Analysis of the denitrification pathway and greenhouse gases emissions in Bradyrhizobium sp. strains used as biofertilizers in South America.

AIMS: Greenhouse gases are considered as potential atmospheric pollutants, with agriculture being one of the main emission sources. The practice of inoculating soybean seeds with Bradyrhizobium sp. might contribute to nitrous oxide (N2 O) emissions. We analysed this capacity in five of the most used strains of Bradyrhizobium sp. in South America. METHODS AND RESULTS: We analysed the denitrification pathway and N2 O production by Bradyrhizobium japonicum E109 and CPAC15, Bradyrhizobium diazoefficiens CPAC7 and B. elkanii SEMIA 587 and SEMIA 5019, both in free-living conditions and in symbiosis with soybean. The in silico analysis indicated the absence of nosZ genes in B. japonicum and the presence of all denitrification genes in B. diazoefficiens strains, as well as the absence of nirK, norC and nosZ genes in B. elkanii. The in planta analysis confirmed N2 O production under saprophytic conditions or symbiosis with soybean root nodules. In the case of symbiosis, up to 26.1 and 18.4 times higher in plants inoculated with SEMIA5019 and E109, respectively, than in those inoculated with USDA110. CONCLUSIONS: The strains E109, SEMIA 5019, CPAC15 and SEMIA 587 showed the highest N2 O production both as free-living cells and in symbiotic conditions in comparison with USDA110 and CPAC7, which do have the nosZ gene. Although norC and nosZ could not be identified in silico or in vitro in SEMIA 587 and SEMIA 5019, these strains showed the capacity to produce N2 O in our experimental conditions. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report to analyse and confirm the incomplete denitrification capacity and N2 O production in four of the five most used strains of Bradyrhizobium sp. for soybean inoculation in South America.

Purple corn-associated rhizobacteria with potential for plant growth promotion.

AIMS: Purple corn (Zea mays var. purple amylaceum) is a native variety of the Peruvian Andes, cultivated at 3000 m since the pre-Inca times without N fertilization. We aimed to isolate and identify native plant growth-promoting rhizobacteria (PGPR) for future microbial-based inoculants. METHODS AND RESULTS: Eighteen strains were isolated from the rhizosphere of purple corn plants grown without N fertilization in Ayacucho (Peru). The 16S rRNA gene clustered the 18 strains into nine groups that contained species of Bacillus, Stenotrophomonas, Achromobacter, Paenibacillus, Pseudomonas and Lysinibacillus. A representative strain from each group was selected and assayed for N2 fixation, phosphate solubilization, indole acetic and siderophore production, 1-aminocyclopropane-1-carboxylic acid deaminase activity and biocontrol abilities. Inoculation of purple corn plants with single and combined strains selected after a principal component analysis caused significant increases in root and shoot dry weight, total C and N contents of the plants. CONCLUSIONS: PGPRs can support growth and crop production of purple corn in the Peruvian Andes and constitute the base for microbial-based inoculants. SIGNIFICANCE AND IMPACT OF THE STUDY: This study enlarges our knowledge on plant-microbial interactions in high altitude mountains and provides new applications for PGPR inoculation in purple amylaceum corn, which is part of the staple diet for the native Quechua communities.

Immunological regulation of neurogenic niches in the adult brain.

