Biological variability in clinical isolates of Trichomonas vaginalis

Eighteen clinical isolates of Trichomonas vaginalis were obtained from women who attended health centers of the Government of Madrid. A total of 1,848 vaginal specimens recovered during the gynaecological examination were seeded in culture tubes containing liquid Diamond medium. Pathogenicity to mice was determined after intraperitoneal inoculation of mice by quantification of mortality and gross damage to abdominal organs. As could be expected, a broad variability was obtained, being some of the isolates more virulent than the reference strain. Regarding to metronidazole susceptibility, none resistant isolate was found but different degrees of susceptibility were determined.     

Limited Genetic Diversity in the Endophytic Sugarcane Bacterium Acetobacter diazotrophicus

Acetobacter diazotrophicus isolates that originated from different sugarcane cultivars growing in diverse geographic regions of Mexico and Brazil were shown to have limited genetic diversity. Measurements of polymorphism in the electrophoretic mobilities of metabolic enzymes revealed that the mean genetic diversity per enzyme locus (among the four electrophoretic types distinguished) was 0.064. The results of the genetic analysis indicate that the genetic structure of A. diazotrophicus is clonal, with one largely predominant clone. Plasmids were present in 20 of 24 isolates, and the molecular sizes of the plasmids ranged from 2.0 to 170 kb. Two plasmids (a 20- to 24-kb plasmid detected in all 20 plasmid-containing isolates and a 170-kb plasmid observed in 14 isolates) were highly conserved among the isolates examined. Regardless of the presence of plasmids, all of the isolates shared a common pattern of nif structural gene organization on the chromosome.     

<Emphasis Type="Italic">Rhizobium etli</Emphasis> maize populations and their competitiveness for root colonization

Rhizobium etli, which normally forms nitrogen-fixing nodules on Phaseolus vulgaris (common bean), is a natural maize endophyte. The genetic diversity of R. etli strains from bulk soil, bean nodules, the maize rhizosphere, the maize root, and inside stem tissue in traditional fields where maize is intercropped with P. vulgaris-beans was analyzed. Based on plasmid profiles and alloenzymes, it was determined that several R. etli types were preferentially encountered as putative maize endophytes. Some of these strains from maize were more competitive maize-root colonizers than other R. etli strains from the rhizosphere or from bean nodules. The dominant and highly competitive strain Ch24-10 was the most tolerant to 6-methoxy-2-benzoxazolinone (MBOA), a maize antimicrobial compound that is inhibitory to some bacteria and fungi. The R. tropici strain CIAT899, successfully used as inoculant of P. vulgaris, was also found to be a competitive maize endophyte in inoculation experiments.     

Effects of Dihydrotestosterone on Brain mRNA Levels of Steroid 5α-Reductase Isozymes in Early Postnatal Life of Rat

We studied the expression of type 1 (5α-R1) and type 2 (5α-R2) 5α-reductase isozymes (5α-R) and their regulation by dihydrotestosterone (DHT) in the prefrontal cortex of male and female rats during postnatal sexual differentiation of the central nervous system (CNS), using one-step quantitative RT-PCR coupled with laser-induced fluorescence capillary electrophoresis. We found a higher expression of 5α-R2, which is considered a masculinizing enzyme, in the female versus male CNS, and observed sexual dimorphism in the regulation of both 5α-R isozymes by DHT. These results open up a new research line that could improve understanding of the role of 5α-R isozymes in the physiology of the CNS.     

Population genetics and phylogenetic inference in bacterial molecular systematics: the roles of migration and recombination in Bradyrhizobium species cohesion and delineation

A combination of population genetics and phylogenetic inference methods was used to delineate Bradyrhizobium species and to uncover the evolutionary forces acting at the population-species interface of this bacterial genus. Maximum-likelihood gene trees for atpD, glnII, recA, and nifH loci were estimated for diverse strains from all but one of the named Bradyrhizobium species, and three unnamed "genospecies," including photosynthetic isolates. Topological congruence and split decomposition analyses of the three housekeeping loci are consistent with a model of frequent homologous recombination within but not across lineages, whereas strong evidence was found for the consistent lateral gene transfer across lineages of the symbiotic (auxiliary) nifH locus, which grouped strains according to their hosts and not by their species assignation. A well resolved Bayesian species phylogeny was estimated from partially congruent glnII+recA sequences, which is highly consistent with the actual taxonomic scheme of the genus. Population-level analyses of isolates from endemic Canarian genistoid legumes based on REP-PCR genomic fingerprints, allozyme and DNA polymorphism analyses revealed a non-clonal and slightly epidemic population structure for B. canariense isolates of Canarian and Moroccan origin, uncovered recombination and migration as significant evolutionary forces providing the species with internal cohesiveness, and demonstrated its significant genetic differentiation from B. japonicum, its sister species, despite their sympatry and partially overlapped ecological niches. This finding provides strong evidence for the existence of well delineated species in the bacterial world. The results and approaches used herein are discussed in the context of bacterial species concepts and the evolutionary ecology of (brady)rhizobia.     

