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Phytophthora cinnamomi is an important plant pathogen responsible for dieback diseases in plant genera including Quercus, Fagus, Castanea, Eucalyptus, and Pinus, among others, all over the world. P. cinnamomi infection exerts tremendous ecological and economic losses. Several strategies have been developed to combat this pathogenic oomycete, including the search for novel anti-oomycete compounds. In this work, a Mediterranean vascular plant, Phlomis purpurea, has been screened for secondary bioactivity against this pathogen. The genus Phlomis includes a group of herbaceous plants and shrubs described as producers of many different bioactive compounds, including several triterpenoids. Triterpenoids are well-known molecules synthesized by plants and microorganisms with potent antioxidant, antitumoral, and antimicrobial activities. We have isolated by HPLC-DAD and characterized by HPLC-MS and NMR two nortriterpenoid compounds (phlomispentaol A and phlomispurtetraolone) from the root extracts of P. purpurea. One of them (phlomispentaol A) is active against the plant pathogenic oomycete P. cinnamomi (based on in vitro inhibition bioassays). Based on their chemical structure and their relationship to other plant triterpenoids, oleanolic acid is proposed to be the common precursor for these molecules. The anti-oomycete activity shown by phlomispentaol A represents a promising alternative to counteract the worldwide-scale damage caused to forest ecosystems by this pathogen. [ABSTRACT FROM AUTHOR]

Two groups of 5 lambs were euthanized at the weaning (T45) and fattening stages (T90) to evaluate the use of microbial ribosomal DNA (rDNA) sequences as potential microbial markers in relation to purine bases (PB) as a conventional marker. Both microbial markers originated similar microbial N concentrations (mg/g of DM), although T45 showed decreased values compared with the T90 group when either PB or rDNA were considered (P = 0.02). The survival of microbial rDNA was determined in 3 digestive sites (omasum, abomasum, and duodenum), but no substantial differences were observed, indicating that rDNA maintains the molecular stability along the sampling sites analyzed. Contrarily PB concentration increased successively along the digestive tract (P < 0.05), likely as a consequence of the endogenous PB secretion. Undegraded milk PB may also explain the overestimation of the microbial N concentration (2.8 times greater) using PB than rDNA sequences. Abomasum was the sampling site where the best agreement between PB and rDNA estimations was observed. Protozoal N concentration was irrelevant in T45 animals, although substantial in T90 lambs (18% of microbial N). In conclusion, bacterial 16S and protozoal 18S rDNA sequences may persist through the gastric digestive tract and their utilization as a highly specific microbial marker should not be neglected. [ABSTRACT FROM AUTHOR]

This study examined the reticulo-rumen characteristics of the microbial community and its fermentative characteristics in milk-fed, at weaning and finished lambs in a conventional fattening system. Five lambs were assigned to each of three groups: milk-fed lambs slaughtered at 30 days (T30), weaned lambs slaughtered at 45 days (T45) and 'finished lambs' slaughtered at 90 days (T90). At slaughter, rumen size, fermentation parameters (pH, volatile fatty acids and microbial enzyme activity) and protozoal counts were recorded. Quantitative PCR was used to quantify the genes encoding 16S and 18S ribosomal DNA of the rumen bacterial and protozoal populations, respectively, and the sequential colonization of the rumen by cellulolytic ( Ruminococcus albus, Ruminococcus flavefaciens) and amylolytic ( Prevotella ruminicola, Streptococcus bovis) bacteria, and protozoa ( Entodinium sp.). Denaturing gradient gel electrophoresis was used to study the development of rumen microbiota biodiversity. Intake of solid food before weaning caused a significant increase in rumen weight (p < 0.0001) and bacterial DNA (p < 0.05) and volatile fatty acid analysis concentration (p < 0.01), whereas pH declined. In milk-fed lambs, cellulolytic bacteria were evident after 30 days. Thereafter, in the 45-day and 90-day groups, the proportions of R. flavefaciens decreased and R. albus increased. Amylolytic bacteria were present in milk-fed lambs; the proportion of P. ruminicola increased in fattening lambs and S. bovis was the least abundant species. Protozoal concentrations were irregular; milk-fed lambs had a significant number of protozoa species from Entodinium and subfamily Isotrichiidae, but they disappeared at weaning. Lamb rumen were refaunated in some individuals at 90 days ( Entodinium and subfamily Diplodiniinae spp.), although individual concentrations were variable. [ABSTRACT FROM AUTHOR]

The use of specific DNA sequences (DS) as a microbial marker in post-rumen digesta requires their persistence and integrity throughout gastric digestion. The aim of this study was to evaluate in vitro the survival of microbial DS during gastric digestion and the factors involved. Gastric pH had a highly significant effect on the integrity of DS. pH 4.2 allows for a significant growth of microbes in the medium, but at pH 1.2, almost all of the DS were hydrolysed. In the presence of carboxymethylcellulose, the effect of pH was reduced, pepsin activity was inhibited and gene survival increased considerably. In the simulated abomasal conditions (pH = 2.3, 2 g/l of carboxymethylcellulose, and 40-min retention time), almost all of the bacterial genes and around 78% of the protozoa gene sequences retained their molecular integrity throughout gastric digestion, although factors such as acidity and viscera retention time might compromise the utilisation of DS as a microbial marker. [ABSTRACT FROM AUTHOR]