactobacillus murinus strain L1

AIMS: The aim of this work was to purify and characterize antibacterial compounds produced by Lactobacillus murinus strain L1. METHODS AND RESULTS: Antagonistic activity was observed in a deferred agar-spot assay against spoilage and pathogenic bacteria, but not against lactobacilli. The inhibitory activity occurred between pH 3.0 and 5.0, and was heat stable. The active compounds were purified by gel filtration chromatography and two peaks of antibacterial activity were observed using Bacillus cereus ATCC 11778 and Shigella sonnei ATCC 11060 as indicator strains. Two active low molecular weight compounds were responsible for this phenomenon and UV spectroscopy, gas chromatography and mass spectrometry were used to characterize them. One of them is lactic acid, while the other is a mono-substituted aromatic ring apparently constituted by group residues of m/z 192 linked in tandem to phenylalanine. CONCLUSIONS: Lactobacillus murinus produces at least two low molecular weight compounds active against B. cereus and Sh. sonnei. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first purification of a new broad-spectrum antibacterial compound from Lact. murinus which inhibits various pathogenic and food spoilage bacteria without acting on other lactobacilli. Using it as a biotechnological control agent of bacterial spoilage may be a promising possibility for the food industry.     

Leishmania braziliensis: a novel mechanism in the lipophosphoglycan regulation during metacyclogenesis

During metacyclogenesis of Leishmania in its sand fly vector, the parasite differentiates from a noninfective, procyclic form to an infective, metacyclic form, a process characterised by morphological changes of the parasite and also biochemical transformations in its major surface lipophosphoglycan (LPG). This lipid-anchored polysaccharide is polymorphic among species with variations in sugars that branch off the conserved Gal(beta1,4)Man(alpha1)-PO4 backbone of repeat units and the oligosaccharide cap. Lipophosphoglycan has been implicated as an adhesion molecule that mediates the interaction with the midgut epithelium of the sand fly in the subgenus Leishmania. This paper describes the LPG structure for the first time in a species from the subgenus Viannia, Leishmania (Viannia) braziliensis. The LPG from the procyclic form of L. braziliensis was found to lack side chain sugar substitutions. In contrast to other species from the subgenus Leishmania, metacyclic forms of L. braziliensis makes less LPG and add 1-2 (beta1-3) glucose residues that branch off the disaccharide-phosphate repeat units of LPG. Thus, this represents a novel mechanism in the regulation of LPG structure during metacyclogenesis.     

Candida sergipensis, a new asexual yeast species isolated from frozen pulps of tropical fruits

Sixteen strains of the new yeast species Candida sergipensis have been isolated from frozen pulps of the tropical fruits umbú ( Spondias tuberosa Avr. Cam.) and mangaba ( Hancornia speciosa Gom.). Candida sergipensis was one of the prevalent species in the yeast community of these substrates. The new asexual ascomycetous yeast is phylogenetically related to Candida spandovensis and Candida sorbophila, species belonging to the Wickerhamiella clade, as evidenced by the sequences of the D1/D2 domains of their large subunit ribosomal DNAs. The species C. sergipensis and C. spandovensis can be separated on the basis of growth on 50% glucose agar, xylose and succinate, negative for the first species and positive for the second. The type culture is strain UFMG-R188 (CBS 9567).     

Determination of ancestral proportions in synthetic bovine breeds using commonly employed microsatellite markers

The International Society of Animal Genetics (ISAG) has chosen nine microsatellites (international marker set) as a standard that should be included in all cattle parentage studies. They are BM1824, BM2113, INRA023, SPS115, TGLA122, TGLA126, TGLA227, ETH10, and ETH225. We decided to ascertain whether this microsatellite set could be used to determine ancestral proportions in individual animals of synthetic breeds produced by crossing zebu and taurine cattle. Since the genotypes of these markers are routinely available, this would constitute a practical and cost-free method to estimate the ancestry of synthetic breed animals. Genotypes of 100 Gir and 100 Holstein animals were examined for this ISAG marker set. As expected, there were very significant allele frequency differences between the two breeds at most loci. We also typed 20 Girolando animals for which there was complete genealogical information. "Structure" software easily distinguished Holstein and Gir animals based on their microsatellite genotypes; it also attributed the genomic proportion of zebu and taurine of each of the 20 Girolando animals. The proportion of Holstein ancestry was then regressed on the genealogical data; there was a highly significant correlation (r = 0.84, P < 0.0001). The nine microsatellites that compose the ISAG international marker set were capable of estimating the ancestral Gir and Holstein genomic proportions in individual Girolando animals within narrow confidence limits. This microsatellite set might also be useful for estimating the proportions of taurine and zebu origins in commercial meat products.     

Dynein mediates retrograde neurofilament transport within axons and anterograde delivery of NFs from perikarya into axons: regulation by multiple phosphorylation events

We examined the respective roles of dynein and kinesin in axonal transport of neurofilaments (NFs). Differentiated NB2a/d1 cells were transfected with green fluorescent protein-NF-M (GFP-M) and dynein function was inhibited by co-transfection with a construct expressing myc-tagged dynamitin, or by intracellular delivery of purified dynamitin and two antibodies against dynein's cargo domain. Monitoring of the bulk distribution of GFP signal within axonal neurites, recovery of GFP signal within photobleached regions, and real-time monitoring of individual NFs/punctate structures each revealed that pertubation of dynein function inhibited retrograde transport and accelerated anterograde, confirming that dynein mediated retrograde axonal transport, while intracellular delivery of two anti-kinesin antibodies selectively inhibited NF anterograde transport. In addition, dynamitin overexpression inhibited the initial translocation of newly-expressed NFs out of perikarya and into neurites, indicating that dynein participated in the initial anterograde delivery of NFs into neurites. Delivery of NFs to the axon hillock inner plasma membrane surface, and their subsequent translocation into neurites, was also prevented by vinblastine-mediated inhibition of microtubule assembly. These data collectively suggest that some NFs enter axons as cargo of microtubues that are themselves undergoing transport into axons via dynein-mediated interactions with the actin cortex and/or larger microtubules. C-terminal NF phosphorylation regulates motor association, since anti-dynein selectively coprecipitated extensively phosphorylated NFs, while anti-kinesin selectively coprecipitated less phosphorylated NFs. In addition, however, the MAP kinase inhibitor PD98059 also inhibited transport of a constitutively-phosphorylated NF construct, indicating that one or more additional, non-NF phosphorylation events also regulated NF association with dynein or kinesin.