Comparison of contamination and growth of Mycobacterium avium subsp. paratuberculosis on two different media

AIMS: The purpose of the study was to compare the growth of Mycobacterium avium subsp. paratuberculosis (Map) and the degree of contamination on Herrold's egg yolk medium (HEYM) and modified L?wenstein-Jensen medium (LJ). METHODS AND RESULTS: Culture of 2513 faecal samples from dairy cows was performed on each of the two media. The media were read after 5, 8 and 12 weeks of incubation. Overall, the proportion of contaminated samples was significantly higher on LJ (14.2%) than on HEYM (13.2%) after 12 weeks but the degree of contamination was slightly less on LJ. After 8 weeks of incubation, only 1.0% of the samples were Map positive in LJ with 4.9% on HEYM. After 12 weeks of incubation, 3.3% of the samples were Map positive in LJ whereas 6.9% were positive in HEYM. All suspect and culture positive samples were confirmed by IS900 PCR. CONCLUSIONS: HEYM supported growth of Map significantly better and faster than LJ, however it could not be determined conclusively which of the two media that provided the highest degree of decontamination when the incubation time was also included. SIGNIFICANCE AND IMPACT OF THE STUDY: HEYM should be the primary medium rather than LJ for detection of Map in cattle.     

Fermentation of a milk-soymilk and Lycium chinense Miller mixture using a new isolate of Lactobacillus paracasei subsp. paracasei NTU101 and Bifidobacterium longum

A milk–soymilk mixture was fermented using Lactobacillus paracasei subsp. paracasei NTU101 and Bifidobacterium longum BCRC11847 at different inoculum ratios (1:1, 1:2, 1:5, 2:1, and 5:1). When the inoculum ratio was 1:2, the cell numbers of both strains were balanced after 12 h of cultivation. The pH and titratable acidity were very similar at the various inoculum ratios of cultivation. The milk–soymilk mixture was supplemented with 5, 10, 15, and 20% Lycium chinense Miller juice and fermented with Lactobacillus paracasei subsp. paracasei NTU101 and B. longum BCRC11847. Sensory evaluation results showed that supplementation with 5% Lycium chinense Miller juice improved the acceptability of the fermented milk–soymilk. The fermented beverage was stored at 4°C for 14 days; variations in pH and titratable acidity were slight. The cell numbers of L. paracasei subsp. paracasei NTU101 and B. longum BCRC11847 in the fermented beverage were maintained at 1.2×10⁹ CFU/ml and 6.3×10⁸ CFU/ml, respectively, after 14 days of storage.     

Characterization of mesentericin ST99, a bacteriocin produced by <Emphasis Type="Italic">Leuconostoc mesenteroides</Emphasis> subsp. <Emphasis Type="Italic">dextranicum</Emphasis> ST99 isolated from boza

Lactic acid bacteria isolated from Boza, a cereal-fermented beverage from Belogratchik, Bulgaria, were screened for the production of bacteriocins. With the first screening, 13 of the 52 isolates inhibited the growth of Listeria innocua and Lactobacillus plantarum. The cell-free supernatant of one of these strains, classified as Leuconostoc mesenteroides subsp. dextranicum ST99, inhibited the growth of Bacillus subtilis, Enterococcus faecalis, several Lactobacillus spp., Lactococcus lactis subsp. cremoris, Listeria innocua, Listeria monocytogenes, Pediococcus pentosaceus, Staphylococcus aureus and Streptococcus thermophilus. Clostridium spp., Carnobacterium spp., L. mesenteroides and Gram-negative bacteria were not inhibited. Maximum antimicrobial activity, i.e. 6,400 arbitrary units (AU)/ml, was recorded in MRS broth after 24 h at 30°C. Incubation in the presence of protease IV and pronase E resulted in loss of antimicrobial activity, confirming that growth inhibition was caused by a bacteriocin, designated here as mesentericin ST99. No loss in activity was recorded after treatment with -amylase, SDS, Tween 20, Tween 80, urea, Triton X-100, N-laurylsarcosin, EDTA and phenylmethylsulfonylfluoride. Mesentericin ST99 remained active after 30 min at 121°C and after 2 h of incubation at pH 2 to 12. Metabolically active cells of L. innocua treated with mesentericin ST99 did not undergo lysis. Mesentericin ST99 did not adhere to the cell surface of strain ST99. Precipitation with ammonium sulfate (70% saturation), followed by Sep-Pack C₁₈ chromatography and reverse-phase HPLC on a C₁₈ Nucleosil column yielded one antimicrobial peptide.     