In mammals, neurogenesis and oligodendrogenesis are germinal processes that occur in the adult brain throughout life. The subventricular zone (SVZ) and subgranular zone (SGZ) are the main neurogenic regions in the adult brain. Therein, resides a subpopulation of astrocytes that act as neural stem cells (NSCs). Increasing evidence indicates that pro-inflammatory and other immunological mediators are important regulators of neural precursors into the SVZ and the SGZ. There are a number of inflammatory cytokines that regulate the function of NSCs. Some of the most studied include: interleukin-1, interleukin-6, tumor necrosis factor alpha, insulin-like growth factor-1, growth-regulated oncogene-alpha, leukemia inhibitory factor, cardiotrophin-1, ciliary neurotrophic factor, interferon-gamma, monocyte chemotactic protein-1 and macrophage inflammatory protein-1alpha. This plethora of immunological mediators can control the migration, proliferation, quiescence, cell-fate choices and survival of NSCs and their progeny. Thus, systemic or local inflammatory processes represent important regulators of germinal niches in the adult brain. In this review, we summarized the current evidence regarding the effects of pro-inflammatory cytokines involved in the regulation of adult NSCs under in vitro and in vivo conditions. Additionally, we described the role of proinflammatory cytokines in neurodegenerative diseases and some therapeutical approaches for the immunomodulation of neural progenitor cells.

Alloxenic distribution of cystacanths of two Profilicollis species in sympatric crustacean hosts in Chile.

The taxonomic status of Profilicollis ( = Falsifilicollis Webster, 1948) species in crustaceans in Chile is examined. Mole crabs, Emerita analoga (Stimpson 1857), living in the splash zone of a sandy beach at Lenga off the coast of central Chile, harbor Polymorphus (Profilicollis) bullocki Mateo, Córdova and Guzmán 1982, while the estuarine crabs, Hemigrapsus crenulatus (Milne-Edwards, 1837), living in an oligohaline inlet at the same site, harbor Profilicollis spp. cystacanths which cannot be distinguished specifically to either Profilicollis antarcticus or P. chasmagnathi Holcman-Spector, Mañé-Garzón and Dei-Cas 1977. We found no morphological data supporting records of P. altmani along the coast of Chile. Therefore, and after examination of both their morphology and the literature, we consider that P. bullocki must be reinstated as a valid species in the genus. There is a widespread distribution of habitats, such as sandy beaches and inlets, as well as a variety of host taxa involved in the life cycle of Profilicollis spp. Consequently, they provide an interesting scenario for testing hypotheses regarding the coevolution and host specificity of these parasites.

[Population and health. Reproductive health in adolescents]. / Poblacion y salud. Salud reproductiva en adolescentes.

PIP: The young age structure of the Mexican population and the large number of adolescents, estimated at 20.1 million in 1990, indicate a high potential demand for sex education and reproductive health services. The 4.9 million women 15-19 years old represented 23.5% of the reproductive-age female population. Adolescent fertility has declined slowly, to a rate of 84/1000 women 15-19 years old in 1986, but the absolute number of births is still increasing. In 1987, 14.1% of women ages 15-19 and 53.3% ages 20-24 had at least 1 child. The arrival of the first child occurs soon after the union. Surveys in 1976, 1982, and 1987 showed that in all educational groups, the first birth is occurring at ever younger ages. In 1987, 35% of births to mothers ages 15-19 and 30% to those 20-24 were premarital. In 1976, only 17% of births to mothers 15-19 years old were premarital. Adolescents become sexually active at young ages and lack adequate contraceptive protection. Reasons given by adolescents for not using contraception include the belief that pregnancy is impossible, the unplanned nature of sexual relations, lack of knowledge of contraceptive methods, and fear of side effects. A 1988 Mexico City survey found that 1% of females and 3% of males 15-25 years old had contracted sexually transmitted diseases. The same survey indicated that young people lack knowledge of the transmission and prevention of sexually transmitted diseases. Clear and timely instruction in management of sexuality is needed from the fifth or sixth grades of primary school so that adolescents will be informed of methods to avoid pregnancy and about the responsibilities and risks of early pregnancy.^ieng

[Malocclusion in the primary dentition]. / Maloclusiones en la denticíon primaria.

In this paper we analyze the type and frequency of malocclusions in a group of 100 health children with complete primary dentition. Bjork's method for epidemiological registration was taken as a basis. Of the examined children, 78% had some malocclusion type. The most frequent was the increased horizontal overbite. In vertical overbite relation we find anterior open bite, increased overbite, anterior open bite, increased overbite.