Marinomonas aquamarina sp. nov., isolated from oysters and seawater

The characterization of three bacterial strains isolated from cultured oysters and seawater at the Spanish Mediterranean coast has been performed. Strains were phenotypically and genetically characterized and the results led us to identify them as members of the genus Marinomonas. A phylogenetic analysis based on the almost complete 16S rDNA sequences clustered all three strains together (with sequence similarities around 99.8%) in the vicinity of M. communis and M. vaga sequences and distantly related to the other four species of the genus. The most closely related species was M. communis that shared 97.4-97.6% with the Mediterranean strains. DNA-DNA hybridizations were performed to clarify the taxonomic position of our isolates and the results confirmed their specific isolation, with interspecific binding ratios below 59%. We propose the bacteria to constitute a new Marinomonas species, i.e. M. aquamarina and strain 11SM4T (CECT 5080T, CIP 108405T, CCUG 49439T) as the type strain.     

Identification and functional characterization of a novel low affinity aromatic-preferring amino acid transporter (arpAT). One of the few proteins silenced during primate evolution

We have identified in silico arpAT, a gene encoding a new member of the LSHAT family, and cloned it from kidney. Co-expression of arpAT with the heavy subunits rBAT or 4F2hc elicited a sodium-independent alanine transport activity in HeLa cells. L-tyrosine, l-3,4-dihydroxyphenylalanine (L-DOPA), L-glutamine, L-serine, L-cystine, and L-arginine were also transported. Kinetic and cis-inhibition studies showed a K(m) = 1.59 +/- 0.24 mM for L-alanine or IC50 in the millimolar range for most amino acids, except L-proline, glycine, anionic and D-amino acids, which were not inhibitory. L-DOPA and L-tyrosine were the most effective competitive inhibitors of L-alanine transport, with IC50 values of 272.2 +/- 57.1 and 716.3 +/- 112.4 microM, respectively. In the small intestine, arpAT mRNA was located at the enterocytes, in a decreasing gradient from the crypts to the tip of the villi. It was also expressed in neurons from different brain areas. Finally, we show that while the arpAT gene is conserved in rat, dog, and chicken, it has become silenced in humans and chimpanzee. Actually, it has been recently reported that it is one of the 33 recently inactivated genes in the human lineage. The evolutionary implications of the silencing process and the roles of arpAT in transport of L-DOPA in the brain and in aromatic amino acid absorption are discussed.     

Differences in open field behavior between heterozygous and homozygous negative gilts for the RYR(1) gene

A test widely used to assess fear and novelty responses in domestic species is the open field. The aim of this study was to investigate the effect of RYR(1) genotype on open field behavior in growing pigs. The study subjected 15 heterozygous (Nn) and 15 RYR(1)-free (NN) gilts of 19 weeks of age to 3 replicates of an open field test 2 days apart from each other. The study measured the number of grid lines crossed and defecation score in the test arena. There was a significant individual correlation among the 3 replicates of the test, both for number of grid lines crossed and defecation score (p <.05). RYR(1) genotype had a significant effect on number of grid lines crossed, with NN gilts showing more overall activity than Nn gilts (p <.05). The study observed no significant differences in defecation score between genotypes. This result suggests that the RYR(1) genotype may have an effect on the appraisal of novelty. Thus, it would be interesting to take this factor into account when using this methodology to assess fear responses in pigs and in interpreting the results with respect to welfare.     

Glucose but not protein or fat load amplifies the cortisol response to psychosocial stress

We previously reported that glucose intake amplifies cortisol response to psychosocial stress and smoking in healthy young men, while low blood glucose levels prevented the stress-induced activation of the hypothalamus pituitary adrenal (HPA) axis. However, it remains unknown whether this modulation is specific for glucose load or a more common effect of energy availability. To elucidate this question, 37 healthy men, who fasted for at least 8 h before the experiment, were randomly assigned to four experimental groups, who received glucose (n = 8), protein (n = 10), fat (n = 10), and water (n = 9), one h before their exposure to the Trier Social Stress Test (TSST). Blood glucose levels were measured at baseline and following stress, while salivary cortisol was assessed repeatedly measured before after the TSST. The results show that both absolute cortisol levels and net cortisol increase were greater in the glucose group in comparison to the other groups (F(3,33) = 3.00, P < 0.05 and F(3,33) = 3.08, P < 0.05, respectively. No group differences were observed with respect to perceived stress and mood. Furthermore, the cortisol response was positively correlated with blood glucose changes (r = 0.49, P < 0.002). In conclusion, the results suggest a central mechanism responsible for regulation of energy balance and HPA axis activation, rather than peripheral mechanisms. We thus recommend controlling for blood glucose levels when studying HPA axis responsiveness.