Rapid evolution of escape ability in Trinidadian guppies (Poecilia reticulata)

Predators are widely assumed to create selection that shapes the evolution of prey escape abilities. However, this assumption is difficult to test directly due to the challenge of recording both predation and its evolutionary consequences in the wild. We examined these events by studying natural and experimental populations of Trinidadian guppies, Poecilia reticulata, which occur in distinct high-predation and low-predation environments within streams. Importantly, in the last two decades several populations of guppies have been experimentally introduced from one type of predatory environment into the other, allowing measurements of the consequences of change. We used this system to test two hypotheses: First, that changes in predatory environments create phenotypic selection favoring changes in escape ability of guppies, and second, that this selection can result in rapid evolution. For the first test we compared escape ability of wild caught guppies from high- versus low-predation environments by measuring survival rates during staged encounters with a major predator, the pike cichlid Crenicichla alta. We used guppies from three streams, comparing two within-stream pairs of natural populations and three within-stream pairs of an introduced population versus its natural source population. In every comparison, guppies from the high-predation population showed higher survival. These multiple, parallel divergences in guppy survival phenotype suggest that predatory environment does create selection of escape ability. We tested our second hypothesis by rearing guppies in common garden conditions in the laboratory, then repeating the earlier experiments using the F2 generation. As before, each comparison resulted in higher survival of guppies descended from the high-predation populations, demonstrating that population differences in escape ability have a genetic basis. These results also show that escape ability can evolve very rapidly in nature, that is, within 26-36 generations in the introduced populations. Interestingly, we found rapid evolutionary loss of escape ability in populations introduced into low-predation environments, suggesting that steep fitness trade-offs may influence the evolution of escape traits.     

Flavonoid glycosides from Centaurea pseudoscabiosa subsp. pseudoscabiosa from Turkey

Three flavonoid glycosides were isolated and characterized, together with a further 13 substances belonging to various classes of compounds, in particular two phenolic acids, a coumarin, a sugar and nine flavonoids from the flowered aerial parts of Centaurea pseudoscabiosa subsp. pseudoscabiosa Boiss. et Buhse (Asteraceae). Some considerations about their evolutionary meaning are provided.     

Floral and vegetative morphometrics of five Pleurothallis (Orchidaceae) species: correlation with taxonomy,phylogeny, genetic variability and pollination systems

Morphometric analyses of vegetative and floral characters were conducted in 21 populations of five Pleurothallis (Orchidaceae) species occurring in Brazilian 'campo rupestre' vegetation. A phylogenetic analysis of this species group was also carried out using nuclear ribosomal DNA internal transcribed spacers (ITS1 and ITS2). Results of the ordination and cluster analyses agree with species' delimitation revealed by taxonomic and allozyme studies. The groups formed in ordination analysis correspond to the pollinator groups determined in a previous pollination study. Relationships among the species in the cluster analysis using only vegetative characters are similar to those found in a previous allozyme study, but those indicated by cluster analysis using only floral characters differ. These results support the hypothesis that floral similarities are due to convergence driven by similar pollination mechanisms, and therefore floral traits may not be good indicators of phylogenetic relationships in this group. The results of the phylogenetic analysis support this conclusion to some extent. There is no correlation between genetic (allozyme) and morphological variability in the populations nor in the way this variability is distributed among conspecific populations. We describe a new subspecies of Pleurothallis ochreata based on differences in vegetative and chemical characters as well as geographic distribution. Absence of differentiation in floral characters, attraction of the same pollinator species, interfertility and genetic similarity support the argument for subspecific rather than specific status.     

Effect of Azospirillum-mediated plant growth promotion on the development of bacterial diseases on fresh-market and cherry tomato

AIMS: Plant growth-promoting (PGP) activity of two Azospirillum strains and their effects on foliar and vascular bacterial diseases were evaluated on fresh market and cherry tomato. METHODS AND RESULTS: Tomato seeds were inoculated with A. brasilense Sp7 or Azospirillum sp. BNM-65. Four-week-old plants were challenge-inoculated with Clavibacter michiganensis subsp. michiganensis (bacterial canker) or with Xanthomonas campestris pv. vesicatoria (bacterial spot). Azospirillum-induced PGP was greater on cherry than on fresh-market tomato. Cherry tomato was more resistant to bacterial canker but more susceptible to bacterial spot than the fresh-market tomato. Canker severity was not affected by Azospirillum seed treatments. However, leaf- and plant-death were delayed on Azospirillum-treated plants compared with nontreated controls. Azospirillum increased the bacterial spot severity on cherry but not on fresh-market tomato. CONCLUSIONS: PGP was observed on both tomato genotypes, although growth effects were larger on cherry tomato. Also, Azospirillum treatments may alter tomato susceptibility to bacterial diseases. SIGNIFICANCE AND IMPACT OF THE STUDY: The interaction between PGP rhizobacteria like Azospirillum spp., not known to induce systemic resistance, with plant pathogens distantly located is frequently overlooked. This work demonstrates the importance of this kind of evaluation.     

Nonlinkage of major histocompatibility complex class I and class II loci in bony fishes

 In tetrapods, the functional (classical) class I and class II B loci of the major histocompatibility complex (Mhc) are tightly linked in a single chromosomal region. In an earlier study, we demonstrated that in the zebrafish, Danio rerio, order Cypriniformes, the two classes are present on different chromosomes. Here, we show that the situation is similar in the stickleback, Gasterosteus aculeatus, order Gasterosteiformes, the common guppy, Poecilia reticulata, order Cyprinodontiformes, and the cichlid fish Oreochromis niloticus, order Perciformes. These data, together with unpublished results from other laboratories suggest that in all Euteleostei, the classical class I and class II B loci are in separate linkage groups, and that in at least some of these taxa, the class II loci are in two different groups. Since Euteleostei are at least as numerous as tetrapods, in approximately one-half of jawed vertebrates, the class I and class II regions are not linked. Received: 30 August 1999 / Revised: 20 October 1999     

Identification and purification of the 69-kDa intracellular protease involved in the proteolytic processing of the crystal delta-endotoxin of Bacillus thuringiensis subsp. tenebrionis

The dynamics of appearance of intracellular proteases in relation to the synthesis of crystal delta-endotoxin was studied to identify the native intracellular protease(s) involved in the proteolytic processing of the 73-kDa protoxin of Bacillus thuringiensis subsp. tenebrionis. In vitro proteolytic activation of the 73-kDa protoxin indicated the possible role of 69-kDa protease in the proteolytic processing of 73-kDa protoxin. The purified 69-kDa protease was able to cause the proteolytic activation of the 73-kDa protoxin to 68-kDa toxin and this conversion was inhibited by ethylenediamine tetraacetic acid and 1,10-phenanthroline.     

紫斑牡丹及其一新亚种

本文回顾了有关紫斑牡丹的调查和分类历史。它曾被混同于 P．suffruticosa,P．papaveracea 及P．suffruticosa var．papaveracea。它以叶2至3回羽状复叶,小叶17～33,花瓣白色,基部有大紫斑, 花丝黄色,花盘和柱头淡黄色区别于近缘种。种下分化为两个异域的亚种;秦岭北坡的紫斑牡丹小叶全 部或大部分分裂,是一个新亚种,P．rockii subsp．taibaishanica,而P.rockii subsp．linyanshanii T.Hong et G．L.ostii则是P．rockii subsp．rockii的多余名。